Science 2 part 1

17. Which best describes a transgenic crop? a. A crop which is a mutant. b. A crop which is an animal. c. A crop that has been bred to exhibit new characteristics. d. A crop that has had a gene from another species inserted.18. Are foods made from genetically modified crops required to pass human testing? a. Yes, because it ensures safety of humans. b. No, because they are safe to be used by humans.19. Are foods derived from genetically modified crops required to be tested for possible allergic reactions in people? a. Yes, because health/safety of humans is important. b. No, because they cause no allergic reactions in people.20. Which of the following was the first mammal to be cloned?a. Dolly the sheep c. Rhesus monkeyb. Piggy the piglet d. Donkey the horse Got a perfect score? Check it out! Key to answers on page 24.Lesson 1. Substance Transport Across the Membrane Look around you. The things you see, and even some things you cannot see, aremade of matter (anything that has mass and takes up space). Living cells that make upyour body are made of matter. Matter is made of small non-living particles called atoms (hydrogen, oxygen, carbon,nitrogen). Atoms are seldom found alone in nature. Usually, they join together to formlarger particles called molecules (combination of two or more atoms). Molecules areassembled to form cells. Each individual cell exists in a liquid environment. The cells of our bodies are bathedin a liquid that was once part of blood. The presence of liquid makes it easier for materialslike food, oxygen and water to move into and out of the cell. -5-

Figure 1.1 Atoms/molecules Source: http://www.chem4kids.com/files/atom_intro.html Have You Heard? Water molecules are very, very small. To get an idea of just how small they are, try to imagine this. If a single drop of water were enlarged until it was the size of the earth, each water molecule in that earth-sized drop of water would be no larger than a golf ball! Just as whole organisms take in food, cells also obtain food, oxygen, and othersubstances from their environment. They also release waste materials. How do these things move into and out of the cell? What controls the movement ofmaterials into and out of the cell? You are right if you say that it is the job of the cell membrane. Have you ever seen marbles in a mesh bag? A mesh bag has holes in it. But themarbles stay inside because they are larger than the holes. What if you replaced marbles with sand? Gotcha! The sand will fall right through theholes because the sand grains are smaller than the holes. The mesh bag is selectively permeable (passable) because it allows some things topass through it but not others. The marbles and sand are models for molecules. For thisreason, biologists describe a cell membrane as selectively permeable. Water and other small molecules can easily pass through a cell membrane. Proteinsand other large molecules must be broken down into smaller parts to enter the cell. Onceinside a cell, the larger molecules can be rebuilt. There are several ways in which materials enter and leave the cell. If materials movethrough a cell membrane without the help of energy, passive transport takes place. Ifmaterials require energy to move through a cell membrane, active transport takes place. -6-

Figure 1.2 Passive transport and active transport Source: http://www.accessexcelence.org/RC/VL/GG/index.htmlWhat you will doActivity 1.1 Can You Do This? Do this simple activity to find out why your fingers wrinkle. Pour 250 ml of water into each of two small bowls. Stir a pinch of salt. Label it salt water. Place slices of raw potato in each bowl. Predict how the potato slices will be affected. After 20 minutes, pick up the slices and examine them. Describe the slices. How do they compare with wrinkled fingers? Key to answers on page 24. -7-

What you will do Self-Test 1.1Answer the question briefly. If the cell membrane were not semi-permeable, a cell might die. Why? ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ Key to answers on page 24.Lesson 2. Passive Transport versus Active TransportHow do molecules move into and out of the cell? Molecules move like a crowd of bump cars in an amusement park. They move fromcrowded areas into places where there are fewer of them. Passive transport involves carriers, channels, or direct diffusion through amembrane. This type of transport always operates from regions of greater concentration toregions of lesser concentration. No external source of energy is required. The force behind the movement of many substances across the cell membrane iscalled diffusion. There are three main types of diffusion: simple, channel, and facilitateddiffusion.Simple diffusion is when a smallmolecule passes through a lipidbilayer. It isclassified as a means of passive transport. Simplediffusion does not involve a protein. An example ofsimple diffusion is osmosis Figure 2.1 Example of simple diffusion Source: http://biology.Kenyon.edu/HHMI/Biol113/ diffusion.htm -8-

Channel diffusion is another type of passivetransport. Channel diffusion involves channelproteins where material moves through an open,aqueous pore. Channel diffusion can be regulated.Ions and charged particles canpass through the open pore. Figure 2.2 Example of channel diffusionSource: hhtp://biology.Kenyon.edu/HHMI/Biol113/ diffusion.htmFacilitated diffusion is a type of passive transport F Dthat is dependent on single transport carriers. A IThese protein carriers operate on a bind, flip, C Frelease mechanism. Facilitated diffusion is non- I Fdiffusional because the molecule moves along with L Uthe carrier. I S T S Figure 2.3 Example of facilitated diffusion A I T O Source: hhtp://biology.Kenyon.edu/HHMI/Biol113/ E N diffusion.htm DDo You Know? You are on a large 10 ft x 10 ft x10 ft elevator. An obnoxiousindividual with a lit cigar gets in on the third floor with the cigar still burning.You are also unfortunate enough to be in a very tall building and the personsays \"Hey we're both going to the 62nd floor!\" Disliking smoke you move tothe farthest corner you can. Eventually you are unable to escape the smoke!This is an example of diffusion in action. Nearer the source theconcentration of a given substance increases. You experience diffusion when someone opens a bottle of perfume ina closed room, or when someone arrives freshly doused in perfume orcologne. Also, when drops of blue ink are added to a glass of water, diffusiontakes place.-9-

What you will do Activity 2.1 MINI-Lab How does temperature affect the rate of diffusion of molecules? Prepare jars/bottles with equal amounts of cold water and hot tap water. Add one antacid tablet to each AT THE SAME TIME. Predict which will dissolve faster. Observe and record how long it takes for the tablet to dissolve in each beaker. Explain any differences you observe. You can do this activity at home. Key to answers on page 25. If you will recall, water makes up a large part of living matter. The movement ofwater into and out of a cell is known as osmosis. The process can cause a cell to swellor get smaller depending on the amount of water around the cell. Water moleculesmove from where they are in large numbers to where they are in small numbers. Whenthe number of water molecules inside and outside the cell is the same, equilibrium(balance) is reached. Figure 2.4 Water relations and cell shape in blood cells. Source: www.sinauer.com & www.whfreeman.com - 10 -

Figure 2.5 Water relations in a plant cell. Source: www.sinauer.com & www.whfreeman.com Figure 2.6 Source: http://www.accessexcelence.org/RC/VL/GG/index.html Three ways in which cells avoid osmotic swelling. The animal cell keeps theintracellular solute concentration low by pumping out ions (A). The plant cell is saved fromswelling and bursting by its tough wall (B). The protozoan avoids swelling by periodicallyejecting the water that moves into the cell (C). What you will do Activity 2.2 Applying a Concept The beaker in the diagram has a selectively permeable membrane separating two solutions. Suppose that the salt molecules are small enough to pass through the membrane but the starch molecules are too large to pass through. Will the water level on either side of the membrane change? Explain your answer. - 11 -

ABConcentrated Selectively permeable salt solution membrane Dilute starch & solution If a cell membrane were not selectively permeable, a cell might die. Explain why. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ Key to answers on page 25.Think about this If you become thirsty, you feel dried up. If cells don’t have the water that they need,they lose water. If you forget to water a plant, it will become dry. Ah! Water is reallyimportant to life. - 12 -

What you will do Self-Test 2.1 PROBLEM SOLVING What happened to the salad? Edith made a salad of lettuce, tomatoes, carrots, and cucumbers. She seasoned the salad with herbs, salt and pepper, then she placed it in the refrigerator for a couple of hours. When Edith returned, she took the salad from the refrigerator. The lettuce had wilted, and the other vegetables were limp. She noticed that there was liquid in the bottle in the bowl. Where did the liquid come from? Think critically: Why had the lettuce wilted (dried up)? Key to answers on page 25. In red blood cells, for example, a carrier protein in the cell membrane transportsglucose (sugar) from one side of the membrane to the other. This process is controlled bydiffusion.Diffusion, osmosis, and facilitated diffusion are forms of passive transport. Sometimes, a cell uses energy to pump molecules through the cell membrane. Thisprocess, active transport, can move molecules from less crowded areas to more crowdedareas. In other words, active transport can move molecules away from the direction inwhich they diffuse (move). This process is the opposite of diffusion and it requires energy. An example of thistype of active transport can be seen when: plant root cells take in minerals from the soil. The cells use energy to move additional minerals into the root cells. in the body, wastes are moved by active transport out of some kidney cells. - 13 -

Where does energy come from for active transport to take place? If your answer is mitochondria, I salute you, you are really learning fast.How are large amounts of material transported through the cell membrane? Some white blood cells in your blood are capable of swallowing whole bacteria.Other cells, such as the single-celled ameoba, are capable of “eating” clumps of sugar, andeven tiny pieces of bread! Many cells will seem to “eat” small particles of food, foreignmaterial, or even other cells. This process is called endocytosis. Phagocytosis is thetype of endocytosis where an entire cell is engulfed. Pinocytosis is when the external fluidis engulfed. Endocytosis occurs when the material to be transported binds to certainspecific molecules in the membrane. Examples include the transport of insulin andcholesterol into animal cells. As you might expect, cells are also capable of sending material out of the cell. Whenother large molecules are removed from the cell, the process is generally known asexocytosis. Endocytosis and exocytosis are forms of active transport. Refer to the diagrambelow. Figure 2.7 Exocytosis and endocytosis Source: http://www.accessexcelence.org/RC/VL/GG/index.html Remember Cells have to stay in balance with their environment. Cells keep this balance, called homeostasis, by controlling what enters and leaves the cells through passive and active transport. You can see that the selectively permeable cell membrane and its transport systems are important in keeping cells and organisms alive and healthy. - 14 -

Now that you have finished the second lesson, let's find out how much you learned from it. What you will do Self-Test 2.2Analyze This1. If you could place a single red blood cell in a glass of distilled water, what do you think would happen to the cell? Explain. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________2. Predict what would happen if you put a cell into very sugary water. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ Key to answers on page 25.Lesson 3. Biotechnology Biotechnology can be broadly defined as \"using living organisms or their products forcommercial purposes.\" As such, biotechnology has been practiced by human society sincethe beginning of recorded history in such activities as baking bread, brewing alcoholicbeverages, or breeding food crops or domestic animals. A narrower and more specific definition of biotechnology is \"the commercialapplication of living organisms or their products, which involves the deliberate manipulationof their DNA molecules\". This definition implies a set of laboratory techniques developedwithin the last 20 years that have been responsible for the tremendous scientific andcommercial interest in biotechnology, the founding of many new companies, and theredirection of research efforts and financial resources among established companies and - 15 -

universities. These laboratory techniques provide scientists with a spectacular vision of thedesign and function of living organisms, and provide technologists in many fields with thetools to implement exciting commercial applications.Biotechnology has helped meet the food needs of today’s society - where would theworld have been without this technology? Learn more about it…Areas of appliedbiotechnologyIn 1885, a scientistnamed Rouxdemonstrated thatembryonic chick cellscould be kept alive outsidean animal's body. For thenext hundred years,advances in cell tissueculture have providedfascinating glimpses intomany different areas suchas biological clocks andcancer therapy.Monoclonalantibodies are new toolsto detect and localizespecific biologicalmolecules. In principle,monoclonal antibodies canbe made against anymacromolecule and usedto locate, purify or evenpotentially destroy amolecule. An example ofmonoclonal antibodies Figure 3.1 Biotechnology: Present and Futurecan be found in Source: http://www.accessexcellence.org/RC/VL/GG/biotechnology.htmlanticancer drugs. Molecular biology is useful in many fields. DNA technology is utilized in solvingcrimes. It also allows searchers to produce banks of DNA, RNA and proteins, while mappingthe human genome. Tracers are used to synthesize specific DNA or RNA probes, essentialto localizing sequences involved in genetic disorders. With genetic engineering, new proteins are synthesized. These can be introducedinto plants or animal genomes, producing a new type of disease resistant plants, capable ofliving in inhospitable environments (i.e. temperature and water extremes). When introduced - 16 -

into bacteria, these proteins can alsoproduce new antibiotics and useful drugs. Techniques of cloning generate largequantities of pure human proteins, whichare used to treat diseases like diabetes. Inthe future, a resource bank for rare humanproteins or other molecules is a possibility.For instance, DNA sequences whichare modified to correct a mutation, toincrease the production of a specific proteinor to produce a new type of protein can bestored . This technique will probably play akey role in gene therapy. Figure 3.2 How human cloning worksSource: http://www.ornl.gov/sci/techresources/ Human_Genome/elsi/cloning.shtmlCelebrity Sheep Died at Age 6Image credit: Roslin Dolly, the first mammal to be clonedInstitute Image Library, from adult DNA, was put down byhttp://www.roslin.ac.uk/ lethal injection Feb. 14, 2003. Prior toimagelibrary/ her death, Dolly had been suffering from lung cancer and crippling arthritis. Although most Finn Dorset sheep live to be 11 to 12 years of age, postmortem examination of Dolly seemed to indicate that, other than her cancer and arthritis, she appeared to be quite normal. The unnamed sheep from which Dolly was cloned had died several years prior to her creation. Dolly was a mother to six lambs, bred the old- fashioned way. - 17 -

Using Biotechnology to Modify Plants and Animals Combining DNA from different existing organisms (plants, animals, insects, bacteria,etc.) results in modified organisms with a combination of traits from the parents. Thesharing of DNA information takes place naturally through sexual reproduction and has beenexploited in plant and animal breeding programs for many years. However, sexual reproduction can occur only between individuals of the samespecies. A Holstein cow can be mated with a Hereford bull because the two animals aredifferent breeds of the same species, cattle. But trying to mate a cow with a horse, adifferent species of animal, would not be successful. What is new since 1972 isthat scientists have been able toidentify the specific DNA genesfor many desirable traits andtransfer only those genes, usuallycarried on a plasmid or virus, intoanother organism. This processis called genetic engineering andthe transfer of DNA isaccomplished using either directinjection or the Agrobacterium,electroporation, or particle guntransformation techniques. Itprovides a method to transferDNA between any living cells(plant, animal, insect, bacterial,etc.). Virtually any desirable traitfound in nature can, in principle,be transferred into any chosenorganism. An organism modifiedby genetic engineering is calledtransgenic. See diagram at theright. Figure 3.3 Transgenic mice Source: http://www.accessexcelence.org/RC/VL/GG/biotechnology.htmlProducts of Genetic EngineeringSpecific applications of genetic engineering are abundant and increasing rapidly in number.Genetic engineering is being used in the production of pharmaceuticals, genetherapy, and the development of transgenic plants and animals. - 18 -

1. Pharmaceuticals human drugs such as insulin for diabetics, growth hormone for individuals with pituitary dwarfism, and tissue plasminogen activator for heart attack victims, as well as animal drugs like the growth hormones, bovine or porcine somatotropin, are being produced by the fermentation of transgenic bacteria that have received the appropriate human, cow, or pig gene.2. Gene Therapy, the first clinical gene therapy is underway to correct an enzyme deficiency called ADA (Adenosine deaminase) in children. Bone marrow cells are removed, defective DNA in bone marrow cells is supplemented with a copy of normal DNA, and the repaired cells are then returned to the patient's body.3. Transgenic Plants. Transgenic plants that are more tolerant of herbicides, resistant to insect or viral pests, or express modified versions of fruit or flowers have been grown and tested in outdoor test plots since 1987. The genes for these traits have been delivered to the plants from other unrelated plants, bacteria, or viruses by genetic engineering techniques.4. Transgenic Animals. Presently, most transgenic animalsare designed to assist researchers in the diagnosis andtreatment of human diseases. Several companies havedesigned and are testing transgenic mammals thatproduce important pharmaceuticals in the animal's milk.Products such as insulin, growth hormone, and tissueplasminogen activator that are currently produced byfermentation of transgenic bacteria may soon be obtainedby milking transgenic cows, sheep, or goats. Figure 3.4 Tissue culture of transgenic plants in a controlled environmental chamber Source: USDAUsing Biotechnology in Diagnostic Applications Since each living creature is unique, each has a unique DNA recipe. Individualswithin any given species, breed, or hybrid line can usually be identified by minor differencesin their DNA sequences - as few as one difference in a million letters can be detected! Usingthe techniques of DNA fingerprinting and PCR (polymerase chain reaction) scientists candiagnose viral, bacterial, or fungal infections, distinguish between closely related individuals,or map the locations of specific genes along the vast length of the DNA molecules in thecells.- 19 -

What you will do Activity 3.1You decide! Although the human genome initiative could mean good things for people withgenetic disorders, the use of such technology may cause problems. Some genetic traitsmay hinder an individual’s ability to perform a job safely. Do you feel that an employershould be given the right to use genetic information to judge an individual’s ability to performa job? What you will do Self-Test 3.11. Are foods derived from genetically modified crops nutritionally superior? a. Yes, they offer substantial health advantages over foods produced from conventional crops. b. Yes, they offer some health advantages over foods produced from conventional crops. c. No, they are neither better nor worse than foods from conventional crops. d. No, they are slightly less healthful than foods from conventional crops. e. No, foods produced from genetically modified crops are a known health risk.2. Which of the following best describes a transgenic organism? a. a cloned organism b. a mutated organism c. an organism produced by sexual reproduction. d. an organism that contain genetic information from another species. Key to answers on page 25. Let’s Summarize 1. Cell membranes act as barriers to most, but not all, molecules. The development of a cell membrane that could allow some materials to pass while constraining the movement of other molecules was a major step in the evolution of the cell. Cell - 20 -

membranes are differentially (or semi-) permeable barriers separating the inner cellular environment from the outer cellular (or external) environment. 2. Passive transport requires no energy from the cell. Examples include the diffusion of oxygen and carbon dioxide, osmosis of water, and facilitated diffusion. 3. Diffusion is the net movement of a substance (liquid or gas) from an area of higher concentration to one of lower concentration. 4. Osmosis is the diffusion of water across a semi-permeable (or differentially permeable or selectively permeable) membrane. 5. Hypertonic solutions are those in which more solute (and hence lower water potential) is present. Hypotonic solutions are those with less solute (again read as higher water potential). Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal. Although there will still be equal amounts of water movement in and out of the cell, the net flow is zero. 6. Active transport requires the cell to spend energy, usually in the form of ATP. Examples include transport of large molecules (non-lipid soluble). 7. Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle. Phagocytosis is the type of endocytosis where an entire cell is engulfed. Pinocytosis is when the external fluid is engulfed. Receptor-mediated endocytosis occurs when the material to be transported binds to certain specific molecules in the membrane. Examples include the transport of insulin and cholesterol into animal cells. 8. Biotechnology can be broadly defined as \"using living organisms or their products for commercial purposes.\" As such, biotechnology has been practiced by human society since the beginning of recorded history in such activities as baking bread, brewing alcoholic beverages, or breeding food crops or domestic animals.Whew, at last! You have finished studying the module. But, before you completely exit fromthis module, let us find out how much you learned. PosttestMultiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. What effect does eating genetically modified foods have on your genes? a. It has no effect on your genes. b. It could cause your own genes to mutate. c. The effects on human genetics are not known. d. It could cause your own genes to absorb the excess genes.2. What are the current benefits of having foods made from genetically modified crops? a. They improve farm profitability and make some farmers' jobs easier. - 21 -

b. They allow farmers to greatly increase the amount of crops produced.c. They improve convenience for consumers, e.g. by creating foods with longer shelf lives.d. They improve the nutritional quality of foods.e. They cause less damage to the environment than conventional chemical intensive agriculture.3. What part of the cell maintains homeostasis in the cell?a. ribosomes c. golgi bodiesb. mitochondria d. cell membrane4. Which solution contains a higher concentration of solute than the solution it is beingcompared with?a. isotonic c. hypertonicb. hypotonic d. equilibrium5. Which refers to a solution containing a greater concentration of solvent than the solutionit is being compared with?a. isotonic c. hypertonicb. hypotonic d. equilibrium6. Which of the following best describes a cell membrane?a. permeable c. semi permeableb. impermeable d. none of these7. Certain types of lymphocytes (white blood cells) in the lymph nodes ingest bacteria anddebris. This function most likely occurs bya. exocytosis d. passive transportb. pinocytosis e. facilitated transportc. phagocytosis8. Which mechanism requires energy? c. active transport a. osmosis d. facilitated diffusion b. diffusion9. If a solution outside a cell is more concentrated so that the cell loses water to itsenvironment, which of the following describes the external solution?a. isotonic c. hypertonicb. hypotonic d. In equilibrium10. Are foods derived from genetically modified crops required to be tested for possible allergic reactions in people? a. Yes, because health/safety of humans is important. b. No, because they cause no allergic reactions in people.11. Are foods made from genetically modified crops required to pass human testing? a. Yes, because it ensures safety of humans. - 22 -

b. No, because they are safe to be used by humans.12. Which of the following was the first mammal to be cloned?a. Dolly the sheep c. Rhesus monkeyb. Piggy the piglet d. Donkey the horse13. A transgenic crop is: a. a crop which is a mutant. b. a crop which is an animal. c. a crop that has been bred to exhibit new characteristic. d. a crop that has had a gene from another species inserted.14. Proteins enter and exit the cell by c. phagocytosis a. diffusion d. facilitated diffusion b. osmosis15. Which of the following molecules can penetrate rapidly across the cell membrane?a. H2O c. sugarb. Na+ d. protein16. A substance that moves across a cell membrane without using the cell’s energy tends to move a. toward the area where it is more concentrated. b. away from the area where it is less concentrated. c. away from the area where it is more concentrated.17. Which process ALWAYS involves movement of materials from inside the cell to outsidethe cell?a. osmosis c. exocytosisb. diffusion d. endocytosis18. In what way do sugar molecules enter or exit a cell?a. diffusion c. facilitated diffusionb. osmosis d. none of the aboveUse the diagram on the next page to answer questions 19 and 20.19. What happens with the water molecules? a. The water molecules will enter the cell. b. The water molecules will move out of the cell. c. The water molecules will remain where they are.20. What happens with the sugar molecules? a. The sugar molecules will enter the cell. b. The sugar molecules will move out of the cell. c. The sugar molecules will remain where they are. - 23 -

Outside Cell Cell Opening Inside Cell Cell Membrane = Water = Sugar Got a perfect score? Check it out! Key to answers on page 26. Key to AnswersPretest1. a 6. c 11. a 16. b2. d 7. c 12. b 17. d3. b 8. c 13. c 18. a4. a 9. c 14. d 19. a5. c 10. a 15. a 20. aLesson 1Activity 1.1What you’ve just seen is the effect of water moving into and out of the potato cells.Self-Test 1.1 If the cell is not semi-permeable then the cell either bursts or shrinks because ofuncontrolled movement of molecules. - 24 -

Lesson 2Activity 2.1 Substances or materials dissolve faster at high temperature. At high temperature, therate of diffusion is faster than at low temperature. Cells must maintain the temperaturewithin the normal range to facilitate the movement of materials into and out of the cell.Activity 2.2Applying a Concept Yes. The water level in A will rise because of the diffusion of water molecules from anarea where they are higher to an area where they are lower. This talks about the principleof osmosis. If the cell membrane is permeable (passable) to all substances, then, the cell mightexpand and eventually burst because of too much pressure. If all the materials will move outof the cell, it might shrink or get smaller. It might also be deprived of materials that the cellneeds to survive.Self-Test 2.1 The liquid came from the vegetables. The lettuce had wilted because the water fromthe lettuce moved out. This shows the process of osmosis.Self-Test 2.2Analyze ThisQ1 The cell expanded and burst because the distilled water moved into the cell. (osmosis)Q2 The cell would shrink or get smaller because the water from the cell would move out.Lesson 3Self-Test 3.1 1. Answer: c. No. They are neither better nor worse than foods from conventional crops. \"Most of the genetically modified crops currently available are designed to reduce farmers' production costs. Under some circumstances there may be less pesticides used, and there is some indication that genetically modified corn is less likely to be infected with fungal toxins that are natural carcinogens, but the overall health effect of these benefits is minor,\" Goldsbrough says. \"In the future these technologies hold the promise of delivering foods that are nutritionally enhanced. For example, foods might provide essential vitamins or contain natural compounds that can help improve your health.\" 2. d. - 25 -

Posttest 6. a 11. a 16. c 7. a 12. a 17. c 1. b 8. c 13. d 18. c 2. a 9. c 14. d 19. b 3. d 10. a 15. a 20. a 4. c 5. bReferencesBooks:Alexander, G., Balzer, L., Collins, A., Goodson, P., Laner, L., and Slesnick, I. (1984). Introduction to Biology. Glenview, Illinois: Scott Foresman and Company.Bigg, A., Daniel, L. & Ortleb, P. (1994). Life Science. Westerville, OH: Merrill Publishing Co., Mcmillan/McGraw – Hill.Campbell, N.A. (1996). Biology. California: The Benjamin/Cummings Publishing Company.Miller, K.R. & Levine, J. (1991). Biology. New Jersey, Massachusetts: Prentice Hall.Hopson, J.L. & Wessells, N.K. (1990). Essentials of Biology. USA: McGraw-Hill Publishing Company.Wong, H.K. & Dolmatz, M.S. (1986). Biology: The key ideas. NY: Globe Book Company, Inc.Electronic Sources:Retrieved December 22, 2004 from www.nal.usda.gov/bic/Education-Res/iaste.info/biol.htmlRetrieved December 22, 2004 from http://www.ornl.gov/sci/techresources/Human_Genome/ elsi/cloning.shtmlRetrieved December 22, 2004 from http://www.chem4kids.com/files/atom_intro.htmlRetrived December 22, 2004 from http://www.accessexcelence.org/RC/VL/GG/ biotechnology.html - 26 -

Module 4 Photosynthesis What this module is about Many people would like to live in places full of plants. Why? The place is alwayscool; it is less dusty and it has abundant water supply. Plants are great food providers.How do plants make food? The food-making process of plants is the main concern of thismodule. The module includes the following lessons:  Lesson 1 – The Sunlight  Lesson 2 – The Leaf  Lesson 3 – Chloroplast and Photosynthetic Pigments  Lesson 4 – Light-dependent Reaction  Lesson 5 – Light-independent Reaction What you are expected to learn After going through this module, you are expected to: 1. Name the factors important to the food-making process. 2. Describe the chloroplast. 3. Name the pigments and describe how pigments are organized in order to trap sunlight efficiently. 4. Differentiate light-dependent reaction from light-independent reaction of photosynthesis. 5. Correlate the internal structure of the leaves to the food-making process of plants. How to learn from this module Here’s a simple guide for you in going about the module: 1. Read the instruction carefully. 2. Take the pretest before reading the rest of the module.

3. Do all activities and exercises.4. Use the concepts discussed in each lesson to explain the results of the activities or exercises.5. Take the posttest after you have finished the lessons and performed all activities or exercises.What to do before (Pretest)Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. The color of the leaves is green. This means that the green light isa. absorbed c. reflectedb. deflected d. transmitted2. Which of the following substances is the origin of oxygen released as oxygen gas bygreen plants during photosynthesis?a. water c. carbon dioxideb. sugar d. ribulose-1,5-biphosphate3. Which of the following gases is important to photosynthesis?a. ozone gas c. water vaporb. oxygen gas d. carbon dioxide4. In which of the following cellular organelles does photosynthesis occur?a. ribosome c. chlorophyllb. chloroplast d. mitochondrion5. Pigments are needed by plants to trap energy from the sun. Which of the following is themost important pigment for trapping energy?a. carotenoid c. chlorophyll bb. xanthophylls d. chlorophyll a6. The final acceptor of the electron during noncyclic electron pathway isa. photosystem I c. ATPb. photosystem II d. NADP+7. What is the temperature in which ribulose biphosphate carboxylase utilizes oxygen gas?a. below 30 oC c. above 30 oCb. at 30 oC d. undetermined -2-

8. What is the special cholorophyll pigment that serves as primary reaction center ofphotosystem I?a. P 700 c. caroteneb. P 680 d. xanthophylls9. Where do we find the water splitting mechanism of the light – dependent reaction ofphotosynthesis?a. photosystem I c. primary reaction centerb. photosystem II d. has not been identified10. Which of the following substances screened out the high-energy components of solarenergy and prevented it from reaching the surface of the earth?a. carbon dioxide c. ozoneb. cloud d. water11. Which of the following rays of light has the lowest energy content?a. blue c. redb. green d. yellow12. Which of the following components of the solar energy has the shortest wavelength?a. ultraviolet rays c. violet lightb. visible light d. gamma rays13. How do you call the sack-like structure in the chloroplast?a. stroma c. matrixb. thylakoid d. granum14. Where does the light-independent reaction occur?a. stroma c. lamellab. grannum d. thylakoid15. How do you call the organization of photosynthetic pigments?a. photosystem c. electron transport chainb. water-splitting complex d. light harvesting antennae16. Which of the following is the first stable product of photosynthesis?a. pyruvic acid c. phosphoglyceraldehydeb. phosphoglyceric acid d. ribulose-1,5-biphosphate17. What is the enzyme that plays an important role in carbon dioxide fixation?a. phosphatase c. ribulose-1,5-biphosphateb. ribulose-1,5-oxygenase d. phosphoenol pyruvate carboxylase18. Landscaping is a very lucrative business today. Which of the following plants can beplanted in sunlit ground of a house or building?a. bermuda c. carabao grassb. peanut grass d. all of them -3-

19. Light-dependent reaction of photosynthesis must come first step before the light-independent reaction because its products are important to the fixation of carbondioxide. Which of the following is/are the product/s of light –dependent reaction?a. ADP only c. NADPH onlyb. ATP only d. NADPH and ATP20. Which plants grow well in the tropics like the Philippines?a. rice c. pineappleb. pine tree d. a and c Key to answers on page 26.Be familiar with the following terms: Terms DefinitionPigment Colored substance present in plantsLight-dependent Process which occurs in the presence ofLight-independent lightCarbon dioxide fixation Process which does not require lightCyclic photophosphorylation Process which converts carbon dioxideNon-cyclic photophosphorylation into carbohydratePhotorespiration Production of ATP in a cyclic manner Production of ATP in Z-pathwayz-pathway Process wherein oxygen gas competes with carbon dioxide in reacting withPhotosystem ribulose-1,5-biphosphateC3 plant Is the pathway followed by excited electrons from photosystem II. It is aC4 plant non-cyclic flow of electron.CAM plant Organization of pigments Plant that fixes CO2 to yield 3-carbonVariegated leaf phosphoglyceraldehyde as the first stable product of photosynthesis Plant that fixes CO2 -4-carbon malate when temperature is above 30 o C Plant in arid environment wherein CO2 is fixed at night and released to Calvin Cycle at day time A leaf with patches or margins that are not colored green -4-

Lesson 1. Sunlight All processes that occur in living and non-living systems require energy.Photosynthesis is no exception. The energy that comes from the sun is called solar energy.It travels as wave and is described in terms of its energy content and its wavelength. Itcomes as discrete packets called photons. The component of solar energy that is importantto photosynthesis is the visible light. Visible light is a white light. What makes up the visiblelight? Discover it as you perform the activity below.What you will doActivity 1.1 Components of the visible lightWhat you need: prism white paper light sourceProcedure:1. Arrange the three objects as shown below light source prism white paper2. Switch the light source on and focus the light into the prism.3. What do you see in the white paper that serves as screen? Describe it.4. Draw what you see on the white paper Key to answers on page 26. When you focused thelight into the prism, you saw arainbow of colors in the whitepaper similar to Figure 1. Thevisible light broke up into violet,blue, blue-green, green, yellow-green, yellow, orange and red. Figure 1Components of solar energy -5-

The components of solar energy before the visible light have short wavelengths suchas gamma rays, x-rays and ultraviolet rays. You do not see them. Short-wavelengthcomponents have more energy. Those components after the visible light have longwavelength. These are also invisible to our naked eyes. They possess less energy. Only 42 % of the solar energy passes through the atmosphere and reaches the earth.High energy, short wavelengths are screened out by ozone and the lower energy longwavelengths are screened out by water and carbon dioxide in air. Only 2 % of the light thatreaches the earth is utilized in photosynthesis.What you will doSelf-Test 1.1Multiple Choice. Choose the letter of the best answer. Write the chosen letter on a separate sheet of paper.1. Which of the following components of solar energy has long wavelength?a. gamma rays c. microwavesb. visible light d. radiowaves2. Which of the following components of solar energy has the most energy?a. visible light c. ultraviolet raysb. infrared rays d. violet light3. Which of the following screens out low energy wavelengths of the solar energy?a. water c. carbon dioxideb. ozone d. carbon dioxide and water Key to answers on page 26.Lesson 2. The Leaf Plant leaves absorb sunlight to manufacture plant sugars through a process calledphotosynthesis. In order to get enough light, leaf surfaces are flattened to have a big areaas shown in Figure 2. Let us do Activity 2.1 to get a closer view of the external structure ofplant leaves. -6-

Figure 2. Leaf Parts The blade is a thin expanded structure on either side of the midrib and is the largest part of the leaf. The leaf is attached to the stem by a petiole. The base of the petiole is attached to the node of the stem. The node where a petiole meets a stem is called a leaf axil. The axil contains single buds or bud clusters, referred to as axillary buds. You can also see a pair of appendages at the base of the petiole called stipules. Stipules protect the young leaf and may be modified into spines or tendrils. What you will do Activity 2.1 Leaf CharacteristicsWhat you need: Notebook and pencilWhat to do: 1. You may have a garden, park or farm in your place. Visit the farm, garden or park. 2. Note the different characteristics of the leaf of the plants you may find in the place. Key to answers on page 26 From your visit to the park, garden or farm, you must have seen several leafcharacteristics. Most of these characteristics make leaves very efficient in trapping energyfrom the sun, which in turn, increases the photosynthetic activity of the leaves. Some ofthese characteristics are the following: -7-

 Leaf structure Simple leaves have a single blade. Compound leaves have more than one blade Leaf Attachment on a single petiole. The multiple blades of a compound leaf are called leaflets. Petiolate Sessile The blade is attached to the stem by a petiole The blade is attached directly to the stem Leaf Arrangement without a petiole.Two leaves grow opposite One leaf grows at each node. Several leaves grow around aeach other at each node. The leaves alternate sides single node. along the stem. -8-

 Leaf ShapeNarrow from Oval-shaped Wide at the base Heart-shaped Deeply lobed like the base to tip and narrow at the fingers of a hand tip Leaf MarginsThe edge of the leaf The edge has The edge of the leaf The edge of the leafis smooth. rounded indentations is finely toothed. is deeply indented. Where does photosynthesis occur in the leaf of plants? You shall do Activity 2.2 tofind out which parts of the leaves are involved in photosynthesis.What you will doActivity 2.2 Where does photosynthesis happen?What you need: petri dish iodine solution any variegated leaf ethyl alcohol 200 mL beaker alcohol lamp tripod wire gauze water water bath medicine dropper -9-

What you will do: 1. Get a variegated leaf. 2. Draw this leaf and indicate the patches or margins that are not colored green 3. Place the leaf in a beaker with water and boil the leaf to remove the water-soluble red and blue pigments. 4. Replace the water with ethyl alcohol, place the beaker in a water bath and apply heat. Be careful because the alcohol is volatile. 5. Pour out the alcohol, replace it with water and apply heat. 6. Spread out the leaf free of pigments carefully in a petri dish. 7. Cover the leaf with a few drops of iodine solution. 8. Observe. 9. A blue black or dark purple coloration in the leaf indicates the presence of starch. 10. Draw the leaf. Darken the parts of the leaf you observed to contain starch. 11. Compare the second drawing of the leaf with the first drawing you made. Iodine solution is a test for starch. In the activity, the green part of the leaf turnedblue black in the presence of iodine solution. This indicated that starch was present. Thegreen part of the leaf carried out photosynthesis. This observation was not observed in thenon-green part. Photosynthesis did not happen in the non-green part because there was nostarch, an indicator of photosynthesis. Clearly, photosynthesis occurs only in the greenparts of the plants such as the green leaves and the green stems of cactus. Have you ever asked yourself what is inside the leaf that makes it a site for foodproduction? Figure 3 shows the inside of the leaf. In Figure 3, you cansee layers of cells sandwichedby the lower and upperepidermis. This is calledmesophyll layer, which iscomposed of palisade cells(arranged like columns) andspongy cells (loosely arrangedcells). These cells haveorganelles that contain greenpigments. These organellesare called chloroplasts.Chloroplasts contain pigmentsthat trap energy from the sun. Figure 3. The inside of the leaf At the lower epidermis, you will see some openings. Each opening is called stoma(stomata). This is where carbon dioxide enters and oxygen passes out. We shall look atthe structure of the stoma. Perform Activity 2.3. - 10 -

What you will doActivity 2.3 Observing the StomataWhat you need: leaf glass slide forceps water microscopeWhat you will do:1. Fold a leaf in half until it cracks.2. Tear the leaf so that a part of the lower layer of cells appears as narrow, colorless border along the torn edge.3. Remove a portion of the lower layer of cells with a pair of forceps.4. Put the portion of the lower layer of cells in a glass slide. Add a drop of water.5. Examine the slide under the low power objective.6. Do you see some openings? Guard cell This is what you are supposed to see - the Stoma stoma, a slit-like structure. Around the stoma is a pair of bean-shaped cells called guard cells. The guard cell is an epidermal cell with chloroplast. It is the only epidermal cell that can carry out photosynthesis. It regulates the opening and the closing of the stoma.Figure 4. The guard cellWhat you will doSelf-Test 2.1Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. The main photosynthetic organ in the plant is the:a. stem c. leavesb. root d. flower2. Which of the following organelles traps energy from the sun?a. epidermis c. chloroplastb. cuticle d. chlorophyll - 11 -

3. Where do we find cells with chloroplasts in the leaves of plants?a. mesophyll layer c. epidermisb. cuticle d. matrix4. Cactus makes food through its c. roots a. leaves d. flowers b. stems5. Where do we find most of the stomata? c. lower epidermis a. upper epidermis d. spongy layer b. mesophyll layer Key to answers on page 26.Lesson 3. The Chloroplast and Other Photosynthetic Pigments Many people find fulfillment by just looking at plants. Why? You see a myriad ofcolors in plants – violet, lavender, red, white, pink. These colored parts of plants are due topigments. Pigments are chemical compounds, which reflect only certain wavelengths ofvisible light. This makes them appear \"colorful\". Flowers, corals, and even animal skincontain pigments, which give them their colors. Most leaves are green. Do you think leavescontain green pigments only? To answer this question, do activity 3.1What you will doActivity 3.1 How many kinds of pigments are there in green leaves?What you need: alcohol beaker mortar and pestle 1 piece of chalk 2 pieces of green leavesWhat you will do:1. Get 2 pieces of leaves and clean them thoroughly.2. Place the leaves in a mortar and pound with pestle along with grains of sand.3. Add enough alcohol to cover the mixture.4. Continue pounding until enough pigments are extracted.5. Decant the extract into the beaker.6. Dip a new piece of chalk into the extract and allow the extract to sip into the chalk.7. Observe the piece of chalk. How many bands of colors do you see in it? - 12 -

As you can see in the piece of chalk, it is not only the green pigment that is present ina green leaf. There are other pigments. Pigments also absorb light rays of certain wavelength. In plants, algae, andcyanobacteria, pigments capture the energy of sunlight and use it in photosynthesis. Eachpigment absorbs only certain rays of light. Plants possess several kinds of pigments. Whatare the different pigments that are important for photosynthesis? There are three basicgroups of plant pigments.  Chlorophylls are green pigments, which contain a ring that allows electrons to move freely so the molecule can gain or lose electrons easily. There are several kinds of chlorophylls – chlorophyll a is present in plants, algae and cyanobacteria; chlorophyll b is present in green algae and plants; and chlorophyll c is found only in photosynthetic diatoms, kelps and dinoflagellates.  Carotenoids are usually red, orange, or yellow pigments. These compounds are composed of two small six-carbon rings connected by a \"chain\" of carbon atoms. They do not dissolve in water. Carotenoids absorb energy and pass it to chlorophyll. Carotenoid is an accessory pigment. An example of carotenoid is fucoxanthin, a brown pigment which colors brown algae like kelps and diatoms brown. Carotenoids also include carotene, which gives carrots their color.  Phycobilins are water-soluble pigments, and are found in the cytoplasm, or in the stroma of the chloroplast. They occur only in Cyanobacteria and Rhodophyta. Phycocyanin (present in cyanobacteria) and phycoerythrin (found in red algae) are examples of phycobilins. Within the thylakoid, pigments form clusters of 2-3 pigment molecules arrangedaround a pair of chlorophyll-a molecules. Some proteins are also found in this cluster. Wecall this cluster a photosystem. The outer pigments of the photosystem act like an antennashuttling photons into chlorophyll-a in the reaction center. There are two photosystems – photosystem I and photosystem II. Photosystem Iabsorbs red light at about 700 nanometer (nm) and its primary reaction center is the specialchlorophyll called P 700. Photosystem II absorbs more orange light at 680 nm and itsprimary reaction center is the special chlorophyll called P 680. A water-splitting complex isassociated with Photosystem II. Where can we find the photosynthetic pigments? They are housed inside thechloroplast. Do Activity 3.2 to see the chloroplast of a leaf. - 13 -

What you will doActivity 3.2 Observing chloroplastWhat you need: microscope glass slide Hydrilla waterWhat will you do:1. Get a hydrilla plant and place it in a wide-mouthed bottle.2. Expose to sunlight for 15 minutes.3. Detach healthy green leaf near the apex and mount it on water in a glass slide.4. Examine the leaf under the low power objective and high power objective of the microscope5. Do you see compartments? What is the shape of each compartment?6. Observe the coin shape chloroplasts moving along with the cytoplasm. Under the microscope you see compartments. In these compartments, you will noticesome green bodies. These green bodies are the chloroplasts. We shall describe the structure of the chloroplast. A chloroplast is enclosed by adouble membrane – an outer membrane and an inner membrane. The outer membrane issmooth while the inner membrane is thrown into tube like structures. Between thesemembranes is a space called intermembrane compartment. Next to the inner membrane isa space called stroma. Stroma contains a complex mixture of enzymes and water.Embedded in the stroma is a complex network of stacked sacs. inner membrane intermembrane space outer membrane Figure 5. The chloroplast Each stack is called a granum (grana). A granum is made up of flattened sacs calledthylakoid. The photosynthetic pigments are found in thylakoids. Figure 5 is a typicalstructure of a chloroplast. One granum is connected to another through stromal lamella. A chloroplast contains40-60 grana. A granum may have two or three – hundred thylakoids. - 14 -

What you will doSelf-Test 3.1Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. Where do we find the chlorophyll in the chloroplast?a. stroma c. intermembrane compartmentb. thylakoid d. carotenes2. What can we find in the stroma of the chloroplast?a. enzymes c. chlorophyllb. carotenes d. thykoid3. Which of the following pigments is an accessory pigment?a. chlorophyll a c. P 680b. P 700 d. carotenoid4. The water-splitting complex is associated with which photosystem?a. photosystem I c. both a and bb. photosystem II5. How do you call the space between the outer and the inner membrane?a. stroma c. intermembrane compartmentb. thylakoid compartment d. stromal lamella6. What makes up a granum? c. thykoid a. stromal lamella d. none of these b. stroma Key to answers on page 26.Lesson 4. The Light-dependent Reaction Light-dependent reaction is the first phase of photosynthesis. In the previous lesson,we learned that pigment molecules form clusters called photosystems. The outer pigmentsserve as antennae for collecting solar energy. The energy is passed from pigment topigment until it is concentrated at the special chlorophyll a (P 700 in PS I and P 680 in PSII), a part of the primary reaction center. The electrons become so excited that they escapeas shown in Figure 6. - 15 -

In PS 1, the excited electrons follow a Figure 6. Photosystemcyclic path. You can see this in Figure 7. Theelectrons that escaped from the chlorophyll Figure 7enter the electron transport system, a series of Cyclic electron flow involving PS Ielectron carriers. At the electron transportsystem, electrons are passed from one carrier Figure 8to the next. In the process, energy is released Hydrogen ions leave the thylakoidand is used to pump hydrogen ions fromstroma to thylakoid compartment. The amountof hydrogen ions in the thylakoid has potentialenergy. The electrons left the electron transportsystem with very low energy. The low- energyelectrons return to PS I and repeat the cyclewhen the system absorbs solar energy. What will happen to the hydrogen ionsthat possess potential energy? They flow fromhigh concentration to low concentration,through a special protein called ATPsynthetase complex. As hydrogen ions flow from inside ofthylakoid to the stroma, ATP is synthesized.The direction of the flow is shown in Figure 8. ADP + P  ATP + H20 Since ATP is synthesized in thepresence of light, the cyclic electron flow isalso called cyclic photophosphorylation. Excited electrons may also follow a non-cyclic electron flow as shown in Figure 9.When does an excited electron follow a non-cyclic path? If PS II antenna complex absorbssolar energy, the high-energy electrons leavethe reaction center- where chlorophyll amolecules are found and enter the electrontransport system. Here, energy is released aselectrons are passed from one carrier toanother. The released energy is stored in theform of Hydrogen ion gradient. This gradient is - 16 -

used by enzyme, ATP synthase complex, to drive the synthesis of ATP. ADP + P ----- ATP + H20 Figure 9. The non-cyclic flow of electrons As you can see in Figure 9, the low-energy electrons move from the electrontransport system to PS I where they gain energy when the pigments absorb solar energy.The excited electrons are passed to an electron carrier. The electron carriers send theenergized electrons to oxidized nicotinamide dinucleotide phosphate (NADP+), also anelectron carrier. Together with the electron, NADP+ picks up hydrogen ion from water tobecome NADPH. This non-cyclic electron flow is also called Z-pathway or non-cyclicphotophosphorylation. The electrons lost at PS II are replenished by a reaction involving water. Water splitsin the presence of light. This is called photolysis. It happens at a system associated withPS II. H20 H+ + 2e- + O2 The synthesis of ATP through cyclic or non-cyclic photophosphorylation is tied up tothe hydrogen ion gradient. This mechanism of ATP production is called chemiosmosis. - 17 -

The products of light-dependent reactions are ATP and NADPH. Cyclicphotophosphorylation produces ATP only. Non-cyclic photophosphorylation produces ATPand NADPH. The by-product is oxygen gas, which comes from water and is released intothe atmosphere.What you will doSelf–Test 4.1Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. Light-dependent reaction occurs in c. thylakoid compartment a. stroma d. intermembrane compartment b. thylakoid membrane2. To store the energy of excited electrons is to pump Hydrogen ions from ___________ and into ___________ a. outside the cell, stroma b. stroma, thylakoid compartment c. thylakoid compartment, stroma d. intermembrane compartment, outside the cell3. The following are produced during light-dependent reaction excepta. ATP c. NADPHb. sugar d. oxygen4. The cyclic pathway of photophosphorylation producesa. ATP only c. ATP and NADPHb. NADPH only d. organic sugars only5. Which of the following replaces the electrons that escape from PS II?a. PS I c. splitting of waterb. NADPH d. the three are correct Key to answers on page 26. - 18 -

Lesson 5. Light- Independent Reaction / Carbon Dioxide Fixation What do plants do with the products of light-dependent reaction – ATP and NADPH?These two substances are high-energy molecules. The energy could be harnessed inmaking food out of carbon dioxide. How do plants fix carbon dioxide into food? First carbon dioxide enters the leaf through the stomata. It goes into the mesophylllayers and moves to the stroma of the chloroplast. Here, carbon dioxide collides with 5-carbon compound called ribulose-1, 5-biphosphate (RUBP) to yield 6-carbon-containingsugar. The process is catalyzed by RUBP carbonxylase. CO2RUBP 2 6-carbon compound H2O The 6-carbon compound is broken into two molecules of 3-carbon sugar,phosphoglycerate (PGA). This requires two molecules of ATP.6-carbon compounds 2 PGA The 2 molecules of PGA are converted into 2 molecules of phosphoglyceraldehyde(PGAL), a 3-carbon compound. PGAL is the first stable product of photosynthesis. It needs2 molecules of NADPH. 2 ATP 2 ADP + 2 Pi2 PGA 2 PGAP 2 PGAL 2 NADPH 2 NADP+ RUBP is regenerated from PGAL for the process to continue. A molecule of ATP isneeded for the regeneration process. 3 ATP 3 ADP + 3 Pi 3 RUBP5 PGAL The process occurs in a cyclic manner as shown in Figure 10. Since the first stableproduct is composed of 3 carbon atoms, it is called C3 Cycle. Melvin Calvin unlocked thisprocess. It is also named as Calvin Cycle. - 19 -

Figure 10. The Calvin Cycle Three turns of Calvin Cycle are necessary to produce one net gain of PGAL. FivePGAL molecules are needed to regenerate 3 molecules of RUBP. The three turns use up 9molecules of ATP and 6 molecules of NADPH. PGAL is a substance used by plants to make other organic substances. An exampleof these organic substances synthesized by plants is glucose. To make one glucosemolecule, a 6-carbon sugar, two molecules of PGAL are linked. This means six turns ofCalvin cycle. Challenge AnswerIf there are 6 rounds of Calvin Cycle, 12 molecules1. How many PGAL molecules are synthesized? 10 molecules2. How many PGAL molecules are used to regenerate 18 molecules RUBP?3. How many ATP molecules were used up to produce 12 molecules 1 glucose?4. How many NADPH molecules were used up? Do you understand now how the energy from the sun is utilized to produce the ATPand NADPH during the light-dependent reaction? The light-independent reaction occurs during daytime, but light is not used directly.- 20 -

What you will doSelf-Test 5.1Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. What is the point of entry of carbon dioxide into the inside of the leaves of plants?a. palisade layer c. guard cellsb. spongy layer d. stomata2. What substance is used to fix carbon dioxide during the light-independent reaction?a. Malate c. ribulose-1,5-biphosphateb. Oxaloacetate d. pyruvate3. What enzyme catalyzes the reaction in question 2? a. Ribulose-1,5- biphosphate carboxylase b. Ribulose-1,5- biphosphate oxygenase c. Phosphoenolpyruvate carboxylase d. Protease4. What is the first stable product of photosynthesis?a. PGA c. malateb. PGAL d. oxaloacetate5. How many PGAL are used to regenerate three molecules of RUBP?a. 2 c. 5b. 3 d. 6 Key to answers on page 26. From Lesson 2, we learned that stomata are present in the plant leaves especially atthe underside. Water passes out and carbon dioxide enters the leaves through theseopenings. When the day is hot and dry, the stomata close to prevent water loss. Theclosure causes the build up of oxygen, but the available carbon dioxide is exhausted. Whenthis happens, oxygen gas competes with carbon dioxide in reacting with RUBP. Thisproduces a 2-carbon molecule. These 2-carbon molecules are broken down to carbondioxide and water. We call this process as photorespiration. Photorespiration makesphotosynthesis inefficient because carbon dioxide is not fixed and ATP molecules are usedup. To escape photorespiration, alternative ways of fixing carbon dioxide evolved inplants. One pathway is called C4 cycle. Carbon dioxide interacts with phosphoenolpyruvate(PEP) to form oxaloacetate, a 4-carbon compound. The process is catalyzed byphosphoenolpyruvate carboxylase. - 21 -

Oxaloacetate is converted to malate, also a 4-carbon compund. Malate is pumpedinto the bundle sheath cells. Once here, carbon dioxide is released from malate. Malate ---------- PEP + CO2 Free carbon dioxide enters Calvin Cycle. This process requires additional 12 ATPmolecules to produce one glucose molecule. What will happen to PEP? It will go back to mesophyll cells to pick up anothercarbon dioxide to repeat the cycle. Many tropical grasses are C4 plants. Good examples of C4 plants are crabgrass,sugarcane, corn and Bermuda grass. Another alternative way of fixing carbon dioxide has evolved in plants found in aridregions such desert biome. Plants found in desert biomes belong to the family ofCrassulaceae, flowering succulent (water-laden). They fix carbon dioxide when the stomataare closed. PEP + CO2 -- 4 – carbon compound Examples of 4- carbon compounds are oxaloacetate and malate. These 4-Carboncompounds are stored in large vacuoles in the mesophyll cells. During the day, the stomata close. There is minimal loss of water but no CO2. So,the stored 4-Carbon compounds release CO2 to Calvin Cycle to produce sugars. Thisadaptation is called crassulacean acid metabolism (CAM). Plants that use CAM mechanismof fixing CO2 are called CAM plants. Many epiphytes (hanging) and desert plants are CAMplants. Good examples are pineapple and cactus. This information is very important to agriculture and in landscaping business. Farmowners and landscaping business operators would know what plants to be planted inshaded and well-lighted area. What you will do Self-Test 5.2Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. Plants evolved alternative ways of fixing CO2. Why? a. Oxygen gas at high temperature competes with CO2 in reacting with RUBP. b. Most photosynthetic plants are present in hot areas. c. The C3 cycle is not very efficient in making food. d. The C4 cycle and CAM are very efficient. - 22 -

2. When do CAM plants utilize CO2 to make sugar?a. daytime c. anytimeb. nighttime3. Which of the following uses C3 Cycle in making sugar?a. pineapple c. cactusb. crabgrass d. barley4. Which of the following conditions leads to the adaptation of C4 and CAM pathways?a. high CO2 and low O2 c. low CO2 and high O2b. low O2 and High CO2 d. low CO2 and low O25. Which of the following pathways produces PGAL as precursor to carbohydratesynthesis?a. C3 d. CAMb. C4 Key to answers on page 26. Let’s Summarize1. Organisms that make food are called producers or autotroph. Autotrophs may be photosynthetic or chemosynthetic.2. Photosynthetic autotrophs use solar radiation to make food.3. Not all components of solar energy is needed in photosynthesis. Photosynthesis uses only the visible light.4. Plant contains pigments that trap energy from the sun. These pigments form clusters called photosystems.5. There are two photosystems – PS I and PS II. Photosystems are light harvesting antenna composed of  several 100 chlorophyll a & b molecules, and carotenoids  a central chlorophyll molecule (P680 or P700)  specialized molecule called the primary electron acceptor6. These pigments are found in the chloroplast. Chloroplasts are found in the leaves of plant. They are found in the guard cell and mesophyll cells.7. There are two stages of photosynthesis – light dependent reaction and light- independent reaction.8. Light-dependent reaction produces ATP and NADPH9. ATP and NADPH are used in the fixation of carbon dioxide, a light-independent reaction.10. There are three ways of fixing CO2 namely, C3 cycle, C4 cycle and CAM.11. Due to the three pathways of carbon dioxide fixation, there are three kinds of plants namely, C3 plants, C4 plants and CAM plants - 23 -

PosttestMultiple Choice. Choose the letter of the best answer. Write the chosen letter on a separate sheet of paper.1. What do we need in order to do work? c. equipment a. work place d. energy b. people2. What do we call organisms that make food?a. photosynthetic c. consumersb. chemosynthetic d. a and b3. Which of the following molecules is very energetic?a. vitamins c. coenzymeb. nucleic acid d. adenosine triphosphate4. Which ray of light has the longest wavelength?a. blue c. orangeb. indigo d. red5. Which ray of light is most energetic? c. orange a. blue d. red b. indigo6. Where does the oxygen gas released during photosynthesis come from?a. water c. pigmentsb. sugar d. carbon dioxide7. Disk-shaped structures with photosynthetic pigments are known asa. thylakoid c. chloroplastb. granum d. stomata8. What are the most common group of photosynthetic pigments in plants?a. anthocyamin c. chlorophyll bb. chlorophyll a d. chlorophyll c9. Stroma are gel-like matrix (a solution) that surrounds thea. chloroplast c. granumb. chlorophyll d. none of the three10. Which of the following substances is produced through cyclic phosphorylation?a. ATP only c. ATP and NADPHb. NADPH only d. sugar - 24 -

11. Plants that use only the Calvin Cycle for photosynthesis are calleda. C3 plants c. CAM plantsb. C4 plants d. all three of them12. CAM Plants can survive in dry, hot deserts because they can fix carbon ata. daytime c. any timeb. nighttime13. Which of the following is the by-product of photosynthesis?a. water c. oxygenb. sugar d. carbon dioxide14. Photosynthesis occurs in what organelle of plants and algae?a. plasma membrane c. lysosomeb. mitochondrion d. chloroplast15. What are the light collecting units of the chloroplast?a. pigments c. stromab. photosystem d. membranes16. A friend asks which of the following plants should be planted in a well-lighted area. Whatis your answer?a. rice c. cattleyab. onion d. bermuda grass17. Carbon fixing reactions occur in a pathway called thea. light-dependent reaction b. light-independent reaction18. Folded thylakoids that resemble stacks of pancakes are calleda. stroma c. granumb. stromal lamella d. none of them19. A five-carbon carbohydrate in the Calvin cycle isa. PGAL c. RUBPb. PGA20. A three-carbon molecule in the Calvin cycle isa. RUBP c. PGALb. malate21. How many PGALs are needed to make one molecule of glucose?a. 1 c. 3b. 2 d. 4 Key to answers on page 27. - 25 -

Key to AnswersPretest 6. d 11. c 16. c 1. c 7. c 12. d 17. b 2. a 8. a 13. b 18. d 3. d 9. b 14. a 19. d 4. c 10. c 15. c 20. d 5. cLesson 1Activity 1.1 A rainbow was observed when light passed through the prism. This means that thevisible light is composed of many colors of light.Self-Test 1.1 1. d 2. c 3. bLesson 2Activity 2.1 Only parts of the leaf that turn blue-black. This means that these parts manufacturedfood.Self-Test 2.1 1. c 2. c 3. a 4. b 5. cLesson 3 Lesson 4 Lesson 5Self-Test 3.1 Self-Test 4.1 Self-Test 5.1 Self-Test 5.21. b 1. c 1. d 1. a2. a 2. c 2. c 2. a3. d 3. b 3. a 3. d4. b 4. a 4. b 4. c5. c 5. c 5. c 5. a6. c - 26 -

Posttest 6. a 11. a 16. d 7. a 12. b 17. b 1. d 8. c 13. c 18. c 2. d 9. c 14. d 19. c 3. d 10. a 15. c 20. c 4. d 21. b 5. aReferencesBooks:Mader, S. (2003). Biology. Englewood Cliffs, New Jersey: John Wiley and Sons.Pickering, W.R. (2000). Complete biology. Oxford, New York: Oxford University Press.Wolf, S. (2000). Molecular cell biology. Boston, MA: Addison Co.Electronic sources:http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html downloaded on November 25, 2004.http://ghs.gresham.k12.or.us/science/ps/sci/soph/energy/photosyn/pigments.htm downloaded on November 26, 2004.http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/eustruct/phofig1.html downloaded on November 30.Kaiser, G. E. Doc Kaiser's Microbiology Home Page downloaded on November 30, 2004 http://fig.cox.miami.edu/~tkoop/spring00/blnphotosyn.html downloaded on December 1, 2004. - 27 -

Module 5 Cellular Respiration What this module is about In Module 4, we learned that the energy trapped from the sun is stored in the food aschemical energy. Photosynthesis is an energy conversion process performed by plants.The present module discusses another energy conversion process carried out by livingorganisms wherein the stored energy in foods is being harvested. This module contains five (5) lessons:  Lesson 1 – Kinds of Food  Lesson 2 – Mitochondrion  Lesson 3 – Cellular Respiration  Lesson 4 – Electron Transport System  Lesson 5 – Energy From a Glucose Molecule What you are expected to learn After going through this module, you are expected to: 1. classify the foods you eat into different food groups; 2. describe the structure of the cell where cellular respiration occurs; 3. discuss the different stages of cellular respiration; 4. count the number of adenosine triphosphate produced from one molecule of glucose; 5. describe how to tap the energy from lipids and proteins; 6. relate dieting to cellular respiration; and 7. list factors that destroy cellular respiration.