SHORT ANSWERS BASIC BIO, I WILL RATE YOU 1-Why do cells require a large surface

Question

SHORT ANSWERS BASIC BIO, I WILL RATE YOU

1-Why do cells require a large surface area to volume ratio to exist? Some neurons are a meter long? That’s a lot of cytoplasm! Do these cells defy this requirement and therefore have a low surface are to volume ratio?

2-What’s the difference in resolution between your eye and a typical laboratory compound light microscope? Between a light microscope and a TEM?

3-Light micrographs are obtained by directing photons through a specimen. In general, how are TEMs and SEMs obtained? What’s the fundamental difference in the images obtained from these two different types of microscopes?

4-In terms of quantity, 98% of a plasma membrane is lipid (most of which are phospholipids) and 2% is protein. However, 50% of the weight of a plasma membrane is lipid and 50% is protein. What does this latter fact say about proteins in the membrane?

5-How does cholesterol in the membrane affect membrane fluidity? If cholesterol is so important in maintaining the integrity of membranes, why is it often seen as bad for you?

6-What is the difference between and integral membrane protein and a peripheral membrane protein? How does a carrier protein differ from a channel protein? What are the 3 different ways in which channels are gated in the human body?

Explanation / Answer

Ans1: cells maintain and require a high surface area to volume ratio in order to meet the needs of the cell by diffusing enough molecules through it's extended surface, which otherwise would have been difficult had the cells maintained a low ratio.

As the size of the cell increases this ratio decreases which in turn decreases the availibility of molecules to the cell. In order to counter this the cells divide when they grow upto a threshold size to maintain high surface area to volume ratio.

The neurons are usually long and thin maintaining a large surface area. This is due to presence of huge number of ion channels required for action potential. So to accomodate these, the dendrites from the cell body extend and increase the ratio of the nerve cell.

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