Enzymes and Their Functions

Enzymes Overview

• Enzymes are organic catalysts that speed up biochemical reactions.
• They are specific to particular reactions or related reaction groups.
• Many reactions cannot happen without the appropriate enzyme.
• Enzymes are commonly named with the suffix "ase" reflecting their substrate (e.g., dehydrogenases remove hydrogen).

Key Terms

• Enzyme: Proteins that act as catalysts in biochemical reactions.
• Substrate: The reactant(s) acted upon by enzymes.
• Active Site: The specific region on an enzyme where the substrate binds.
• Enzyme-Substrate Complex: The temporary complex formed when a substrate binds to the active site of an enzyme.

Lock and Key Model

• The shape of the enzyme's active site is complementary to the substrate.
• Only substrates that fit the active site can bind, illustrating enzyme specificity.

Induced Fit Theory

• The enzyme's active site may change shape to fit the substrate closely during binding.
• This change can lower the energy required to break or form bonds in chemical reactions.
• Enzymes do not form permanent bonds with substrates and are reusable.

Denaturation

• High temperatures, extreme pH changes, heavy metals, and UV radiation can denature enzymes.
• Denaturation alters the enzyme's shape, impacting its function.
• If denaturation is mild, some enzymes can regain their original structure.

Effects of Temperature

• Increased temperatures enhance molecular movement, raising the rate of enzyme-substrate interactions.
• However, excessively high temperatures can cause denaturation, reducing enzyme functionality.

pH Levels

• Each enzyme has an optimal pH, determined by its typical biological environment (e.g., pepsin in acidic stomach conditions, trypsin in neutral small intestine).
• Altering an enzyme's pH can disrupt ionic interactions and hydrogen bonding, resulting in a loss of shape and function.

Metabolic Pathways

• Metabolism is the sum of all chemical reactions within cells, with specific enzymes catalyzing each step.
• Each substrate may be processed by multiple enzymes through metabolic pathways.

Regulation of Enzymes

• Enzyme activity can be regulated by genetic mechanisms, adjusting the concentration of enzymes.
• Regulation can be achieved via feedback inhibition, competitive inhibition, and noncompetitive (allosteric) inhibition.

Competitive Inhibition

• A molecule similar in shape to the substrate competing for the active site, preventing substrate binding.

Noncompetitive/Allosteric Inhibition

• An inhibitor binds to a site other than the active site, altering the shape of the enzyme and its active site functionality.

Allosteric Regulation

• Activators: Bind to allosteric sites to stabilize the active form of an enzyme.
• Inhibitors: Stabilize the inactive form of the enzyme.

Feedback Inhibition

• A product of a metabolic pathway can inhibit its own production to maintain homeostasis (e.g., heat inhibiting thermoregulation).

Coenzymes

• Many vitamins act as coenzymes, assisting enzyme function.
• Significant coenzymes include NAD+, FAD, and NADP+, which serve as electron carriers in metabolic processes.

NAD+ (Nicotinamide Adenine Dinucleotide)

• Involved in cellular respiration, it carries two electrons and facilitates oxidation reactions by removing hydrogen atoms.

FAD (Flavin Adenine Dinucleotide)

• Can be reduced to FADH2 and transfers electrons in metabolic reactions.

NADP+ (Nicotinamide Adenine Dinucleotide Phosphate)

• Functions similarly to NAD+, carrying electrons involved in photosynthesis and facilitating the reduction of CO2 into carbohydrates.

This quiz covers the essential concepts of enzymes, including their role as catalysts in chemical reactions. It highlights the specificity of enzymes, their organic nature, and the importance of the right enzyme for reactions to occur. Test your knowledge on key terms and functions related to enzymes.