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Chapters 9 & 10 – Cellular Respiration & Photosynthesis - Coggle…
Chapters 9 & 10 – Cellular Respiration & Photosynthesis
Overview of Cellular Respiration
Purpose: extract energy from glucose to make ATP
Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Types of Pathways
Aerobic respiration (with O₂)
Anaerobic respiration (without O₂)
Fermentation (partial breakdown without O₂)
Redox Reactions
Oxidation = loss of electrons
Reduction = gain of electrons
Glucose is oxidized, oxygen is reduced
NAD⁺ and FAD = electron carriers (coenzymes)
Reduced to NADH and FADH₂
Stages of Cellular Respiration
Glycolysis (cytoplasm)
Glucose → 2 pyruvate
Net: 2 ATP, 2 NADH
Occurs in all organisms; anaerobic
Pyruvate Oxidation (mitochondrial matrix)
Pyruvate → Acetyl-CoA
Produces CO₂ and NADH
Citric Acid Cycle (Krebs Cycle)
Acetyl-CoA enters cycle
Per glucose: 2 ATP, 6 NADH, 2 FADH₂, 4 CO₂
Occurs in mitochondrial matrix
Oxidative Phosphorylation
Includes Electron Transport Chain (ETC) + Chemiosmosis
ETC: transfers electrons to O₂, pumping H⁺
Chemiosmosis: H⁺ flows through ATP synthase → makes ATP
Yields ~26–28 ATP per glucose
Fermentation
Lactic Acid Fermentation
Pyruvate → lactate (no CO₂)
Used by muscle cells
Alcohol Fermentation
Pyruvate → ethanol + CO₂
Used by yeast
Metabolic Integration
Other molecules (fats, proteins) feed into respiration
Intermediates used in biosynthesis (anabolism)
Regulation of Respiration
Controlled by feedback inhibition
ATP inhibits phosphofructokinase
AMP activates it
Maintains energy balance
Overview of Photosynthesis
Purpose: convert solar energy into chemical energy (glucose)
Equation:
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Occurs in chloroplasts of plants, algae, and some bacteria
Structure of the Chloroplast
Thylakoids: membrane sacs, site of light reactions
Grana: stacks of thylakoids
Stroma: fluid between thylakoids, site of Calvin cycle
Nature of Light and Pigments
Light = electromagnetic energy
Pigments absorb visible light
Chlorophyll a = main pigment
Chlorophyll b and carotenoids = accessory pigments
Absorption spectrum = what wavelengths are absorbed
Action spectrum = what wavelengths drive photosynthesis
Light Reactions (Thylakoid Membrane)
Output: ATP + NADPH + O₂
Input: light + H₂O
Photosystem II (PSII)
Absorbs light → splits water → releases O₂
Transfers e⁻ to ETC
Electron Transport Chain
Pumps H⁺ into thylakoid space → ATP via chemiosmosis
Photosystem I (PSI)
Re-excites electrons → passed to NADP⁺ → NADPH
ATP Synthase
H⁺ flows back into stroma → ATP generated
The Calvin Cycle (Stroma)
Input: CO₂, ATP, NADPH
Output: G3P (sugar precursor)
Carbon Fixation
CO₂ + RuBP → catalyzed by Rubisco
Reduction
G3P produced using ATP and NADPH
Regeneration
RuBP regenerated using ATP
Photorespiration
Occurs when O₂ binds to Rubisco instead of CO₂
Wastes energy and carbon
Problem in hot, dry climates
Adaptations in Hot Climates
C₄ Plants (e.g., corn)
Separate carbon fixation spatially (mesophyll + bundle-sheath)
Use PEP carboxylase (no affinity for O₂)
CAM Plants (e.g., cactus)
Fix carbon at night, store as organic acids
Calvin cycle occurs during the day