Problem Set 3 - Problem Set 3 1. Review the different...

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Problem Set 3 1. Review the different mechanisms by which solutes cross a biological membrane. What are the factors that determine how a given solute is transported. Simple unassisted diffusion Facilitated Diffusion - involves assistance from a transport protein - energy independent - glucose uptake by RBCs or aqueous pore Active Transport - energy dependent - uptake of glucose in small intestine non polar and small polar - simple diffusion Charge, size and polarity 2. For each of the following, identify a feature that is similar and a feature that is different in terms of transport a. a pump and a transporter (carrier) protein Transporter: Solute moves to the protein and binds to a specific site. Alternating conformational change due to the binding of molecule to the protein. This conformational change allows the molecule to release. Powered by concentration gradient. Example is facilitative transporter protein. Pump has to be activated. It pumps against the concentration gradient and requires energy. Needs hydrolysis of ATP. b. a solute and an ion Lipid bilayers are impermeable to solutes and ions. Uncharged polar molecules can rapidly diffuse against membrane if they are small enough. Lipid bilayers are highly impermeable to all ions and charged molecules no matter how small. c. simple diffusion and facilitated diffusion Simple diffusion is unassisted net movement of a solute down a concentration gradient. It is a spontaneous process and depends on thermal motion of molecules. It is an exergonic process due to increase in entropy. Ex. Exchange of o2 and co2 in lungs Facilitated diffusion protein-mediated by ion channel and carrier proteins; no energy input required; solute like glucose binds to transmembrane segment of integral protein (=facilitative transport protein); conformational change leads to diffusion down a concentration gradient; passive process; no energy released; activity can be regulated. .Examples: movement of glucose from blood stream into a red blood cell, muscle or fat cell utilizing; facilitative glucose transporters (Glut1; a uniport protein); also: anion exchange protein (co-transport; movement of bicarbonate and chloride ions out/into red blood cells). d. indirect and direct active transport
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Problem Set 3 - Problem Set 3 1. Review the different...

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