1.3 proteins Flashcards
how many amino acids are found in biology
20
structure of amino acid
H 2NCHRCOOH
amine group
r group
carboxhylic group
what is different for each of the twenty amino acids
R group
what elements are contained in the general structural of amino acid
nitrogen,hydrogen,carbon,
oxygen
some contain sulphur
How do polypeptides form
when we join 3 or more amino acids we get a polypeptide
through condensation reaction (-CONH-)
(removal of water)
name all levels of protein structure
primary structure
secondary structure
tertiary structure
quaternary structure
define primary structure
sequence of amino acids
why is primary structure important
helps determine final 3D shape of the protein molecule to carry out its function effectively.
define secondary structure of a protein
is the curling or folding of the polypeptide chain into a-helices and b pleated sheets due to the formation of hydrogen bonds.
N-H +
C=O -
^ attracted together, twists and fold into shapes (secondary structure)
hydrogen bonds form all between polypeptide chain
describe the 2 types of secondary protein structure
a-helix
all N-H bonds on same side of protein chain
spiral shape
H-bonds parallel to helical axis
B-pleated sheet
N-H AND C=O groups alternate from one side to the other
define ‘tertiary structure’ of a protein. name types of bonding present
the 3D folding of the secondary structure into a complex shape. The shape is determined by between R groups and properties of R groups
such as hydrogen bonding, ionic bonding (salt bridges, form between oppositely charged groups on the R groups) and disulfide bridges (covalent bonds between sulphur atoms in cysteine) .
describe disulfide bridges in the tertiary structure of proteins
strong covalent S-S bonds between molecules of the amino acids cysteine
describe ionic bonds in the tertiary structure of proteins
relatively strong bonds between charged R groups
ionic bonds are broken by changes to Ph
describe the hydrogen bonds in the tertiary structure of proteins
intermolecular force between positive hydrogen of o-h or n-h and lone pair on o or n of an adjacent molecule
numerous and easily broken
define ‘quaternary structure’ of a protein
is a specific 3-D shape of a protein that is determined by the multiple polypeptide chains and/or prosthetic groups bonded together.
describe the structure and function of globular proteins
spherical and compact
hydrophilic R groups face outwards and hydrophobic inside
fibrous proteins
Long parallel polypepdes * Very lile terary/quaternary structure - mainly secondary structure. * Occasional cross-linkages which form microfibres for tensile strength * Insoluble * Used for structural purposes
collagen
Collagen is an example of a fibrous protein. It has high tensile strength due to the large number of hydrogen bonds in the structure. Collagen molecules are made up of three disnct α-chains which form a triple gamma helix.
