Ocr As Biology - Factors Affecting Enzyme Activity

Front 1

Explain how temperature has an affect on the rate of reaction.

Back 1

• A higher temperature means more kinetic energy in the molecules, resulting in the molecules moving faster.
• This makes the enzyme more likely to collide with a molecule and also the energy of these collisions also increase, which means that each collision is more likely to result in a reaction.

Front 2

Explain how temperature has an affect of the enzyme itself.

Back 2

• A rise in temperature makes the enzymes molecules vibrate more.
  
• If the temperature goes above a certain level, this vibration breaks some of the bonds holding the enzyme in shape.
• This makes the active site change shape and the substrate can no longer fit.
  
• At this point, the enzyme is denatured (it no longer functions as a catalyst).

Front 3

What is the optimum temperature of most enzymes in a human?

Back 3

37°C.

Front 4

What is the temperature coefficient (Q10)? How does it work?

Back 4

• It shows how much the rate of a reaction changes when the temperature is raised by 10°C.
  
• At temperatures before the optimum, a Q10 value of two means that the rate doubles when the temperature is raised by 10. A Q10 value of 3 means that the rate would triple.
• Most enzyme-controlled reactions have a Q10 value of around 2.

Front 5

All enzymes have an optimum pH value. What pH do most human enzymes work best at? Name an exception to this.

Back 5

• Most human enzymes work best at pH 7 (neutral).
• Pepsin, works best at pH 2 (acid) as it is found in the stomach.

Front 6

What effect does pH have on an enzyme itself?

Back 6

• Above and below the optimum pH level, the H+ and OH- ions found in acids and alkali's can break the ionic and hydrogen bonds that hold the enzymes tertiary structure in place.
  
• This causes the enzymes active site to change shape, causing the enzyme to denature.
  

Front 7

Explain how enzyme concentration affects the rate of reaction. What could limit the rate of reaction when looking at this variable?

Back 7

• The more enzyme molecules there are in a solution, the more likely it is for a substrate molecule to collide with an enzyme. So increasing the concentration of enzyme increases the rate of reaction.
• But if the substrate amount is limited, there comes a point where there's more than enough enzyme molecules to deal with the available substrate, so adding more has no affect.

Front 8

Explain how substrate concentration affects the rate of reaction. What could limit the rate of reaction when looking at this variable?

Back 8

• The higher the substrate concentration, the faster the reaction - more substrate molecules means a collision between a substrate molecule and enzyme is more likely, therefore more active sites will be used up.
  
• This is only true until the saturation point, which is then all active sites are used up and the rate of reaction will begin to level of, adding substrate will make no difference to the rate of reaction.

Front 9

What happens to substrate concentration as the reaction progresses and how does this affect the rate of reaction? What point in the reaction has the highest rate of reaction?

Back 9

Substrate concentration decreases during a reaction (unless more is added), this results in a decrease in rate of reaction over time. This makes the initial rate of reaction the highest.