Proteins Flashcards
What elements make up proteins
Carbon hydrogen oxygen nitrogen and sometimes sulphur
How many different naturally occurring amino acids are there
20
Protein examples P
Haemoglobins enzymes hormones antibodies
Describe general formula for amino acids / backbone for every protein
R group is different for every protein, amine group → NH 2
Carboxylic acid group → Coo H
What happens when 2 amino acids undergo-condensation reaction
Polymerisation → dipeptide formed with peptide bond between nitrogen and carbon + water molecule produced
.are amino acids polar
Originally no but h+ ion from hydroxide ion moves to amine group making it polar
Primary structure
Order of amino acids in polypeptide chain joined by peptide bonds → type, number + sequence of amino acids linked by peptide chains
Secondary structure
Folding of the primary structure / polypeptide chain to form alpha helix or beta pleated sheet held together by multiple weak hydrogen bonds between peptide bonds of polypeptide chain
Tertiary structure → shown by globular protein
Further folding of polypeptide chain to form very specific 3D complex shapes → bonds between R groups, ionic bonds between. - and negative r groups, hydrogen bonds between non-polar groups, hydrophobic interactions between non-polar r groups clustering in middle and disulphide bonds between S in cysteine amino acids in R group (covalent)
Quaternary structure
2 or more polypeptide chains in tertiary form joined together with same bonds as tertiary → only few proteins
Note:
In alpha helix (tertiary) r groups project from it and may interact to form bondsto maintain the 3d shape
How is a protein’s function determined
By its structure
Globular protein examples
Enzymes antibodies hormones haemoglobin
Fibrous protein examples
Keratin + collagen → alpha helices linked into strands
Properties of globular proteins
Soluble, prosthetic group, metabolic role spherical+ compact
