[BIO] question

[299678]

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Need ur explanation to support your answer

If one compares the primary structure of the protein cytochrome C in organisms that are separated in evolutionary time, e, g, human and yeast, one discovers that

a) hydrophilic amino acids are usually substituted for hydrophobic amino acids
b) the overall tertiary structure of the molecules is quite different
c) the proteins have evolved different functions
d) considerable sequencees similarity exists between the two proteins
e) no differences exist in the primary structure

 

[txlonghorn]

I think it might be b. Can you please post the answers with your questions? Cytochrome c is used in the etc and can be used to compare how similar two different organisms are. Since bacteria and humans are different - a lot different. I would guess the amino acid sequences are different enough to translate to a different 3 structure.

 

[299678]

I didn't put answer initially, so give you opportunity to solve the problem. The correct answer is d)

 

[pinhi]

Yes but both use the ETC....so wouldnt their primary structures be similar?..this question isnt asking about the tertiary structure at all

 

[pinhi]

I didn't put answer initially, so give you opportunity to solve the problem. The correct answer is d)

thats what i thought

 

[txlonghorn]

You are right. I was debating between the 2, and just rememered from biochem that two proteins can have similar 3 structure and different sequences.

 

[yjdentist]

d) considerable sequences similarity exists between the two protein

i answered D, although the organisms are separated in evolutionary time, cytochrome c still serves a same function in the electron transport system. therefore, it must have considerable amino acids sequences. key word = considerable.

a) hydrophilic amino acids are usually substituted for hydrophobic amino acids
(just knowing that cytochrome is highly soluble protein in GENERAL, i assumed likelihood of it being replaced by hydrophobic is not high.)

b) the overall tertiary structure of the molecules is quite different
(it's not safe to assume that tertiary structure is quite different because the function is the same- if anything, i felt like it's safer to assume that the AA sequence is different and codes for similar tertiary structure because i read over and over that things can be sequenced differently and yet lead to same structure to function alike.)

c) the proteins have evolved different functions
(this is obviously a no)

e) no differences exist in the primary structure
(not a good assumption because question stated that the organisms separated during evolution)