What Are Proteins? Central Dogma of Molecular Biology
What are Proteins?
Proteins occupy a number of roles in the body. Enzymes control all biological reactions; antibodies protect the body; membrane carriers and pores allow molecules into and out of cells; hormones signal changes throughout the body. All of the above are examples of proteins...but what are they?
Put simply, proteins are polypeptide molecules - long strings of amino acids joined together by peptide bonds. They come in two forms: globular and fibrous; and are made in the cytoplasm by biological machines called ribosomes.
It is through proteins that DNA exerts its' control over the action of the cell. As said by Marshall Nirenberg said:
"DNA makes RNA makes Protein"
...and proteins either control, protect, build or signal everything. This is known as the central dogma of molecular biology.
The Central Dogma of Biology
There are 20 different amino acids, each differing only by the R group. Plants make all the amino acids they need by combining nitrates from the soil with products of photosynthesis. Animals eat protein which they break down during digestion and use the products of this digestion to make amino acids and proteins. Around 10 amino acids cannot be synthesised by the body and must be consumed in the diet - so called "essential amino acids"
Surplus amino acids cannot be stored - the amino group makes them toxic. If amino acid levels build up the liver removes amino groups from amino acids in a process called deamination. These amino groups are then converted into urea, which is diluted with water and passed out of the body as urine.
This series will cover the following topics:
- Making and breaking proteins
- Protein synthesis
- Protein structure
- Proteins in Action
Enzymes, RNA and DNA will be covered in separate hub series. If I have piqued your interest then, please, read on and investigate the alien other-world of proteins.
Knowledge is Power
Where Next? Proteins
- Central Dogma of Molecular Biology
Francis Crick's 1970 paper outlining the now famous Central Dogma, which describes the relationship between DNA and proteins