Session 2

Question 1

Define Primary structure

Answer 1

The amino acid sequence of a protein.

Question 2

Define Secondary structure

Answer 2

Stretches of the polypeptide chain that form Alpha-helices and Beta-sheets. Bonds on either side of the peptide bond can rotate freely

Question 3

Define Tertiary structure

Answer 3

The full 3D structure of the protein. Involves the folding up of the secondary structures and some have molecular chaperones (to aid)

Question 4

What is Amyloidosis?

Answer 4

Where the tertiary structure of a protein is not folded correctly

Question 5

Define Quaternary structure

Answer 5

Interaction between and arrangement of different polypeptide chains (subunits) within the same protein

Question 6

Define Homomeric

Answer 6

Polypeptide chains in the Quaternary structure are identical

Question 7

Define Heteromeric

Answer 7

Polypeptide chains in the Quaternary structure are different

Question 8

Define Globular protein

Answer 8

Several types of secondary structure. eg Enzymes and regulatory proteins

Question 9

Define Fibrous protein

Answer 9

One repeating primary structure. eg Structure, support, protection

Question 10

What are the key features of an alpha helix?

Answer 10

Right handed
3.6 AA per turn
0.54 nm pitch
Pro/Gly act as helix breakers

Question 11

What are the key features of a beta sheet?

Answer 11

Can be parallel or anti parallel

Multiple H bonds

Question 12

What is Myoglobin?

Answer 12

A single subunit protein that contains one Haem group for the binding and transport of oxygen

Question 13

What type of binding does Myoglobin exhibit?

Answer 13

Hyperbolic O2 binding – no cooperativity.

Question 14

What is Haemoglobin?

Answer 14

A tetrameric protein (2xalpha, 2xbeta subunits) containing four Haem groups.

Question 15

What type of binding does Haemoglobin exhibit?

Answer 15

Sigmoidal O2 binding. (Cooperative binding)

Question 16

What is Haemoglobin’s oxygen affinity in the T state?

Answer 16

Low

Question 17

What is Haemoglobin’s oxygen affinity in the R state?

Answer 17

High

Question 18

What state is deoxyhaemoglobin in?

Answer 18

Can exist in a low affinity T-state (tense) or a high affinity R-state (relaxed). The binding of O2 promotes the stabilisation of the R-state

Question 19

How does 2,3-bisphosphoglycerate (BPG) effect the binding of O2?

Answer 19

Decreases the affinity of Hb for O2. Curve shifts right. BPG concentration increases at high altitudes and made during metabolism

Question 20

How does CO2 and H+ effect the binding of O2?

Answer 20

Decrease the affinity of Hb for O2. Sites of low pH and increased CO2, eg muscle in exercise

Question 21

How does CO interact with Haemoglobin?

Answer 21

Binds to Hb 250x more readily than oxygen.
Fatal when COHb is > 50%.
Binding of CO also acts to increase the affinity of unaffected subunits for oxygen.

Question 22

Explain Sickle cell Anaemia

Answer 22

Autosomal recessive. Single nucleotide polymorphism resulting in substitution of hydrophilic amino acid to hydrophobic in the Beta-subunit of Hb
Distortion of RBC’s into the sickle cell shape, cell lysis

Question 23

What are Thalassaemias?

Answer 23

group of genetic disorders where there is an imbalance between Alpha and Beta subunits.

Question 24

What are the 2 types of Thalassaemias?

Answer 24

Beta-Thalassaemias – Decreased or absent Beta-chains. Alpha chains unable to form stable tetramers. Symptoms appear after birth.
Alpha-Thalassaemias – Decreased or absent Alpha- chains. Beta-Chains can form stable tetramers with increased affinity for oxygen. Onset before birth