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Questions and Answers
Citrate synthase catalyses the condensation of acetyl-CoA and oxaloacetate to form ______.
Citrate synthase catalyses the condensation of acetyl-CoA and oxaloacetate to form ______.
citrate
Isocitrate dehydrogenase converts isocitrate to ______ while reducing NAD+ to NADH.
Isocitrate dehydrogenase converts isocitrate to ______ while reducing NAD+ to NADH.
a-ketoglutarate
Oxidative phosphorylation occurs in the inner ______ membrane.
Oxidative phosphorylation occurs in the inner ______ membrane.
mitochondrial
Complex IV, known as Cytochrome c oxidase, facilitates the transfer of electrons to ______, forming water.
Complex IV, known as Cytochrome c oxidase, facilitates the transfer of electrons to ______, forming water.
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ATP synthase uses the proton gradient generated by the ______ to synthesize ATP.
ATP synthase uses the proton gradient generated by the ______ to synthesize ATP.
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GLYCOLYSIS is the first stage of cellular respiration, it occurs in the ______ and involves the breakdown of one molecule of glucose.
GLYCOLYSIS is the first stage of cellular respiration, it occurs in the ______ and involves the breakdown of one molecule of glucose.
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The investment phase of glycolysis uses 2 ______ molecules to phosphorylate glucose.
The investment phase of glycolysis uses 2 ______ molecules to phosphorylate glucose.
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Phosphofructokinase is a key regulatory enzyme in glycolysis that is activated by ______.
Phosphofructokinase is a key regulatory enzyme in glycolysis that is activated by ______.
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In the payoff phase, glycolysis yields 4 ______ molecules and 2 NADH molecules.
In the payoff phase, glycolysis yields 4 ______ molecules and 2 NADH molecules.
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The pyruvate generated in glycolysis is transported to the ______ for further oxidation.
The pyruvate generated in glycolysis is transported to the ______ for further oxidation.
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Pyruvate is oxidized into acetyl-CoA in a reaction catalyzed by the ______ dehydrogenase complex.
Pyruvate is oxidized into acetyl-CoA in a reaction catalyzed by the ______ dehydrogenase complex.
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For each acetyl-CoA molecule, the citric acid cycle produces 3 ______ and 1 FADH.
For each acetyl-CoA molecule, the citric acid cycle produces 3 ______ and 1 FADH.
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The citric acid cycle releases 2 ______ molecules as waste products.
The citric acid cycle releases 2 ______ molecules as waste products.
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Study Notes
Cellular Respiration in Eukaryotic Cells
- Cellular respiration is a multi-step process converting glucose into ATP
- Primarily occurs in the cytoplasm and mitochondria
- Consists of three main stages: glycolysis, citric acid cycle, and oxidative phosphorylation
Glycolysis
- First stage of cellular respiration, occurring in the cytoplasm
- Breaks down one glucose molecule (6C) into two pyruvate molecules (3C)
- Anaerobic process (does not require oxygen)
- Divided into two phases: investment and payoff
-
Investment phase: Uses 2 ATP to phosphorylate glucose, preparing it for cleavage
- Hexokinase phosphorylates glucose to glucose-6-phosphate
- Phosphofructokinase converts fructose-6-phosphate to fructose-1,6-bisphosphate
- Key regulatory enzyme; activated by AMP, inhibited by ATP
-
Payoff phase: Further metabolizes 3C molecules, yields 4 ATP and 2 NADH (substrate-level phosphorylation)
- Pyruvate kinase converts phosphoenolpyruvate to pyruvate
- Pyruvate production
- Pyruvate transported to mitochondria in presence of oxygen for further oxidation
Pyruvate Oxidation (Bridge reaction)
- Occurs in the mitochondrial matrix
- Pyruvate dehydrogenase complex oxidizes pyruvate to acetyl-CoA
- Multi-enzyme complex (E1, E2, E3)
- Decarboxylates pyruvate, reduces NAD+ to NADH, attaches CoA to the 2C acetyl group
- Produces one CO2 per pyruvate
Citric Acid Cycle (Krebs Cycle)
- Completes oxidation of acetyl-CoA molecule
- Per acetyl-CoA molecule: 3 NADH, 1 FADH2, 1 GTP (converted to ATP) produced
- Releases 2 CO2 molecules as waste products
- Key enzymes:
- Citrate synthase (condensation of acetyl-CoA and oxaloacetate to citrate)
- Isocitrate dehydrogenase (conversion of isocitrate to α-ketoglutarate; produces NADH and releases 2 CO2)
- α-ketoglutarate dehydrogenase (conversion of α-ketoglutarate to succinyl-CoA; produces NADH and releases CO2)
- Succinate dehydrogenase (oxidation of succinate to fumarate; reduces FAD to FADH2)
Oxidative Phosphorylation
- Final stage in cellular respiration, occurs on the inner mitochondrial membrane
- Two stages: electron transport chain (ETC) and chemiosmosis
-
Electron Transport Chain (ETC):
- NADH and FADH2 donate electrons to the ETC, composed of protein complexes and electron carriers
- Electrons lose energy as they pass through complexes, releasing energy that pumps H+ into the intermembrane space
- Complexes:
- Complex I (NADH dehydrogenase): Oxidizes NADH, transfers electrons to ubiquinone (Q), pumps protons
- Complex II (Succinate dehydrogenase): Transfers electrons from FADH2 to Q, no proton pumping
- Complex III (Cytochrome bc1 complex): Passes electrons, pumps protons
- Complex IV (Cytochrome c oxidase): Transfers electrons to oxygen (final electron acceptor), forms water
-
Chemiosmosis:
- ATP synthase uses the proton gradient generated by the ETC to synthesize ATP from ADP and inorganic phosphate
- Outputs approximately 26-28 ATP per glucose molecule.
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Description
This quiz explores the process of cellular respiration, focusing on glycolysis, the first stage that occurs in the cytoplasm. Participants will learn about the investment and payoff phases, key enzymes involved, and the overall conversion of glucose into ATP. Test your understanding of how energy is produced in eukaryotic cells.
