Amino Acids & Proteins

Question 1

Why are RNA viruses an exception to the central dogma?

Answer 1

1. they can make templates for another rna strand that can then be translated.
2. The genome can be used directly by the host cell

Question 2

tRNA and rRNA are both types of what RNA?

Answer 2

non coding RNA

Question 3

What is the main difference between proteolysis and acid hydrolysis?

Answer 3

Proteolysis is specific cleavage with proteases and acid hydrolysis is non-specific.

Question 4

Why does Histidine’s pka make it unique?

Answer 4

Its pka is 6.5 (physiological pH) and it can exist in protonated or deprotonated forms. Allows it to stabilize/destabilize a protein at active site

Question 5

What are the 2 key differences of L and D enantiomers?

Answer 5

1. not superimposable

2. Only L is found in the body

Question 6

Zwitterions are unique because of what?

Answer 6

they have both acceptor and donator sites

Question 7

What does it mean for a charged ion ( either + or - ) to reach a neutral state?

Answer 7

It means that the ion has reached its isoeletric point

Question 8

Which amino acids are nonpolar hydrophobic? (6)

Answer 8

Alanine, glycine, methionine, valine, isoleucine, proline

Question 9

Which amino acids are nonpolar hydrophobic and aromatic? (2)

Answer 9

Phenylalanine and tryptophan

Question 10

Which amino acids are hydrophilic and neutral? (6)

Answer 10

serine, threonine, asparagine, cysteine, tyrosine, glutamate

Question 11

Which amino acids are polar, hydrophilic and acidic? (2)

Answer 11

aspartic acid and glutamic acid

Question 12

Which amino acids are polar, hydrophilic and basic? (3)

Answer 12

histidine, lysine, and arginine

Question 13

Why does this certain type of bond only happen with 2 or more cysteines?

Bond choices are:

1. covalent
2. ionic
3. disulfide

Answer 13

Disulfide, because cysteines have sulfur( -SH ) atoms

Question 14

If heat is added to a protein, what degree structures would NOT be disturbed?

Answer 14

1st degree structure is not affected

Question 15

If chemicals are added to a protein, why are 2nd, 3rd, and 4th degree structures affected?

Answer 15

Because the chemicals will tear down H bonds

Question 16

If a pH change is introduced to a protein, why will the 3rd and 4th degree structures be affected?

Answer 16

The pH change will break down ionic bonds

Question 17

Hydrogen bonding between separate SUBUNITS of DNA polymerase is an example of which of the following?

1. 1st degree structure
2. 2nd degree structure
3. 3rd degree structure
4. 4th degree structure

Answer 17

4th degree structure: subunits are 3D arrangements found in multi-unit proteins

Question 18

Electrophoretic separation of leucine from a protein sample would be least effective at which of the following pH values?

1. 8.4
2. 7.4
3. 6.4

Answer 18

pH 7.4 (physiological resting pH)

Question 19

Electrophoretic separation at pH 6 of a sample of polypeptide 1 (mw 100) polypeptide 2 (mw 200) and polypeptide 3 (mw 400) would result in which of the following? (Note: the isoelectric point of each polypeptide occurs at pH 6)

Answer 19

None of the fragments would move since the isoeletric point of each ion is at pH 6 and electrophoresis separation requires a NEGATIVE net charge

Question 20

Because proline is so strerically strained, where is it likely to be found in a protein?

Answer 20

In the immobile regions

Question 21

Because glycine is the least sterically strained, where is it likely to be found within a protein?

Answer 21

In the high mobility regions

Question 22

Where in a cell are you most likely to find the nonpolar proteins?

Answer 22

Within the cell gathered with other nonpolar hydrophobic proteins