Chapter 5

Question 1

What is a protein’s primary structure?

Answer 1

It’s amino acid sequence.

Question 2

How are amino acid sequences read?

Answer 2

From the N-terminal to the C-terminal (left to right).

Question 3

How are amino acids connected?

Answer 3

By a peptide bond.

Question 4

When there are below 40 residues, what is it called?

Answer 4

A peptide.

Question 5

How many residues is the minimum needed for a polypeptide chain to work?

Answer 5

40 residues appear to be near the minimum for a polypeptide chain to fold into a discrete and stable shape that allows it to carry out a particular function.

Question 6

What is the limit of efficiency of the protein synthetic machinery of polypeptides?

Answer 6

Well over 1000.

Question 7

What do multisubunits contain?

Answer 7

Several identical and/or nonidentical chains called subunits.

Question 8

The longer the polypeptide, the greater the likelihood of what?

Answer 8

Introducing errors during transcription and translation.

Question 9

What are the four types of column chromatography? (Purification techniques of proteins)

Answer 9

1. cation exchange column
2. anion exchange column
3. size-exclusion column
4. affinity chromatography

Question 10

What is affinity chromatography good for?

Answer 10

Purifying proteins and nucleic acids.

Question 11

What are the 3 types of electrophoresis?

Answer 11

1. 1D electrophoresis
2. 2D electrophoresis
3. Isoelectrophoresis

Question 12

What is isoelectric focusing?

Answer 12

A technique of electrophoresis in which the resolution is improved by maintaining a pH gradient between the electrodes

Question 13

What is 2D electrophoresis?

Answer 13

Separates the complex mixture of samples using two different properties of the proteins.

Question 14

In electrophoresis, does DNA travel towards the anode or cathode?

Answer 14

They all move towards the anode.

Question 15

What do proteases do?

Answer 15

Digest proteins into smaller peptide fragments.

Question 16

How do you calculate the mass of a peptide, as determined by mass spectrometry?

Answer 16

First, determine the number of peptide bonds. Each of the bonds can have 1 water molecule. After that, multiply the number of bonds for each A.A by its molecular weight, and then add the different A.A’s together. Next, subtract (molecular weight of water x # of bonds) from the number previously found, and that’s your answer.

Example:
N= 114 g/mol K= 128 g/mol
H20= 28 g/mol
(114 g/mol x 4 bonds) + 128 g/mol = 584 g/mol
584 g/mol - (18g/mol water x 4 bonds) = 512 g/mol