Topic 5 - Energy Transfers Flashcards
What is the initial role of chlorophyll in photosynthesis?
Chlorophyll absorbs light energy, causing photoionisation — the loss of electrons from chlorophyll
What happens to the electrons lost from chlorophyll during photoionisation?
They enter the electron transport chain, where their energy is used to produce ATP and reduced NADP.
How is ATP produced in the light-dependent reaction?
Via chemiosmosis: electrons move down the ETC releasing energy at each redox reaction, pumping protons across the thylakoid membrane. Protons diffuse back through ATP synthase, driving ATP synthesis.
What is the role of photolysis of water in the light-dependent reaction?
Photolysis splits water into protons (H⁺), electrons, and oxygen. The electrons replace those lost from chlorophyll.
What enzyme catalyses ATP synthesis in the chloroplast?
ATP synthase.
What enzyme catalyses the fixation of CO₂ to RuBP?
RubisCO
What is formed when CO₂ reacts with RuBP?
Two molecules of glycerate-3-phosphate (GP).
How is GP converted to triose phosphate (TP)?
Using ATP and reduced NADP from the light-dependent reaction.
What happens to triose phosphate in the Calvin Cycle?
Some is used to regenerate RuBP; some is used to form useful organic molecules like glucose.
Name three environmental factors that limit photosynthesis.
Light intensity, CO₂ concentration, and temperature.
How can commercial greenhouses overcome limiting factors?
By controlling temperature
Poviding supplementary light and CO₂,
Optimising watering and nutrient supply.
Where does glycolysis occur?
In the cytoplasm.
What are the stages of glycolysis?
1) Phosphorylation of glucose using ATP
2) Formation of triose phosphate
3) Oxidation of triose phosphate to pyruvate (net gain of ATP and reduced NAD)
What happens to pyruvate in anaerobic conditions?
Converted to lactate (in animals) or ethanol and CO₂ (in yeast), regenerating NAD for glycolysis.
What happens to pyruvate in aerobic respiration?
Pyruvate is actively transported into mitochondria, then oxidised to acetate, producing reduced NAD.
What does acetate combine with to form acetyl-CoA?
Coenzyme A (in the link reaction)
What are the products of the Krebs Cycle?
Reduced NAD, reduced FAD, ATP (by substrate-level phosphorylation), and CO₂.
How is ATP generated in oxidative phosphorylation?
Electrons pass through the ETC, pumping H⁺ across the inner mitochondrial membrane; protons flow through ATP synthase, producing ATP.
What is the role of oxygen in oxidative phosphorylation?
Final electron acceptor, combining with electrons and protons to form water.
Name two alternative respiratory substrates
Lipids (fatty acids) and amino acids (deaminated).
What is biomass?
The mass of living material, measured as dry mass or mass of carbon.
How is chemical energy in biomass measured?
Using calorimetry.
What is Gross Primary Production (GPP)?
Total chemical energy converted by producers in a given area/volume.
What is Net Primary Production (NPP)?
GPP minus respiratory losses (R):
NPP = GPP – R
