the role of enzymes

Question 1

what are enzymes

Answer 1

• biological catalysts
• they make reactions occur faster by reducing the activation energy needed to convert substrates into products
• enzymes are globular proteins - the substrates bind into a ‘pocket’ called the active site formed by the R groups of 3-12 amino acids

Question 2

what is a globular proteins

Answer 2

• polypeptide chain that ‘rolls up’ into a spherical shape
• relatively unstable structure
• soluble
• metabolic functions - e.g. all enzymes, antibodies, some hormones (such as insulin) and hemoglobin

Question 3

active site

Answer 3

unique-shape cleft part of an enzyme which binds to its complementary substrate

Question 4

activation energy

Answer 4

the minimum amount of energy required for a reaction to occur

Question 5

enzyme substrate complex

Answer 5

• forms when an enzyme and substrate successfully collide and bind which results is a lowered activation energy
• enzyme specificity - each enzyme can only catalyse one particular reaction - e.g. maltase can only hydrolyses maltose, not lactose or sucrose
• the active site of an enzyme has a unique shape which is only complementary to its own substrate. other molecules do not have the correct shape to fir into its active site

Question 6

denature

Answer 6

when the active site changes shape - this means the substrate can no long bind to the active site and no more enzyme substrate complexes can be formed

Question 7

enzyme inhibitor complex

Answer 7

• when an enzyme and inhibitor successfully collide and bind
• prevents the enzyme-substrate complexes from forming

Question 8

lock and key hypotheses

Answer 8

• model stating the enzyme is like a lock and the substrate is the key
• the substrate fits into the enzyme due to the enzymes specific tertiary structure
• they MUST be complementary to one another to form an enzyme-substrate complex - ESC

Question 9

induced fit hypothesis

Answer 9

• The modified model of enzyme activity
• The enzyme and its active site (and sometimes the substrate) can change shape slightly as the substrate molecule enters the enzyme
• These changes in shape are known as conformational changes
• The conformational changes ensure an ideal binding arrangement between the enzyme and substrate is achieved
• This maximizes the ability of the enzyme to catalyse the reaction
• this puts strain on the substrate weakening the bonds
• lowering the activation energy

Question 10

describe one similarity and one difference between the induced fit model of enzyme and the lock and key model of enzyme action

Answer 10

similarity - substrate fits/binds to the active site or enzyme substrate complex formed

difference - active site changes shape but does not change in key
active site not complementary with induced fit but is complementary with lock and key

Question 11

Explain why maltase:
- only breaks down maltose
- allows this reaction to take place at 37 degrees (3)

Answer 11

maltase’s tertiary structure means it has an active site only complementary to maltose.
- induced fit model means that it alters the shape of its active site to be more complementary to maltose.
- maltase is a biological catalyst so it lowers the activation energy by forming an enzyme-substrate complex