Enzymes

Question 1

Define enzymes

Answer 1

Enzymes are biological catalysts that speed up the rate of reactions without themselves being chemically changed at the end of reactions so they can be reused and are effective in small concentrations

Question 2

What are anabolic reactions

Answer 2

Anabolic reactions are reactions that build up simpler molecules into complex molecules

Question 3

What are catabolic reactions

Answer 3

Catabolic reactions are reactions that break down complex molecules into simpler molecules

Question 4

Define activation energy

Answer 4

Activation energy is the minimum energy that must be supplied to reacting molecules for them to react

Question 5

Explain the induced fit model

Answer 5

• Active site of enzyme is complimentary in shape but not perfect fit for substrate
• When substrate binds to enzyme, it induces a change in shape of active site
• This allows substrate to fit more tightly in active site, forming an enzyme-substrate complex
• Products released into surroundings once formed as they no longer fit in active site

Question 5

Explain the lock and key hypothesis

Answer 5

• Substrate is a key and enzyme is a lock
  -Substrate has a shape that is complimentary to shape of active site of enzyme
• Active site of enzyme has shape that substrate can fit into exactly
• Substrate binds to active site of enzyme, forming an enzyme-substrate complex
• products released into surrounding medium once formed as they no longer fit in active site of enzyme

Question 6

What are the characteristics of enzymes

Answer 6

• Speed up chemical reactions by lowering activation energy
• Remain chemically unchanged after reactions
• Required in small concentrations
• Specific in action

Question 7

What are the factors affecting rate of enzyme-catalysed reaction

Answer 7

• Temperature
• pH
• Enzyme concentration
• Substrate concentration

Question 7

Explain how varying temperature affects rate of reaction

Answer 7

• At low temperatures, rate of enzyme activity is low as they are inactive
• As temperatures increase, kinetic energy of substrate and enzyme molecules increases
• Enzymes start becoming more active
• Frequency of effective collisions between substrate and enzyme molecules increases
• Number of enzyme-substrate complexes formed increases
• Rate of reaction is highest at enzyme’s optimum temperature
• As temperature increases beyond enzyme’s optimum temperature, rate of reaction decreases
• Enzymes become denatured, losing their 3D shape

Question 7

Explain how varying pH affects rate of reaction

Answer 7

• Rate of reaction is highest at the enzyme’s optimum pH
• Any pH that deviates from optimum pH will cause rate of reaction to decrease
• At extreme pH, enzymes become denatured, losing their 3D shape

Question 7

Explain how varying enzyme concentration affects rate of reaction

Answer 7

• Rate of enzyme reaction is dependent on number of effective collisions between enzyme and substrate molecules
• Increase in enzyme concentration will increase rate of reaction to a certain point
• Rate of reaction will remain constant even when enzyme concentration increases beyond this point
• Substrate concentration is now the limiting factor as there are not enough substrates for the enzymes

Question 7

Explain how varying substrate concentration affects rate of reaction

Answer 7

• Rate of reaction is dependent on number of effective collisions between enzyme and substrate molecules
• Increasing substrate concentration will increase rate of reaction to a certain point
• Rate of reaction remains constant even when substrate concentration increases beyond that point
• Enzyme concentration is now the limiting factor
• Not enough enzymes for the substrates