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Salters-Nuffield Edexcel Biology Past Paper Exam Questions and Solutions .
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Salters-Nuffield Edexcel Biology PastPaper Exam Questions and Solutions
The concentration of potassium ions inside an animal is many times higher than the
concentration of potassium ions in the extracellular fluid.
Which mechanism is responsible for the uptake of potassium ions by this animal cell? -
ANS-Active transport.
Describe the events of fertilisation that occur after the acrosome reaction. 3 marks. -
ANS-The sperm cell membrane fuses with the egg cell membrane. The cortical
granules release contents into the zona pellucida. The contents of cortical granules
react with the zona pellucida and the zona pellucida thickens/hardens. The sperm and
egg haploid nuclei fuse.
Some epithelial cells secrete mucus. If the mucus is too 'sticky', it cannot be easily
removed from the lungs. Other epithelial cells contain CFTR proteins in their cell surface
membranes.
Describe the role of the CFTR protein in ensuring that the mucus produced in the lungs
has the right consistency. - ANS-Chloride ions leaves cells through the CFTR protein.
Sodium ions leave the cells, following the chloride ions. This increases the solute
concentration in the mucus and water moves out of the cells by osmosis into the
mucus.
What's the word that is used to describe a protein that can be made by more than one
triplet DNA code? - ANS-Degenerate.
Describe how DNA is organised in a bacterial cell. - ANS-Bacteria have large circular
DNA and the DNA is not associated with his tone proteins. Bacteria have small or
several plasmids and the DNA is in the cytoplasm and not inside a nucleus.
In an experiment, a mixture of radioactive bases was added to a culture of dividing
bacteria and were left to reproduce for 100 minutes.
Explain why the experiment would have been improved if all the bases were provided
but only thymine was radioactive. - ANS-Thymine is only found in DNA. Other
, radioactive bases are taken up by all nucleic acids. Making thymine the only radioactive
base would ensure that only DNA would be measured.
Photosynthesis is a two-stage process by which plants fix carbon dioxide. Describe the
LIGHT-DEPENDENT reactions of photosynthesis. 5 marks. - ANS-Light energy hits PSII
and excites the electrons in the chlorophyll. This energy is used for photolysis to
produce O2, electrons and H ions. The electrons are used in the electron transport
chain to replace those lost by chlorophyll. This energy is used for photophosphorylation
to synthesise ATP and to reduce NADP.
In which part of the chloroplast do the LIGHT-INDEPENDENT reactions happen? -
ANS-Stroma.
What is the name of the enzyme used by plants to fix CO2? - ANS-RUBISCO.
What is the IMMEDIATE product of the LIGHT-INDEPENDENT reactions of
photosynthesis? - ANS-GP.
Explain how studying pollen grains can provide evidence of climate change. 4 marks. -
ANS-Pollen is preserved in peat bogs as they are resistant to decay. A plant species
can be identified from its pollen. The climate affects the type of plants growing. The
depth of peat correlates with the period of time since the pollen was produced and the
changes in pollen over time indicate changes in climate.
Disaccharides can be split by h......... of g.......... b.... - ANS-Hydrolysis of glycosidic
bonds.
Amylose is an example of a p............. - ANS-Polysaccharide.
The role of starch is to s.... e...... i. p...... - ANS-Store energy in plants.
Proteins are polymers of amino acids joined by peptide bonds formed between the
c....... g..... and the a.... g..... - ANS-Carboxyl group and the amino group.
The 3D structure of a protein is held together by d......... b......, h....... and i.... b..... -
ANS-Disulphide bridges, hydrogen and ionic bonds.
DNA consists of mononucleotides joined by bonds between one d.......... s..... and one
p......... g.... - ANS-Deoxyribose sugar and one phosphate group.
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