2018 paper 2 Flashcards
Heat stress is a condition that often occurs in plants exposed to high temperatures for
a prolonged period of time. Heat stress is a major factor in limiting the rate of
photosynthesis.
Heat stress decreases the light-dependent reaction of photosynthesis.
Explain why this leads to a decrease in the light-independent reaction.
- (Less/no) ATP;
- (Less/no) reduced NADP;
A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis.
Explain why.
- (Less/no) carbon dioxide (reacts) with RuBP;
- (Less/no) GP;
Suggest one reason why it was important that the student left the apparatus for one
hour after the yeast culture reached a constant temperature.
(So the) oxygen is used/absorbed/respired
During her investigation, the coloured liquid moved to the right.
Explain why it moved to the right
- Anaerobic respiration produces carbon dioxide;
- Increase in pressure/volume (of gas);
The scientists concluded that the results shown in Figure 5 were due to succession
taking place.
Use Figure 5 to explain why the scientists reached this conclusion.
- Beach grass is the pioneer (species);
- Pioneers/named species change the (abiotic)
environment/habitat/conditions/factors; - (So) less hostile for named species
- Conifer/hardwood trees represent climax
community
Furosemide and CVT are drugs used to remove excess fluid from the body.
Scientists investigated the effect of these drugs on the volume of urine produced by human volunteers.
All the volunteers were given the same food for 3 days.
Suggest and explain one reason why they were given the same food.
- Affects water potential (of blood/body);
- Affects volume of urine (produced/removed)
Furosemide inhibits the absorption of sodium and chloride ions from the filtrate
produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced.
1.Water potential of filtrate/tubule decreased;
2. Less water (reabsorbed) by osmosis (from
filtrate/tubule);
3. Collecting duct (is where osmosis occurs);
Dopamine is a neurotransmitter released in some synapses in the brain. The
transmission of dopamine is similar to that of acetylcholine.
Dopamine stimulates the production of nerve impulses in postsynaptic neurones.
Describe how.
Do not include in your answer the events leading to the release of dopamine and the
events following production of nerve impulses at postsynaptic neurones.
- (Dopamine) diffuses across (synapse);
- Attaches to receptors on postsynaptic
membrane; - Stimulates entry of sodium ions and
depolarisation/action potential;
GABA is a neurotransmitter released in some inhibitory synapses in the brain. GABA
causes negatively charged chloride ions to enter postsynaptic neurones.
Explain how this inhibits postsynaptic neurones.
neurone becomes more
negative/hyperpolarisation/inhibitory
postsynaptic potential;
. More sodium ions required (to reach threshold)
. For depolarisation/action potential;
Lactase persistence is caused by a mutation in DNA. This mutation does not occur in
the gene coding for lactase.
Suggest and explain how this mutation causes LP.
- Mutation in promoter (DNA/gene) for
transcription factor
Lactase gene continues to be transcribed/active
Complete achromatopsia is a form of complete colour blindness. It is caused
by having only rods and no functional cone cells. People with complete
achromatopsia have difficulty in seeing detail.
No (functional) cones
Cones are connected to a single neurone
(Cones) Separate (sets of) impulses to brain
People with red-green colour blindness are unable to distinguish between red and
green, and also between other colours (lines 8–10).
Explain why.
Green sensitive pigment/cones non-functional
2. Three different types of pigment/cone;
Other/different colours (‘seen’) due to stimulation
of more than one cone/pigment;
