AQA Bio A Level Unit 5 Flashcards
What is the role of chlorophyll in photosynthesis?
Chlorophyll absorbs light energy, which excites electrons and drives the process of photophosphorylation during the light-dependent reactions of photosynthesis.
What are the two main stages of photosynthesis?
The two main stages are the light-dependent reactions (which produce ATP and NADPH) and the light-independent reactions (Calvin cycle, where glucose is synthesised).
Where does the light-dependent reaction of photosynthesis take place?
The light-dependent reaction takes place in the thylakoid membranes of the chloroplasts
What is photolysis, and why is it important in photosynthesis?
Photolysis is the splitting of water using light energy to produce electrons, protons, and oxygen. The electrons replace those lost from chlorophyll in photosystem II, and the protons contribute to ATP synthesis
What are the products of the light-dependent reactions of photosynthesis?
The products are ATP, NADPH, and oxygen (O₂).
Where does the Calvin cycle take place?
The Calvin cycle takes place in the stroma of the chloroplasts.
What is the role of RuBP and RuBisCO in the Calvin cycle?
RuBP (ribulose bisphosphate) reacts with CO₂ in a reaction catalyzed by the enzyme RuBisCO, forming two molecules of GP (glycerate-3-phosphate), which are then used to produce glucose.
What is oxidative phosphorylation, and where does it occur?
Oxidative phosphorylation is the process of ATP production using energy derived from electron transfer in the mitochondrial inner membrane, involving the electron transport chain and chemiosmosis.
What are the main stages of aerobic respiration?
The main stages are glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation.
What is the net gain of ATP molecules in glycolysis?
The net gain of ATP in glycolysis is 2 ATP molecules per molecule of glucose.
What is the purpose of the Krebs cycle?
The Krebs cycle generates reduced coenzymes (NADH and FADH₂), ATP, and carbon dioxide, which are used in oxidative phosphorylation to produce more ATP.
How is ATP synthesized during chemiosmosis in respiration?
Protons are pumped into the intermembrane space of the mitochondria, creating a proton gradient. ATP is synthesised as protons flow back into the mitochondrial matrix through ATP synthase.
What is anaerobic respiration and what are its products in animal cells?
Anaerobic respiration occurs without oxygen, producing lactic acid and a small amount of ATP in animal cells.
What is the difference between gross primary production (GPP) and net primary production (NPP)?
GPP is the total amount of energy captured by producers through photosynthesis, while NPP is the energy remaining after respiration, available to consumers in the ecosystem.
How do energy transfers between trophic levels affect the energy available in an ecosystem?
Only about 10% of energy is transferred to the next trophic level, with the rest lost as heat, through respiration, or in waste, limiting the number of trophic levels in an ecosystem.
What is a pyramid of biomass, and what does it represent?
A pyramid of biomass represents the total mass of organisms at each trophic level in an ecosystem, showing the decrease in biomass at higher levels.
What is the nitrogen cycle, and why is it important for ecosystems?
The nitrogen cycle involves the conversion of nitrogen between its various chemical forms (e.g., nitrogen fixation, nitrification, and denitrification), making nitrogen available for organisms to synthesize proteins and nucleic acids.
What role do saprobionts play in nutrient cycles?
Saprobionts (decomposers) break down organic material from dead organisms, releasing nutrients like nitrogen and phosphorus back into the soil for reuse by plants.
What is eutrophication, and how is it caused?
Eutrophication is the excessive growth of algae and aquatic plants due to increased nutrient levels (often from agricultural runoff), leading to oxygen depletion and harm to aquatic life.
What is the role of NADP in photosynthesis?
NADP acts as an electron carrier. In the light-dependent reactions, it is reduced to NADPH, which then carries high-energy electrons and protons to the Calvin cycle for the synthesis of carbohydrates.
