Proteins and Enzymes: Intro to Cell Biology

Proteins and Enzymes Overview

• The lesson focuses on proteins and enzymes within Unit 1 (Cell Biology).
• Prior knowledge of key areas 1, 2, and 3 is recommended.
• Refer to the national 5 biology course specification for assessable content.
• Learning intentions include understanding protein production, types, enzyme functions, properties, specificity, and the impact of temperature/pH on enzyme activity.

Types of Proteins

• Protein shape determines its specific function.
• The sequence of amino acids dictates protein shape and function.
• Five main types of proteins exist in plants and animals: structural, hormones, antibodies, receptors, and enzymes (SHARE mnemonic).
• Structural proteins are found in skin, hair, nails, and provide protection.
• Hormones are chemical messengers transported via blood to target organs.
• Antibodies are produced by lymphocytes (white blood cells) to combat pathogens.
• Receptors are proteins on cell membranes that bind to substances like hormones.
• Enzymes speed up chemical reactions.

Enzymes: Properties

• Enzymes main properties are that they a biological catalysts speeds up chemical reactions in living things.
• It's crucial for life because key reactions wouldn't occur fast enough without enzymes.
• All living cells produce enzymes.
• Enzymes remain unchanged during reactions, allowing reuse.
• Enzymes are specific to their substrate.

Enzyme Reactions

• Enzyme reactions structure: substrate -> enzyme -> product.
• The substrate is the molecule the enzyme acts upon.
• The enzyme goes above the arrow in reaction diagrams, not beside the substrate.
• The enzyme's placement above the arrow signifies that it isn't consumed in the reaction.

Stages of Enzyme Reaction

• Substrate binds to the enzyme at the active site.
• The active site's share is complementary to the substrate, is specific.
• Formation of an enzyme-substrate complex occurs, facilitating the reaction.
• Products are created and released from the active site.
• The enzyme reverts to its original shape and can be reused.

Types of Enzyme Reactions

• Two types of reactions: degradation and synthesis.
• Degradation reactions involve breaking down larger molecules into smaller ones.
• Synthesis reactions involve building up smaller molecules into larger ones.

Degradation Reactions: Examples

• Starch broken down by amylase into maltose (Starch Amylase Maltose).
• Hydrogen peroxide broken down by catalase into oxygen and water (Hydrogen Peroxide Catalase).
• Fats broken down by lipase into fatty acids and glycerol.
• Protein broken down by pepsin into amino acids.
• Most enzymes have an "ase" ending.

Synthesis Reactions: Example

• Glucose-1-phosphate built up by phosphorylase to make starch (G1PPs).

Factors Affecting Enzyme Activity

• Each enzyme has optimum conditions where it's most active.
• Temperature and pH affect enzyme and protein activity.

Temperature and Enzyme Activity

• Temperature-enzyme activity graphs have a characteristic shape.
• The optimum temperature is where enzyme activity is highest.
• As temperature increases from zero, enzyme activity increases until the optimum.
• Beyond the optimum temperature, enzyme activity decreases, DO NOT say denatures.
• At very high temperatures, the enzyme denatures (active site changes shape)
• Different enzymes have different optimum temperatures, not always 37°C.

Denaturing

• Denaturing means the enzyme's active site changes shape, preventing substrate binding.

Enzyme Activity Factors

• Enzymes exhibit substrate specificity due to their active site's shape.
• Change in the active site shape prevents substrate binding, halting enzyme activity.
• pH influences enzyme activity; each enzyme has an optimal pH for peak activity.
• Enzymes generally function best at a neutral pH of around 7

Enzyme Examples

• Pepsin (stomach enzyme) functions at an optimum pH of 2
• Trypsin (small intestine enzyme) has an optimum pH of 8
• Pepsin functions within a pH range of 0-4, while Trypsin operates between 5.5-10
• Enzymes do not share optimum pH or temperature levels

Quick review questions

• Enzymes are made of proteins, not carbohydrates
• Catalase, not starch, breaks down hydrogen peroxide into water
• The optimum is the name given to the conditions in which an enzyme is most active
• Temperature and pH, not sunlight, are factors affecting enzyme activity
• Enzymes are proteins