Chapter_6-METABOLISM

Chapter 6: Metabolism

Energy in Building and Breaking Down Molecules

• Energy Gained: Anabolic reactions (building molecules) gain energy.

• Energy Released: Catabolic reactions (breaking down molecules) release energy.

Catabolism vs. Anabolism, Exergonic vs. Endergonic Reactions

• Catabolism:

  • Breaking down complex molecules into smaller ones.

  • Releases energy.

  • Example: Digestive enzymes breaking down food.

• Anabolism:

  • Synthesizing larger molecules from smaller ones.

  • Requires energy.

  • Consumes energy to build complex molecules from simpler ones.

  • Examples: Linking amino acids to form proteins, photosynthesis.

• Exergonic Reactions:

  • Release energy.

  • Spontaneous.

  • ΔG < 0

• Endergonic Reactions:

  • Absorb energy from surroundings.

  • Non-spontaneous.

  • ΔG > 0

Energy and ATP

• Energy: Capacity to do work.

• ATP (Adenosine Triphosphate): Molecule that carries energy in the cell.

• ATP Cycle: ATP is used for cellular functions, becomes ADP (Adenosine Diphosphate), and then is recharged back into ATP.

• Energy Source for ATP Recharge: Comes from food, specifically from catabolic reactions.

• ATP is a renewable and reusable energy shuttle.

Enzymes

• Definition: Proteins that speed up chemical reactions.

• Function: Biological catalysts.

• Reduced activation energy of a reaction.

• Important for metabolic processes.

• Active Site: The region on the enzyme where the substrate binds.

• Substrate: The material upon which an enzyme acts, which is converted into a product.

• Catalyst: An agent that speeds up a chemical reaction without being consumed by the reaction.

Environmental Factors Affecting Enzyme Activity

• Temperature

• pH

• Salt concentration

• Specific chemicals

ATP Metabolism

• Adenine -- Ribose -- 3 Phosphate groups

Endergonic vs. Exergonic Reactions

Allosteric Inhibitors

• Modify the active site of the enzyme.

• Reduce or prevent substrate binding.

• Regulate metabolism by altering enzyme activity.

Enzyme Denaturation Example

• Enzyme in tube "B" likely denatured due to high heat.

• Denaturation means the enzyme lost its active site and can no longer function.

Mechanism of Enzyme Action

• Reduce activation energy.

• Speeds up the chemical reactions.

Characteristics of Enzymes

• Most are proteins.

• Lowers activation energy.

• Specific to their substrate.

• Reusable.

• Unchanged by the reaction.

Catalase and Hydrogen Peroxide

• Catalase enzyme breaks down hydrogen peroxide (H202) into water (H2O) and oxygen (O2)

• Catabolism H202 (big) ——→ H2O + O2 (small) =release of energy

• This process illustrates the principle of catabolism, where larger molecules are broken down into smaller ones, resulting in the release of energy, which is essential for cellular functions and metabolic processes. Catalase plays a crucial role in preventing oxidative damage by facilitating this reaction, thereby maintaining cellular health.

• O2 → H2O + O2, which highlights its role in cellular detoxification by converting harmful peroxide into harmless products.

• This reaction prevents the accumulation of toxic hydrogen peroxide, a byproduct of cellular metabolism in aerobic organisms.

Coupling of Exergonic and Endergonic Reactions

• Energy released by an exergonic reaction is used to drive an endergonic reaction.

Exergonic and Endergonic Reactions Diagrams

• Exergonic: Reactants have higher energy than products; ΔG is negative.

• Endergonic: Reactants have lower energy than products; ΔG is positive.