a level biology question (water channel protein)?

Question

suggest how the structure of the water channel protein relates to its function....
its a 2 mark question...
i was goin to put something about how its hydrophilic...
but im not sure

Answer 1

structure always dictates function in biology. With ion channels, it is particularly true that steric hindrance and/or charge tend to act as the gating mechanism. In Na+ channels four cytoplasmic loops with strategically located negatively charged amino acids sit around the channel, resulting in stabilization (Na is usually "stabilized" in solution by complexing with the neg. pole of water- because H20 is literally too bulky to enter this channel, it must be stabilized (( the delta G kept negative)) by these loops). So you can see the size of the channel and the stabilizing forces for the molecule its designed to tranport, dictate transport. Keep in mind that any change in structure/shape can serve as an on/off switch, or rather "open/closed". Phosphorylation or ionic environment are two examples, the latter causing the opening of "voltage gated" channels in neuronal membranes.



sorry to meader because i haven't looked into aquaporins specifically, but there must be some size exclusion mechanism as well as a "selectivity filter" that is composed of amino acid residues with oxygens in close contact to the channel to allow for hydrogen bonding. most things are conserved in nature so i'd look for an analogous relationship to the Na channel.

Answer 2

In multicell organisms, which is the most complex level of cellular organization? (Points : 3) order from most complex to least systems organs tissues cells 4. Which structure would you not find in a prokaryotic cell? (Points : 3) membrane-bound organelles 5. Which molecule forms the bulk of a cell membrane? (Points : 3) phospholipid 6. Which is the best definition of diffusion? (Points : 3) the movement of particles from a region of high concentration to a region of low concentration 7. Which substance is commonly found in a cell membrane? (Points : 3) proteins They are enzymes that help actively transport things through the membrane. 8. What is the process whereby molecules in vesicles are exported out of a cell? (Points : 3) exocytosis 9. In a eukaryotic cell, where is most of the DNA located? (Points : 3) in the nucleus 10. A cell membrane is semipermeable. Which phrase best explains the term semipermeable? (Points : 3) flexible and fluidlike true but not defining most materials can pass through not true only certain materials can pass through the correct answer. 11. Which description is true about eukaryotes but not prokaryotes? (Points : 3) They do not have membrane-bound organelles. false They are all composed of a single cell. sometimes They are always multicellular. not true They have a nucleus. True 12. A cell membrane is a phospholipid bilayer. What major benefit does the arrangement of lipids in the membrane provide to a cell? (Points : 3) The surfaces of the membrane can interact with water solutions. true, probably the correct answer The surfaces of the membrane are nonpermeable. they are semipermiable The bilayer makes the cell strong and rigid. not really true but it is subjective The phospholipids help the cell easily change size. sort of true 13. Read the paragraph and use the information to answer Questions 13 and 14. Despite its name, the Pacific sea horse is actually a type of fish. Its horse-shaped head gives it its name. This creature lives in the Pacific waters off the west coast of the Americas, from Peru to Southern California. Like many other saltwater fishes, sea horses face the constant challenge of preventing too much salt from building up in their cells. Not true but I will accept it for the question as a given. We have no sea horses around here. When sodium and chloride ions from the saltwater environment enter a Pacific sea horse’s body, which process is most likely responsible? (Points : 3) diffusion 14. To keep the right amount of salt in its body, the sea horse has to get rid of extra salt using a process that takes energy. Which process does it most likely use? (Points : 3) active transport 15. The amoeba is a single-cell organism that gets food by engulfing its prey with outstretched parts of its cell membrane, and then bringing the food inside. Which process does an amoeba use to eat? (Points : 3) endocytosis

Answer 3

sure it`s water soluble so it can pass throught the hydrogen bonds from inside to out side or vice versa