EXAM 3 - LESSON 5/6/7

Introduction to Metabolism

  • Energy in Biological Systems

    • The body utilizes and converts energy; energy is not created.

    • Mitochondria are described as the powerhouse of the cell for their role in energy conversion, not creation.

Energy Basics

Definition of Metabolism

  • Metabolism: Totality of an organism's chemical reactions.

    • Includes breakdown of biomolecules (catabolism) and building of cellular components (anabolism).

Catabolism vs. Anabolism

  • Catabolism:

    • Breakdown of molecules (e.g., polymers to monomers).

    • Releases energy; contributes to universe (chaos).

  • Anabolism:

    • Building of molecules (e.g., monomers to polymers).

    • Requires energy; less favored by the universe (increases order).

Enzymatic Reactions

  • Enzymes are proteins that facilitate metabolic reactions.

    • Lower activation energy for reactions.

    • Specific substrates must bind to their corresponding enzyme's active site.

Laws of Thermodynamics

First Law

  • Energy cannot be created or destroyed, only transformed.

    • Energy from glucose is transferred to ATP (adenosine triphosphate).

Second Law

  • Entropy: disorder or chaos in systems tends to increase.

    • Breakdown processes (catabolism) are favorable, increasing entropy.

Energy Forms and Measurement

  • Types of Energy:

    • Kinetic Energy: Energy in motion.

    • Potential Energy: Stored energy (e.g., food).

  • Calories as a measure of energy in food; higher calories indicate more potential energy stored.

Metabolic Pathways

  • Chemical reactions form metabolic pathways that are linked.

    • Pathways have specific substrates and enzymes at each step.

    • Each reaction step produces an intermediate product that may lead to a final product.

Free Energy and Reaction Spontaneity

  • Free energy change (9;G9) determines spontaneity:

    • Negative 9;G9 indicates a spontaneous (exergonic) reaction (energy released).

    • Positive 9;G9 indicates non-spontaneous (endergonic) reaction (energy needed).

  • Activation energy is required to initiate reactions, even exergonic ones.

Feedback Inhibition in Metabolism

  • Body can modulate enzyme activity to prevent overproduction of products.

    • End product can inhibit earlier enzymes in the pathway (non-competitive inhibition).

Summary of Key Concepts

  • Understand metabolism, energy transformations, and the role of enzymes in metabolic pathways.

  • Recognize laws of thermodynamics and how they govern energy in biological processes.

  • Importance of metabolic pathways, reaction types, and enzyme functions for future topics like cellular respiration and photosynthesis.

Overview of Energy Conversion

Energy conversion involves transforming light energy into cellular energy (ATP), essential for cellular functions such as growth and metabolism. Glucose breakdown releases energy for cellular activities.

Cellular Respiration

Cellular Respiration converts glucose into ATP and has two major types:

  • Aerobic Respiration: Requires oxygen, occurs in mitochondria, yielding more ATP.

  • Anaerobic Respiration: Occurs when oxygen is scarce, producing less ATP and includes processes like alcohol fermentation in yeast.

Mitochondria and ATP Production

Mitochondria are known as the powerhouse of cells, where ATP is primarily synthesized. ATP is crucial for assembling biological polymers, transporting materials, and supporting cell movement and reproduction.

the cyto[plasma in the mitochondria is called the matrix

Energy Flow in Ecosystems

Energy flows from producers (plants converting sunlight into chemical energy) to consumers (animals) and decomposers (microorganisms recycling nutrients).

Photosynthesis vs. Cellular Respiration

  • Cellular Respiration: C6H12O6 + O2 -> CO2 + H2O + ATP

  • Photosynthesis: H2O + CO2 + light energy -> C6H12O6 + O2 Both processes form a cyclical relationship sustaining life.

Catabolic Pathways

Catabolic pathways degrade larger molecules, like glucose, to release energy. Aerobic respiration yields more ATP than fermentation, which occurs under low oxygen conditions.

Glycolysis and Subsequent Steps

Glycolysis occurs in the cytoplasm, converting glucose to pyruvate and yielding 2 ATP. Pyruvate oxidation, the Krebs cycle, and the electron transport chain follow.

Oxidative Phosphorylation

Oxygen acts as the final electron acceptor, enabling high ATP yields (26-28 ATP per glucose) through the electron transport chain.

Fermentation Processes

  1. Alcohol Fermentation: Occurs in yeast, converting pyruvate into ethanol and CO2.

  2. Lactic Acid Fermentation: Occurs in muscle cells under low oxygen, converting pyruvate into lactic acid.

Importance of Electron Carriers

Electron carriers (NADH, FADH2) transport high-energy electrons to the electron transport chain, crucial for ATP production.

Overview of Photosynthesis

  • Photosynthesis is the process through which plants, algae, and some bacteria convert light energy into chemical energy (glucose) using carbon dioxide and water.

Key Concepts

Cellular Respiration Review

  • Process: Glucose (C6H12O6) + Oxygen → Carbon Dioxide + Water + Energy (ATP)

  • Type: Exergonic (energy is released)

  • Location: Mitochondria in eukaryotes; occurs in the cell membrane for bacteria.

  • ATP Production: More ATP produced via aerobic respiration (30-38 ATP) than fermentation (2 ATP).

Photosynthesis Definition

  • Equation: Carbon Dioxide + Water + Light Energy → Glucose + Oxygen

  • Type: Endergonic (energy is required to build glucose from smaller molecules).

  • Organelles: Occurs in chloroplasts in eukaryotic cells; in prokaryotes (like cyanobacteria), it occurs in the cytoplasm.

Roles of Producers and Consumers

  • Producers (Autotrophs): Organisms that make their own food using light (photoautotrophs).

  • Consumers (Heterotrophs): Organisms that obtain energy by consuming other organisms.

  • Decomposers: Break down dead material, returning nutrients to the environment.

Light Energy & Photosynthesis

  • Photon: The light energy captured by plants.

  • UV Radiation: Three types (UVA, UVB, UVC); UVA contributes to skin aging and skin cancer.

Plant Structure Related to Photosynthesis

  • Stomata: Openings on leaves for gas exchange (CO2 in, O2 out).

  • Chloroplasts Structure:

    • Outer and inner membranes.

    • Thylakoids: Folded membranes where light-dependent reactions occur.

      • contains proteins that are part of the electron transport chain

    • Stroma: Fluid surrounding thylakoids where light-independent reactions (Calvin Cycle) occur. (liquid portion of the chloroplasts)

Photosynthesis Phases

  1. Light-Dependent Reactions:

    • Capture light energy and convert it to ATP and NADPH. (light energy and chemical energy)

    • Water is split to release electrons (oxidation) and produce oxygen.

    • electron transport chain/ chemosis

    • assists in light-independent

    • pumps out hydrogen proteins from the stroma into the thyolods

    • ATP synthase pumps out the hydrogen protons across the membrane, it produces ATP

  2. Light-Independent Reactions (Calvin Cycle):

    • Use ATP and NADPH to convert CO2 into glucose.

    • Carbon fixation occurs via the enzyme Rubisco (combines CO2 with ribulose bisphosphate).

    • build bonds to generate glucose

    • going from a 1 carbon chain to a 6-carbon chin, which is an endergonic

    • electron transport chain creates ATP and NADPH, which are essential for the subsequent stages of photosynthesis, particularly in the Calvin cycle where glucose is synthesized.

Energy Coupling

  • Both cellular respiration and photosynthesis involve electron transport chains for ATP production.

  • Light-Dependent Reaction Products: ATP and NADPH.

  • Calvin Cycle Needs: Requires ATP and NADPH from the light-dependent reactions.

Important Terms

  • Carbon Fixation: Conversion of CO2 into organic compounds during the Calvin Cycle.

  • Rubisco: Enzyme that catalyzes the first step of the Calvin Cycle.

  • G3P (Glyceraldehyde 3 Phosphate): A three-carbon molecule produced that can be used to form glucose.

Environmental Impact

  • Increased CO2 from human activities (e.g., driving) affects climate change.

  • Trees and plants help mitigate CO2 levels, thus cutting them down exacerbates climate issues.

pumping hydrogen protein back into the matrix you’re making ATP