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level: 1.4 Membrane Transport

Questions and Answers List

level questions: 1.4 Membrane Transport

QuestionAnswer
How does membrane transport occur? (2)Passive: along a conc G and doesn't use ATP (high = low) Active: against a conc G, uses ATP (low = high)
What are 3 types of passive transport?simple = small / lipophilic molecule can freely cross the membrane facilitated = large / charged molecules need transport with membrane proteins osmosis = water movement that depends on solute concs
What does simple diffusion mean?net movement of particles from high conc to low conc (along a conc g) until equilibrium is reached
What does facilitated diffusion mean? (4)uses membrane proteins for certain substances that can't easily cross the membrane (ions, polar macromolecules) uses: protein channels = hydrophilic pores for ions carrier proteins = allows changing of shape to allow translocation
How do carrier proteins work? (3)integral glycoproteins binds to a solute to undergo conformational change = translocate solute across membrane only binds to a specific molecule move molecules against conc gradient with ATP
How do channel proteins work?integral lipoproteins have a pore in which ions can ceoss from one side of the membrane to another ion selective only move molecules across a conc g faster than carrier proteins
How do potassium channel proteins work for facilitated diffusion? (4)they have a hydrophilic inner pore to transport K+ ions a filter restricts the passage of other ions the channels open / close depending on membrane polarity = voltage-gated or NT binding = ligand gated
How does the nerve cells transmit electrical impulses with sodium and potassium channels?by translocating ions to create a voltage difference across membrane at rest: Na-K pumps remove Na ions from the nerve cells while K ions build up within when the neuron fires these ions swap places by facilitated diffusion
What is osmosis?net movement of water molecules across a semi permeable membrane from low solute conc to high solute conc
What is osmolarity?measure of solute concentration
What does it mean if a solution is hypertonic?higher relative solute concentration = gain water by osmosis too much solute = hyper causes shriveling (crenation)
What does it mean if a solution is hypotonic?lower relative solute concentration = lose water by osmosis hypo= hypnotic = calm = less solute causes lysis= rupturing of the cell
What does it mean if a solution is isotonic?same relative solute concentration no net water movement
Why do plant cells have a fixed shape compared to animal cells?because they have a rigid cell wall hypertonic: cytoplasm shrinks (plasmolysis but cell wall maintains the shape hypotonic: cytoplasm expands but doesn't rupture because of the cell wall (turgor)
What is active transport?uses energy to pump molecules against a conc gradient (low to high)
What are the 2 types of active transport?direct (primary): ATP hydrolysis indirect (secondary): joined with another molecule to move across an electrochemical gradient = contransport
How does a sodium-potassium protein pump work for active transport? (4)3 Na+ ions attach to the binding sites on the pump ATP hydrolysis changes shape of pump (conformation) = expose extracellular binding sites 2 K+ ions attach to these sites = ions are exchanged once the phosphate group is released to make the pump return to its original conformation translocate potassium across membrane
What is vesicular transport? (3)Ribosomes make secretory proteins into the lumen of rough ER ER membrane create a vesicle to transport the protein into the golgi body = membrane bulges and buds to create a vesicle around the material the protein is transported from the golgi body to the membrane via a vesicle
How does bulk transport happen with the cell membrane?bilayer is held with hydrophobic interactions bw fatty acid tails = can be easily broken and reformed with ATP hydrolysis = allows materials to be transported in bulk
What is endocytosis?when substances enter the cell without passing across the membrane = is kept inside a vesicle endo = enter
What are the 2 types of endocytosis?phagocytosis: ingestion of solid substances (food particles) Pinocytosis: ingestion of liquid (dissolved solutes)
What is exocytosis?when materials exit a cell without crossing the membrane by being packaged and stored in the golgi complex before secretion
What are the 2 types of exocytosis?constitutive secretion: immediately released after synthesis regulatory secretion: delayed until a signal is received
What can the rate of diffusion be affected by?temp: affects kinetic energy of particles molecule size: larger particles have greater resistance in a fluid gradient: higher diffusion with a higher conc gradient