Protein Function

Question 0

Define competitive inhibition

Answer 0

A type of enzyme inhibition where the inhibitor competes with the substrate for the binding site.

Characterised by increase in the Km for the substrate but the Vmax stays the same

Question 1

Define allosterism

Answer 1

The binding of a ligand/substrate at one site in a multi subunit protein that influences the subsequent binding of other ligands/s bust rates to other subunits

Question 2

Define Bohr effect

Answer 2

Decrease in oxygen binding affinity of haemoglobin caused by a decrease in pH

Question 3

What is an enzyme

Answer 3

Biological catalyst that increases the rate of a reaction by lowering the activation energy

Question 4

What is haem

Answer 4

A porphyrin derivative found in haemoglobin and myoglobin.

The central iron atom is the site of reservable oxygen binding

Question 5

What are:

Km

Vmax

Answer 5

• the substrate concentration that will give half the maximal rate (Vmax)
• the maximal velocity of an enzymes catalysed reaction

Question 6

Define Non-competitive inhibition

Answer 6

A type of enzyme inhibition where the inhibitor binds at a site other than the active site.

Decreased Vmax but the same Km

Question 7

Define Sickle cell anaemia

Answer 7

A haemoglobinpathy caused by a Glu to Val mutation in beta-globin molecules resulting in deformed RBC

Question 8

Define thalassaemia

Answer 8

A group of haemoglobinpathies that are caused by mutations in globin genes resulting in an imbalance between globin proteins

Question 9

What are some key features or myoglobin and haemoglobin

Answer 9

Both oxygen transporting

Haem contains proteins (tetrametic) to allow for binding of 4 oxygen
Mb is single subunit protein that can bind to one molecule oxygen

HB exhibits sigmoidal binding kinetics
Mb hyperbolic oxygen binding

Question 10

What are the 6 main classes of enzymes

Answer 10

Oxidoreductases - oxidation reduction reactions
Hyrdolases - catalyse cleave of bonds by the addition of water
Transferase - transfer C- N- or P- containing groups
Lyases - addition or removal of groups to form double bonds
Isomerase - transfer of groups within molecules to form isomers
Ligases - formation bonds between C and O S or N at expense of ATP

Question 11

What is the michaelis-menten equation

Answer 11

Vo = Vmax(S) / Km + (S)