Fall 2024 Ch 5 Student Slides

Chapter 5: ENERGY

Learning Objectives

• Metabolic Pathways: Understanding the processes by which organisms convert food into energy.

• Laws of Thermodynamics:

  • First Law: Energy cannot be created or destroyed.

  • Second Law: Energy conversions are not perfectly efficient; some energy is converted into heat.

• Kinetic vs. Potential Energy:

  • Kinetic Energy: Energy of motion.

  • Potential Energy: Stored energy based on position or state.

• Energy Flow in Life:

  • Photosynthesis: Plants convert sunlight into chemical energy.

  • Cellular Respiration: Organisms convert food into usable energy (ATP).

• Role of ATP: Cell energy currency, recycling between ATP and ADP.

• Alternative Energy Pathways: Different methods organisms use to acquire energy.

Energy Conversions

• Life depends on capturing solar energy and converting it into usable forms.

• Key processes include:

  • Photosynthesis: Conversion of sunlight into chemical energy.

  • Cellular Respiration: Breakdown of glucose to release energy.

What is Energy?

• Defined as the capacity to do work, which involves:

  • Work: Moving matter against opposing forces.

Forms of Energy

• Kinetic Energy: Energy involved in motion.

• Potential Energy: Energy stored due to position (e.g., in chemical bonds).

  • Food: Contains potential chemical energy.

  • Chemical Energy: A type of potential energy stored in the bonds of food molecules.

Energy Dynamics

• Energy Transformation: As energy is transformed, the total usable energy decreases, often becoming heat.

• Path of energy transformation:

  • Light energy -> Chemical energy (in plants) -> Kinetic energy (movement).

Thermodynamics in Biological Systems

• First Law of Thermodynamics: Energy is conserved; it changes from one form to another.

• Second Law of Thermodynamics: Energy transformations are not 100% efficient; some energy dissipates as heat.

Metabolic Pathways

• Anabolic Pathways: Synthesize larger molecules from smaller units, requiring energy input.

• Catabolic Pathways: Break down larger molecules into smaller units, releasing energy.

• Both pathways are crucial for maintaining cellular energy balance.

Photosynthesis and Cellular Respiration

• Photosynthesis: Converts solar energy into ATP, creating sugar molecules.

  • Input: Carbon dioxide + Water + Light Energy.

  • Output: Oxygen + Glucose.

• Cellular Respiration: Converts glucose back into usable energy (ATP).

  • Stages of respiration:

    1. Glycolysis (Cytoplasm)

    2. Krebs Cycle (Mitochondria)

    3. Electron Transport Chain (Mitochondria): Generates ATP.

Structure of ATP

• ATP is described as free-floating rechargeable batteries in cells.

  • Components include:

    • Adenine: Nitrogen base.

    • Ribose: Sugar molecule.

    • Phosphate Groups: Three phosphate groups with high-energy bonds.

• Energy is released when ATP is converted to ADP (adenosine diphosphate) through the loss of a phosphate group.

Cellular Respiration Overview

• Glycolysis: Breakdown of glucose into pyruvate, producing a small amount of ATP.

• Krebs Cycle: Further breakdown of pyruvate, releases CO2, produces ATP, NADH, and FADH2.

• Electron Transport Chain: Produces the bulk of ATP from NADH and FADH2 by transferring electrons.

  • Oxygen is critical as the final electron acceptor, completing the process.

Nutritional Energy Sources

• Organisms can utilize fats, carbohydrates, and proteins for energy:

  • Fats: Yield high energy during breakdown.

  • Carbohydrates: Quick energy source, converted via glycolysis.

  • Proteins: Can be used as energy when carbohydrates and fats are insufficient.

Photosynthesis Details

• Kinetic Energy: Light energy captured during the "photo" reactions.

• Plants utilize sunlight to convert carbon dioxide and water into glucose, releasing oxygen as a byproduct.

• Process occurs in chloroplasts:

  • Thylakoids: Site for the energy-capturing reactions ("photo" reactions).

  • Stroma: Site of sugar synthesis ("synthesis" reactions).

Photosynthesis Steps

1. "Photo" Reactions:

   • Convert light energy into chemical energy (ATP, NADPH).

   • Water is a key input, and oxygen is released.

2. "Synthesis" Reactions:

   • Fix carbon dioxide into glucose using the energy from ATP and NADPH.