Chemical components of a cell: DNA
Monomer Polymer
Nucleotides DNA, RNA
Amino acids Proteins
Fatty acids Lipids
sugars Polysaccharides
Nucleotides are the building blocks of DNA.
Nucleotide are:
• Nitrogen-contain baes which include Adenine, Thymone,
Guanine and Cytosine
• Five-carbon sugar -> deoxyribose
• Phosphate group
• Supply of nucleoside triphosphates needed for nucleic acid
synthesis
• By convention the carbons in the sugar are labelled 1’ to 5’
Nucleotides are covently linked by a sugar phosphate backbone in
order to form nucleic acids.
The DNA strand has a 5’ end due to a 5’ phosphate group and a 3’ end due to a 3’ hydroxyl.
Phosphodiester bonds are formed between the 5’ and 3’ carbons in the deoxyribose sugar.
DNA is double stranded:
The bases are either purines or pyrimidines.
Purines are double ringed and examples of this are adenine and gaunine.
Pyrimidines are single ringed and examples of this are thymine and cytosine
A purine always pairs with a pyrimidine -> allows there to be constant sugar-phosphate backbone
and no distortion
The A-T base pairing is weaker than the G-C pair.
Single stranded DNA is already helical -> when nucleotides stack together they adopt the helical
structure as they are asymmetric allowing to determine bond angles of the sugar-phospgate
backbone.
Hydrogen bonds between bases on the different strands allows stablitly
The DNA turns clockwise -> as its right handed helix -> 2 x sugar-PO4 backbones wind into this
Bases are 0.34nm apart and make a complete turn every 3.4nm (every 10 bases)
DNA has a chemical polarity -> polairty of one stand is oriented opposite to the that of the other
strand
Polymerase moves forward unwinding DNA as it goes -> polymerisation goes from 5’ to 3’ direction
more nucleotides are added to the 3’ end of the growing chain
Monomer Polymer
Nucleotides DNA, RNA
Amino acids Proteins
Fatty acids Lipids
sugars Polysaccharides
Nucleotides are the building blocks of DNA.
Nucleotide are:
• Nitrogen-contain baes which include Adenine, Thymone,
Guanine and Cytosine
• Five-carbon sugar -> deoxyribose
• Phosphate group
• Supply of nucleoside triphosphates needed for nucleic acid
synthesis
• By convention the carbons in the sugar are labelled 1’ to 5’
Nucleotides are covently linked by a sugar phosphate backbone in
order to form nucleic acids.
The DNA strand has a 5’ end due to a 5’ phosphate group and a 3’ end due to a 3’ hydroxyl.
Phosphodiester bonds are formed between the 5’ and 3’ carbons in the deoxyribose sugar.
DNA is double stranded:
The bases are either purines or pyrimidines.
Purines are double ringed and examples of this are adenine and gaunine.
Pyrimidines are single ringed and examples of this are thymine and cytosine
A purine always pairs with a pyrimidine -> allows there to be constant sugar-phosphate backbone
and no distortion
The A-T base pairing is weaker than the G-C pair.
Single stranded DNA is already helical -> when nucleotides stack together they adopt the helical
structure as they are asymmetric allowing to determine bond angles of the sugar-phospgate
backbone.
Hydrogen bonds between bases on the different strands allows stablitly
The DNA turns clockwise -> as its right handed helix -> 2 x sugar-PO4 backbones wind into this
Bases are 0.34nm apart and make a complete turn every 3.4nm (every 10 bases)
DNA has a chemical polarity -> polairty of one stand is oriented opposite to the that of the other
strand
Polymerase moves forward unwinding DNA as it goes -> polymerisation goes from 5’ to 3’ direction
more nucleotides are added to the 3’ end of the growing chain
