QUESTIONS FROM BIOLOGY MODULE 6 June 2003

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People what did you write on Monday for the following questions

Why is glycerol able to pass through the plasma membrane into the epithlial cells ? (1)

How could you determine experimentally whether a small mammal was respiring triglycerides or carbohydrates? (2)

Suggest why triglycerides are more valuable to a small desert mammal as a food store than carbohydrates. (1)

How does an Action potential pass along a non-myelinated neurone ?(3)



They asked to explain two types of synapes what did you write ?
(2)

The presence of an air bubble in a xylem vessel in the stem blocks the movement if water through taht vessel. Use cohesion Tension theory to explain why. (4)
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This is what I put, dunno if it's right!

Glycerol can pass through the membrane as it is lipid soluble- it can pass through the phospholipids.

Work out the repiritory quotient (RQ): volume of CO2 produced divided by volume of O2 used. If it is triglycerides it will be 0.7 approx, if it is carbs it will be 1.

Because respiration of triglycerides produces more water as a by-product than carbs.

Action potential makes the axon membrane more permeable to Na+ ions, causing an influx at each successive sodium gate as it arrives. This causes a change in the potential difference of the membrane from -70mV to 40mV- an action potential, triggering the increase in permeabilty at the next sodium gate.

I didn't do the synapse Q, but its inhibitory & exitatory synapses.

Didn't do the cohesion-tension Q either.
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the second synapse thing is temporal summation when one comes after another in quick sucession and this causes a larger generator potential the first part to that question was that they come at the same time i think
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The presence of an air bubble in a xylem vessel in the stem blocks the movement if water through taht vessel. Use cohesion Tension theory to explain why. (4)

water evaporates from stomatal pores causing a negative water potential in the spongy mesophyll as water molecules have hydrogen bonds between them they form an unborken chain of water a bubble will disrupt this chain forcing the water to go through slit pores instead
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triglycerides also have more energy to be released than carbs so they can be stored for longer in times when there is not much food /.... hope this has helped
i think thou once an exam is done dont go over it 2 much coz i went over mine loads and i really dont feel better for it jus put it out of yr head and move on 2 the nxt 1
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