Core Idea I - Enzymes

What are enzymes?

Enzymes are biological catalysts.

What type of proteins are most enzymes considered to be?

Most enzymes are 🟢globular proteins🟢.

What is the main function of enzymes in the context of the rate of chemical equations?

Enzymes ⬆speed up chemical processes⬆ while remaining unchanged in the process.

What are the 4 categories of amino acids that enzymes consist of?

1. Catalytic residues

   • Make/Break chemical bonds

2. Binding residues

   • Hold the substrate in place during catalysis.

3. Structural residues

   • Maintain the correct gloublar (RECAP: Enzymes are gloublar proteins) shape of the active site.

4. Non-essential residues

   • No specific function → Can be removed/replaced without loss of function!!

What are some properties of enzymes?

• Highly efficient in very small amounts!

• Highly specific → responsible for ability to catalyse only certain chemical reactions.

• 🛞REVERSIBLE🛞 reactions [enzyme-catalysed]

• Enzymes are easily denatured at high temperature/heat.

• Activity can be affected by various factors!

What are the 2 types of metabolic reactions?

1. Anabolic reactions: Help to synthesize complex substances → using up energy in the process.

2. Catabolic reactions: Help to breakdown complex substances into simpler ones → releasing energy in the process.

What happens to the rate of metabolic reactions without enzymes?

The rate of metabolic reactions 💀cannot be fast enough to sustain life💀.

What is the active site?

It is a 🚸small groove/cleft🚸 on the surface of an enzyme!

What does the active site consist of?

The active site typically consists of 3 to 12 amino acids from different parts of a single polypeptide chain, held together by hydrophobic interactions, hydrogen bonds, ionic bonds, and/or disulfide bonds.

What is the function of the catalytic and the binding residues in the active site?

• CATALYTIC residues: R-groups help to catalyse the ➡conversion of the substrate to the product➡.

• BINDING residues: Hold the substrate in the active site by 😭weak interactions😭.

What components of the active site is complementary to the substrate?

• Specific 3-dimensional configuration

• Charge

What is the specificity of the enzyme determined by?

Determined by the primary structure of the polypeptide; this determines the 🥉three-dimensional configuration🥉!!

Describe the lock-and-key hypothesis!

• The hypothesis views 🪨enzymes as rigid🪨, having an active site with a fixed shape!

• The enzyme (LOCK) is ✅perfectly complementary✅ to the substrate (KEY) in terms of shape, size and charge!

• The substrate binds to the enzyme’s active site to form the enzyme-substrate complex.

Describe the induced-fit hypothesis!