C1.1 enzymes & metabolism

What are biological catalysts?

They are substances that speed up chemical reactions without being used up.

How do enzymes speed up reactions?

By lowering the activation energy

What does it mean that enzymes are specific?

It means one enzyme usually catalyzes only one specific reaction or a closely related set of reactions.

What is the physical structure of an enzyme?

They are globular proteins that are soluble and compact.

What is an active site?

A small, precisely shaped pocket formed by the 3-D folding of the polypeptide; the area where the enzyme bind to its specific substrate

How do side chains in the active site contribute to catalysis?

They position, stabilize, or stress bonds in the substrate.

What happens if a mutation changes active-site residues?

It can lead to a loss or change of enzyme function.

What is metabolism?

All of the enzyme-catalyzed reactions in a cell

How do enzymes provide direction and control to metabolic pathways?

They can turn steps on or off and route intermediates.

How are enzymes organized in a metabolic pathway?

Each step needs a different enzyme; the products of one reaction become the substrates for the next.

What is an induced-fit binding?

The active site is flexible, and substrate binding induces a better fit to improve orientation and strain bonds.

What is the effect of induced fit on activation energy?

It aligns catalytic groups to lower the activation energy (

What are anabolic reactions?

Reactions that build larger molecules, require energy (ATP), and often involve condensation.

What are catabolic reactions?

Reactions that break molecules apart, release energy, and often involve hydrolysis.

How do molecules move in a solution?

They move randomly via Brownian motion.

What is required for a successful collision in catalysis?

The substrate and active site must collide with the correct orientation and sufficient energy.

What does enzyme specificity depend on?

The shape and chemical complementarity of the active site.

What is denaturation?

The disruption of weak bonds leading to a loss of shape, meaning the active site no longer fits the substrate and activity falls.

What does the graph of enzyme activity vs. pH typically look like?

A bell-shaped curve with an optimal peak.

What does the graph of enzyme activity vs. temperature look like?

An asymmetrical curve that rises to an optimum and then drops sharply due to denaturation.

What does the graph of enzyme activity vs. substrate concentration look like?

The rate increases rapidly at first and then plateaus as all active sites become saturated.

How can you measure enzyme-catalyzed reactions?

By measuring product formed (e.g.,

What controls should be kept constant during enzyme measurements?

Enzyme amount, temperature, and pH.

Advantage of enzyme-substrate specificity

1. control when the reaction occurs

2. control where the reaction occurs

3. ​ enzymes are specific to one substrate