protein function

Question 1

Every third residue in the protein collagen is ___________.

Answer 1

glycine

Question 2

In haemoglobin what is the transition from a low-affinity state to high-affinity state triggered by?

Answer 2

oxygen binding

Question 3

In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:

Answer 3

hyperbolic

Question 4

hyperbolic meaning

Answer 4

At low oxygen concentrations, even small changes in oxygen concentration lead to significant changes in the fraction of occupied binding sites. As the concentration of oxygen increases, myoglobin quickly becomes saturated, reaching a point where further increases in oxygen concentration have minimal effect on binding.

Question 5

Myoglobin and the subunits of haemoglobin have:

Answer 5

very similar tertiary structures, but different primary structures.

Question 6

The amino acid substitution of valine for glutamate in Haemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.

Answer 6

hydrophobic

Question 7

The fundamental cause of sickle-cell disease is a change in the structure of:

Answer 7

haemoglobin

Question 8

What is the Bohr effect?

Answer 8

the regulation of haemoglobin-binding by hydrogen ions and carbon dioxide

Question 9

What type of binding is indicated by a sigmoidal-shaped binding curve?

Answer 9

cooperative

Question 10

what’s the difference between haemoglobin and myoglobin?

Answer 10

Haemoglobin exhibits cooperative binding of O2 while myoglobin does not.

Question 11

Why is the sickle-cell haemoglobin mutation so prevalent in Africa and other tropical regions?

Answer 11

people with the sickle-cell trait are resistant to malaria, increasing the prevalence of the sickle-cell haemoglobin allele.

Question 12

what is the major fibrous protein present in skin, bone, tendon, cartilage, and teeth.

Answer 12

collagen

Question 13

what is the fibrous protein and is the primary component of wool and hair.

Answer 13

α-Keratin

Question 14

what does the globin chain of myoglobin have

Answer 14

an extensive α-helix structure.

Question 15

what happens to the diameter of the iron ion in myoglobin when oxygen binds

Answer 15

decreases

Question 16

what state is the iron of the haem group in myoglobin

Answer 16

Fe2+ oxidation state.

Question 17

what’s the function of myoglobin

Answer 17

oxygen storage in muscle.

Question 18

what binds the haem group to the globin chain in myoglobin

Answer 18

coordinated interactions
attachment of the heme iron to a histidine residue within the globin chain

Question 19

myoglobin structure

Answer 19

• single polypeptide chain of 154 amino acids
• eight α-helices assigned the letters A–H chain
• contains a heme prosthetic group, which includes a porphyrin ring iron ion.
• heme-bound Fe cation can exist in the 2+ (reduced) or 3+ (oxidized) state.

Question 20

why is lower oxygen binding better

Answer 20

function as a better oxygen-transport protein

Question 21

When oxygen binds to a haem-containing protein what are the two open coordination bonds of Fe2+ are occupied by?

Answer 21

one oxygen molecule and one amino acid atom.