Photosynthesis: Light-Dependent and Independent Reactions

Photosynthesis

Light-Dependent Reactions

• Occur in thylakoid membranes of chloroplasts
• Light energy excites electrons, which are passed along electron transport chains
• ATP and NADPH produced
• Water is split, releasing oxygen as a byproduct

Light-Independent Reactions (Calvin Cycle)

• Occur in stroma of chloroplasts
• ATP and NADPH from light-dependent reactions used to convert CO2 into glucose
• Regeneration of RuBP (ribulose-1,5-bisphosphate) occurs

Overall Equation

6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2

Factors Affecting Photosynthesis

• Light intensity
• Temperature
• Water availability
• CO2 concentration

Respiration

Aerobic Respiration

• Occurs in mitochondria
• Glucose broken down into CO2 and H2O, releasing energy (ATP)
• Energy released from electron transport chain used to produce ATP

Anaerobic Respiration

• Occurs in cytoplasm
• Glucose broken down into lactic acid or ethanol and CO2, releasing energy (ATP)
• No electron transport chain, less ATP produced

Respiration Equation

C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + ATP

Factors Affecting Respiration

• Temperature
• Oxygen availability
• Glucose concentration

Ecosystems

Trophic Levels

• Producer (plants, algae)
• Primary consumer (herbivore)
• Secondary consumer (carnivore)
• Tertiary consumer (apex predator)

Energy Transfer

• Energy lost as heat at each trophic level (10% rule)
• Energy available to each trophic level decreases

Food Chains and Webs

• Food chain: linear sequence of trophic levels
• Food web: complex network of food chains

Ecosystem Services

• Provisioning services (food, water, timber)
• Regulating services (climate regulation, pollination)
• Cultural services (recreation, tourism)
• Supporting services (soil formation, nutrient cycling)

Ecosystem Succession

• Primary succession: new habitat formation (e.g., volcanic island)
• Secondary succession: disturbance to existing habitat (e.g., forest fire)

Photosynthesis

• Light-dependent reactions occur in thylakoid membranes of chloroplasts, producing ATP and NADPH through electron transport chains.
• Water is split, releasing oxygen as a byproduct during light-dependent reactions.
• ATP and NADPH from light-dependent reactions are used to convert CO2 into glucose during light-independent reactions (Calvin Cycle).
• Regeneration of RuBP (ribulose-1,5-bisphosphate) occurs during light-independent reactions.
• The overall equation of photosynthesis is: 6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2.
• Factors affecting photosynthesis include light intensity, temperature, water availability, and CO2 concentration.

Respiration

• Aerobic respiration occurs in mitochondria, breaking down glucose into CO2 and H2O, releasing energy (ATP).
• Energy is released from electron transport chain during aerobic respiration, producing ATP.
• Anaerobic respiration occurs in cytoplasm, breaking down glucose into lactic acid or ethanol and CO2, releasing energy (ATP).
• Anaerobic respiration has no electron transport chain, resulting in less ATP production.
• The respiration equation is: C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + ATP.
• Factors affecting respiration include temperature, oxygen availability, and glucose concentration.

Ecosystems

Trophic Levels

• Producers (plants, algae) form the base of trophic levels.
• Primary consumers (herbivores) feed on producers.
• Secondary consumers (carnivores) feed on primary consumers.
• Tertiary consumers (apex predators) feed on secondary consumers.

Energy Transfer

• Energy is lost as heat at each trophic level (10% rule).
• Energy available to each trophic level decreases.

Food Chains and Webs

• Food chains are linear sequences of trophic levels.
• Food webs are complex networks of food chains.

Ecosystem Services

• Provisioning services provide essential resources like food, water, and timber.
• Regulating services regulate climate, pollination, and other ecosystem processes.
• Cultural services provide recreational and tourism opportunities.
• Supporting services include soil formation and nutrient cycling.

Ecosystem Succession

• Primary succession occurs in new habitat formations (e.g., volcanic island).
• Secondary succession occurs in response to disturbances to existing habitats (e.g., forest fire).