BIO 1111 Fall 2025 Exam 3 Study Guide

Metabolism Study Guide

1. Catabolism vs. Anabolism

  • Catabolism:

    • Definition: The metabolic pathways that break down molecules into smaller units, releasing energy.

    • Characteristics:

    • Involves the breakdown of complex substances.

    • Produces ATP and other high-energy molecules.

    • Generally exergonic (releases energy).

  • Anabolism:

    • Definition: The metabolic pathways that construct molecules from smaller units, consuming energy.

    • Characteristics:

    • Involves the synthesis of complex molecules from simpler ones.

    • Requires input of energy (endergonic).

2. Bacteria in Hot Springs

  • Found in environments with high temperatures; capable of thriving in extreme conditions.

  • Carry out specialized metabolic pathways, such as thermophilic metabolism.

3. Exergonic Reactions

  • Definition: A type of reaction that releases energy to the surroundings.

  • Characteristics:

    • Have a negative change in Gibbs free energy ($\Delta G < 0$).

    • Facilitates spontaneous reactions.

4. ATP Structure and Comparison

  • ATP (Adenosine Triphosphate)

    • Structure:

    • Consists of adenine (a nitrogenous base), ribose (a sugar), and three phosphate groups.

    • Comparison:

    • Similar to GTP (Guanosine Triphosphate), but different in the nitrogenous base and roles in metabolism.

5. Key Definitions

  • Entropy: A measure of disorder or randomness in a system.

  • Energy Coupling: The process of using energy released from exergonic reactions to drive endergonic reactions.

  • Bioenergetics: The study of energy flow through living systems.

  • Feedback Regulation: A mechanism where the end product of a metabolic pathway inhibits an earlier step to regulate the pathway.

  • Catalyst: A substance that increases the rate of a chemical reaction without being consumed.

  • Enzyme: A biological catalyst that accelerates metabolic reactions.

  • Thermodynamics: The study of energy transformations in a system.

6. Increasing Rate of Reaction

  • Strategies include:

    • Increasing temperature, concentration of reactants, or surface area.

    • Addition of catalysts or enzymes.

7. Chemical Energy

  • Type of energy stored in the bonds of chemical compounds, released during chemical reactions.

8. Laws of Thermodynamics

  • 1st Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

  • 2nd Law of Increasing Entropy: In an isolated system, entropy will increase over time, leading to the spontaneous direction of energy dispersion.

9. ATP Hydrolysis

  • Type of reaction: Hydrolysis breaks chemical bonds between phosphate groups, resulting in ADP and a free inorganic phosphate.

  • The released phosphate group can be transferred to another molecule, facilitating energy transfer.

10. Respiration

10.1. Oxidative Phosphorylation

  • Direct energy source that causes ATP synthase to move, utilizing the proton gradient created by the electron transport chain.

10.2. Final Acceptor of Aerobic Respiration

  • Oxygen (O2) acts as the final electron acceptor.

10.3. Comparison of Fermentation and Cellular Respiration

  • Fermentation occurs in the absence of oxygen and produces less energy compared to cellular respiration.

  • Cellular respiration uses oxygen to fully oxidize glucose into CO2 and water, releasing more energy.

10.4. Redox Reactions

  • Reduction: Gaining of electrons (decrease in oxidation state).

  • Oxidation: Loss of electrons (increase in oxidation state).

  • Reducing Agent: Donates electrons and gets oxidized.

  • Oxidizing Agent: Accepts electrons and gets reduced.

10.5. Respiration Products and Reactants

  • Stage Composition:

    • Glycolysis: Glucose converts to pyruvate, producing ATP and NADH.

    • Citric Acid Cycle: Acetyl-CoA oxidized to CO2, producing NADH, FADH2, and ATP.

    • Electron Transport Chain: NADH and FADH2 donate electrons, producing ATP via oxidative phosphorylation.

10.6. Stages of Respiration

  • Names: Glycolysis, Citric Acid Cycle, and Oxidative Phosphorylation

  • Similarities: All involve oxidation and reduction reactions, producing energy.

  • Differences: Vary in molecular inputs/outputs, location, and ATP yield.

  • ATP Yield:

    • Glycolysis: 2 ATP

    • Citric Acid Cycle: 2 ATP

    • Oxidative Phosphorylation: ~28 ATP

  • Carbon Stripping: Number of carbon atoms from glucose entering the cycle.

10.7. ATP Production Methods

  • Substrate-level Phosphorylation: Occurs in Glycolysis and Citric Acid Cycle.

  • Oxidative Phosphorylation: Takes place in the mitochondria during the ETC.

10.8. Alcohol vs. Acid Fermentation

  • Alcohol fermentation produces ethanol; acid fermentation produces lactic acid.

  • Both occur under anaerobic conditions and regenerate NAD+.

10.9. Glycolysis and Citric Acid Cycle Diagrams

  • Interpretation of schematic diagrams crucial for understanding pathways and outputs.

  • Original carbons entering the Citric Acid Cycle: 2 carbons from Acetyl-CoA.

10.10. Electron Acceptors and Donors

  • Acceptors: NAD+ and FAD; donors: NADH and FADH2.

  • During the electron transfer down the electron transport chain, protons (H+) are pumped from the mitochondrial matrix to the intermembrane space, creating a proton gradient.

11. Chemiosmosis

  • Definition: The process by which ATP is synthesized using the proton gradient created by the electron transport chain.

  • Connection: Links to oxidative phosphorylation, enabling ATP generation in mitochondria.

12. Citric Acid Cycle

  • Features:

    • Known as a cycle because it regenerates the starting substrate (oxaloacetate).

    • Total of 8 steps involved, primarily in mitochondrial matrix.

13. Product Molecules of Cellular Respiration

  • Number of product molecules produced per glucose oxidized: 38 ATP (ideal conditions), along with carbon dioxide and water.

14. Photosynthesis Overview

14.1. Light Reactions

  • Produce ATP and NADPH via photophosphorylation, occurring in the thylakoid membranes.

  • Chemiosmosis: Establishes an H+ gradient from stroma to thylakoid space, enabling ATP production.

14.2. Dark Reactions (Calvin Cycle)

  • Occurs independent of light, requiring ATP, NADPH, and CO2 to convert carbon into glucose.

14.3. Flow of Electrons

  • From water to NADPH, eventually utilized in the Calvin Cycle for sugar production.

14.4. C4 and CAM Plant Comparison

  • C4 plants utilize PEP carboxylase instead of rubisco for carbon fixation in a different cell type.

  • CAM plants perform carbon fixation at night to reduce water loss.

14.5. Comparison of Photophosphorylation and Oxidative Phosphorylation

  • Photophosphorylation: Light energy drives electron transfer in photosystems.

  • Oxidative Phosphorylation: Uses energy from electrons passing through the ETC.

14.6. Role of Antennae Pigment Molecules

  • Harvests light energy and transfers it to chlorophyll reaction centers for photosynthesis.

14.7. Photosystems Comparison

  • Photosystem II: Absorbs light, splits water to release oxygen, starts the electron transport chain.

  • Photosystem I: Re-energizes electrons, leading to NADPH production.

14.8. Chemiosmotic Mechanism

  • Both photosynthesis and respiration employ a chemiosmotic mechanism to generate ATP via proton gradients and ATP synthase.

14.9. Electron Transfer

  • Electron acceptor during photosynthesis: NADP+; electron donor: water.

14.10. Light Energy and Wavelengths

  • Relationship: Higher energy corresponds to shorter wavelengths of light; used in the light reactions of photosynthesis.

15. Photorespiration

  • Occurs when rubisco fixes O2 instead of CO2, metabolizing ATP and producing CO2 in the process.