Recording-2025-03-12T20:10:44.429Z

Photosynthesis and Electron Flow

• Pigments: Primary pigments are chlorophyll a and b, which absorb blue and red photons.

Cyclic Electron Flow

• During cyclic electron flow, electrons circulate between Photosystem I and the cytochrome b6f complex.

• This process leads to solar-powered ATP synthesis but does not produce NADPH, release oxygen, or split water.

Calvin Cycle Phases

• Three Phases of the Calvin Cycle:

  • CO2 Capture: By ribulose bisphosphate (RuBP) catalyzed by the enzyme Rubisco.

  • Carbon Fixation: Produces three-carbon molecules called 3-phosphoglycerates (3-PGA).

  • Reduction Phase: Uses ATP and NADPH to convert 3-PGA into glyceraldehyde-3-phosphate (G3P).

• Enzyme Specificity: Rubisco has difficulty discriminating between CO2 and O2, leading to oxygen being inserted occasionally.

• Stomata Closure: On sunny days, plants may close stomata to prevent water loss via transpiration, leading to CO2 depletion.

C4 and CAM Plants

• C4 Plants: Include crops like corn and sugarcane; separate carbon capture and Calvin cycle spatially.

• Photosynthesis Variants: C4 plants perform an adaptation to prevent photorespiration and maximize efficiency under high light and temperature conditions.

Cellular Respiration

• Controlled vs. Uncontrolled Energy Release:

  • Uncontrolled Burning: Carbohydrates can oxidize directly, producing CO2 and water but lack control (degrades energy efficiency).

  • Controlled Breakdown: Cellular respiration maintains control of energy release in a series of small reactions, maximizing energy extraction.

• Enzyme Complexes: Breakdown involves a complex of multiple enzymes rather than a single type.

Electron Transport Chain (ETC)

• Location: The ETC is embedded in the inner mitochondrial membrane.

• Proton Pumping: Complexes I, III, and IV pump protons across the membrane to create a proton motor force.

• Complex II (Succinate Dehydrogenase):

  • Accepts electrons from FADH2 but does not pump protons.

  • Participates in the Krebs cycle.

Q Cycle

• Coenzyme Q: Involved in electron transfer but requires a more complex understanding (not covered extensively in this resource).

• Redox Potential: Involvement of the redox potential of hydrogen gas and protons through the electron transport chain, which is an exergonic process.