General Zoology Lecture_241213_080924 PDF

Cell Lecture 2  II. Cell Structure & Function Cell Theory All living things are made of one or more cells. Cells are the basic units of Structure & Function. Cells originate from existing cells.  Cell Diversity 1. Not all cells are alike. 2. C...

Cell Lecture 2  II. Cell Structure & Function Cell Theory All living things are made of one or more cells. Cells are the basic units of Structure & Function. Cells originate from existing cells.  Cell Diversity 1. Not all cells are alike. 2. Cells differ in size, shape and function. 3. The female egg is the largest cell in the body & can be seen without microscope.  Cell Diversity 4. Bacterial cells are some of the smallest cells & are only visible with microscope.  Cell Diversity 5. Cells are limited in size by the ratio between their outer surface area & their volume. 6. Cells need surface area of their cell membrane large enough to adequately exchange materials with environment ( wastes, gases and nutrients). 7. Small cells have more surface area for their volume of cytoplasm than large cells. 8. As cells grow, the amount of surface area becomes too small to allow materials to enter & leave the cell quickly enough. Cell Diversity  Cell Diversity 9. Cell size is also limited by the amount of cytoplasmic activity that the cell’s nucleus control. 10. Cells come in a variety of shapes & the shape helps determine the function of the cell ( e.g. Nerve cells and red blood cells).  Cell diversity  Cell Types Prokaryotes Eukaryotes  1. Prokaryotes Prokaryotic cells are less complex Unicellular. Don’t have a nucleus & No membrane bound organelles. Most have a cell wall surrounding the cell membrane& a single looped chromosome. Include bacteria & blue green bacteria. Found in kingdom Monera. Prokaryotes or bacteria lack a nucleus.  2. Eukaryotes More complex cells. Include both unicellular & Multicellular. Do have a true nucleus and membrane bound organelles. Organelles are internal structures that perform specific function. Organelles Surrounded by single or double membrane. Eukaryotic cells surrounded by a thin cell membrane that controls what leaves or enters the cell. Nucleus located in the center of the cell, contains genetic material & controls activity of the cell. Eukaryotes includes plant cell, animal cell, fungi, algae & Protests.  Structure & Function of Cell Organelles I. Cell Membrane It composed mainly from a lipid bi-layer made of phospholipids molecules in addition to protein and carbohydrate content  Fluid Mosaic Model Phospholipid & Proteins can move side to side making the membrane appear fluid. Proteins embedded in cell membrane form a pattern or mosaic.  Functions of the cell membrane Separates the cytoplasm from external environment and gave the cell its characteristic shape. Protects the cell & Regulate exchange of materials with surroundings ( Cell transport ). Cell membranes are selectively permeable only allowing certain materials to enter/leave. Cell membrane proteins help moving materials in/out the cells ( Ion Protein Channels, Transmembrane proteins binding substance, Carbohydrate binding chemical signals). Endocytosis and Exocytosis. Sodium - Potassium pump which is responsible for polarization of cell membrane. Cell membrane take part in formation (Myline sheath, Microvilli, Cilia and Flagella)  Cell Membrane  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis Molecules tend to move from higher concentration Cell to lower concentrations until it reach homeostasis. Transport The cell membrane is selectively preamble so it controls the movement of substances in/out.  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis In the movement of molecules from higher concentration Passive to lower concentrations without use energy. Transport Movement is due to unequal concentration inside and outside the cell.  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis Diffusion is one principle method of movement Diffusion of small molecules within cells as Co2, Oxygen. Gas exchange in gills of fishes and lungs of animal, is operated by diffusion.  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis Osmosis Is the diffusion of water a cross a semi-preamble, preamble and selective preamble membrane.  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis Large molecules ( Sugar/Amino acids ) are carried into/out with Active use of energy. Also during transportation from lower to higher concentrations. Transport In this case, Proteins have to move against the concentration gradient ( Sodium-potassium pump in nerve cells ).  Cell Transport Passive Active Selective Transport Transport Transport Diffusion Osmosis Selective The presence of cell receptors allows the cell to select and to determine which Transport material enter the cell and which to be shut out.  Endocytosis & Exocytosis Taking solid matters in the surroundings into the cytoplasm called Endocytosis. Taking fluid droplets in from the surroundings into the cytoplasm called Pinocytosis. Exocytosis is reversed to Endocytosis (extrude membrane vesicle from cytoplasm).