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General Biology: Metabolism and Cellular Respiration

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Termini in questo insieme (30)

  • What is metabolism?

    Metabolism is the sum of all chemical reactions in an organism that transform matter and energy to sustain life.

  • What are the two types of chemical reactions in metabolism?

    Exergonic reactions release energy, while endergonic reactions store energy.

  • What role do enzymes play in metabolism?

    Enzymes are proteins that lower the activation energy of chemical reactions, speeding them up to support life.

  • State the 1st law of thermodynamics in relation to cells.

    Energy is transferred or transformed but not created or destroyed; cells transform energy in metabolic processes.

  • What is the 2nd law of thermodynamics and its relevance to living organisms?

    Entropy of a closed system increases over time; living organisms are open systems that exchange energy to maintain order.

  • Where is energy stored in molecules?

    Energy is stored in the chemical bonds of molecules, especially in high-energy phosphate bonds like those in ATP.

  • What does a negative change in Gibbs free energy (ΔG) indicate?

    A negative ΔG means the reaction is spontaneous and releases energy (exergonic).

  • How are endergonic and exergonic reactions related in metabolism?

    Endergonic reactions are often coupled with exergonic reactions to drive energy-requiring processes.

  • What structural feature makes ATP a useful energy source?

    ATP has three phosphate groups with high-energy bonds, especially the bond to the 3rd phosphate, which releases energy when broken.

  • Describe the ATP cycle.

    ATP is hydrolyzed to ADP and inorganic phosphate, releasing energy; ADP is then recycled to ATP using energy from cellular respiration.

  • How do enzymes affect activation energy?

    Enzymes lower the activation energy needed to start a reaction, increasing reaction rate without changing ΔG.

  • Define substrate and active site in enzyme function.

    The substrate is the molecule an enzyme acts on; the active site is the enzyme region where the substrate binds.

  • What is induced fit in enzyme activity?

    Induced fit is the enzyme's active site changing shape to better bind the substrate and catalyze the reaction.

  • Name four mechanisms enzymes use to lower activation energy.

    Enzymes: 1) Orient substrates correctly, 2) Strain substrate bonds, 3) Provide a favorable microenvironment, 4) Covalently bond to substrate.

  • How do temperature and pH affect enzyme activity?

    Temperature and pH affect enzyme shape and function; extremes can denature enzymes and reduce reaction rates.

  • Difference between competitive and noncompetitive inhibitors?

    Competitive inhibitors bind the active site; noncompetitive inhibitors bind elsewhere, altering enzyme shape.

  • Why do cells regulate enzyme activity?

    To control metabolic pathways, conserve energy, and respond to environmental changes.

  • List four modes of enzyme regulation.

    1) Gene regulation, 2) Enzyme activation/deactivation, 3) Feedback inhibition, 4) Localization and compartmentalization.

  • What is the overall equation for cellular respiration?

    \(\mathrm{C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy}\); it is an exergonic reaction.

  • What are oxidation and reduction in cellular respiration?

    Oxidation is loss of electrons; reduction is gain of electrons. Glucose is oxidized; oxygen is reduced.

  • Why does cellular respiration involve many steps and enzymes?

    Multiple steps allow controlled energy release and efficient ATP production rather than one explosive reaction.

  • Where does glycolysis occur?

    In eukaryotes, glycolysis occurs in the cytoplasm; in prokaryotes, also in the cytoplasm.

  • What are the net inputs and outputs of glycolysis?

    Inputs: glucose, 2 ATP, 2 NAD+; Outputs: 2 pyruvate, 4 ATP (net 2 ATP), 2 NADH.

  • What happens to NADH in aerobic respiration vs fermentation?

    In aerobic respiration, NADH donates electrons to the electron transport chain; in fermentation, NADH is oxidized back to NAD+ to sustain glycolysis.

  • Where does the citric acid cycle occur?

    In the mitochondrial matrix of eukaryotic cells.

  • What are the major products of the citric acid cycle?

    Carbon dioxide, NADH, FADH2, and ATP (or GTP).

  • What is the role of NADH and FADH2 in cellular respiration?

    They shuttle electrons to the electron transport chain, becoming oxidized back to NAD+ and FAD.

  • Where is the electron transport chain located?

    In the inner mitochondrial membrane.

  • What is chemiosmosis?

    Movement of protons down their gradient through ATP synthase to produce ATP.

  • How does brown fat generate heat without ATP?

    By uncoupling oxidative phosphorylation, allowing protons to flow without ATP synthesis, releasing energy as heat.