History of Photosynthesis
- Cyanobacteria: 2.4 bya
- Eukaryote Photosynthesis: 1.4 bya
- 1st fossil evidence for photosynthesis in red algae.
Cellular Respiration
This is a complimentary, but reverse, process.
- Cellular Respiration
- Catabolic
- Uses sugar to make ATP.
- Spontaneous electron transport pulled by O2.
Photosynthesis
- Metabolism
- Catabolic (breakdown bonds) & anabolic (building bonds)
- Refers to how macromolecules are broken down or build up.
- Photosynthesis
- Is glucose anabolic
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- Creates carbohydrates.
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- Creates macromolecules.
- Uses light to make sugar.
- Light driven electron transport.
Electron Transport Chain
- Electron Transport Chain
- Creates photon gradient (potential energy).
- Proton Gradient
- Creates potential energy.
- Electron transfers drive H⁺s (hydrogen ions) across the inner membrane.
- Oxidative Phosphorylation
- Makes ATP using the ATP Synthase enzyme.
Molecules
- ATP
- High-energy
- 3 negative phosphates
- NADPH
- Electron carrier
Chloroplasts
- Chloroplast
- Has two membranes.
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- Thylakoid Membranes
- Contains thylakoid lumen.
- When stacked: granum
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- Stroma
- Fluid around thylakoid lumen.
- Light Dependent Reactions
- Occur in the thylakoid membrane.
- Makes ATP and NADPH and O₂ from ADP and NADPH
- Light Independent Reactions Calvin Cycle Depends on Light Dependent Reactions
- Occur in stroma
- Uses ATP and NADPH and CO₂ to make sugar.
Light Dependent Reactions
- Forster Resonance Energy Transfer
- How photons excite electrons.
- Antenna Complex
- Light harvesting
- PQ A lipid
- Accepts electrons
- Reaction Center
- Accepts and donates and electron to and from chlorophyll.
- Water donates an electron to chlorophyll and gives off oxygen.
- Redox Reactions
- Stands for REDuction/OXygen.
- Gains electrons or loses electrons.
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- Reduction
- GAIN electrons +e
- Oxidation
- LOSE electrons -e
Excited molecules must return to their ground state. Light energy can be lost as:
- Transfers to another molecule (chlorophyll)
- Fluorescence (light)
- Heat
PhotoSystem II
Makes ATP. Photons can be scattered, reflected, transmitted, or absorbed.
- Chlorophyll
- Reflects green light
- Absorbs photons.
Photons excite electrons, increasing energy,
- Electron is less stable, more reactive.
- Some electrons escape to the electron transport chain.
PhotoSystem I
Makes NADPH. Goes through electron transport chain again, second photon is used to re-excite the electron.
Light Independent Reactions
_Calvin Cycle
Takes place in the stroma.
- RuBisCO RuBP
- An enzyme that "fixes" carbon.
- Most abundant protein on Earth.
Magnesium counter balances H+ ions in proton gradients.
H+ ions are just protons. Hydrogen has 1 proton, neutron and electron, and when it loses the electron (+) it becomes just a proton. Acidic solution has higher H+ ions than a basic solution.
pH is the concentration of Hydrogen (H+) ions in a solution.
Assignment
| Photosynthesis | Cellular Respiration | |
|---|---|---|
| Takes place in which organisms: bacteria, plants, and/or animals? | Cyanobacteria, plants | Plants, animals |
| Takes place in which organelle in eukaryotic organisms? | Chloroplasts | Mitochondria |
| What is the purpose of this metabolic pathway? | Makes sugars | Makes ATP |
| What source of energy drives this metabolic process? | Sunlight (photons) | Glucose |
| What is the initial electron donor to the electron transport chain? | Chlorophyll | Glucose |
| What is the final electron acceptor in the electron transport chain? | NADP+ | O₂ |
| What are the final products from the electron transport chain? | O2, ATP, NADPH | H₂O, ATP, CO₂ |
| Which type of electron transport is involved? cyclic and/or non-cyclic? | Non-cyclic | Non-cyclic |
| What electron carriers are involved? | NADPH | NADH |
| Is ATP synthesized? How? | Light reactions, photosystem II-photophosphorylation. | Yes, breakdown of glucose in kreb's cycle. |
| What “cycle” is used in this metabolic pathway? What happens during the cycle? | Calvin cycle. Fixes CO₂ using ATP&NADPH into sugar. | Kreb's cycle. Pyruvate oxidizes to make ATP+CO2+H2O. |