BIO H HW.pdf

CELL -: THE FUNDAMENTAL UNIT OF LIFE... Contribution of various biologists in CELL DISCOVERY & Structure and Function of CELL ORGANELLES- lysosomes and Mitochondria...

CELL • Cells are the basic, fundamental unit of life. • They are responsible for all life processes. • The study of cells is called as Cell Biology or Cytology. • Cells are complex and are of different shapes and sizes, pretty much like bricks of the buildings. • The basic structure of cells include a thin semi-permeable membrane called plasma membrane or cell membrane which protects the inner content of the cell that includes a thick, jelly like fluid called the cytoplasm. It contains the membrane bound cell organelles important for performing life functions. The central part of the cell includes the nucleus which is also referred to as the 'brain of the cell' and is the most important component of cell.

DISCOVERY OF CELLS Biologists who contributed- Robert Hooke, A.V. Leeuwenhoek, Robert Brown, Schleiden & Schwann, Rudolf Virchow and many more...!!!

ROBERT HOOKE • Discovery of cells is one of the remarkable advancements in the field of science. • The cell was first discovered and named by ROBERT HOOKE in 1665. He remarked that it looked strangely similar to cellula or small rooms, cells, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope. He had used a simple microscope for this. • Hooke was the first person to use the word \"cell\" to identify microscopic structures when he was describing his attempt.cork.

ANTONIE VAN LEEUWENHOEK • A.V. Leeuwenhoek, with his improved microscope discovered free living cells in pond water in 1674. • He described the cells he discovered in a drop of pond water as “animalcules”. • He is thus famously termed as the “Father of Ancient Microbiology. • Van Leeuwenhoek even discovered the \"protozoa“!!.

ROBERT BROWN • Robert Brown was a Scottish botanist who discovered the nucleus of the cell. • He collected, studied and classified thousands of plant flora. • He discovered Brownian motion & wrote one of the earliest detailed descriptions of the cell nucleus and cytoplasmic streaming.



Theodor Schwann & Matthias Jakob Schleiden •Developed the ‘CELL THEORY’. • Cell theory states: 1}All living things are made up of cells.. 2} Activities of an organism are the sum total of activities of a cell 3} Cells are the basic building blocks of life or the structural and functional unit of life. 3} All cells come from pre-existing cells created through the process of cell division.

RUDOLF VIRCHOW • Rudolph Virchow (1821-1902) was a German physician, anthropologist, politician and social reformer, but he is best known as the founder of the field of cellular pathology . • In 1855 Virchow published a statement based on his observations ’Omnis cellula e cellula’ which means that all cells arise from pre-existing cells....

Jan Evangelista Purkinge • J.E. Purkinge was a Czech anatomist and physiologist. • In 1839, he coined the term 'protoplasm’ (living part of a cell) for the fluid substance of a cell. • He was one of the best known scientists of his time.

THE CELL & ITS ORGANELLES...

CELL ORGANELLES 1} Lysosomes- The sphere-shaped sacs in the cytoplasm are called as lysosomes. They are filled with hydrolytic enzymes. Its digestive enzymes are very strong and effective as help in the cleaning of the cell by digesting & breaking the outside material like bacteria or worn out cell organelles into small pieces.  Discovered by Christian de Duve They are often termed as the ‘suicidal bags’. This is so because, whenever there is any disturbance in the cellular metabolism, or any malfunctioning, lysosome secretes the enzyme into the cell. They may burst and digest its own cell. Hence, they are called as ‘Suicide bags’.

CELL ORGANELLES (Contd...) 2} MITOCHONDRIA- Also called the powerhouses of the cell as they produce energy-rich molecules in the form of ATP (Adenosine Tri Phosphate) for the cell. ATP is called as the ENERGY CURRENCY OF CELL’  It is double-membraned - An outer continuous membrane and an inner membrane thrown into folds called Cristae.  Mitochondria are the sites of Aerobic respiration in the cell..  Mitochondria have their own circular DNA, RNA molecules, and a few other molecules that help in protein synthesis. Hence, they are also called as ‘Semi-autonomous organelles’.



MADE BY- PRACHI SOOD CLASS- IX-A ROLL NO.- 29