topic 5 Flashcards
Which chemicals are needed for the
light-dependent reaction?
-NADP
-ADP
-Pi
-water
Describe how crop plants use light
energy during the light-dependent
reaction.
- Excites electrons / electrons removed (from chlorophyll);
Accept: higher energy level as ‘excites’. - Electrons move along carriers/electron transfer chain
releasing energy;
Accept: movement of H + /protons across membrane releases
energy.
Reject: ‘produces energy’ for either mark but not for both. - Energy used to join ADP and Pi to form ATP;
Reject: ‘produces energy’ for either mark but not for both. - Photolysis of water produces protons, electrons and oxygen;
- NADP reduced by electrons / electrons and protons /
hydrogen;
Describe what happens during
photoionisation in the light-
dependent reaction
- Chlorophyll absorbs light
OR
Light excites/moves electrons in chlorophyll;
Ignore photosystems. - Electron/s are lost
OR
(Chlorophyll) becomes positively charged
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
During the light-independent
reaction of photosynthesis, carbon
dioxide is converted into organic
substances. Describe how.
- Carbon dioxide combines with ribulose bisphosphate / RuBP;
- Produces two glycerate (3-)phosphate / GP;
Accept: any answer which indicates that 2 x as much GP produced
from one RuBP. - GP reduced to triose phosphate / TP;
Must have idea of reduction. This may be conveyed by stating m.p.
4. - Using reduced NADP;
Reject: Any reference to reduced NAD for m.p.4 but allow
reference to reduction for m.p. 3. - Using energy from ATP;
Must be in context of GP to TP. - Triose phosphate converted to glucose / hexose / RuBP / ribulose bisphosphate / named organic substance;
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
Where precisely is rubisco found in a
cell?
Stroma
Where precisely in a cell does the
Calvin cycle take place?
Stroma
A herbicide binds to proteins in the
electron transfer chain in
chloroplasts of weeds, reducing the
transfer of electrons down the chain.
Explain how this reduces the rate of
photosynthesis in weeds.
- Reduced transfer of protons across thylakoid membrane
OR
Reduced chemiosomotic gradient / proton gradient across
thylakoid membrane; - (So) less ATP produced;
- (So) less reduced NADP produced;
Accept NADPH / NADPH 2 / NADPH +
Reject reduced NAD - (So) light-independent reaction slows / stops;
OR
Less reduction of GP to triose phosphate.
Chromatography - Explain why the
student marked the origin using a
pencil rather than using ink
Ink and (leaf) pigments would mix
OR
(With ink) origin/line in different position
OR
(With pencil) origin/line in same position
OR
(With pencil) origin/line still visible;
Describe the method the student
used to separate the pigments after
the solution of pigments had been
applied to the origin.
- Level of solvent below origin/line;
Reject water or any named aqueous solution.
Accept named organic solvent. - Remove/stop before (solvent) reaches top/end;
The pigments in leaves are different
colours. Suggest and explain the
advantage of having different
coloured pigments in leaves.
(Absorb) different/more wavelengths (of light) for
photosynthesis;
Other than temperature and pH,
give two factors which should be
kept constant during a
photosynthesis investigation.
- Intensity of light;
Accept: distance from light - Amount / number / mass / species of algae /
photosynthesising cells; - Carbon dioxide (concentration / partial pressure);
- Time.
Explain why the scientists measured
the rate of production of oxygen in a
photosynthesis investigation.
- Oxygen produced in light-dependent reaction;
- The faster (oxygen) is produced, the faster the light-
dependent reaction.
Describe how acetylcoenzyme A is
formed in the link reaction.
- Oxidation of / hydrogen removed from pyruvate and carbon
dioxide released; - Addition of coenzyme A.
In Krebs cycle, oxaloacetate (4C) is the first substrate to bind with the enzyme citrate synthase. This induces a change in the enzyme, which enables the acetylcoenzyme A to bind.
Explain how oxaloacetate enables the acetylcoenzyme A to then bind to the enzyme.
- Change (in shape) of active site / active site moulds around
the substrate;
Reject: reference to inhibitor
Accept: change in tertiary structure affecting active site - (Substrate / active site) now COMPLEMENTARY
In muscles, pyruvate is converted to
lactate during prolonged exercise.
Explain why converting pyruvate to
lactate allows the continued
production of ATP by anaerobic
respiration.
- Regenerates/produces NAD
OR
oxidises reduced NAD;
Reject NADP and any reference to FAD.
Accept descriptions of oxidation e.g. loss of hydrogen. - (So) glycolysis continues
Where in a cell
does glycolysis occur?
Cytoplasm
Explain how anaerobic
respiration enables glycolysis to
continue.
- Regenerates/produces NAD / oxidises reduced NAD;
- NAD reduced in glycolysis / NAD accepts hydrogen in
glycolysis
Aerobic respiration produces more
ATP per molecule of glucose than
anaerobic respiration.
Explain why
- Oxygen is final/terminal (electron) acceptor / oxygen
combines with electrons and protons; - (Aerobic respiration) oxidative phosphorylation / electron
transfer chain; - Anaerobic (respiration) only glycolysis occurs / no Krebs / no link reaction;
Explain why an increase in biomass
can be taken as a measurement
of net primary productivity.
- Represents dry mass / mass of carbon;
- Represents gross production minus respiratory losses;
Explain why CO 2 uptake is a measure
of net productivity.
Shows (gross) photosynthesis / productivity minus respiration /
more carbon dioxide used in photosynthesis than produced in
respiration;
Suggest appropriate units for gross
productivity.
Unit of energy / mass, per area, per year.
Explain the decrease in gross
productivity as the woodland
matures
- Less light / more shading / more competition for light;
Neutral: references to animals - Reduced photosynthesis
In a climax community biomass
shows little increase after 100 years.
Use your knowledge of net
productivity to explain why.
- Net productivity = gross productivity minus respiratory loss;
- Decrease in gross productivity / photosynthesis / increase in
respiration
Why is most light falling on
producers NOT used in
photosynthesis
- (Light is) reflected;
- (Light is) wrong wavelength;
- (Light) misses chlorophyll/ chloroplasts/photosynthetic
tissue; - CO 2 concentration or temperature is a limiting factor.
Nitrate from fertiliser applied to
crops may enter ponds and lakes.
Explain how nitrate may cause the
death of fish in fresh water.
- Growth of algae / surface plants / algal bloom blocks light;
- Reduced / no photosynthesis so (submerged) plants die;
- Saprobiotic (microorganisms / bacteria);
- Accept: Saprobiont / saprophyte / saprotroph
- Neutral: decomposer
- Aerobically respire / use oxygen in respiration;
- Less oxygen for fish to respire / aerobic organisms die;
Explain how microorganisms in the
soil produce a source of nitrates
from crop plant remains.
- Protein/amino acids/DNA into ammonium compounds /
ammonia;
Accept: any named nitrogen containing compound e.g. urea. - By saprobionts;
Accept: saprophytes. - Ammonium/ammonia into nitrite;
- Nitrite into nitrate;
- By nitrifying bacteria/microorganisms;
Describe the role of saprobionts in
the nitrogen cycle
- (They use enzymes to) decompose proteins/DNA/RNA/urea;
- Producing/releasing ammonia/ammonium
compounds/ammonium ions;
Give two examples of biological
molecules containing nitrogen.
- amino acid / protein / polypeptide / peptide;
- nucleic acid / nucleotide / base;
- DNA;
- RNA;
- ATP / ADP;
- NAD / NADP (reduced or not);
- Cyclic AMP / cAMP;
- Chlorophyll;
Describe the role of microorganisms
in producing nitrates from the
remains of dead organisms
- Saprobiotic (microorganisms / bacteria) break down remains
/ dead material / protein / DNA into ammonia / ammonium; - Ammonia / ammonium ions into nitrite and then into nitrate;
- (By) Nitrifying bacteria / nitrification;
Leguminous plants have nodules
containing nitrogen-fixing bacteria
on their roots.
Explain how nitrogen-fixing bacteria
could increase the growth of maize.
- Nitrogen-fixing bacteria convert nitrogen (in the air) into
ammonium compounds (in the soil) which are converted into
nitrates / nitrification occurs; - Maize uses nitrates (in soil) for amino acid / protein / ATP / nucleotide production;
Explain how microorganisms
contributed to the increase in
temperature during processing of
organic waste.
1.Respiration/metabolism/ammonification;
2. (Releases/produces) heat;
Suggest one way in which an
increase in the uptake of phosphate
could increase plant growth.
Used to produce named phosphate compound in cells;
e.g. ATP / ADP / phospholipids / DNA / RNA / RuBP / TP /GP etc
Suggest and explain two reasons
why a poor supply of phosphate ions
results in poor growth of plants
- (Required to) make ATP / glucose phosphate, so less
respiration / less energy for growth; - (Required to) make nucleotides, so less DNA / mRNA / tRNA
for cell division / production of protein (for growth); - (Required to) make RuBP / NADP, so less CO 2 fixed / reduced
into sugar; - (Required to) make phospholipids for membranes;
Calorimetry [5]
- Take the mass of the sample
- Burn in pure oxygen in a sealed container surrounded by water
- Measure the increase in temperature
- Use specific heat capacity of water (amount of energy to increase 1kg of water by 1°C)
- Energy released can be measure (kJkg-1)
How to measure dry mass [4]
- Take the mass of the sample.
- Heat for 1 hour at temperature that will evaporate water, but
not burn the sample - Take the mass of the sample
- Repeat heating and taking mass until mass remains constant
Dry Mass [2]
- Dry mass often measured due to varying water content
- measuring will kill the organism
- Gives more accurate results
