Protein structure and function
Black print – notes
Red print – syllabus content
Amino acids are linked by peptide bonds to form polypeptides.
Amino Acids
These represent amino acids
There are 20 different amino acids in the body eg. Phenylalanine, asparagine, glutamic acid
Amino acids are linked by peptide bonds to form polypeptide chains
Amino Acids
Peptide bonds
This is polypeptide chain. The protein is not yet completed
Proteins are held in a three dimensional shape by peptide bonds, hydrogen bonds, interactions between individual amino acids.
Polypeptide chains fold to form the three dimensional shape of the protein.
Proteins have a large variety of structures and shapes resulting in a wide range of functions.
The amino acid sequence is the primary structure of the protein.
Hydrogen bonds form between certain amino acids twisting the
polypeptide into a helix or a pleated sheet.
Peptide bonds, hydrogen bonds and other types of bonds and
interactions between amino acids give the protein a three
dimensional shape:
Different polypeptide chains are
joined and folded to give the
final shape of the protein
molecule.
Protein molecules may be rope
shaped (fibrous proteins) or
globe shaped (globular proteins)
Summary of protein structure
Fibrous Proteins
Fibrous protein
Body tissue where protein found
Collagen
Bone
Actin
Muscle
Myosin
Muscles
Keratin
Hair, nails
Elastin
Lining of Arteries
Table for illustration
not for memorising
Globular Proteins
Table for illustration
not for memorising
Globular Protein
Use of globular protein
Enzymes
Biological catalysts. Each folded in a way to expose an active surface to
combine with a specific substrate
Hormones
Chemical messengers made by an endocrine gland. Transported to
target tissue in blood to exert specific effect such as a regulatory effect
on growth or metabolism
Antibodies
Made by white blood cells called lymphocytes and defend the body against antigens
Transport proteins
Responsible for transporting substances from one part of the body to
another eg transferrin binds with iron entering bloodstream from the gut
or released during the destruction of red blood cells and transports it to
the bone marrow for re-use
Structural proteins
Forms essential part of all membranes possessed by structures within
the cell such as the nucleus. So plays a vital structural role in every living
cell
Conjugated Proteins
A conjugated protein consists of a globular protein associated with a non-protein chemical.
Conjugated
Protein
Use
Glycoprotein
Composed of protein and carbohydrate, eg
mucus, a slimy, viscous substance secreted by
epithelial cells to lubricate or protect parts of
the body
Lipoprotein
Complex molecule consisting of protein and
lipid. Products of fat digestion absorbed from
the small intestine are coated with lipoprotein
before being transported around the body.
Haemoglobin
The oxygen transporting pigment in the blood.
Is a conjugated protein consisting of the
globular protein globin associated with haem, a
non-protein part containing iron.
Table for illustration
not for memorising