A-Level AQA Biology ATP, Water & Inorganic Ions: 1. Describe the induced-fit mode

Question

1. Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst.

The induced-fit model suggests that when a substrate binds to the active site of an enzyme, the active site undergoes a conformational change. This change helps to better fit the substrate and promotes the formation of enzyme-substrate complexes.

More specifically, the substrate binds to the active site, which may not initially match perfectly. Upon binding, the active site alters its shape slightly, allowing for a more effective interaction with the substrate. This fit is not completely rigid but flexible, indicating a dynamic relationship between the enzyme and substrate.

This model emphasizes that the enzyme lowers the activation energy required for the reaction to occur, thus acting as a catalyst.

2. Scientists investigated the action of the enzyme ATP synthase. They made reaction mixtures each containing:
   - a ATP synthase
   - buffer (to control pH)
   - substrates.
   One of the substrates required in these reaction mixtures is inorganic phosphate (Pi).
   Tick (✓) one box to show which other substrate the scientists must add to the reaction mixtures to produce ATP.

√ Adenosine diphosphate

3. The scientists investigated the effect of concentration of inorganic phosphate (Pi) on ATP synthase activity.
   After 2 minutes, they stopped each reaction and then measured the concentration of ATP.
   
   Figure 1 shows the scientists’ results.
   Suggest and explain a procedure the scientists could have used to stop each reaction.

A procedure to stop the reactions could involve boiling the mixtures. This would denature the enzyme (ATP synthase) and prevent any further reactions from taking place.

4. Explain the change in ATP concentration with increasing inorganic phosphate concentration.
   With increasing concentrations of inorganic phosphate, more enzyme-substrate complexes are formed, increasing the production of ATP. Until a certain point, where all enzyme active sites are fully occupied, further increases in inorganic phosphate concentration do not significantly increase ATP production.

1. Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst - AQA - A-Level Biology - Question 1 - 2021 - Paper 1

Worked Solution & Example Answer:1. Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst - AQA - A-Level Biology - Question 1 - 2021 - Paper 1

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst.

Tick (✓) one box to show which other substrate the scientists must add to the reaction mixtures to produce ATP.

Suggest and explain a procedure the scientists could have used to stop each reaction.

Explain the change in ATP concentration with increasing inorganic phosphate concentration.

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