Calvin Cycle
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Biology
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Calvin Cycle
Also known as the light-independent reactions.
Takes place in plants to produce glucose using carbon dioxide from the air.
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Carbon Fixation
Process: Plant takes CO₂ from the air.
Enzyme: RuBisCO combines CO₂ with a 5-carbon molecule (RuBP).
Product: Unstable 6-carbon compound splits into two 3-carbon molecules (3-PGA).
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Reduction
Energy Use: ATP and electrons from NADPH convert 3-PGA into G3P.
Output: For every 6 CO₂ fixed, 2 G3P produced (building blocks for glucose).
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Regeneration of RuBP
Usage: Some G3P forms glucose; most regenerate RuBP for the cycle.
Energy Requirement: More ATP is needed to convert G3P back to RuBP.
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Overview of the Calvin Cycle
Converts CO₂ into sugars using ATP and NADPH.
Main stages: Carbon fixation, reduction, regeneration of RuBP.
Sugars can be used for growth, energy, or stored as starch.
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Aerobic Respiration
Requires: Oxygen.
Location: Mitochondria.
Energy Output: 36 to 38 ATP per glucose molecule.
Byproducts: CO₂ and H₂O.
Example: Used by humans and animals during breathing.
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Anaerobic Respiration
Requires: No oxygen.
Location: Cytoplasm.
Energy Output: 2 ATP per glucose molecule.
Byproducts: Lactic acid (in animals) or ethanol and CO₂ (in yeast).
Example: Muscles switching to anaerobic respiration leads to fatigue.
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Summary of Respiration Types
Aerobic: Needs oxygen, produces 36-38 ATP.
Anaerobic: No oxygen needed, produces only 2 ATP.
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Cellular Respiration Components
Organelles: Mitochondrion (aerobic), Cytosol (anaerobic).
Key Terms: Carbon, ATP, Glucose, Pyruvic Acid.
Steps: Glycolysis, Krebs Cycle, Electron Transport Chain (ETC).
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Glycolysis
Location: Cytoplasm.
Process: Glucose is split into 2 pyruvate.
Energy Output: 2 ATP and 2 NADH produced.
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Krebs Cycle
Location: Mitochondria.
Input: Each pyruvate turns into Acetyl-CoA and enters the cycle.
Energy Output: 2 ATP, 6 NADH, 2 FADH₂, and releases 4 CO₂.
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Electron Transport Chain (ETC)
Location: Inner mitochondrial membrane.
Process: Electrons from NADH and FADH₂ power ATP production.
Energy Output: 32-34 ATP produced; byproducts are H₂O.
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Total ATP from One Glucose
Glycolysis: 2 ATP.
Krebs Cycle: 2 ATP.
Electron Transport Chain: 32-34 ATP.
Total: About 36-38 ATP.
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Comparison of Cellular Respiration Stages
Features of Glycolysis, Krebs Cycle, ETC, and Chemiosmosis.
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Glycolysis Details
Where: In cytoplasm.
What Happens: Glucose to 2 pyruvate.
Energy Output: 2 ATP and 2 NADH.
Oxygen Requirement: None, anaerobic.
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Krebs Cycle and ETC Details
Krebs Cycle
Where: Mitochondria.
Process: Pyruvate → Acetyl-CoA → further breakdown.
Energy Output: 2 ATP, 6 NADH, 2 FADH₂, 4 CO₂.
Electron Transport Chain
Where: Inner mitochondrial membrane.
Process: NADH and FADH₂ donate electrons.
Byproducts: H₂O produced.
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Key Differences in Respiration
Glycolysis: Outside mitochondria, no oxygen.
Krebs Cycle: Inside mitochondria, uses glycolysis products.
ETC: Inner membrane, creates proton gradient.
Chemiosmosis: Uses gradient to make ATP.
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ATP Production and Consumption
Pathways producing and consuming ATP in respiration.
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ATP Production Stages
Glycolysis
Where: Cytoplasm.
What Happens: Glucose → 2 pyruvate.
ATP: 2 ATP through substrate-level phosphorylation.
Krebs Cycle
Where: Mitochondria.
ATP: 2 ATP by substrate-level phosphorylation.
Chemiosmosis
Where: Inner mitochondrial membrane.
ATP: 32-34 ATP produced.
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ATP Consumption Stages
Activation of Glucose
Where: Cytoplasm.
ATP: 2 ATP used to prepare glucose.
Transport of Pyruvate
Where: Mitochondrial membrane.
ATP: Small amount used.
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Role of Oxygen in Respiration
Oxygen is crucial for aerobic respiration efficiency.
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Oxygen's Role
Final electron acceptor in ETC; forms H₂O.
Creates proton gradient for ATP production.
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Anaerobic Pathways
Utilize fermentation when oxygen is absent.
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Fermentation Processes
In Organisms
Use molecules like nitrate or sulfate as electron acceptors.
Lactic Acid Fermentation: Converts pyruvate to lactic acid.
Alcoholic Fermentation: Converts pyruvate to ethanol and CO₂.
ATP: Only 2 ATP produced.
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Fermentation vs. Aerobic Respiration
Comparison of advantages and disadvantages in energy production.
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Advantages of Aerobic Respiration
High ATP yield, complete glucose breakdown, more efficiency for long-term energy.
Disadvantages: Requires oxygen, slower process.
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Advantages of Fermentation
Quick ATP production, no oxygen required, allows glycolysis continuation.
Disadvantages: Low ATP yield, waste product buildup.
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Conclusion on Energy Production
Aerobic respiration is efficient with oxygen; fermentation is quick but less efficient.