ch.12 Flashcards
(31 cards)
Chemoautotrophs
Energy Source: Chemical compounds.
Carbon Source: CO₂.
Example: Bacteria in deep-sea hydrothermal vents.
Photoheterotrophs
Energy Source: Light.
Carbon Source: Organic compounds.
Photoautotrophs
Energy Source: Light.
Carbon Source: CO₂.
Examples: Plants, cyanobacteria, algae, and some protists.
Ecological Role of Primary Producers
Role: Primary producers convert solar energy into chemical energy, forming the base of the food web and supporting all other life forms by providing oxygen and organic compounds.
Oxygenic Photosynthesis Equation and Carbon Cycle
Equation:
6CO2+6H 2O+lightenergy→C6H12O6+6O2
Comparison with Cellular Respiration:
Photosynthesis converts CO₂ and water into glucose and oxygen.
Cellular respiration breaks down glucose and oxygen into CO₂ and water.
Role in Carbon Cycle: Photosynthesis removes CO₂ from the atmosphere, and cellular respiration returns it, maintaining the balance of carbon.
Oxygenic Photosynthesis
Performed by plants, algae, and cyanobacteria.
Produces oxygen as a byproduct (uses water as an electron donor)
Anoxygenic Photosynthesis
Performed by certain bacteria (e.g., purple sulfur bacteria).
Does not produce oxygen (uses H₂S instead of water as an electron donor).
Plant Structures in Photosynthesis
Vascular Tissue: Transports water and nutrients to leaves and sugars throughout the plant.
Stomata: Openings in leaves for gas exchange (CO₂ in, O₂ out).
Mesophyll: Leaf tissue where most photosynthesis occurs; contains chloroplasts.
Structure of a Chloroplast
Components:
Outer Membrane: Protective boundary.
Inner Membrane: Encloses the stroma.
Intermembrane Space: Between outer and inner membranes.
Thylakoids: Flattened sacs where light reactions occur.
Grana: Stacks of thylakoids.
Stroma: Fluid surrounding thylakoids, site of the Calvin cycle.
Organelles Group: Chloroplasts are part of the plastid family in eukaryotes.
Definition and Properties of Pigments
Pigment: Molecule that absorbs specific wavelengths of light.
Absorption Spectrum: Graph showing the absorption of different wavelengths by a pigment.
Primary Photosynthetic Pigments
Primary Pigments: Chlorophylls (a and b).
Structure:
Porphyrin Ring: Absorbs light.
Hydrocarbon Tail: Anchors pigment in the thylakoid membrane.
Accessory Pigments
Carotenoids: Another pigment group in oxygenic photoautotrophs.
Functions:
Absorb light energy for photosynthesis.
Protect chlorophyll from photooxidation.
Absorption and Excitation of Photons by Pigments
Photon Absorption: Energy from a photon excites an electron.
Blue Light: Higher energy, excites electrons to a higher state.
Red Light: Lower energy, excites electrons to a lower state.
Outcomes of Excited Electrons
Electron Transfer: Excited electron can be transferred to an acceptor.
Energy Release: Electron returns to ground state, releasing energy as heat or fluorescence.
Photosystem Components
Antenna Complex: Array of pigments that capture and transfer light energy.
Reaction Center: Contains chlorophyll molecules where electron transfer initiates light reactions
Electron Donor and Oxygen Production
Electron Donor in Oxygenic Photosynthesis: Water (H₂O).
Oxygen Byproduct: Produced when water is split in PSII.
Byproduct of H₂S Use: Sulfur is produced instead of oxygen in anoxygenic photosynthesis.
Linked Reactions in Photosynthesis
Light Reactions: Occur in thylakoid membranes, convert light energy to chemical energy.
Calvin Cycle: Occurs in the stroma, uses ATP and NADPH to fix carbon.
Photosystem Locations
PS Location: In chloroplast thylakoid membranes and in the plasma membranes of photosynthetic bacteria.
Energy vs. Electron Transfer in a Photosystem
Energy Transfer: Relays light energy from pigment to pigment.
Electron Transfer: Transfers electrons through the ETC in light reactions.
Photosystem II and I Functions
PS II:
Function: Produces oxygen and creates an H⁺ gradient.
Electron Transfer: Water → P680 → ETC.
Electron Replenishment: From water splitting.
PS I:
Function: Reduces NADP⁺ to NADPH.
Electron Transfer: P700 → ETC → NADP⁺.
Electron Replenishment: From PSII.
Oxygen Evolving Complex of PSII
Reaction: Splits water into oxygen, electrons, and H⁺ ions.
Importance: Supplies electrons to PSII and releases oxygen.
H⁺ Electrochemical Gradient in Light Reactions
Location: Generated in the thylakoid lumen.
Contributors:
Water splitting in PSII.
H⁺ pumping by the ETC.
NADP⁺ reduction at the end of the ETC.
Evolutionary Link Between Photosynthesis and Cellular Respiration
Similarity: Both use an ETC and ATP synthase for energy conversion
Linear and Cyclic Electron Flow
Linear: Produces both ATP and NADPH; occurs in high light conditions.
Cyclic: Produces ATP only; occurs when NADPH levels are high.
