Topic 5 SNAB, On The Wild Side

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Topic 5: On the Wild Side
Suggest reasons why 95% of the light hitting the surface of a leaf is not used by the
chloroplasts. (2)*Reflection; *incorrect wavelength/colour/ frequency; *light doesn't hit the
chloroplast/ chlorophyll, it is transmitted; *light being in excess e.g. at max. photosynthesis so no
more light can be used.
The light dependent reactions The
products of the light-dependent reactions that are used in the light-independent reactions are
reduced NADP and.... ATP
Oxygen is produced when water molecules are split in the process of......photolysis
When light is absorbed by chlorophyll, it excites.......electrons
Describe the structures in a chloroplast that are involved in the LD reactions (3) The
LD reactions involve the *thylakoids that are arranged into stacks of granum. *The grana are
connected by lamellae. The *thylakoid membrane contains electron carriers, proteins and
*photosynthetic pigments such as chlorophyll which are *arranged into photosystems/quantasomes;
the membrane also has *ATPase/ ATPase channels.
Explain how the energy from light is made available in ATP molecules for the synthesis of
organic materials. (6)
*The light dependent reactions occur in the thylakoids *in the granum in *accessory pigments such as
chlorophyll. The process begins when *light energy raises the energy level of two electrons so that
they are excited, the electrons are then *released from the chlorophyll/ photosystem. They then
travel down the *electron carrier chain, travelling to each carrier molecule through a series of
*oxidation and reduction (redox) reactions, releasing energy/ *the electrons' energy level falls. The
energy released is used to *synthesise ATP from ADP and an organic phosphate ion
*(phosphorylation); the *enzyme synthase/ synthetase is needed to make the ATP. *Photolysis of
water produces 2 electrons which are used to replace those lost from the chlorophyll.
Explain how oxygen is produced during the light-dependent reactions of photosynthesis. (2)
Using *energy from light the *photolysis *of water occurs that produces/releases oxygen
The light independent reactions/ The Calvin Cycle
RuBP combines with carbon dioxide in...... The light-independent reactions of the Calvin cycle.
RUBISCO the enzyme that catalyses carbon fixation.
Carbon fixation takes place in..... the stroma of a chloroplast.
Explain why the light-independent stage cannot take place without the light-dependent stage.
(3) Because the *products of the light-dependent stage are needed for/used in the
light-independent stage/Calvin cycle. *Thee products of the light-dependent stage are reduced
NADP and ATP, *rNADP is used in the reduction GP/carbon dioxide whilst *ATP is used as a source of

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Topic 5: On the Wild Side
Suggest why the development of plants depends on the rate of carbon fixation. (3)
*Carbon fixation produces {GP / eq}, this *product is converted to glucose/ starch/ eq. *The faster
the C- Fixation the faster the glucose/ starch production, as the *rate of growth of a plant is
dependent on the rate of C-Fixation, if this increases so will the *GPP of the crop/plant.
Suggest how GALP may be used to synthesise cellulose.…read more

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Topic 5: On the Wild Side
there are *great fluctuations in most climate change data suggest that there is no real trend (as
scattered) and thus *poor representation of raw data. *A scatter of results may show poor
In addition the method of* estimating temperature from growth rings of trees is questionable as
*other environmental changes affecting the trees are not taken into account.
Scientists have estimated that........ will reduce CO2 production. Suggest why the ......…read more

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Topic 5: On the Wild Side
maximum to be able to complete development/ above the lethal temperature limit. *Species may
also move north/ to cooler regions or they may have a *change to their food source/predators/
Suggest why the lower and upper lethal temperatures limit the range of latitudes inhabited by
(different species of frog). (2)
*Temperature affects the survival/development/growth/metabolism/cell division of animals and
*the development/growth/metabolism/cell division is affected by enzymes which are *affected by
temperature.…read more

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Topic 5: On the Wild Side
Suggest why an increase in temperature may cause an increase in NPP. (2) *The
rate of (bio)chemical/metabolic/photosynthetic reactions increases due to an *increase in
movement/kinetic energy of enzyme/substrate/molecules; *thus increasing the reaction rate
because of more enzyme substrate interaction/ collisions.
What is the unit J m­2 year­1? Joules/ energy per metre squared per year/ unit time.
Explain what is meant by the term niche, using the sea anemone as an example.…read more

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Topic 5: On the Wild Side
Why is a climax community stable? (4)
*A climax community is where (both) animals and plants are present/has many species/has high
biodiversity; *there will be interaction between these species but they *will have reached a
balanced equilibrium of species. *There may be a (co)dominant plant or animal species present.
*This is stable as long as there's no change to the environment/human influence.
Speciation and evolution
A gene mutation is....a change in DNA due to the change/deletion/addition/duplication/substitution
bases/nucleotides.…read more

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Topic 5: On the Wild Side
advantageous features/mutations would allow the plants to *survive and reproduce, passing on new
genes and creating *differences between gene pools.
Suggest how ecological isolation contributes to speciation. (2)
*There may be different conditions /environments in each region, i.e. a temperature difference, so
*there will be different selection pressures. The geographical isolation will mean that the two
populations are *reproductively isolated from one another *causing a restricted gene flow/
separation of gene pools.…read more

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Topic 5: On the Wild Side
Describe the chemical nature of cellulose. (3)
Cellulose is a *polysaccharide with an *unbranched/ straight chain. The cellulose is made up of *B
glucose joined by *1-4 glycosidic bonds between the glucose molecules. Between each chain there
are *intermolecular hydrogen bonds to hold the structure together.
Suggest two advantages of growing crops of wheat in glasshouses with artificial lighting
rather than growing them in open fields.…read more

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Topic 5: On the Wild Side
How does mRNA form during transcription in the nucleus? (3)
First the *DNA strands unzip, *one side of the DNA strand is the template strand that is used to from
a mRNA strand *from free nucleotides. The nucleotides join by *complementary base pairing, *joined
together by hydrogen bonds. *RNA- polymerase/ DNA Helicase are the enzymes involved in these
Describe how free nucleotides are bonded together in the correct sequence in pre-mRNA.…read more

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Topic 5: On the Wild Side
Explain how the work of zoos could be important to the survival of endangered species. (2)
Zoos may run *captive-breeding programmes *which conserve alleles/genes/ the gene pool of a
species and may run *reintroduction programmes/ re-introduce species into suitable habitats in the
Suggest why it is important to conserve rare and endangered plants. (2
*This will conserve genetic diversity/genetic variation/biodiversity. It may also *prevent extinction.…read more


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