3.6 & 3.7 proteins

what is the structure of amino acid

Central carbon (alpha carbon), four atoms or groups of atoms bonded to alpha Carbon NH2 (amino group), COOH (carboxyl group), H, R (side group)

what is the R group

Different in each amino acid, determines how the amino acid interacts and bonds with other amino acids in the polypeptide

what are the amino acids at each end of chain

N-terminal (amine terminal), C-terminal (carboxyl terminal)

what is a peptide bond

when two amino acids react together covalent bond, water is produced, called a dipeptide (condensation, hydrolysis to break peptide bond)

what is it called when many amino acids are joined by peptide bonds

polypeptide

what enzyme catalyses the joining of amino acids

peptidyl transferase ( in ribosomes)

what is the primary structure of protein

the sequence amino acids are joined, particular amino acids in sequence influence how polypeptide will fold give protein final shape, shape determines function, only bonds are peptide bonds

what is the secondary structure of protein

O, H and N atoms of repeating structure of amino acids interact, H bonds may form within amino acid chain, pull into a coil shape called an alpha helix

what is another secondary structure other than the alpha helix

polypeptide chains can also lie parallel to one another joined by h bonds, form sheet like structure, pattern formed by individual amino acids cause structure to appear pleated

tertiary structure of proteins

folding of a protein into final shape, includes sections of secondary structure, bring R-groups of different amino acids closer together to interact for further folding

what type of interactions with occur in tertiary structure

hydrophobic and hydrophilic interactions (polar and non-polar R-groups), hydrogen bonds (weak), ionic bonds (stronger and form between oppositely changed R-groups), disulfide bonds (covalent and strongest, only between R-groups that contain sulfur atoms)

quarternary structure in proteins

association of two or more individual proteins called subunits, can be identical or different

how many subunits in enzymes

two identical subunits

how many subunits in insulin

two different subunits

how many subunits in haemoglobin

four (two sets of two identical subunits)

features of a globular protein

compact, water-soluble and usually roughly spherical in shape

how are globular proteins formed

proteins folds into tertiary structure, hydrophobic on inside, hydrophobic on outside, soluble

what is insulin role as a globular protein

hormone included in the regulation of blood glucose concentration, transported in bloodstream so need to be soluble, precise shapes to fit into specific receptors on plasma membranes

what is a conjugated protein

globular protein that contain a prosthetic group

different types of prosthetic groups

lipids or carbohydrates can combine with proteins forming lipoproteins or glycoproteins, metal ions and molecules derived from vitamins also form prosthetic groups

about the conjugated protein haemoglobin

quaternary protein made from four polypeptides, two alpha and two beta subunits, each subunits contain prosthetic haem group, iron II ions present able to combine reversibly with an oxygen molecule, transport oxygen around around body

conjugated protein catalase

enzyme, quaternary protein containing four haem prosthetic groups, presence of iron II ions allow catalase to interact with hydrogen peroxide and speed up break down

features of a fibrous protein

formed from long, insoluble molecules, high proportion of amino acids with hydrophobic R-groups in their primary structure, limited range off amino acids, repetitive and very organised, strong, long molecules

fibrous protein keratin

present in hair, skin and nails, large proportion of sulfur-containing amino acid (cysteine), many strong disulfide bonds (strong, inflexible and insoluble)

how does number of disulfude bonds affect flexibility

hair = fewer bonds = more flexible, nails = more bonds = less flexible

fibrous protein elastin

found in elastic fibres (and small protein), in the walls of blood vessels and in alveoli, gives structures flexibility to expand when needed and to return to normal size, quaternary structure made from tropoelastin

fibrous protein collagen

connective tissue found in skin, tensions, ligaments and nervous system, all different forms made out of three polypeptides wound together in long strong rope-like structure, has collagen