Bio 111 Study Guide Chapter 4 - Energy and Membranes

Energy

• Energy is the ability to do work.

  • Kinetic energy: energy of motion.

    • Thermal (heat) energy: movement of atoms and molecules (directly related to temperature)

    • Light (solar) energy: wavelengths of electromagnetic radiation visible to the eye, photons are packets of energy.

  • Potential energy: stored energy available to do work.

    • Chemical energy: a form of potential energy, which is released when a molecules bonds break.

• Thermodynamics: the study of energy transformations.

  • 1st Law: Energy is conserved; it cannot be created or destroyed, only converted.

  • 2nd Law: Every reaction loses some energy as heat; entropy (disorder) always increases.

• Chemical Reactions:

  • Metabolism: sum of all chemical reactions in an organism.

  • Anabolism (Anabolic): Builds complex molecules from simpler ones.

  • Catabolism (Catabolic): Breaks down complex molecules into simpler ones, releasing energy.

  • Endergonic: Requires a net input of energy; products contain more energy than reactants.

  • Exergonic: Releases energy; products contain less energy than reactants.

  • Oxidation: Loss of one or more electrons (LEO - Loss of Electrons is Oxidation).

  • Reduction: Gain of one or more electrons (GER - Gain of Electrons is Reduction).

• Biological Reactions:

  • Photosynthesis: Converts light energy into chemical energy (sugars).

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

  • Hydrolysis: Breaks bonds by adding water, releasing energy.

  • Dehydration Synthesis: Removes water to form bonds.

ATP

• ATP components: Adenine, ribose sugar, and three phosphate groups.

• Stores energy by phosphorylating ADP to ATP, creating covalent bonds that store potential energy and electrostatic repulsion.

• Enzymes receiving ATP undergo mechanical changes enabling their function.

Enzymes

• Enzymes: Catalysts that speed up reactions by lowering activation energy.

  • Catalyst: substance that speeds up the rate of a chemical reaction without being consumed.

  • Activation Energy: Energy needed to start a reaction.

  • Active Site: Location on enzyme where substrate binds.

  • Substrate: Reactant that binds to the enzyme.

  • Product: The result of the enzymatic reaction.

  • Cofactors/Coenzymes: Inorganic or organic substances required for enzyme activity.

  • Inhibitors: Decrease enzyme activity.

    • Competitive: Bind to the active site, blocking substrate.

    • Noncompetitive: Bind elsewhere, changing enzyme shape.

  • Activators: Increase enzyme activity.

  • Denature: Loss of enzyme's natural shape and function.

• Enzymes are Reusable because they are not consumed in the reaction.

• Enzymes function within narrow environmental conditions (pH, temperature).

• Metabolic Pathway: Series of reactions, each catalyzed by a specific enzyme, converting initial reactants to final products through intermediates.

• Feedback Mechanisms:

  • Negative: Accumulation of product slows down the pathway.

  • Positive: Accumulation of product speeds up the pathway.

Membrane Function

• Transport proteins facilitate movement of molecules across the membrane.

• Transport:

  • Passive: No ATP needed; moves molecules down the concentration gradient (high to low).

    • Simple Diffusion: Molecules move directly across the membrane.

    • Facilitated Diffusion: Requires a transport protein.

  • Active: Requires ATP; moves molecules against the concentration gradient (low to high).

• Diffusion:

  • Net movement of particles from high to low concentration; individual particles move randomly.

    • Down/With: Movement from high to low concentration.

    • Up/Against: Movement from low to high concentration.

• Osmosis: Diffusion of water molecules.

• Tonicity:

  • Hypertonic: Higher solute concentration outside the cell; water moves out, cell shrinks.

  • Hypotonic: Higher solute concentration inside the cell; water moves in, cell swells.

  • Isotonic: Equal solute concentrations; no net water movement.

• Central Vacuole in plants maintains turgor pressure, providing structural support.

• Pumps: Use energy (active transport) to move molecules against their concentration gradient.

• Proton Pump: Transports protons across the membrane, creating a proton gradient.

• Bulk Transport:

  • Endocytosis: Moves bulk material into the cell.

  • Exocytosis: Moves bulk material out of the cell.