5. Enzymes (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025) @IGCSEStudyBuddy

Summary

This IGCSE study video covers the role of enzymes in biology. Enzymes are proteins that act as biological catalysts, accelerating metabolic reactions without being consumed. They are specific to their substrates, fitting like a lock and key. Factors like temperature and pH affect enzyme activity, with each enzyme having an optimum level for maximum efficiency. Deviations from this optimum can cause denaturation, rendering enzymes ineffective.

Takeaways

• 🧬 Enzymes are biological catalysts that speed up metabolic reactions in living organisms without being consumed in the process.
• 🔑 The active site of an enzyme is a specific region that fits the substrate like a lock and key, ensuring that enzymes are highly specific to their substrates.
• 🔄 Enzymes remain unchanged after the reaction, allowing them to be used repeatedly in catalyzing reactions.
• 🍽️ Digestive enzymes are crucial for breaking down food molecules efficiently, providing necessary energy and nutrients for survival.
• 🌡️ Temperature affects enzyme activity, with an increase in temperature generally leading to an increase in reaction rate due to greater kinetic energy of molecules.
• 🌡️ Each enzyme has an optimum temperature at which it functions best, and temperatures too high can denature enzymes, altering their active site and inactivating them.
• 📉 Low temperatures can reduce enzyme activity without denaturing them, as molecules have less kinetic energy and fewer successful collisions occur.
• 📊 The rate of enzyme-catalyzed reactions typically increases with temperature up to an optimum point, after which it decreases due to denaturation.
• 🅿️ pH is another critical factor influencing enzyme activity, with each enzyme having an optimum pH level at which it works best.
• 🔄 Deviations in pH from the optimum can cause enzyme denaturation by breaking bonds, altering the active site shape, and reducing enzyme function.

Q & A

What is a catalyst and how does it relate to enzymes?

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. Enzymes are biological catalysts that are proteins made in living cells, which speed up the rate of metabolic reactions.

Why are enzymes essential for living organisms?

Enzymes are essential because they speed up metabolic reactions that would otherwise occur too slowly to sustain life. They maintain the necessary reaction rates for processes like digestion, which provide energy and nutrients.

What is a substrate in the context of enzymes?

A substrate is the substance upon which an enzyme acts. It is the molecule that the enzyme binds to and transforms during a metabolic reaction.

How does the shape of an enzyme's active site relate to its function?

The shape of an enzyme's active site is crucial as it must fit the substrate exactly for the enzyme to function. This is known as the lock and key mechanism, where the enzyme's active site and the substrate's shape are complementary.

What is meant by the term 'enzyme specificity'?

Enzyme specificity refers to the fact that an enzyme will only act on certain substrates with which it has a complementary shape, ensuring that the enzyme binds only to its specific substrate.

How does temperature affect enzyme activity?

As temperature increases, so does the rate of enzyme-catalyzed reactions due to increased molecular motion and kinetic energy. However, each enzyme has an optimum temperature beyond which it can become denatured and lose its function.

What happens to an enzyme if the temperature becomes too high?

If the temperature is too high, the enzyme's structure can become denatured, causing the bonds in the enzyme to break and altering the shape of the active site, which prevents the enzyme from functioning.

What is the significance of an enzyme's optimum pH?

An enzyme's optimum pH is the pH level at which it works most efficiently. Deviations from this pH can cause the enzyme to denature by breaking the bonds in its structure, changing the active site's shape and reducing its activity.

How do different enzymes have different optimum pH levels?

Different enzymes have evolved to function optimally in different pH environments depending on their location within the body. For example, pepsin in the stomach works best at a low pH, while amylase in saliva functions best at a neutral pH.

Can you provide an example of how pH affects enzyme function?

Yes, pepsin, which is found in the stomach, has an optimum pH of around 2 and will not function effectively at the neutral pH of 7, unlike amylase, which is found in saliva and works best at a pH of 7.