BIOL1P91 Final Exam Prep test Questions With 100% Verified Answers

BIOL1P91 Final Exam Prep test Questions With 100% Verified Answers what are the 3 influences on cell membrane fluidity? 1. length of hydrophobic tails (shorter tails lead to more fluidity 2. double bonds in tails (leads to bent structure and more fluidity) 3. presence of cholesterol (stabilizes membrane) In what conditions do membrane proteins not move across the cell membrane? when proteins are attached to cytoskeleton or extracellular matrix How did Larry Frye and Michael Edin prove proteins move laterally across the cell membrane? they fused mouse and human cells, at 0C there was no protein movement, at 37C mouse proteins moved across the cell How did Matt Webb prove proteins move laterally? bleached one half of the cell, examined that bleached portion eventually moved across the cell What are the 3 reasons why the cell membrane is semi-permeable? 1. allows essential molecules to enter the cell 2. allows waste products to exit the cell 3. allows metabolic intermediate to remain inside the cell What molecule allows the cell membrane to be semi permeable? proteins What are the 3 ways to move molecules across the cell membrane? 1. simple diffusion - without the aid of a transport protein 2. facilitated diffusion - with the aid of a transport protein 3. active transport - movement of molecules against concentration gradient (low to high concentration), requires energy input Passive transport movement of molecules with the concentration gradient (high to low concentration), does not require energy input includes simple and facilitated diffusion What are 4 factors that effect ability for molecule to pass through cell membrane without aid of transport protein (simple diffusion)? size, polarity, charge, and concentration of molecule what molecules are highly permeable to the cell membrane? gases and small uncharged molecules what molecules are moderately permeable to the cell membrane? water and urea what molecules are poorly permeable to the cell membrane? polar organic molecules what molecules are very poorly permeable to the cell membrane? ions, charged polar molecules, macromolecules What is the gradient across the cell membrane transmembrane gradient - concentration of solute is higher in extracellular space electrochemical gradient - difference in ion concentration across membrane Osmosis movement of water across cell membrane from low solute concentration to high solute concentration What are the 3 types of possible solute concentrations across the cell membrane? 1. isotonic - solute concentration is equal on both sides of the cell 2. hypertonic - solute concentration is greater than opposite side of cell membrane 3. hypotonic - solute concentration is less than opposite side of cell membrane describe a hypertonic cell environment and how it differs between plant and animal cells cells lose water and shrink in animal cells: crenation in plant cells: plasmosis describe a hypotonic cell environment and how it differs between plant and animal cells cells take up water and grow in animal cells: cell swells and burst in plant cells: cell wall prevents expansion (turgor pressure) Turgor pressure when a hypotonic environment generate pressure in a plant cell, it is essential for plant health because it gives the plant structure What 5 mechanisms allow membrane channels to open? 1. ligand gated channels - ligand bonding triggers gate to open 2. non covalent bonding of regulatory proteins 3. covalent attachment of small molecules 4. voltage gated channels - open in response to electrical gradient 5. mechanosensitive channels - open in response to changes in membrane tension aquaporin water channel protein in a cell transporters molecules that bind to solutes to make is permeable to the cell membrane through facilitated diffusion or active transport what are the 3 functions of transporters? 1. pathways for organic molecules, hormones, and neurotransmitters 2. export of waste products 3. regulating pH and cell volume what are 3 categories of transporters? uniporters - bind to one molecule co-transporters - bind to two or more molecules that move in the same direction ani-porters - bind to two or more molecules that move in different direction primary active transport vs secondary active transport primary active transport - uses energy directly secondary active transport - uses stored energy from existing gradient What are the mechanisms of Na+ K+ pump? - electrogenic pump with net one positive charge (3Na+ out, 2K+ in) - 3 Na+ bind to pump, ATP is hydrolyzed - 3+ Na released - 2 K+ bind to pump - 2 K+ and phosphate relased What are 6 functions of electrochemical gradients? 1. ion and molecule transport 2. production of energy