Untitled Flashcards Set

Metabolism and Energy Concepts

Key Terms:

• Metabolism: All chemical reactions within a cell.

• Catabolism: Breakdown of molecules, releasing energy (exergonic).

• Anabolism: Building of molecules, requiring energy (endergonic).

• Exergonic: Reactions that release energy (e.g., cellular respiration).

• Endergonic: Reactions that absorb energy (e.g., protein synthesis).

• Hydrolysis: Breaking molecules by adding water (e.g., ATP → ADP + Pi).

• Dehydration Synthesis: Building molecules by removing water (e.g., forming proteins).

• Denature: Structural change in a protein (e.g., enzyme) that inhibits function.

• Activation Energy: Minimum energy needed to start a chemical reaction.

• Heterotrophs: Organisms that consume organic molecules for carbon.

• Autotrophs: Organisms that use CO₂ as their carbon source.

• Phototrophs: Obtain energy from light.

• Chemotrophs: Obtain energy from chemical compounds.

• Oxidative Phosphorylation: Produces ATP via the electron transport chain (ETC).

• Aerobic Respiration: Uses oxygen as the final electron acceptor in the ETC.

• Anaerobic Respiration: Uses a non-oxygen molecule (e.g., nitrate, sulfate) as the final electron acceptor.

First Law of Thermodynamics

• Law: Energy cannot be created or destroyed, only transformed.

• Biochemical Pathways: Cells convert chemical energy in nutrients into usable energy (ATP) through pathways like cellular respiration and photosynthesis.

ATP (Adenosine Triphosphate)

• Structure: Composed of adenine, ribose, and three phosphate groups.

• Energy Storage: Energy is stored in high-energy phosphate bonds.

• Energy Transfer: When ATP is hydrolyzed to ADP + Pi, energy is released (exergonic reaction).

  • Energy Release: Drives cellular work (e.g., muscle contraction, biosynthesis).

  • Energy Storage: When energy is required, ADP + Pi are converted back to ATP (endergonic reaction).

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• Role in ETC: As electrons are passed through the electron transport chain, energy is released and used to pump H⁺ ions, generating a proton gradient.

Cellular Respiration Steps

1. Glycolysis

• Location: Cytoplasm.

• Inputs: Glucose, 2 ATP, 2 NAD⁺.

• Outputs: 2 Pyruvate, 4 ATP (net 2 ATP), 2 NADH.

2. Production of Acetyl-CoA

• Location: Mitochondrial matrix (eukaryotes) / Cytoplasm (prokaryotes).

• Inputs: 2 Pyruvate, 2 NAD⁺.

• Outputs: 2 Acetyl-CoA, 2 CO₂, 2 NADH.

3. Krebs Cycle (Citric Acid Cycle)

• Location: Mitochondrial matrix (eukaryotes) / Cytoplasm (prokaryotes).

• Inputs: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD.

• Outputs: 4 CO₂, 2 ATP, 6 NADH, 2 FADH₂.

4. Electron Transport Chain (ETC)

• Location:

  • Eukaryotes: Inner mitochondrial membrane.

  • Prokaryotes: Plasma membrane.

• Process:

  • Electron carriers (NADH, FADH₂) donate electrons to the ETC.

  • H⁺ ions are pumped across the membrane, creating a proton gradient.

  • ATP synthase uses this gradient to convert ADP + Pi to ATP.

• Final Electron Acceptor:

  • Aerobic: Oxygen, producing H₂O.

  • Anaerobic: Other molecules (e.g., nitrate, sulfate).

Fermentation

• Location: Cytoplasm.

• Process: Generates ATP through glycolysis alone, regenerating NAD⁺ for glycolysis.

• When: Occurs when oxygen (or final electron acceptor) is not available.

1. Lactic Acid Fermentation

• Inputs: Glucose.

• Outputs: Lactic acid, 2 ATP.

• Example: Muscle cells, Lactobacillus bacteria.

2. Alcohol Fermentation

• Inputs: Glucose.

• Outputs: Ethanol, CO₂, 2 ATP.

• Example: Yeast, used in bread and alcohol production.

ATP Production Comparison

• Respiration (Aerobic): Produces ~38 ATP per glucose.

• Fermentation: Produces only 2 ATP per glucose.

Catabolism of Different Molecules

• Carbohydrates: Enter as glucose in glycolysis.

• Lipids: Broken down to glycerol (enters glycolysis) and fatty acids (enter Krebs cycle via β-oxidation).

• Proteins: Broken down to amino acids, deaminated, and enter glycolysis or Krebs cycle.

Enzymes

Composition:

• Made of proteins, sometimes with cofactors (e.g., vitamins, metal ions).

Key Terms:

• Substrate: The reactant that binds to the enzyme's active site.

• Product: The result of the enzymatic reaction.

• Active Site: The region on the enzyme where the substrate binds.

Enzyme Function:

• Activation Energy: Enzymes lower the activation energy, allowing reactions to occur faster.

Enzyme Specificity:

• Each enzyme works with a specific substrate.

• Example: Lactase only acts on lactose.

Factors Influencing Enzyme Activity:

1. Temperature:

   • Optimal range: Too high or too low denatures the enzyme.

2. pH:

   • Each enzyme has an optimal pH. Extreme pH can denature enzymes.

3. Substrate Concentration:

   • Increasing substrate increases activity until the enzyme is saturated.

4. Inhibitors:

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

   • Non-Competitive Inhibitors: Bind elsewhere, changing enzyme shape.

This structured breakdown covers essential concepts, pathways, and mechanisms needed for a solid understanding of metabolism and enzyme activity. Would you like more details on specific metabolic pathways or enzyme examples?