Biochemistry question....?

[Sarah]

Actually, I have two.... So if you know the answer to either (or both) of these please help me out!

1. The side chains of which of the following amino acids are mostly likely found on the outside of a globular proteint? On the inside? Explain each answer.
Phenylalanine Lysine Glutamate Tryptophan

(I know this is a tough question but the reason i'm asking is i have no idea why what would be on the outside and what would be on the inside, so if you know why something might be on the outside/inside or have ANY idea at all about this, i'd appreciate it)


2. Why must diabetics receive insulin subcutaneously by injection rather than orally?

Please supply anything you know that might be helpful, and maybe i can figure it out from there! Thank you!

[Alchemist]

Well, Trytophan is a derivative that occurs as an amino acid and is bonded after a catalytic reaction, thus causing secondary bonding.

Insulin is absorbed rather than digested and taking it orally rather than injecting it would simply cause it to pass through the digestive track and it would be quickly removed from the body by the small and large intestines. Since the symptoms of insulin depletion are associated with voiding, obviously the insulin would not be absorbed. By injecting it subcutaneously. the process of absorption is slower and more efficient.

[(f-_-)f]

1. Outside: Glutamate, Lysine
Inside: Phenylalanine, Tryptophan

Both glutamate and Lysine have charges on the ends of their side chains and are hydrophilic. They would be on the outside because the protein is dissolved in water in a biological environment. Phenylalanine and Tryptophan both have large aromatic rings that are hydrophobic, and will try to stay away from the surrounding water.

2. If the diabetic were to take insulin orally, the harsh environment of the stomach would denature it and render it useless. By injecting the insulin, the stomach is avoided and the insulin retains its properties.

[aftabac]

well good answers, i will only add that
the globular protein are actually water soluble proteins so the hydrophilic amino acids will be present outside and will have interaction with the water, and in all the globular protein the hydrophobic portion is present inside, as it has no interaction with water and so stayed away from water.
secondly about insulin, yes, if taken orally it will be chewed up the the stomach and intestine enzymes and will not remain effective as it will break up in amino acids, the only way is to genetically engineer this protein in a way that it resist the enzyme action then you can take it orally.

best regards
aftab

[littlesti]

The answer to a is that hydrophillic proteins are on outside and hydrophobic are inside.

[daltaleighis]

Hi, if anyone could help me with this it would be much appreciated. I have just started reading about gluconeogenesis and while I can understand the need to maintain adequate blood sugar to some extent I don't fully understand it. Why is pyruvate reconverted into glucose? I thought the idea of having glucose in your blood was so that it can be eventually converted to pyruvate and then put through the TCA cycle to produce energy. What is the point of reconverting pyruvate to glucose and then turning it back into glucose again?! The only reason I can think of is that because the brain metabolizes glucose almost exclusively, maybe gluconeogenesis occurs in order to allow it to allow glucose to travel in the blood stream in the brain where it can then be converted to pyruvate and undergo the TCA cycle there.... Please help if you can! I know it's a very basic question but I'm feeling very confused and several books and the internet are not really turning up answers. Thanks

[danfive]

Originally Posted by daltaleighis

Hi, if anyone could help me with this it would be much appreciated. I have just started reading about gluconeogenesis and while I can understand the need to maintain adequate blood sugar to some extent I don't fully understand it. Why is pyruvate reconverted into glucose? I thought the idea of having glucose in your blood was so that it can be eventually converted to pyruvate and then put through the TCA cycle to produce energy. What is the point of reconverting pyruvate to glucose and then turning it back into glucose again?! The only reason I can think of is that because the brain metabolizes glucose almost exclusively, maybe gluconeogenesis occurs in order to allow it to allow glucose to travel in the blood stream in the brain where it can then be converted to pyruvate and undergo the TCA cycle there.... Please help if you can! I know it's a very basic question but I'm feeling very confused and several books and the internet are not really turning up answers. Thanks

Check out glucagon entry in Wikipedia --> [Only registered users see links. ]
If you like also gluconeogenesis and insulin.

[daltaleighis]

I have already read those entries in wiki and they still don't answer my question.