BIOL 1411 1st Edition Lecture 6 Outline of Last Lecture 1 Cell theory 2 How we study cells 3 Common features of cells 4 Prokaryotic cells features 5 Eukaryotic cells features Outline of Current Lecture 1 Finish up last lecture on organelles 2 Function of cellular membranes 3 Membrane structure Current Lecture Continuation finishing of last lecture Golgi apparatus o Flattened sacs of membranes o Receives modifies and packages proteins from RER o Manufacture of cell wall polysaccharides plant cells o Lysosomes Membrane vesicles that contain digestive enzymes animal cells Mitochondria o Site of chemical reactions of cellular respiration that supply much cellular energy o Transform the energy that was in the bonds of food into energy held in many molecules of ATP o Great energy demand of a cell more mitochondria it will have Chloroplasts o site of chemical reaction of photosynthesis o transform energy of sunlight into organic molecules sugars that can be used as building blocks or as an energy source for other cell functions Vacuoles plant o Large fluid filled organelles o Store dissolved waste products and toxic compounds o Store anthocyanins pink and blue pigments in flowers and fruits o Provide structure for plant cells water enters the vacuole by osmosis creating turgor pressure Cell Wall plant o Made of cellulose fibers embedded in other complex polysaccharides and proteins o Functions as a barrier gives cell shape and support Cytoskeleton o Supports and maintains cell shape o Holds organelles in position o Moves organelles in cytoplasm o Interacts with extracellular structures to hold cell in place o Composed of 3 filamentous networks Microfilament Intermediate filaments Microtubules Form rigid internal skeleton in some cells Act as framework for motor proteins Made from the protein tubulin a dimer Have and ends Can change length rapidly by adding or losing dimers Cellular Membranes Lecture 6 Chapter 6 Functions of Cellular membranes Boundaries o Between cells and environment o Between a compartment and the rest of the cell Regulators o Selective permeability o Makes materials go in and out of cell Intracellular transporters o Shuttling of materials from one location to another Identify cells communication amongst other cells adhesion to others cells Location of some biochemical reactions Membrane Structure All membranes are a fluid mosaic of lipids proteins and carbohydrates Phospholipids along with cholesterol form a fluid bilayer o Occurs spontaneously in water o Hydrophobic interactions of tails help membranes fuse during phagocytosis vesicle formation etc Variety of proteins float in the bilayer o Often serve as gates and pumps for substances o Carry out biological reactions next page Carbohydrates o Attach to lipids or proteins usually on outer surface of plasma membrane o Important for cell cell recognition and adhesion Phospholipids o Vary in fatty acid chain length degree of saturation and phosphate groups o Percentage of cholesterol up to 25 o Have hydrophilic heads o Have a hydrophobic fatty acid tails o Tails make up inside of the bilayer o Heads make up outside of bilayer Membrane composition can vary o Number of proteins as well as the kinds of proteins o Fatty acids tails allow bilayer to be flexy and fluid Rapid lateral movement of molecules Degree of fluidity depends on temp and lipid composition Membrane proteins o Mostly independent of the lipids o Most lipids and proteins have weak hydrophobic interactions proteins can move laterally in bilayer also o Few proteins are covalently attached to membrane lipids or cytoskeleton proteins o Flip flop from one side of bilayer to the other is rare Three types of Cell Junctions Connect Adjacent Cells Tight junctions o cell adhesion and sealing Desmosomes o cell adhesion with out sealing Gap junctions o Cell adhesion and molecules moves between cells