Looking for CIE A Level Biology notes? These Nucleic acids and Protein synthesis notes are compiled directly from CIE 9700 AS Level Biology mark schemes. With every single specification point labelled and covered, simply memorising these notes guarantees you will get top marks on the day. These poi...
NOTES: Italics indicates NOT from the mark scheme (often means no
mark schemes relating to the spec point). These are taken instead
from the CIE A Level textbook, which occasionally includes extra
detail to help my own understanding. All others are directly copied
from CIE 9700 mark schemes.
Mark scheme abbreviations: I = ignore, A = accept, R = reject. A
semi-colon “;” separates marking points, which are sometimes
numbered. “AVP” = any valid point. See the start of any mark
scheme for full abbreviations.
6. Nucleic acids and protein synthesis
Helpful tip: remember ‘y’ for pyrimidines. So cytosine, thymine are
pyrimidines. Remember thymine and uracil have very similar
structures (both pair with adenine). Uracil is also a pyrimidine. So
pyrimidines: C, T, U. (Purines: A, G)
Pyrimidines are single rings, purines are two/double ringed.
Nucleotide structure : nitrogenous base, pentose sugar
(deoxyribose or ribose), phosphate group
ATP structure: adenine, ribose (adenosine), three phosphates
mRNA structure: single polynucleotide strand. (i.e. many
nucleotides joined together in one strand)
structure of a DNA molecule as a double helix:
• the importance of complementary base pairing between the 5′ to 3′
strand and the 3′ to 5′ strand (antiparallel strands)
• differences in hydrogen bonding between C–G and A–T base pairs
C≡G (3), A=T (2)
• linking of nucleotides by phosphodiester bonds
Semi-conservative replication:
1 DNA (double helix / molecule) unwinds ; by DNA helicase
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