proteins Flashcards
what is a protein
macromolecule consisting of aminos acids arranged in a particular structure that enables it to carry out specific function
structural protein example
actin within a cell or keratin in skin
whats transcription
DNA—-> mRNA
-comes before translation
whats translation
mRNA—> protein synthesis
-mRNA used by cell as a code to make chains of AA’s that go onto form proteins
whats does uracil replace in mRNA
thymine
how many naturally occurring AA’s are there
20
describe an AA’s structure
amine group and carboxylic group and R group which is different each time
amine group
N-H2
what does chiral mean
its mirror image is not the same as itself
how are AA’s affected by a low Ph
carboxylic acid group takes up a hydrogen, and becomes slightly positive
the reverse is true at a high Ph
aliphatic amino acids
R group consisting of hydrocarbon chains
eg. glycine
aromatic amino acids
R group consisting of hydrocarbon ring
eg. phenylalanine
sulphur containing amino acids
contains a sulphur group
di-sulphide bridges
covalently bonded linkages that are contained between 2 sulphur containing AA’s and help increased strength
acid amino acids
eg. glutamate
basic amino acids
eg. lysine
polar amino acids
can carry a charge at the end of the R group
eg. serine
miscellaneous amino acid
proline- has a unusual ring shape
primary strcuture
sequence in which AA monomers are bonded together to form a polypeptide chain
-amino acid sequence
peptide bond
c=O, NH2
secondary struture
local interactions between stretches of a polypeptide chain
- alpha helices
- beta plated sheets
tertiary structure
overall 3D arrangement when R groups of different amino acids interact
- van der waals, ionic, hydrogen, disulphide bridges and hydrophobic interactions
- functional proteins can’t exist without tertiary structure
quaternary structure
more than one polypeptide chains join together
eg. HAEMOGLOBIN
functions of proteins
enzymes structural receptors hormones transport storage defensive contractile
conjugated proteins
protein to which another chemical group eg. carbohydrate is attached, by covalent bonding or other interactions
glycoproteins
proteins with 1 or more carbohydrate molecules covalently attached
ogliosaccharide
when a few carbohydrate monomers exist together in a chain, the carbohydrate is termed this
glycosylation
when carbohydrate molecules are attached to a protein
effects of glycosylation
stability
solubility
cell signalling
orientation
lipoproteins
proteins that combine with lipids
functions of lipoproteins
found in cell membranes to transport hydrophobic molecules eg. cholesterol
apolipoprotiens
when lipoproteins form complexes with other lipoproteins
transport fat around body, blood and CSF
metalloportines
protein molecules with a metal ions within their structures
example of metalloprotiens
haemoglobin
describe haemoglobin structure
- quaternary structure
- 4 polypeptide chains- 2 alpha and 2 beta subunits
- each subunit contains haem, and within each is 1 iron
what are the 3 categories proteins can be divided into functionally
globular
fibrous
membranous
globular proteins functions
storage enzymes hormones transporters structural
