GCSE Biology - Enzymes - How Temperature and pH Affect Rate of Reaction

Summary

This video explains how temperature and pH affect enzyme activity and the rate of enzyme-controlled reactions. It highlights that increasing temperature initially boosts the reaction rate due to higher kinetic energy but beyond a certain point (around 37°C), the enzyme becomes denatured and loses function. Similarly, deviations in pH from the enzyme’s optimal range can cause denaturation. The video also introduces key terms like 'optimum temperature' and 'optimum pH,' and provides examples such as stomach enzymes functioning best in acidic conditions. Viewers are invited to explore more on the accompanying learning platform.

Takeaways

• 🌡️ Temperature affects enzyme activity: higher temperatures increase the reaction rate up to a point.
• ⚡ Increased kinetic energy at higher temperatures makes particles collide more often, speeding up the reaction.
• 🌡️ Above 37°C, the enzyme's bonds start to break, altering the shape of the active site.
• 🛑 At 45°C, enzymes become denatured, meaning they can't function anymore, and the damage is permanent.
• 🎯 The optimal temperature for enzyme activity is 37°C, where the reaction rate is highest.
• 🔄 Each enzyme has a specific optimal temperature that varies depending on its environment.
• 🧪 pH also influences enzyme function; too high or too low pH decreases the reaction rate.
• 🔗 Like temperature, pH can break bonds in enzymes, changing their active site and slowing down reactions.
• ❌ Extreme changes in pH can denature enzymes, rendering them unable to catalyze reactions.
• 📊 Enzymes in the human body generally have an optimal pH of 7, but stomach enzymes work best at pH 2.

Q & A

What happens to the rate of an enzyme-controlled reaction as the temperature increases initially?

As the temperature increases initially, the rate of the enzyme-controlled reaction also increases. This is because the particles gain more kinetic energy, making collisions between enzymes and substrates more likely.

Why does the rate of reaction decrease after 37°C?

The rate of reaction decreases after 37°C because high temperatures begin to break the bonds holding the enzyme's structure together. This causes the enzyme's active site to change shape, reducing its ability to bind with the substrate, eventually leading to denaturation.

What is the term used when an enzyme permanently loses its ability to function due to high temperatures?

The term used is 'denatured.' When an enzyme becomes denatured, its structure changes permanently, and it can no longer bind to the substrate, even if the temperature is lowered.

At what temperature does the enzyme in the video become denatured?

In the video, the enzyme becomes denatured at around 45°C.

What is meant by the 'optimum temperature' for an enzyme?

The 'optimum temperature' is the temperature at which the enzyme's rate of reaction is highest. For most human enzymes, this is around 37°C.

How does pH affect enzyme activity?

pH affects enzyme activity by altering the bonds holding the enzyme together. If the pH is too high or too low, it can change the shape of the enzyme's active site, reducing its ability to bind with substrates and ultimately denaturing the enzyme.

What happens to the enzyme's active site when pH levels are outside the optimal range?

When pH levels are outside the optimal range, the enzyme's active site starts to change shape. Initially, the substrate can still fit but less efficiently, slowing the reaction. Eventually, the active site changes so much that the substrate can no longer bind, and the enzyme becomes denatured.

What is the optimal pH for most enzymes in the human body?

The optimal pH for most enzymes in the human body is around neutral, or pH 7.

Why do enzymes in the stomach have a different optimal pH than other enzymes in the body?

Enzymes in the stomach have an optimal pH of around 2 because they need to function in the stomach's highly acidic environment, unlike other enzymes that operate in more neutral conditions.

Can an enzyme regain its function if the temperature is lowered after it has been denatured?

No, once an enzyme has been denatured due to high temperatures, the damage is permanent, and it cannot regain its function even if the temperature is lowered.