Fibrous and globular proteins

Properties of globular proteins

\-spherical and have a hydrophobic R group inside and a Hydrophilic R group outside

\-soluble in H2O(because of the hydrophobic strands)

\-has a specific shape for specific functions

roles of globular proteins

\-acts as a transport protein(hemoglobin)

\-acts as hormones(insulin)

\-acts as enzymes(pepsin)

Haemoglobin structure

\-has 4 polypeptide chains (has a quaternary structure) -has an alpha globin(alpha helix) and beta-globin(beta pleated sheet)

\-has the prosthetic group haem(contains a Fe2+ion) making it a conjugated protein

\-one haem group can bond to 1 oxygen molecule, so haemoglobin can carry 4 oxygen molecules

prosthetic group

a non-protein component that is necessary for the protein to function

Insulin structure

-is secreted by the pancreas
-has 2 chains- an alpha helix and beta-sheet
-chains are joined by disulphide links
-the shape of insulin allows it to bind to receptors in the membrane to lower blood-sugar conc
-has hydrophilic R groups so its soluble and can be dissolved to be transported in the bloodstream

Pepsin structure

-catalyzes the digestion of proteins by breaking down polypeptides
-has a primary structure of a few basic R groups so the tertiary structure isn't affected by the PH in the stomach
-tertiary structure is stabilized by H bonds and disulphide links

Properties of fibrous proteins

-contains long peptide chains with many repeating sequences of amino acids
-has a non-polar R group so it's insoluble in water
-polypeptide chains can form fibers to make the protein stronger

roles of fibrous proteins

-structural role
-forms tendons and gives a hard structure(collagen
-hardens fingernails(keratin)
-makes tissues stretchy(elastin)

Collagen function

-forms strong fibres- provides strength to parts of the body
-prevents arteries from bursting under pressure
-makes tendons so the skeleton can move
-makes bone

keratin function

\-forms hard parts of the body (e.g.nails)

Elastin function

\-It is stretchy due to the elastin coiling and the cross

\-links that keep the molecules together

-found in the lungs so it can inflate and deflate during respiration

-found in the arteries so it can maintain blood pressure by stretching and recoiling

-found in the bladder so it can expand