Exam 2

Chapter 5

Energy Metabolism

  • Understanding energy in chemical reactions

  • Physical laws of energy: cannot be created or destroyed

Enzymes

  • Role of enzymes in chemical reactions

  • Mechanisms for activating and deactivating enzymes in cells

Metabolism Overview

  • Definition: all chemical reactions in an organism

  • Diagram of chemical reactions in a cell (not memorization required)

  • Importance of enzymes in controlling reactions

Categories of Metabolic Reactions

Catabolic Pathways

  • Definition: breakdown processes

  • Example: Starch to glucose (polymer to monomer)

  • Energy release during breakdown

  • Key terms: exergonic reactions

  • Model activity with toys to illustrate breaking down a molecule

Anabolic Pathways

  • Definition: building processes

  • Example: Glucose to glycogen (monomer to polymer)

  • Energy input required for synthesis

  • Key terms: endergonic reactions

  • Model activity with toys to illustrate building a molecule

Laws of Thermodynamics

  • First Law: Energy of the universe is constant

    • Energy can be transformed, not created or destroyed

  • Second Law: Energy is released as heat in reactions

    • Causes disorder or entropy to increase

Entropy

  • Definition: disorder or chaos

  • Examples of increasing entropy: heat production and breakdown of organized structures

Energy in Reactions

Exergonic Reactions

  • Spontaneous reactions that release energy

  • Products have less energy compared to reactants (negative delta G)

  • Examples: Hydrolysis reactions such as breaking down ATP

Endergonic Reactions

  • Non-spontaneous reactions that require energy input

  • Products have more energy than reactants (positive delta G)

  • Examples: Building reactions such as polysaccharides from simple sugars

Role of ATP

  • Definition: Adenosine triphosphate (energy currency of the cell)

  • Structure: three phosphate groups and ribose sugar

  • Hydrolysis of ATP: ATP → ADP + inorganic phosphate + energy

    • Classified as an exergonic reaction

  • ATP powers endergonic reactions in metabolism

ATP Cycle

  • ATP is produced through catabolic processes (breaking down food)

  • ATP provides energy for endergonic reactions (building processes)

  • Examples of ATP use: transport work (moving solutes) and mechanical work (movement along cytoskeleton)

Chapter 6

Energy Metabolism

  • Focus on understanding energy during chemical reactions.

  • Importance of physical laws, primarily that energy cannot be created or destroyed (First Law of Thermodynamics).

Role of Enzymes

  • Enzymes regulate chemical reactions in cells.

  • Key questions: How do cells activate/deactivate enzymes? How is this control achieved?

Overview of Metabolism

  • Metabolism: All chemical reactions in an organism.

  • Must understand categories and themes of these reactions.

  • Enzymes determine the timing and location of reactions.

Categories of Metabolic Reactions

  • Catabolic reactions: Breakdown pathways.

    • Example: Breaking down starch into glucose (releases energy).

  • Anabolic reactions: Building pathways.

    • Example: Building glycogen from glucose (requires energy).

Catabolic Pathways

  • Definition: Reactions that break down larger molecules into smaller ones.

  • Key point: Each step involves enzymes acting as catalysts.

Anabolic Pathways

  • Definition: Reactions that build larger molecules from smaller units.

  • Example: Glucose being converted into glycogen.

  • Requires energy input.

First Law of Thermodynamics

  • Energy of the universe is constant; it can be transformed but not created or destroyed.

Second Law of Thermodynamics

  • Every reaction results in some energy being lost as heat.

  • Increases disorder or entropy in the universe (example: a bear metabolizing food).

Exergonic Reactions

  • Type of reaction that releases energy.

  • Characteristics:

    • Products have less energy than reactants (negative delta G).

    • Spontaneous reactions that can occur without extra energy input.

Endergonic Reactions

  • Type of reaction that requires energy input.

  • Characteristics:

    • Products have more energy than reactants (positive delta G).

    • Non-spontaneous, does not occur naturally without additional energy.

ATP Cycle

  • ATP (Adenosine Triphosphate): Main energy currency of the cell.

    • Composed of three phosphate groups.

    • Hydrolysis of ATP (ATP to ADP + inorganic phosphate) is an exergonic reaction releasing energy.

  • ATP powers endergonic reactions and is regenerated through catabolic processes.

Chapter 7

Cellular Respiration Intro

  • Focus on glucose metabolism: primarily through cellular respiration and fermentation.

  • Key Questions:

    • How is energy released from carbohydrates?

    • What are the major steps of cellular respiration and where do they occur?

  • Major Components of Cellular Metabolism:

    • Understanding macromolecule interactions with the body.

    • Importance of cholesterol, sugars, and protein production.

Terms to Remember

  • Redox Reactions:

    • Involve the transfer of electrons/hydrogen atoms.

    • Oxidation: Loss of electrons (e.g., glucose to CO2).

    • Reduction: Gain of electrons (e.g., O2 to H2O).

    • Mnemonic: "Oil Rig" (Oxidation Is Losing, Reduction Is Gaining).

Steps of Cellular Respiration

  1. Glycolysis:

    • Occurs in the cytosol.

    • Breaks glucose (6 carbons) into two pyruvate (3 carbons each).

    • Produces:

      • 2 ATP (net gain)

      • 2 NADH

  2. Pyruvate Oxidation (in mitochondria):

    • Converts pyruvate to acetyl CoA (2 carbons) and CO2.

    • Produces NADH.

  3. Citric Acid Cycle (Krebs Cycle) (in mitochondria):

    • Completes breakdown of glucose carbon skeleton.

    • Produces:

      • 2 ATP

      • 6 NADH

      • 2 FADH2

      • 4 CO2

  4. Oxidative Phosphorylation:

    • Electron Transport Chain:

      • High energy electrons released from NADH and FADH2, pumping protons (H+) across the membrane to create a gradient.

    • Chemiosmosis:

      • Protons flow back through ATP synthase, generating ATP from ADP.

      • Oxygen is the final electron acceptor, forming water.

Learning Points

  • Importance of ATP as usable energy.

  • Role of NADH and FADH2 in energy transfer.

  • Glycolysis and citric acid cycle produce ATP directly (substrate-level phosphorylation).

  • Oxidative phosphorylation accounts for the majority of ATP production (32 ATP expected from one glucose).

Fermentation

  • Goal: To replenish NAD+ for glycolysis in anaerobic conditions.

  • Types of Fermentation:

    1. Lactic Acid Fermentation:

      • Pyruvate is converted to lactic acid; NADH is oxidized back to NAD+.

      • Occurs in muscles during intense exercise.

    2. Alcoholic Fermentation:

      • Pyruvate is converted to ethanol and CO2; NADH is oxidized back to NAD+.

      • Common in yeast and some bacteria.

Conclusion

  • Review of crucial steps in cellular respiration and fermentation processes.

  • Importance of understanding metabolic pathways for energy production.

  • Prepare for upcoming assessments by reviewing class notes and understanding key concepts.

Chapter 8

Cellular Respiration Practice

  • Many students submitted; if not, please submit as soon as possible.

  • Access code for Chapter 8 quiz: z4wp (lowercase).

Chapter 8 Overview

  • Coral Reef Ecology introduced through Dr. Ruth Gates' work on how coral reacts to rising temperatures.

  • Coral ejects algal symbionts when stressed, leading to starvation (coral bleaching).

Photosynthesis Introduction

  • Two main events occurring in chloroplasts:

    • Light Reactions: Convert light energy into chemical energy (ATP and NADPH).

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

  • Key process to memorize: Redox reaction where CO₂ is reduced to glucose and water is oxidized to oxygen.

Key Concepts in Photosynthesis

  • Light Reaction Inputs: Light, H₂O, NADP⁺, ADP + Pi.

  • Light Reaction Outputs: O₂, ATP, NADPH.

  • Calvin Cycle Inputs: CO₂, ATP, NADPH.

  • Calvin Cycle Outputs: G3P (to form glucose), ADP + Pi, NADP⁺.

Photosystem Functionality

  • Photosystem II (PS II): Energizes electrons, creates a proton gradient to generate ATP.

  • Photosystem I (PS I): Re-energizes electrons to produce NADPH.

Steps in the Electron Transport Chain

  1. Light excites electrons in PS II, electrons travel through the chain, creating a proton gradient.

  2. PS I re-energizes electrons which are used to reduce NADP⁺ to NADPH.

  3. Protons flow back through ATP synthase, producing ATP from ADP and Pi.

Calvin Cycle Process

  • Phase 1 - Carbon Fixation: CO₂ is attached to RuBP by rubisco, forming 3-PGA.

  • Phase 2 - Reduction: ATP and NADPH convert 3-PGA into G3P.

  • Phase 3 - Regeneration: G3P is transformed back into RuBP to continue the cycle.

  • Glucose Production: Requires two G3P molecules to form one glucose.