Module 6: Amino Acids and Proteins

Question 1

Amino acid

Answer 1

Monomers of proteins

Organic molecules consisting of at least one amino group and one carboxyl group

Question 2

Primary structure of protein

Answer 2

The unique sequence of amino acids that are linked by covalent peptide bonds to form a polypeptide chain

Question 3

Secondary structure of protein

Answer 3

The repeated twisting or folding of neighbouring amino acids in the polypeptide chain Common: alpha helix and beta pleated sheets Stabilized by hydrogen bonds

Question 4

Tertiary structure of protein

Answer 4

The three-dimensional shape of a polypeptide chain

Question 5

Quaternary structure of protein

Answer 5

In those proteins that contain more than one polypeptide chain, the arrangement of the individual polypeptide chains relative to one another

Question 6

The cells that secrete hydrochloric acid in the stomach are the _______ cells

Answer 6

Parietal cells

Question 7

Pepsinogen is secreted by which type of cell in the stomach?

Answer 7

Chief cells

Question 8

Chief cells in the stomach secrete:

Answer 8

Pepsinogen

Question 9

Parietal cells in the stomach secrete:

Answer 9

Hydrochloric acid

Question 10

Five bands visualized in serum protein electrophoresis

Answer 10

albumin
alpha-1 globulin
alpha-2 globulin
beta-globulin
gamma-globulin

Question 11

Reference range for total protein

Answer 11

60 - 80 g/L

Question 12

Reference range for albumin

Answer 12

35 - 55 g/L

Question 13

General principle for the Biuret method for Total Protein

Answer 13

Peptide bonds of proteins react with copper ions at an alkaline pH, producing a violet colour proportional to the amount of protein

Question 14

Purpose of potassium iodide in the Biuret method

Answer 14

Prevents auto-reduction of Cu++ to Cu+

Question 15

Purpose of sodium-potassium-tartrate in the Biuret method

Answer 15

Maintains Cu++ in solution at alkaline pH

Question 16

Why don’t we use the Biuret method for protein in urine?

Answer 16

Ammonia in urine interferes with the method

Question 17

Why don’t we use the Biuret method for protein in CSF?

Answer 17

The method is not sensitive enough to detect low levels of protein in CSF

Question 18

The dye used in many dye-binding methods for albumin

Answer 18

Bromcresol Green (BCG)

Question 19

Why do we use constant current in SPE?

Answer 19

To stabilize migration rates

Question 20

Haptoglobin and ceruloplasmin are found in which SPE band?

Answer 20

Alpha2 globulin band

Question 21

Transferrin and hemopexin are found in what band in SPE?

Answer 21

Beta globulin band

Question 22

pI is the pH at which:

Answer 22

The protein carries a net zero charge, the protein is the least stable and least soluble (most subject to precipitation)

Question 23

How is it that 20 amino acids are required to build our body proteins but only 9 are essential in our diet?

Answer 23

The remaining 11 amino acids can be synthesized from the 9 essential types

Question 24

A conjugated protein minus its prosthetic group is called:

Answer 24

An apoprotein

Question 25

If an SPE was performed on a hemolyzed sample, what would the pattern show?

Answer 25

Increase in the Beta-globulin band

Question 26

If an SPE was performed on a plasma sample, what would the pattern show?

Answer 26

A distinct band near the point of application (beta-gamma interzone), indicating fibrinogen