Enzymes and Metabolic Regulation

This page focuses on the role of enzymes in metabolic pathways and introduces concepts of enzyme regulation and inhibition.

Enzymes are crucial in lowering the activation energy (Ea) of reactions, thereby increasing reaction rates without changing the overall energy change (ΔG) of the reaction. The page illustrates this concept with an energy diagram showing how enzymes reduce the energy barrier.

Vocabulary: Activation energy (Ea) is the energy difference between the reactant state and the transition state, representing the energy barrier that must be overcome for a reaction to proceed.

The document introduces feedback inhibition as a regulatory mechanism in metabolic pathways. This process involves the end product of a pathway inhibiting an earlier enzyme in the same pathway.

Definition: Feedback inhibition is a regulatory mechanism where the final product of a metabolic pathway inhibits one of the earlier enzymes in that pathway, effectively turning off the production when sufficient product has accumulated.

Two types of enzyme inhibition are discussed:

1. Competitive inhibition: An inhibitor molecule competes with the substrate for the enzyme's active site.
2. Non-competitive inhibition: The inhibitor binds to an allosteric site, changing the shape of the active site.

Highlight: Competitive and non-competitive enzyme inhibition in metabolic pathways are crucial mechanisms for regulating cellular metabolism and maintaining homeostasis.

The page also touches on the differences between endotherms (mammals and birds) and ectotherms (reptiles and amphibians) in terms of energy use and temperature regulation.

Cellular Respiration Overview

This page provides an introduction to cellular respiration, presenting its overall formula and a basic flow chart of the process.

The general formula for cellular respiration is given as:

Fuel (glucose) + Oxygen + ADP + Pi → CO₂ + H₂O + ATP

Definition: Cellular respiration is the metabolic process by which cells convert the energy stored in nutrients (like glucose) into ATP, the cell's primary energy currency.

The page presents a balanced equation for the complete oxidation of glucose:

C₆H₁₂O₆ + 6O₂ + ADP + Pi → 6CO₂ + 6H₂O + ATP

The document then introduces the initial stage of cellular respiration: glycolysis. This process breaks down glucose into smaller molecules and can occur without oxygen present.

Highlight: Glycolysis is the first step in cellular respiration and can proceed under both aerobic and anaerobic conditions, generating a small amount of ATP.

The role of electron carriers, specifically NAD+ (nicotinamide adenine dinucleotide), is mentioned. NAD+ picks up high-energy electrons, becoming NADH in the process.

Vocabulary: NAD+ (nicotinamide adenine dinucleotide) is an important coenzyme in cellular respiration that acts as an electron carrier, accepting electrons and protons to become NADH.

The page briefly touches on fermentation, which can occur in the absence of oxygen, but does not elaborate on the process.

Example: The transition from NAD+ (empty carrier) to NADH (full carrier) illustrates how electron carriers function in the cellular respiration process.

This overview sets the stage for a more detailed exploration of the cellular respiration pathway in subsequent lessons.