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EDEXCEL IAL BIOLOGY UNIT 3 QUESTIONS
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EDEXCEL IAL BIOLOGY UNIT 3 QUESTIONS
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EDEXCEL IAL BIOLOGY UNIT 3 QUESTIONSDescribe the difference between a semi-quantitative and a quantitative test - Answers-
A semi-quantitative test gives {an estimate / a range} of the concentration of a
substance
A quantitative test determines the exact concentration of a substance
Describe how you could test for protein - Answers- addition of {biuret reagent / base
and copper sulfate}
it turns to a purple colour
Some of the total nitrogen content of a food is not due to protein. Give one other type of
organic molecule that contains nitrogen. - Answers- nucleic acids, lipids, amino acids,
ATP
Describe how a suitable pH could be decided on experimentally. - Answers- carry out
the experiment described at constant {temperature / substrate / enzyme concentration}
At a range of pHs (controlled by buffers) choose the pH which gives a time which is not
{too short / too long} (for practicality)
Describe a safe method to prepare and examine the structure of human cheek cells. -
Answers- bud into disinfectant/sterile/fresh bud/toothpick/wear gloves/ goggles/safe use
of microscope/slides/careful use of bud/stain to prevent injury
use of cotton bud, followed by use of stain/dye, place cells (on slide) under coverslip,
use of high power of microscope
State two differences you would observe between a plant cell and a human red blood
cell when using a light microscope. - Answers- plant cell has nucleus, RBC does not
allow one mark if both statements correct but not comparative
plant has /vacuole/large(r) vacuole/chloroplasts/cell wall/regular shape unlike RBC
Explain the role of the pollen tube in plant reproduction. - Answers- it {carries /
transports} the male gametes / nuclei / generative nucleus to the ovule / micropyle /
ovary / ovum / female gamete to {fuse with / fertilise} {ovum / egg (cell) / female gamete
/ female nucleus / polar nuclei digest tissue of style
Explain why pollen tubes grow in the same direction from the stigma, after pollination. -
Answers- the tubes grow towards the {micropyle / ovule / ovary / ovum / female gamete}
{due to chemicals (released by the embryo sac) / it is chemotropic}
Explain why changes in temperature will affect an investigation. - Answers- it involves
{enzymes / (chemical) reactions} and enzymes / (chemical) reactions are affected by
temperature
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