Cellular basis of life History of cell Biology Year Name of the scientist Importance 1590 Jansen 1650 Anton van Leeuwenhoek 1665 Robert Hooke 1831 Matthias Schleiden 1831 Theodore Schwann 1855 Rudolf Virchow perkinjee All organisms are composed of cells, some of a single cell some of many cells. Recall the hierarchy of life, the levels of organization mentioned earlier. The basic unit which can be called living is the cell, which may form a single celled organism (e.g., Chlamydomonas, Yeast) or a multicellular plant or animal. The cell is the basic structural and functional unit of life.the level of organization of matter represented by a cell shows all the characteristics of life. Any stage below level of a cell cannot be considered living, whether it is a single celled organism or multicellular plant or an animal. Robert Hooke (1663), while trying to understand why, cork which is a solid substance can float, examined thin slices using a microscope and found that they are made up of pores and coined the term cells to describe the pores. Anton Van Leeuwenhoek (1650), a contemporary of Robert Hooke was the first to describe and record living single celled organisms, Euglena & bacteria Matthias Schleiden (1831), a botanist, studying plant tissues concluded that all plants are made up of cells. Theodore Schwann a zoologist and Shleiden (1839),concluded that animal tissues are also made up of cells. Virchow (1855) showed that all cells arise from pre existing cells by cell division,schleiden,schwann and Virchow presented the Cell Theory which included the following. Cell theory. 1. All organisms are composed of one or more cells. 2. The basic structural and functional unit of organisms is the cell. 3. All cells arise from pre-existing cells. 1
Organization of cells Two kinds of cellular organization - Prokaryotic and Eukaryotic Prokaryotic Eukaryotic 2
Character Prokaryotic cell Eukaryotic cell Nucleus Cell wall Cytoplasm 3
Plant cell Structures and functions of organelles and sub cellular components. Nucleus Stores genetic information of the cell. Most cells possess one nucleus, some have several nuclei. (e.g., fungi) Functions of nucleus. 1. Control cellular activities. 2. Synthesizes DNA to produce new nuclei for cell divisions. 3. Synthesizes ribosome and RNA required for protein synthesis. 4
Endoplasmic reticulum Network of internal membranes forming flattened or tubular sacs separating cytosol from ER lumen. Continuous with the outer membrane of nuclear envelope Two types of ER; Rough ER and Smooth ER Rough ER Rough ER consists of flattened sacs, and ribosomes bound to surface Proteins synthesized by ribosomes move into lumen of ER. Synthesize membrane phospholipids and membrane glycolipids Transport enzymes and other proteins within cell. Produce transmission vesicles for transport 5
Smooth ER Network of tubular sacs without ribosomes Presence of membrane bound enzymes.. Synthesize lipids, steroids and carbohydrates Transport within cell. Produce transmission vesicles for transport. Detoxification Stores Ca2+ ions Golgi complex Stacks of flattened vesicles or Golgi bodies Inner and outer surfaces can be identified Functions of Golgi complex Proteins and lipids manufactured in endoplasmic reticulum (ER) are transported through channels of ER or vesicles into Golgi complexes Lipids and proteins combine with polysaccharides to form glycolipids and glycoprotein respectively within the cisternae of Golgi complex.. When necessary,vesicles containing glycoproteins or glycolipids are budded off from cisternae and move into other locations of the cell Produce lysosomes. 6
Lysosomes Membrane bounded vesicles contributing to digestive activity Contain hydrolytic enzymes which catalyze breakdown of carbohydrates,proteins, lipids and nucleic acids.. Digest food particles received by phagocytosis Digest worn out organelles Transport residue material out of cell by exocytosis Autolysis causing cell death. 7
Mitochondria Organelle bound by two membranes. Inner membrane bearing cristae... Functions of mitochondria Matrix carries enzymes for reactions of Krebs cycle. Cristae carry out electron transport chain and oxidative phosphorylation system. Synthesize ATP by oxidizing reduced coenzymes using oxygen. 8