BIOL 348 CHAPTER 12: TRANSPORT ACROSS CELL MEMBRANE EXAM QUESTIONS AND 100% APPROVED CORRECT ANSWERS GRADED A+ 2025

BIOL 348 CHAPTER 12: TRANSPORT ACROSS CELL MEMBRANE EXAM QUESTIONS AND 100% APPROVED CORRECT ANSWERS GRADED A+ 2025 2025 EXAM  BIOL 348 CHAPTER 12: TRANSPORT ACROSS CELL MEMBRANE EXAM QUESTIONS AND 100% APPROVED CORRECT ANSWERS GRADED A+ 2025 PRINCIPLES OF TRANSMEMBRANE TRANSPORT - CORRECT ANSWER -Transporting nutrients and wastes across cell membranes is a critical function for life -In addition, cells must maintain very specific ion concentrations both inside and outside -But, only very small, non-ionic molecules can cross membranes on their own by simple diffusion -Semi-permeable membrane -Cell membranes contain several transport proteins to specifically allow various substances to cross the membrane -Selectively permeable membrane -Maintaining proper ion concentration inside and outside of a cell is critical for life and for several important metabolic processes (Ion's won't pass through cell without help) **Look at images** Passive Transport - CORRECT ANSWER -Requires no energy -Molecules move from high concentration to low concentration, down their concentration gradients Passive Transport Includes - CORRECT ANSWER Simple diffusion Facilitated diffusion Osmosis Active Transport - CORRECT ANSWER Requires energy to pump molecules from low to high concentration against their concentration gradient membrane transport proteins - CORRECT ANSWER -Transport proteins are highly specific for the solute that crosses through them -The types of transport proteins found in a given membrane will dictate what may enter and leave that membrane, which is cell type- (or organelle type-) specific **look at image** Two main types of transport proteins for facilitated diffusion and/or active transport: - CORRECT ANSWER channels transporters channels - CORRECT ANSWER -form pores that cross the membrane and will selectively allow specifically sized/charged molecules to cross -Only used for passive transport Transporters - CORRECT ANSWER -Substances bind to specific binding sites on one side of a membrane, and the transporter protein changes conformation to transfer the molecule to the other side of the membrane -Both forms of transport proteins are very specific Solutes can cross membranes by either - CORRECT ANSWER passive or active transport Passive Glucose Transporter - CORRECT ANSWER -Found in liver cells (and other cells) -Has two conformations, one exposing a glucose binding site to the exterior of the cell, and one exposing a glucose binding site to the interior of the cell -If the [glucose] is high outside the cell, glucose will bind to external binding site, conformation will change and it will be released to the cell interior *Vice versa if the [glucose] is high inside the cell -Going down the concentration gradient, too big to do itself, so glucose uses a transporter Passive transport: osmosis - CORRECT ANSWER -Special form of diffusion of water across a membrane -Water can passively diffuse rapidly across a membrane through special transport protein channels called aquaporins -Water will move from areas with high [H2O] to low [H2O], meaning from low [solute] to high [solute], i.e. hypotonic to hypertonic osmotic pressure - CORRECT ANSWER driving force of osmosis -may drive a cell to swell or shrink depending on the environment around the cell aquaporins - CORRECT ANSWER water channel proteins Water will move from - CORRECT ANSWER areas with high [H2O] to low [H2O], meaning from low [solute] to high [solute], i.e. hypotonic to hypertonic **look at images** Passsive Transport: controlling osmosis - CORRECT ANSWER -Different cell types respond to (control) osmotic pressure in different ways -Animal cells use the sodium-potassium pump to maintain a proper osmotic balance across the membrane -Plant cells are surrounded by a cell wall which prevents cell from expanding and bursting *As water moves into a cell, cytoplasm expands, forcing the PM against the cell wall, creating turgor pressure, leading the cell to be rigid -Protozoa living in freshwater send incoming water into contractile vacuole; the vacuole that contracts, forcing the water out of the cell