1.6 Proteins Flashcards
What are the monomers of proteins?
Amino acids
What is a dipeptide?
Two amino acids joined together
What is a polypeptide?
More than two amino acids joined together
What is a protein made of?
One or more polypeptides
Describe the structure of an amino acid
- a carboxyl group ~ -COOH
- amine group ~ -NH2
- R group ~ variable side group
How many amino acids do living things share?
20
How are polypeptides formed?
- amino acids are linked together by condensation reactions
- molecule of water is released
- bond formed is a peptide bond
Describe the primary structure of proteins
Sequence of amino acids in the polypeptide chain
Describe the secondary structure of a protein
- hydrogen bonds form between amino acids in the chain
- either coil into an α helix
- or fold into a β pleated sheet
Describe the tertiary structure of a protein
- coiled or folded structure in secondary is often coiled or folded further
- more bonds form between parts of the chain ~ hydrogen or ionic
- disulfide bridges form when two molecules of cysteine are close together
- single chain proteins = tertiary structures is the final 3D structure
Describe the quaternary structure of a protein
- for proteins made of several different polypeptide chains
- proteins made of more than one chain (haemoglobin, insulin, collagen) the quaternary structure is the final 3D shape
List 3 examples of proteins
- enzymes
- channel proteins
- transport proteins
What is the function of enzymes?
- roughly spherical in shape due to tight folding of polypeptide chains
- soluble
- have roles in metabolism like digestives enzymes
- some help to synthesise (make) large molecules
What is the function of a transport enzyme?
- channel proteins
- they’re in membranes - - hydrophobic and hydrophilic amino acids
- these amino acids cause the protein to fold up into a channel
- these proteins transport molecules and ions across the membrane
What is the function of a structural protein
- physically strong
- consist of long polypeptide chains lying parallel to each other with cross links
- eg keratin and collagen