Cellular Respiration

Key Definitions

• Catabolism: The breakdown of complex molecules into simpler ones, releasing energy.

• Anabolism: The synthesis of complex molecules from simpler ones, requiring energy input.

• Oxidation: Loss of electrons from a molecule, often associated with gaining oxygen or losing hydrogen.

• Reduction: Gain of electrons by a molecule, often associated with losing oxygen or gaining hydrogen.

• Beta Oxidation: The metabolic process by which fatty acids are broken down in the mitochondria to generate acetyl-CoA, NADH, and FADH2.

NAD+ in Cellular Respiration

• NAD+ is reduced to NADH during glycolysis, the TCA cycle, and beta oxidation, carrying electrons to the electron transport chain.

ATP Production in Glycolysis

• Substrate-level phosphorylation: ATP is produced directly in glycolysis by transferring a phosphate group from a substrate molecule to ADP.

• Net ATP yield: Glycolysis produces a net gain of 2 ATP per glucose molecule.

Role of O2 in Cellular Respiration

• Final electron acceptor: Oxygen accepts electrons at the end of the electron transport chain, forming water.

Metabolic Reactions in Complete Oxidation of Glucose

• Glycolysis: Glucose is split into two pyruvate molecules.

• Pyruvate oxidation: Pyruvate is converted to acetyl-CoA.

• TCA (Krebs) cycle: Acetyl-CoA is oxidized, producing CO2, NADH, and FADH2.

• Oxidative phosphorylation: NADH and FADH2 donate electrons to the electron transport chain, generating ATP.

Metabolic Processes: Aerobic vs. Anaerobic

• Require O2: Pyruvate oxidation, TCA cycle, oxidative phosphorylation.

• Do not require O2: Glycolysis, fermentation.

Products of Glycolysis and TCA Cycle

• Glycolysis: 2 pyruvate, 2 ATP, 2 NADH.

• TCA Cycle: Per glucose: 4 CO2, 2 ATP (GTP), 6 NADH, 2 FADH2.

Phosphorylation Impact

• Phosphorylation: Addition of a phosphate group to a molecule, often activating or deactivating enzymes and signaling molecules.

Pyruvate Entry into TCA Cycle

• Each pyruvate: Converted to acetyl-CoA (2 carbons), which enters the TCA cycle.

Metabolic Process Producing Most ATP

• Oxidative phosphorylation: Produces the majority of ATP per glucose molecule.

Locations of Metabolic Processes

• Glycolysis: Cytoplasm.

• TCA cycle: Mitochondrial matrix.

• Oxidative phosphorylation: Inner mitochondrial membrane.

ATP Production in Oxidative Phosphorylation

• 0% via substrate-level phosphorylation: All ATP in oxidative phosphorylation is produced by chemiosmosis, not direct substrate-level phosphorylation.

Proton Gradient Requirement

• Oxidative phosphorylation: Requires a proton gradient across the inner mitochondrial membrane to drive ATP synthase.

Fate of Lactate

• Lactate: Produced during anaerobic glycolysis; can be converted back to pyruvate or transported to the liver for gluconeogenesis.

Photosynthesis

Relationship Between Light Reactions and Calvin Cycle

• Light reactions: Generate ATP and NADPH.

• Calvin cycle: Uses ATP and NADPH to fix CO2 into sugars.

Electron Transport Chain: Highest Initial Energy Molecule

• NADH (cellular respiration) or primary electron donor (photosynthesis): Has the highest initial energy entering the electron transport chain.

Events of the Electron Transport Chain

• Electrons are transferred through a series of protein complexes.

• Protons are pumped across the membrane, creating a gradient.

• ATP synthase uses the gradient to produce ATP.

Immediate Source of Energy for ATP Synthase

• Proton gradient: The flow of protons down their gradient powers ATP synthase.

Organisms Capable of Photosynthesis

• Plants, algae, cyanobacteria: All can perform photosynthesis.

Locations of Light Reactions and Calvin Cycle

• Light reactions: Thylakoid membranes of chloroplasts.

• Calvin cycle: Stroma of chloroplasts.

Pigment Types Absorbed by Orange Plants

• Orange appearance: Indicates absorption of blue and green wavelengths; carotenoids are likely present.

Products of Light Reactions Used by Calvin Cycle

• ATP and NADPH: Both are required for the Calvin cycle.

Role of Pigment in Light-Harvesting Complex

• Pigments: Absorb light energy and transfer it to the reaction center for photosynthesis.

Wavelength and Energy of a Photon

• Inverse relationship: Shorter wavelength = higher energy.

• Equation:

• Where E is energy, h is Planck's constant, c is the speed of light, and \lambda is wavelength.

Location of Electron Transport Chain in Plants

• Thylakoid membrane: Site of the photosynthetic electron transport chain.

Photorespiration

• Photorespiration: Occurs when Rubisco combines O2 with RuBP instead of CO2, leading to a wasteful pathway.

Electron Flow During Photosynthesis

• Electrons flow from water to NADP+, forming NADPH.

Process in Photosynthesis Driven Directly by Light Energy

• Light reactions: Directly driven by light energy, resulting in the production of ATP and NADPH.

Summary Table: Cellular Respiration vs. Photosynthesis

Additional info: Table summarizes the main metabolic processes, their locations, inputs, outputs, and ATP production, for clarity and exam review.