SB1. Key Concepts in Biology - Factors affecting enzymes

Question 1

SB1e - What are enzymes and what are they made up of made up of?

Answer 1

• Enzymes are biological catalysts that speed up reactions.
• They break down proteins/substances called substrates.
• Enzymes are made up of amino acids and they are proteins.
• They are needed to speed up reactions we cannot live without

Question 2

SB1g - What is the lock and key model?

Answer 2

• The lock and key model is a model of how enzymes work - it compares enzyme action to a lock and key because of how the substrate and active site fit together
• When the substrate binds to the active site, it forms the Enzyme-Substrate complex.
• After the enzyme catalyses the reaction, the products are released because they no longer fits tightly into the active site
• The enzyme is free to be used again

Question 3

SB1g- How are enzymes denatured?

Answer 3

• Changes in pH and temperature can affect the shape of an enzymes active site.
• When the active site can no longer accept any substrates, it is said to have become denatured.

Question 4

SB1h - Explain how the rate of enzyme reaction is affected by temperature

Answer 4

• At very low temperatures, the particles do not have enough energy to move, so the enzyme is inactive; the rate of reaction is very low
• As the temperature increases, particles begin to move more as they gain kinetic energy; the rate of reaction will increase
• Eventually, the enzyme reachs an optimum temperature where it is working at it’s fastest
• However, if the temperature increases too far beyond that, the active site will begin to chagne shape and the rate of reaction will decrease
• Eventually, if high enough temperatures are reached, the shape of the active site is changed to a point where the substrate is no longer able to bind to it. It becomes denatured.

Question 5

SB1h - How is enzyme activity affected by pH?

Answer 5

• An enzyme has an optimum pH where it works best.
• The further away from this, it will get slower till it becomes denatured

Question 6

SB1h- Explain how the rate of enzyme action is affected by substrate concentration

Answer 6

• At first, the more substance you use, the higher the rate of reaction as it causes more collisions to occur
• However, at high concentrations most enzyme active sites conatin substrate molecules therefore there is no benefit to adding more substrate, the rate of reaction won’t increase beyond that point

Question 7

SB1h CP - How do you calculate rate of reaction in enzyme-controlled reactions?

Answer 7

1/time