Sp 2024-Exam3-SV

Exam 3 Material Overview

• Chapters Covered:

  • Transformation of Energy by Life

  • Chapter 6: Basics of Energy & Metabolism

  • Chapter 7: Cellular Respiration – capturing energy from food

  • Chapter 8: Photosynthesis – capturing light energy in food

Energy Transformation

• Energy is a fundamental characteristic of life, defined as the capacity to do work or create change.

  • Types of Energy:

    • Potential Energy: Stored energy (e.g., chemical bonds, concentration gradients).

    • Kinetic Energy: Energy of movement.

Metabolism

• Definition: The sum of all chemical reactions in an organism.

  • Types of Metabolic Reactions:

    • Anabolic Reactions: Build larger molecules from smaller units; these reactions require energy.

    • Catabolic Reactions: Break down larger molecules into smaller ones; energy is released.

Laws of Thermodynamics

• First Law: Energy cannot be created or destroyed, only transformed. The total energy remains constant.

• Second Law: During energy transformations, some energy becomes unavailable for doing work; no transformation is 100% efficient.

  • Terms:

    • Free Energy: Usable energy.

    • Entropy: Measure of disorder or randomness.

Chemical Reactions

• Reactions can be summarized as:

  • Reactants → Products

• Change in Free Energy (ΔG):

  • Positive ΔG: Free energy consumed (Endergonic reaction).

  • Negative ΔG: Free energy released (Exergonic reaction).

  • Example: Glucose and glucose-6-phosphate reactions with ΔG values.

Endergonic Reactions

• Require energy to proceed.

  • Example: Condensation Reaction

    • Converts small molecules into more complex ones by removing water (H₂O).

Exergonic Reactions

• Release energy.

  • Example: Hydrolysis Reaction

    • Breaks down complex molecules into smaller units, releasing free energy.

ATP (Adenosine Triphosphate)

• Function: ATP captures and transfers free energy; stored in the phosphate bonds.

• Hydrolysis: ATP + H₂O → ADP + P + free energy (ΔG = -7.3 kcal/mole).

Enzymes

• Biological catalysts that speed up reactions by lowering activation energy (Ea).

  • Characteristics:

    • Enzymes are specific to reactants (substrates).

    • Active sites are where substrates bind; shape changes slightly upon binding (Induced Fit Model).

Metabolic Pathways

• Enzymes in pathways work in sequence, each catalyzing a specific reaction.

• Can be activated or inhibited by various molecules and conditions.

Cellular Respiration Overview

• Process: Breakdown of glucose to produce ATP.

• Equation: C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + ~36 ATP.

• Major Steps:

  • Glycolysis

  • Pyruvate Oxidation

  • Citric Acid Cycle

  • Oxidative Phosphorylation

Glycolysis

• Inputs/Outputs: 1 glucose, 2 ATP input, outputs include 2 pyruvate, 4 ATP, and electron carriers.

Pyruvate Oxidation & Citric Acid Cycle (CAC)

• Pyruvate converted to Acetyl CoA for entry into CAC.

• Outputs: Includes NADH, FADH₂, ATP, and CO₂.

Electron Transport Chain (ETC)

• Function: Most ATP is produced here; requires O₂ and produces H₂O.

  • Process: NADH and FADH2 provide electrons to the ETC, driving H+ ions against the concentration gradient.

Photosynthesis

• Overview: Converts solar energy into chemical energy stored in glucose.

• Equation: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

• Stages:

  • Light Reactions: Use light to generate ATP and NADPH.

  • Calvin Cycle: Uses ATP and NADPH to convert CO₂ to sugar.

Light Reactions (Thylakoid Membranes)

• Inputs: Light, water, ADP, NADP+.

• Outputs: O₂, ATP, NADPH.

• Involves electron transport and ATP synthase activity.

Calvin Cycle (Stroma)

• Fixation of CO₂ to produce sugars.

• Rubisco enzyme plays a critical role.

• Requires ATP and NADPH generated from light reactions.

Summary of Processes

• Cellular respiration breaks down glucose to produce ATP; photosynthesis builds glucose from CO₂ and water using light.

• There are two main types of fermentation (lactic acid and alcoholic) when aerobic respiration cannot proceed.