Lecture 8 - Enzymes

Question 1

Enzyme Structure - Unconjugated and Conjugated

Answer 1

Unconjugated - no other factor needed for enzyme to work

Conjugated - cofactor is needed by enzyme

Question 2

What is the difference between a Holoenzyme and an Apoenzyme?

Answer 2

Holoenzyme (active) - enzyme + cofactor

Apoenzyme (inactive) - enzyme - cofactor

Question 3

What is Enzyme Activity?

Answer 3

The rate that an enzyme can catalyse a reaction

Question 4

Enzyme-Substrate Interaction

Answer 4

Lock and key
Active site has a fixed geometry and only a substrate with a matching geometry will fit
Active site of enzyme and substrate, have a flexible shape that changes upon binding

Question 5

The ES Complex

Answer 5

Contributes to specificity of enzymes

Increases probability of collisions between reacting molecules to produce products

Question 6

Why does an enzyme not hold onto its substrates or products too tightly?

Answer 6

Catalysis depends on making a reaction go faster
- a tightly bound molecule takes longer to dissociate
Product must dissociate to allow the enzyme to bind to another substrate

Question 7

What are the 3 characteristics of Enzymes?

Answer 7

Increase reaction rate
High affinity and specificity for substrates
High capacity for regulation

Question 8

What is Affinity?

Answer 8

Measure of the total strength of binding

Question 9

What is Specificity?

Answer 9

Conformational precision of the binding interaction between the substrate molecules and the residues in the active site of the enzyme

Question 10

Different types of Specificity

Answer 10

Absolute - enzyme will catalyse only one reaction that involves particular substrates
Broad - enzymes catalyse reactions using substrates with a similar structure to the most specific substrate
Stereochemical - enzyme will catalyse reactions that involve only a particular stereochemical