Edexcel GCSE Biology B2

Class notes for Edexcel Biology B2 topics 1-4

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  • Created on: 22-05-12 11:36
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B2 revision May 22, 2012
DNA molecule
· First described by Watson & Crick
in 1953
· Double Stranded
· Twisted into a helix (spiral)
· Sugar Phosphate backbone
· Complimentary pairing of bases
Adenine = Thymine
Cytosine = Guanine
· Sections of DNA contain genes
responsible for producing proteins
Protein Synthesis
2 stage process!
Transcription (transcribe/copy)
· DNA strand unwinds
· complimentary mRNA strand made
· mRNA leaves though the nuclear pore
Translation (translate)
· mRNA attaches to ribosome
· attracts tRNA molecules showing triplet
· tRNA codons stick specific amino acids
together Triplet Code (3 bases) control
order of amino acids
· makes a polypeptide chain

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· Can be used to produce human insulin
· More effective than pig insulin
· Does not cause allergic reactions in
3…read more

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Advantages Disadvantages
· Wide range of products · optimum conditions required
e.g. human insulin, for most efficient growth
medicines, beer · low risk of contamination
· Can be used to grow · human views on eating
mycoproteins e.g. quorn microorganisms
· Quick and efficient
· easy to keep and
· can grow anywhere i.e.
not climate dependent
· can use waste products
from other industries e.g.…read more

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Exercise and respiration
Yeast can respire anaerobically
and are used to produce beer
and wine
glucose ethanol + carbon + energy
Anaerobic Respiration dioxide
The point at which your heart can no longer supply the muscles
fast enough.
glucose lactic acid + energy
· Does not produce much energy (0.8kJ/g compared with 16.…read more

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What is growth?
An increase in size or weight
Organisms of the same species can very in size
Some animals are able to regenerate e.g. star fish, gecko
Growth factors can be used to enhance performance
Look up examples of how these work and the reasons
behind banning them.…read more

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Growth depends upon:
Differentiation Stem cells becoming other types of cell e.g skin,
bone, blood, nerve
Elongation Cells grow in size and length e.g.…read more

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Meiosis Production of gametes
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mitosis meiosis
Provides cells for
growth and repair
Creates gametes
Daughter cells are
genetically identical
Four daughter
Daughter cells
are diploid
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B2 revision May 22, 2012
Summarise the views of people who are for or against
legal induced abortion.
Use evidence to decide whether the law should be
changed or not.…read more



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