Unit 3: Energy & Enzymes

  • Core Concepts:

    • Substrate

    • Product

    • Enzyme (catalyst)

SLO1: Definitions and Differentiations

  • Differentiate between potential energy and Gibb's free energy.

Energy Overview

  • Energy: Capacity to do work or promote change.

  • Potential Energy: Energy due to position.

  • Chemical Potential Energy: Energy stored in bonds (specifically, the position of electrons).

    • Inquiry: Do polar or nonpolar bonds have higher potential energy?

Glucose Structure Analysis

  • Representation of Glucose:

    • Red = Oxygen

    • White = Hydrogen

    • Grey = Carbon

  • Bonds with High Potential Energy in Glucose:

    • O-H

    • C-C

    • C-H

    • C-O

Energy Conversion

  • Energy can transform into various forms, but total energy remains constant:

    • Potential: Ep (top)

    • Kinetic: Ek; transformations can include:

    • Sunlight (converted into chemical energy)

    • Heat

    • Mechanical energy

    • Sound energy

    • Example of energy conversion involves chlorophyll molecules in an excited state during photosynthesis, leading to high-energy electrons and chemical-bond energy from electromagnetic (light) energy.

Gibb's Free Energy (G)

  • Gibb's Free Energy (G): Energy within a molecule that is available for doing work.

    • Within a molecule, multiple sources of energy exist, but only a portion is available for work, such as vibrations, rotations, and energy stored within atomic bonds (chemical potential energy).

Gibb's Free Energy and Disorder

  • Connection between Gibb's Free Energy and Entropy:

    • The amount of disorder (entropy) within a system can influence Gibb's Free Energy.

    • More disorder (higher entropy) leads to less energy available for work.

SLO2: Endergonic vs. Exergonic Reactions

  • Definitions/Contrasts:

    • Endergonic Reactions:

    • Endergonic reactions require a continual input of energy.

    • Represented by a positive change in Gibb's free energy (+ΔG).

    • Energetically unfavorable (non-spontaneous).

    • Associated with a decrease in entropy.

    • Typically correlate with anabolic reactions (building processes).

    • Exergonic Reactions:

    • Release energy during the reaction.

    • Represented by a negative change in Gibb's free energy (-ΔG).

    • Energetically favorable (spontaneous).

    • Associated with an increase in entropy.

    • Typically correlate with catabolic reactions (breaking processes).

SLO3: Anabolic vs. Catabolic Reactions

  • Definitions:

    • Anabolic Reactions: Engage in building larger molecules and structures from smaller ones (e.g., protein synthesis).

    • Catabolic Reactions: Break down larger molecules into smaller ones (e.g., cellular respiration).

SLO4: Correlation of Terms

  • Relationships:

    • Endergonic/Exergonic: Describe energy changes during reactions.

    • Anabolic/Catabolic: Define processes of building versus breaking down.

    • Condensation/Hydrolysis:

    • Condensation: A reaction that combines molecules with the release of a water molecule (anabolic process).

    • Hydrolysis: A reaction that breaks down molecules by adding water (catabolic process).

SLO5: Analyzing Energy Graphs

  • Identifying Reaction Types:

    • Analyze graphs of free energy change to determine if a reaction is endergonic or exergonic based on the energy curve's behavior.

Free Energy Changes Over Reactions

  • Free Energy Change (ΔG) Assessment during Reactions:

    • If ΔG increases, the reaction is endergonic (+ΔG).

    • If ΔG decreases, the reaction is exergonic (-ΔG).

SLO6: Activation Energy and Free Energy Changes

  • Graph Elements:

    • Activation Energy: The energy required for reactants to reach the high-energy transition state.

    • Change in Free Energy (ΔG): Overall energy change associated with reaction.

    • Transition State: The intermediate stage of a reaction where bonds are breaking and forming.

Biological Reaction Assessment

  • Examine Reactions:

    • Determine if a biological reaction is exergonic or endergonic.

    • Describe the changes in free energy throughout the reaction.

Energy Profile of a Biological Reaction

  • Activation Energy:

    • The energy needed to initiate the reaction to move from reactants to transition state.

    • Activation energy is often absorbed as heat from the surroundings, suggesting that it is not included in the overall change in free energy (ΔG).

Reaction Rates and Activation Energy

  • Reaction Type Assessment:

    • Determine if reactions are anabolic or catabolic.

    • Identify if they are endergonic or exergonic based on their characteristics.

  • Example: Glucose reactions are crucial but need to be sped up for cellular utilization.

  • Role of Enzymes:

    • Catalysts that accelerate reactions without being consumed.

Enzyme Functions and Mechanisms

  • Enzymatic Action:

    • Reactants (substrates) bind to the enzyme's active site, which is highly specific to the substrate(s).

    • Binding alters the enzyme's shape, facilitating the transition state.

    • Products are released, allowing the enzyme to be reused.

SLO8: Inhibition Types

  • Allosteric Inhibition vs. Competitive Inhibition:

    • Allosteric Inhibition: Regulatory molecules bind to a site other than the active site, altering the enzyme's shape for activation or inhibition.

    • Competitive Inhibition: Drugs or substances mimic a substrate’s shape and bind to the active site, preventing the natural substrate from binding.

SLO9: Negative Feedback Inhibition

  • Feedback Inhibition Review:

    • Common in multi-step biochemical pathways.

    • The final product often interacts with an early enzyme in the pathway.

    • May act as competitive or allosteric inhibitors; crucial for regulating metabolic pathways.

SLO10: Role of Cofactors and Coenzymes

  • Definitions and Structures:

    • Cofactors: Inorganic ions (e.g., Mg²⁺, Zn²⁺) that may bind anywhere on the enzyme, necessary for function.

    • Coenzymes: Organic molecules that bind to the active site, improving substrate binding (e.g., Vitamin C is an example).

SLO11: Consequences of Nonfunctional Enzymes

  • Impact on Cells:

    • Nonfunctional enzymes can disrupt metabolic pathways, leading to inadequate responses to cellular needs.

  • Enzyme Regulation Role:

    • Crucial for ensuring that specific reactions occur in controlled environments, influencing overall cellular function.

  • Alterations in Enzyme Shape:

    • Changes in enzyme conformation can drastically affect enzymatic activity, impacting the overall metabolic processes within a cell.