Unit 5 Flashcards
(41 cards)
Describe the light-dependent reaction of photosynthesis.
Light excites electrons in chlorophyll;
Electrons moves along the electron transport chain (ETC);
Energy released is used to phosphorylate ADP and Pi to form ATP;
Photolysis of water produces protons, electrons, and oxygen;
NADP is reduced by electrons and protons to form reduced NADP.
As electrons move through the ETC, protons (H⁺) are pumped across the thylakoid membrane, creating a proton gradient.
This gradient activates the enzyme ATP synthase, which makes ATP (energy for the Calvin Cycle).
Describe the Calvin Cycle (light-independent reaction).
CO₂ reacts with RuBP, catalysed by rubisco;
Produces 2 molecules of GP;
GP is reduced to 2 x TP using reduced NADP;
ATP provides energy for this reduction;
Some (2) TP converted to glucose or organic substances;
Rest (5 TP) regenerates RuBP using ATP.
How are chloroplasts adapted for photosynthesis?
Thylakoid membranes have large surface area with photosystems;
ATP synthase embedded in membrane;
Stroma contains enzymes for Calvin Cycle;
DNA and ribosomes for protein synthesis.
Why do weedkillers cause plants to give off heat?
Excited electrons release energy; ETC is blocked so energy isn’t used to form ATP, and is lost as heat.
Why does increased light intensity increase plant growth?
Increases production of ATP and reduced NADP;
Faster light-independent reaction;
More glucose for respiration; More energy for growth;
More/faster synthesis of organic materials.
How would you investigate the effect of light intensity on the rate of photosynthesis?
Use aquatic plant (e.g. Elodea);
Use light source at varying distances;
Measure O₂ production with gas syringe / count bubbles;
Control temp and CO₂;
Repeat and calculate mean rate.
What are the stages of photosynthesis?
Light-dependent reaction (in thylakoid membrane);
Produces ATP and reduced NADP;
Light-independent reaction (Calvin Cycle in stroma);
Uses ATP and reduced NADP to produce glucose.
What is the role of reduced NADP and ATP in the Calvin Cycle?
Reduced NADP reduces GP to TP; ATP provides energy for the reaction and regeneration of RuBP.
What are the stages of aerobic respiration?
Glycolysis (cytoplasm);
Link reaction (matrix);
Krebs cycle (matrix);
Oxidative phosphorylation/ETC (inner mitochondrial membrane).
Where does glycolysis occur and what are the products?
Occurs in the cytoplasm. Glucose → 2 pyruvate, 2 ATP (net), and 2 NADH.
What happens in the link reaction?
Pyruvate decarboxylated ( releases CO2)
Forming acetyl CoA - coenzyme a
NAD reduced - gains electron
What are the products of the Krebs cycle?
3 NADH, 1 reduced FAD, 1 ATP per cycle; 2 CO₂ released; Occurs twice per glucose.
What is the role of oxygen in aerobic respiration?
Acts as the final electron acceptor in the ETC, forming water.
Describe how ATP is produced during respiration.
- ATP produced in glycolysis;
- Involving the oxidation of glucose/TP to pyruvate;
- ATP production/ Substrate level phosphorylation directly from Krebs cycle;
- Glycolysis/Krebs cycle produce reduced NAD/FAD;
- Reduced NAD/FAD transfer electrons to electron transport chain;
- Electrons transferred down a chain of carriers;
- (Carriers) at decreasing energy levels;
- Energy (lost by electrons) used to produce ATP;
- From ADP and (inorganic) phosphate;
- Protons move into intermembrane space;
- ATP synthase;
Describe the process of chemiosmosis.
Electrons pass down the ETC; Energy used to pump H⁺ into intermembrane space; Protons diffuse back into matrix via ATP synthase; Drives ATP synthesis.
Why is less ATP produced in anaerobic respiration?
No final electron acceptor; ETC stops; Only glycolysis continues; Less ATP formed.
Describe anaerobic respiration in animals.
Pyruvate converted to lactate; NADH oxidised to NAD⁺; NAD⁺ allows glycolysis to continue; ATP still formed via glycolysis; Occurs in absence of O₂.
How would you investigate the rate of respiration in seeds?
Use respirometer with living seeds and control; Soda lime absorbs CO₂; Measure O₂ uptake via capillary movement; Control temperature; Repeat and compare rates.
Why is energy transfer along a food chain inefficient?
Light not all absorbed; Energy lost in respiration; Lost in faeces/excretion; Inedible parts not consumed; Heat loss in respiration.
What is Gross Primary Production (GPP)?
Total chemical energy converted by producers in a given area/time.
What is Net Primary Productivity (NPP)?
Energy left after respiration: NPP = GPP – R.
Why do food chains rarely have more than 4–5 trophic levels?
Energy loss at each level means insufficient energy to support higher levels.
How is energy transfer efficiency calculated?
(Energy transferred ÷ Energy available) × 100.
How can farming practices increase net productivity in animals?
Slaughter animals young; Control diet; Restrict movement; Use heated shelters; Selective breeding.
