September 8 2015 BSC 215 READING pages 68 85 CHAPTER 3 THE CELL The cell smallest unit of life Transport of substances Communication b w cells Cell reproduction Structure o The fence Cell processes Metabolism chemical rxns that a cell carries out to maintain life anabolic building catabolic breaking down oxidation reduction convert energy from nutrients to chem energy ATP Plasma membrane support communication cell identification Intracellular space space w in cells that contains cytosol Extracellular space space outside that contains extracellular fluid or ECF Cytoplasm inside membrane o Fluid cytosol and structures organelles cytoskeleton Cytosol intracellular fluid ICF of cell s total volume o Mostly water o Site of protein synthesis o Site of glycolysis Inclusions clusters of identical storage molecules in cytosol o Stores nutrients from ECF cell made proteins Organelles molecular machines that perform specific functions o They keep cell organized compartmentalized Cytoskeleton network of protein filaments o Supports maintains shapes hold organelles in place o Also responsible supports transportation w in cell Nucleus surrounded by phospholipid bilayer nuclear envelope o Contains DNA and makes most of RNA Structure function core principle cells are shaped differently based on function Phospholipid Bilayer Requirements cytosol phospholipids are amphiphillic have both nonpolar and polar parts o 1 Molecules must have parts that can interact w water in ECF membrane s hydrophilic regions that interact w water must have polar covalent bonds o Molecules must also have parts that repel water to keep eater in ECF and cytosol separate Fluid mosaic model current model of the plasma membrane plasma membrane is a structure w multiple components whose arrangement is dynamic it changes all the time Fluidity ability of phospholipids and other components to move w in the membrane this is very important Membrane proteins carry out many of the membrane s functions and give different cell types their unique properties Integral proteins normally span the width of the membrane o When they reach both sides of the membrane transmembrane proteins Peripheral proteins only on one side of the membrane or the other Transporting substances most transmembrane proteins serve as protein o Some integral proteins called carrier proteins transport molecules in o Membrane proteins that bind to chemical messengers are called o Receptor ligand interactions are responsible for physiology of most Functions of membrane proteins channels and out of the cell Act as receptors ligands systems Act as enzymes Provide structural support Link adjacent cells Plasma membrane components Cholesterol stabilizes the plasma membrane structure when temperature changes glycolipids glycoproteins o both function in cell recognition Passive Transport NO energy needed Active requires energy ATP What determines if a process is passive or active type of substance crossing 1 2 membrane s permeability 3 concentration of substance inside outside of the cell concentration gradient drives passive transport Diffusion movement of solute molecules from area of high concentration low rate of diffusion depends on size phase of particles Temperature size of concentration gradient barriers Simple diffusion nonpolar solutes ex hydrocarbons lipds that don t have assistance from a membrane protein Facilitated diffusion charged polar solutes that cross the phospholipid bilayer w help of a membrane protein rely on carriers channels because they are repelled by the phospholipid bilayer s fatty acid tails Osmosis movement of solvent H2O across a membrane with channel proteins called aquaporins in the plasma membrane some H2O molecules pass directly b w membrane phospholipids but its not super common driven by osmotic pressure pulling force that solutes exert on water molecules solutions w higher solute concentration has greater osmotic pressure Tonicity way to compare osmotic pressure b w 2 solutions in our cells it is used to compare cytosol and ECF body s ECF is isotonic to the cytosol of a cell meaning ECF has about the same solute as cytosol hypertonic extracellular solution cell LOSES water cell can crenate shrivel and die hypotonic extracellular solution cell GAINS water cell can lyse swell and burst Primary Active Transport protein in plasma membrane binds transports pumps a solute against its concentration gradient using energy from hydrolysis of ATP uniport pump drives a single substance in out of a cell symport drives 2 or more substances in the same direction anitport drives 2 or more in opposite directions Na K pump main primary active transport pump in body o Homeostasis requires the maintenance of the concentration gradient of these Na K pump shape 1 Pump binds 3 sodium ions from cytosol 2 ATP is hydrolyzed phosphate binds to the pump and the pump changes 3 Pump releases 3 sodium ions into the ECF and binds 2 K ions 4 Phosphate detaches and pump changes back into its original shape 5 Pump releases 2 K ions into cytosol Secondary Active Transport important for absorption secretion for many cells REVIEW PROCESS Electrical potential source to potential energy really just an electrical gradient Membrane potential electrical potential found across the plasma membrane of all cells Resting membrane potential value of membrane potential when a cell is rest Larger particles are transported in out of the cell via vesicles Vesicular transport active transport that requires vesicles requires energy from ATP hydrolysis Endocytosis take substances into the cell phagocytosis particles cell eating pinocytosis fluids cell drinking Receptors mediated endocytosis same as pinocytosis except is doesn t use receptors Exocytosis molecules leave the cell Transcytosis molecules are brought in via endocytosis transported through the cell and then released via exocytosis Rate at which material is added to plasma membrane rate of which material is removed