Enzymes

Question 1

What are enzymes?

Answer 1

Biological catalysts that increase the rate of reaction by lowering the activation energy.

Question 2

What are 2 other ways of increasing a reaction rate and how?

Answer 2

Temp - increase no of molecules with activation energy.

Conc - Increase chance of collisions.

Question 3

What type of bonds bond a substrate to an active site and why?

Answer 3

Non covalent bonds e.g. Hydrogen bonds. Can’t be too tight as need to release substrate.

Question 4

Name 5 properties of enzymes.

Answer 4

Highly specific, unchanged after a reaction, do not affect reaction equilibrium, increase rate of reaction, are proteins.

Question 5

In a product vs time graph, why does the product curve off to flat, constant line?

Answer 5

Because as all substrate is used up, product slows down.

Question 6

What is the name of the equation that calculates V0?

Answer 6

The Michaelis - Menten equation

Question 7

What is VMAX?

Answer 7

Vmax is the maximum rate where all enzyme active sites are saturated with substrate.

Question 8

What is KM?

Answer 8

Concentration of substrate that gives half max velocity (vmax).

Question 9

Fill in:
Low km = X affinity for substrate
High km = Y affinity for substrate

Answer 9

X = high
Y = low

Question 10

What does 1 unit of enzyme amount to? What unit is it in?

Answer 10

1 unit = amount of enzyme that converts 1 Umol of PRODUCT per MIN (In L or g).

Question 11

Two types of inhibitors?

Answer 11

Irreversible - bound with covalent bonds e.g. Nerve gases

Reversible - bound with non covalent bonds, freely dissociate.

Question 12

Two types of reversible bonds?

Answer 12

Competitive and non-competitive

Question 13

What is a competitive inhibitor and what effect does it have on km and vmax?

Answer 13

Inhibitors resemble a substrate, bind to the active site of enzymes e.g. influenza virus.
Vmax remains the same as the enzyme will be saturated either way - substrate or inhibitor
Km increases as more substrate is needed to keep up competition with inhibitor
INCREASES KM NOT VMAS

Question 14

What are non - competitive inhibitors and their affect on vmax / km?

Answer 14

Bind to another area of the enzyme not the active site, but change conformation of enzyme inhibiting them for binding correctly and making an ES complex.
VMAX DECREASES - cannot reach full enzyme capacity
KM UNAFFECTED - can put in as much substrate as you want is still unaffected.
VMAS DECREASE KM UNCHANGED.