Enzymes control all the chemical reactions that occur inside our body.
It is important to remember that all enzymes are proteins.
Since DNA codes for proteins, it determines:
which enzymes are produced in each cell,
and therefore which chemical reactions take place inside cells.
The structure of DNA contains bases. The information is found in the sequence of bases along the length of DNA.
The sequence of bases in a gene determines the sequence of amino acids used to make a specific protein.
DNA also controls cell function by controlling the production of proteins, including enzymes, membrane carriers, and receptors for neurotransmitters.
DNA carries information to build proteins from amino acids. The information moves from the DNA to the site of protein synthesis in the ribosomes via a kind of messenger molecule.
This messenger molecule is called the RNA. The name given is messenger RNA(mRNA).
The role of mRNA is to carry a copy of the base sequence on DNA out of the nucleus to the ribosomes in the cytoplasm where protein synthesis occurs.
A, T, C and G are the four different bases found in DNA.
Each amino acid is coded for, by a sequence of three of these bases on DNA.
There are about 20 different amino acids and each is coded for by a different base triplet on DNA.
Different sequences of amino acids give different shapes to protein molecules.
When mRNA copies the base sequence on DNA, it does so by the rule of base pairing.
The rule of base pairing states that specific nitrogenous bases in DNA and RNA always pair up with each other through hydrogen bonds.
In terms of DNA base pairing rules, A is always paired with T and C is always paired with G.
mRNA does not have the base T, therefore it is replaced with base U(uracil). A on DNA will code for U on mRNA.
The coded information on mRNA is used to assemble amino acids in the correct sequence for each protein.
Scroll down for what the syllabus says for how a protein is made.
The mRNA arrives at the ribosomes from the nucleus.
The mRNA strand contains the base triplets for each particular amino acid in the protein.
The mRNA then passes through the ribosomes and each ribosome assembles amino acids into protein molecules.
The amino acids bond together forming a long chain, the protein.
The specific order of amino acids is determined by the sequence of bases in the mRNA and each amino acid is joined to the next one by a peptide bond.
All body cells in an organism contain the same genes. However, in a particular cell, many genes may not be expressed because the cell makes only the specific proteins it needs.