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Cellular Respiration - General Biology

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  • Overall equation for cellular respiration

    Glucose and oxygen are converted to carbon dioxide, water, and ATP. It is an exergonic reaction releasing energy.

  • Where is carbon dioxide produced in cellular respiration?

    Carbon dioxide is produced during the oxidation of pyruvate to acetyl-CoA and in the citric acid cycle inside the mitochondrial matrix.

  • Where is oxygen used in cellular respiration?

    Oxygen is the final electron acceptor in the electron transport chain, located in the inner mitochondrial membrane.

  • Explain oxidation and reduction in terms of electron transfer (OIL RIG)

    Oxidation is loss of electrons; reduction is gain of electrons.

  • Which substrate is oxidized and which is reduced in cellular respiration?

    Glucose is oxidized; oxygen is reduced to form water.

  • How do changes in hydrogen atoms indicate oxidation or reduction?

    Loss of hydrogen atoms indicates oxidation; gain of hydrogen atoms indicates reduction.

  • Why does cellular respiration occur through multiple enzyme-catalyzed steps?

    To gradually release energy in manageable amounts and efficiently capture it as ATP rather than losing it as heat.

  • Four major steps of cellular respiration

    Glycolysis, Pyruvate oxidation, Citric acid cycle, and Oxidative phosphorylation.

  • Location of glycolysis in eukaryotes and prokaryotes

    Occurs in the cytoplasm in both eukaryotes and prokaryotes.

  • Why is ATP needed to start glycolysis?

    ATP provides activation energy to initiate the breakdown of glucose.

  • Net inputs and outputs of glycolysis

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

  • What molecule is reduced during glycolysis?

    NAD+ is reduced to NADH as glucose is oxidized.

  • Fate of 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 allow glycolysis to continue.

  • Products of pyruvate oxidation

    Each pyruvate produces one molecule of carbon dioxide, one NADH, and one acetyl-CoA.

  • Location of the citric acid cycle

    Occurs in the mitochondrial matrix.

  • Major products of the citric acid cycle

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

  • Why is the citric acid cycle called a cycle?

    Because the starting molecule oxaloacetate is regenerated after each turn.

  • Role of NADH and FADH2 in cellular respiration

    They shuttle electrons to the electron transport chain in their reduced forms and become oxidized back to NAD+ and FAD.

  • Location of the electron transport chain

    Embedded in the inner mitochondrial membrane.

  • Purpose of the electron transport chain

    To transfer electrons through protein complexes, releasing energy to pump protons and create a proton gradient.

  • Source and final electron acceptor in the electron transport chain

    Electrons come from NADH and FADH2; oxygen is the final electron acceptor forming water.

  • Does electronegativity increase or decrease along the electron transport chain?

    Electronegativity increases, electrons move to more electronegative carriers ending with oxygen.

  • Why does the electron transport chain not directly make ATP?

    It creates a proton gradient that drives ATP synthase to produce ATP via chemiosmosis.

  • Direct energy source for ATP synthase

    The flow of protons down their electrochemical gradient through ATP synthase.

  • Substrates and products of ATP synthase

    Substrates: ADP and inorganic phosphate; Product: ATP.

  • Which process produces the most ATP in cellular respiration?

    Oxidative phosphorylation produces the most ATP.

  • How does brown fat generate heat without producing ATP?

    By uncoupling the proton gradient from ATP synthesis, releasing energy as heat.

  • What is fermentation?

    A process that regenerates NAD+ by oxidizing NADH when oxygen is absent, allowing glycolysis to continue.

  • Difference between alcohol and lactic acid fermentation

    Alcohol fermentation produces ethanol and CO2; lactic acid fermentation produces lactate.

  • Where do fatty acids enter cellular respiration?

    As acetyl-CoA after beta-oxidation, entering the citric acid cycle.

  • Which produces more ATP per gram: glucose or fatty acids?

    Fatty acids produce more ATP per gram, explaining why animals store energy as fat.

  • Where do amino acids enter cellular respiration?

    After deamination, amino acids enter as intermediates in glycolysis or the citric acid cycle.

  • Role of the citric acid cycle in amino acid anabolism

    It provides intermediates for amino acid synthesis and is regulated by feedback inhibition.

  • Example of feedback inhibition in cellular respiration

    Phosphofructokinase is inhibited by ATP to regulate glycolysis based on energy needs.