Biology: Chapter 3: Enzymes: Basics

Biology: Chapter 3: Enzymes: Basics

• Enzyme: Protein molecules that act as biological catalysts.
• Biological catalyst: Molecule which speeds up a chemical reactions and remains unchanged at the end of the reaction.

Features of enzymes

• Intracellular: Enzymes that operate within cells.
• Extracellular: Enzymes secreted by cells and catalyse reactions outside cells.
• Globular: Hydrophilic R groups on the outside - Soluble
• Active site: Region (cleft or depression) that another molecule can bind to.
• Substrate: Molecule that binds to enzyme
• Enzyme-substrate complex: Binding of substrate and enzyme through temporary bonding between the R groups of the enzyme's amino acids and the substrate.
• Product: What you're left with after substrate binds with enzyme - Product of the reaction
• Anabolic: Making bonds
• Catabolic: Breaking bonds 

Induced fit

• Lock and key hypothesis: Each type of enzyme is specific to only one type of substrate; only one type of substrate fits in each type of enzyme's active site. However, this has been shown to be not exactly accurate, but instead enzymes and substrates have an induced fit.
• Induced fit: Enzyme, and sometimes substrate, can change shape slightly as the substrate enters the active site to ensure a perfect fit.

• Activation energy: Energy needed before a reaction occurs 
• Many necessary substrates in the body need a higher temperature than 37C before they can react, but it is impossible for us to raise our body temperature that high. 
• Enzymes lower the activation energy without increasing the heat by holding the substrates or substrate in such a way (physically breaking the bonds) they catalyse or by adding another chemical (H20 for hydrolysis/ ions).

Examples of enzymes

• Lactase: Breaks lactose into glucose and galactose. Found in the small intestine.
• Catalase: Breaks Hydrogen Peroxide into water and oxygen. Found in all living organisms.