protein Flashcards
what is proteins made up of
carbon, hydrogen, oxygen, nitrogen
what are the functions
- enzymes to catalyse reactions
- carrier proteins transport molecules across membranes
- antibodies defend against diseases
- structural proteins support cells and tissues
- hormones transmit information
- transport proteins (haemoglobin) carry oxygen
- contractile proteins enable muscles to contract
why do diffrent proteins carry out different functions
have different shapes
what are make up proteins
amino acid polymer
what 4 molecules are in an amino acid
-carboxylic acid group
- amine group
- hydrogen
- R- one of 20 different groups
how many essensial amino acids are there
8
- cant be synthesised by the body
what reaction joins amino acids
condensation reaction
- removes wtare molecule and forms a peptide bond between the amino group and carboxylic group of the other amino acid
how is a polypeptide chain formed
the amino end and the carboxylic end of a dipeptide react with another amino acid
what are the levels of protein structure
- primary
- secondary
- teritary
- quaternary
what is the primary structure
the sequence of amino acids is held togtehre by peptide bonds (polypeptide)
what is the secondary structure
folding of the primary structure
types of secondary structure
alpha helix- when polypeptide chain coils
beta pleated sheet- folds
both held togteher by weak carbon bonds
examples of secondary structure
keratin- functional protein
what is the tertiary structure
further folding of the polypeptide chain to give more compex 3D shape
what is found in both teriary and quaternary structure
- hydrogen bonds between polar R groups
- disulphide bonds- covalent bonds formed between sulphurs in the R group of amino acid cystiene
- ionic bonds between positively and negatively cahrges R groups
- hydrophobic interactions- between non-polar R groups which cluster together towards centre of molecule
what is the quaternary stucture
made of more than one polypeptide chain
example of quaternary structure
haemoglobin
how do proteins denature
heating increases the kinetic energy causing atoms to vibrate and weak bonds to break
this can lead to the whole tertiary structure unraveling and the protein will be permanently denatured
types of proteins
globular, fibrous
properties of fibrous
proteins
- from fibres
- insoluble in water
- have structural roles found in skin, tendons, bones, cartilage
- doesnt contain a prosthetic group
properties of globular
proteins
- rolls up to form balls
- soluble in water
- metabolic role- carries oxygen in red blood cells
- contains a prosthetic group- haem
properties of haemoglobin
- 4 folded polypeptide chains
- 4 iron conatining haem group
- compact and spherical
- soluble in water
why is collagen strong
the collagen molecules cross link through covalent bonds to form fibres which give collagen its strength
properties of collagen
- made from 3 identical left handed helix polypeptide cahins wound to make a triple helix
- in each cahin, the third amino acid is glycine
- chains held together by hydrogen bonds
- very stable/insoluble in water
