A Level Biology Revision "The Effect of Temperature on Enzyme Controlled Reactions" | Freesciencelessons YouTube Video Summary

Temperature and Enzyme Reactions

Freesciencelessons begins by outlining the key objectives: describing the impact of temperature on enzymes and understanding the temperature coefficient (Q10) for OCR syllabus followers.

Enzyme-Substrate Collisions

The video reinforces that the rate of enzyme-controlled reactions depends on the frequency of successful collisions between the substrate and enzyme's active site. The frequency is quantified as collisions per second. By plotting the amount of product formed against time, one can derive the rate of an enzyme controlled reaction.

Investigating Temperature Effects

To investigate, you need to select an enzyme to measure product formation against time. These procedures should be repeated over a range of different temperatures to measure any fluctuations. Tangents are drawn on these graphs to measure the rate of reaction at each temperature, and it's important to draw tangents at the same time point for each of the reactions.

Results of Enzyme Reactions

The video uses an example graph of a hypothetical experiment showcasing the amount of product against time, at different temperature values, to showcase this principle. Each graph represents the same enzyme controlled reaction, each time the temperature differs. An increase in temperature, up to 40 degrees celsius shows an increase in the rate of reaction. A line indicating a 50 degree celsius reaction rate is a much flatter line, showcasing that the reaction is much slower, to the point where enzymes may not function at all.

Temperature's Effect on Reaction Rate

The presenter at Freesciencelessons shares that the rate increases with temperature, due to increased kinetic energy of both enzyme and substrate. This is until it hits its optimum temperature, and begins to decrease. Molecules moving more rapidly will increase the chances of collisions between the substrate with an active site. After the optimum temperature has been surpassed, the vibrations of enzyme molecules cause hydrogen bonds to break, which causes the tertiary structure of enzymes to change. Due to this change, the active site no longer is complementary to the substrate, which then causes the enzyme to denature.

Temperature Coefficient (Q10)

Q10, or temperature coefficient, measures how reaction rate changes with a 10°C increase. It's the rate at temp X + 10°C divided by the rate at temp X. As a general rule, a 10°C increase doubles the reaction rate, giving a Q10 of around 2, but only until after it passes the optimum temperature, in which enzymes denature.