3.1.4 proteins Flashcards
what are amino acids?
proteins are huge three dimensional molecules
building blocks of monomers are the 20different amino acids found in nature
these amino acids combine to form a polymer called a polypeptide
structure of an amino acid
amino group (-NH2) = basic group from which the amino name is formed
carboxyl group (-COOH)
hydrogen atom
R side = each amino acid has a different R group
describe a proteins function
type of protein, function, example
structural, support, collagen, keratin
transport, transport, haemoglobin
hormonal, coordination, insulin
receptor, chemical stimuli, CD4
contractile, movement, actin, mysin
enzymatic, action of chemical response, digestive enzymes
defensive, protection against defensive, anitbodies
what are proteins?
polymers of amino acids are called polypeptides
a protein consists of one or more foiled and coiled polypeptides
conformation: thousands of different kinds of protein, each with a unique 3D structure
proteins always contain = nitrogen, hydrogen, oxygen
(sulfur and phosphorous are sometimes present)
describe a basic molecule of amino acids
amino acid has an amino (basic) group in the R group
2 basic groups and 1 acidic group
amino acid = basic molecule
diagram on notes
what is a carboxylic amino acid?
amino acid has a carboxylic acid group in its R group
2 acid groups and 1 base group
amino acid = acidic molecule
diagram on notes
describe an alanine protein
alanine = posses a CH3 group as its R group
posses a acidic and base group
amino acid is a neutral molecule
diagram on notes
what do simple amino acids possess?
simplest of amino acids = posses a hydrogen atom for its R group
amino acid = glyciene
diagram on notes
what are individual amino acids?
individual amino acids display a terrahedral shape due to the angle of bonds between the atoms
diagram on notes
describe a protein structure
protein is more or one polypeptides, precisely twisted and coiled into a molecule of unique shape
proteins must be globular (roughly spherical) or fibrous (rope like)
non protein elements may be incorparated into protein structure = prosthetic groups eg haemoglobin contains iron
4 levels of protein structure are frequently cleted with respect to protein structure
describe the formation of a dipeptide
hydroxyl group is lost from one’s carboxylic group and H from the others amino acid
to form a peptide bond
what are dipeptides?
two linked amino acids = dipeptide
joined by peptide bonds (covalent bond)
any number of extra amino acids can be added by further condensation reactions
molecule of many amino acids = polypeptides (polymer and macromolecule)
happes in a process called polymerisation
describe the quaternary structure of proteins
secondary and tertiary structure are all still single polypeptides
quarternary structure is the way in which 2 polypeptides may join together to form larger proteins
held by the same 3 bonds in tertiary structure: hydrogen, ionic and disulphide bridges
describe the tertiary structure of proteins
secondary structure can be twisted and folded even more to give a complex precise 3D structure
held in shape by bonds between amino acids side groups in different parts of the chain
- hydrogen bonds = can form between a range of R groups. numerous but easily broken
- disulphide bonds = between two cysteine residues. strong covalent bonds, not easily broken
- ionic bonds = between R groups that have amino acids and carboxyl groups
weaker than disulphide bonds, easily broken by changes in pH
describe the secondary structure of proteins
polypeptide chains often coil or fold in a regular pattern to make 3D shapes
often coil into a shape called an ALPHA HELIX, this is due to the attraction between the oxygen on the -CO group on one aa and the -NH on a 4 places ahead
hydrogen bonding
sections of alpha helix can be linked to areas of polypeptide chain with no regular arrangements