biology paper 2 focus areas

• In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. (5 marks)

  1. Light (energy) excites / raises energy level of electrons in chlorophyll;
  2. Electrons pass down electron transfer chain;
  3. (Electrons) reduce carriers / passage involves redox reactions;
  4. Electron transfer chain / role of chain associated with chloroplastmembranes / in thylakoids / grana;
  5. Energy released / carriers at decreasing energy levels;
  6. ATP generated from ADP and phosphate / Pi / phosphorylation of ATP;
• When investigating how light intensity affects plant growth what variables should you control?

  temperature

  concentration carbon dioxide

  volume of water

  concentration of ions in the soil

  pH of soil
• How can we measure the rate of the light-dependent reactions of photosynthesis?

  Measure the volume of oxygen produced.

  Over time.
• Describe the Calvin Cycle

  1. CARBON FIXATION - Rubisco enzyme catalyses the reaction of RuBP with CO2to produce 2x Glycerate-3-Phosphate (G-3-P).
  2. REDUCTION - NADPH reduces G-3-P into 2x Triose Phosphate (TP) with energy being provided by ATP.
  3. REGENERATION - 2 x TP are converted into orgnaic compounds e.g. glucose OR ATP is used to convert TP into RuBP for more turns of the Calvin cycle.
• Does the Calvin Cycle require light to function?

  No

  BUT

  The reactions will stop eventually in the absence of light because essential ATP and NADPH from light reactions will run out.
• During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. (6 marks)

  1. Carbon dioxide combines with ribulose bisphosphate / RuBP;
  2. Produces two glycerate-3-phosphate / GP;
  3. GP reduced to triose phosphate / TP;
  4. Using reduced NADP; and…
  5. …Using energy from ATP;
  6. Triose phosphate converted to glucose / RuBP / ribulose bisphosphate
• Heat stress decreases the LDR - why does this lead to a decrease in the LIDR?

  Less ATP

  Less reduced NADP
• where is Rubisco found?

  stroma (of chloroplast)
• Define ecosystem


  All the organisms living in a particular area and all the abiotic conditions.
• What are producers?


  Organisms that make their own food - usually by photosynthesis.
• What is biomass?


  The mass of living material in a given area (g per m2)
• How do you measure dry mass?

  The sample is dried in a over (low temperature). The sample is then reweighed at intervals until a constant mass is reached.
• How can you estimate the chemical energy stored in biomass?

  Burn it in a calorimeter. The amount of heat given off tells you how much energy is in it.
• What does GPP stand for?

  Gross primary production
• Define GPP


  The total amount of chemical energy converted from light energy by plants, in a given area, in a given time.
• What does the pancreas do?

  Detects changes in the blood and contains endocrine cells in the islets of Langerhans which release the hormone insulin and glucagon to bring blood glucose levels back to normal
• Adrenanline


  Secreted by the adrenal glands, when the body detects danger and this results in more glucose being released from stores of glycogen in the liver
• Define Glycogenesis

  The process where excess glucose is being converted to glycogen when blood glucose is higher than normal
• Define glycogenolysis

  The hydrolysis of glycogen back into glucose in the liver. Normally occurs when the glucose levels are lower than normal.
• Homeostasis in mammals?


  Involves physiological control systems that maintain the internal environment within restricted limits.
• The action of insulin?

  • attaching to receptors on the surfaces of target cells
  • controlling the uptake of glucose by regulating the inclusion of channel proteins in the surface membranes of target cells
  • activating enzymes involved in the conversion of glucose to glycogen.
• Action of glucagon

  • attaching to receptors on the surfaces of target cells
  • activating enzymes involved in the conversion of glycogen to glucose
  • activating enzymes involved in the conversion of glycerol and amino acids into glucose.
• Role of adrenaline

  • attaching to receptors on the surfaces of target cells
  • activating enzymes involved in the conversion of glycogen to glucose.