Topic 5- Energy transfer and nutrient cycles Flashcards
Describe what happens during photoionisation in the light-dependent reaction.
(2 Marks)
- Chlorophyll absorbs light
OR light excites electrons in chlorophyll. - Electrons are lost
OR chlororphyll becomes positively charged.
Describe the method the student would use to separate pigments after solution of pigments had been applied to the origin.
(2 Marks)
- Level of solvent below the origin line
- Remove/ stop before solvent reaches the top/ end.
Heat stress is a condition that often occurs in plants exposed to high temperatures for prolonged periods of time.
This decreases the light-dependent reaction of photosynthesis.
Explain why this would lead to a decrease in the light- independent reaction.
(2 Marks)
- less/no ATP
- Less/no reduced NADP
A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis.
Explain why.
(2 Marks)
- Less/ no carbon dioxide reacts with RuBP.
- Less/ no GP
Where precisely is rubisco found in a cell.
(1 Mark)
Stroma of chloroplast.
Explain how chemicals that inhibit the decolourisation of DCPIP could slow the growth of weeds.
(2 Marks)
- Less/ no ATP produced.
- Less/no reduced NADP produced
- Less/ no GP reduced/ converted to TP.
Other than a thermometer, explain how two features of a calorimeter would enable a valid measurement of the total heat energy released.
(2 Marks)
- Stirrer distributes heat energy.
- Insulation/ space/ air reduces loss/ gain of heat.
- Water has high specific heat capacity.
In natural ecosystems, most of the light falling on producers is not used in photosynthesis.
Suggest two reasons why.
(2 Marks)
- Light is reflected.
- Light is the wrong wavelength.
- Light misses chlorophyll/ chloroplasts.
- CO2 concentration or temperature is a limiting factor.
Name the two products of the light-dependent reaction that are required for the light-independent reaction.
(2 Marks)
- ATP
- Reduced NADP.
Describe the process of glycolysis.
(4 Marks)
- Phosphorylation of glucose using ATP.
- Oxidation of TP to pyruvate.
- Net gain of ATP.
- NAD is reduced.
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell.
(2 Marks)
- Less/ no reduced NAD/ coenzymes.
OR fewer electrons removed and passed to the ETC. - Oxygen is the final electron acceptor.
In muscles, pyruvate is converted to lactate during prolonged exercise.
Explain why converting pyruvate to lactate allows the continued production of ATP by aerobic respiration.
(2 Marks)
- Regenerates/ produces NAD.
OR oxidises reduced NAD. - So glycolysis continues.
Describe the advantage of the Bohr effect during intense exercise.
(2 Marks)
- Increases dissociation of oxygen.
- For aerobic respiration at the tissue/ muscles/ cells.
OR anaerobic respiration is delayed at the tissue/ muscles/ cells.
EPO is a performance enhancing drug that can increase the percentage of red blood cells in the blood.
A heart attack is caused by a lack of glucose and oxygen being delivered to cardiac muscles via the coronary arteries.
Suggest how the overuse of EPO can increase the risk of a heart attack.
(2 Marks)
- EPO causes blood to thicken.
- The thickened blood could block the coronary arteries.
OR thickened blood would slow blood flow.
OR thickened blood cause clots.
Freshwater marsh soils are normally waterlogged, this creates anaerobic conditions.
Use your knowledge of the nitrogen cycle to suggest why these soils contain relatively high concentrations of ammonium compounds and low concentrations of nitrite ions and nitrate ions.
(2 Marks)
- Less nitrification.
OR fewer/ less active nitrifying bacteria.
OR nitrification requires oxygen . - Less oxidation to nitrite ions and to nitrite ions.
- More denitrification
- so more nitrate ion reduced.
Describe the role of saprobionts in the nitrogen cycle.
(2 Marks)
- The enzyme used to decompose proteins/ DNA/ RNA.
- Producing / releasing ammonia/ ammonium.
Describe the process of glycolosis.
(4 marks)
1) phosphorylation of glucose using ATP
2) Oxidation of TP to pyruvate
3) Net gain of ATP
4) NAD reduced
Malonate inhibits a reaction in the krebs cycle.
Describe why malonate would decrease the uptake of oxygen in a respiring cell.
(2 marks)
1) Less/ no reduced NAD.
2) Oxygen is the final electron acceptor.
Explain how a resting potential is maintained across the axon membrane in a neurone.
(3 marks)
1) Higher concentration of potassium ions inside and higher concentration of sodium ions outside the neurone.
2) Membrane more permeable to potassium ions (leaving than sodium ions entering)
3) Sodium ions are actively transported out and potassium ions in.
Explain why the speed of transmission of impulses is faster along a myelinated axon than along a non-myelinated axon.
(3 marks)
1) myelination provides electrical insulation.
2) in myelinated saltatory conduction
3) in non-myelinated depolarisation occurs along the whole length of the axon.
Where does glycolysis occur?
Mitochondrial matrix
Suggest why the membrane of the mitochondria is impermeable to hydrogen ions.
(2 marks)
1) If hydrogen ions leak, there would be no concentration gradient (between inter membrane space and matrix) allows hydrogen/ PH/ electrochemical gradient
2) So no chemiosmosis would occur.
What is meant by a limiting factor?
(1 mark)
A factor/ variable that limits the rate of reaction/ stops reaction from going any faster.
