Proteins Flashcards
(30 cards)
monomer?
amino acids
chemicals?
C, H, O, N
some have sulfur
amino acid structure
look at notes
How is a dipeptide formed?
2 amino acids join together by a peptide bond in a condensation reaction where water is released
What happens in a hydrolysis reaction?
water is used to break the peptide bonds so a dipeptide breaks into amino acids
What is a protein made of?
proteins are made of 1 or more polypeptides
primary structure of proteins
- sequence of amino acids in a polypeptide chain
- peptide bonds only
- a change in one amino acid may change the structure of the whole protein
secondary structure of proteins
- hydrogen bonds form between nearby amino acids in chain making it automatically coil into an alpha-helix or fold into a beta-pleated sheet
tertiary structure of proteins
- further folding or coiling of chain
- more bonds form between different parts of the polypeptide chain
- it forms the final 3D structure for proteins with a single polypeptide chain
What is the tertiary structure responsible for?
- the shape of the active site in enzymes
- the shape of channels in channel proteins
quarternary structure of proteins
- the way 2 or more polypeptide chains are assembled together
- the cross-linking of 2 or more polypeptide chains
- forms the final 3D structure for proteins with more than 1 polypeptide chain
bonds in primary structure
peptide bonds only
bonds in secondary structure
peptide and hydrogen bonds
bonds in tertiary structure
- ionic bonds
- disulfide bonds
- hydrophobic + hydrophilic interactions
- Hydrogen bonds
Ionic bonds
attractions between negatively charged R groups and positively charged R groups.
Disulfide bonds
when 2 molecules of amino acid cysteine come close together, the sulphur atom in one cysteine bonds to the sulphur atom in another cysteine forming a disulfide bond
Hydrophobic and hydrophilic interactions
when hydrophobic R groups come close together in protein, they clump together. Hydrophilic R groups are more likely to be pushed to the outside affecting how the protein folds up in its final structure.
Hydrogen bonds
weak bonds between slightly positively charged hydrogen atoms in some R groups and slightly negative charged atoms in other R groups on the polypeptide chain
bonds in quarternary structure
- determined by tertiary structure of individual polypeptide chains being bonded together which allows it to be influenced by all bonds
globular proteins properties
- ball shaped
- hydrophilic R groups pushed outwards forming Hydrogen bonds with water causing hydrophobic and hydrophilic interactions making it soluble so easily transported in fluids
Examples of globular proteins
- haemoglobin
- insulin
- amylase
Haemoglobin
- carries oxygen around the body in red blood cells
- conjugated protein (protein with a non-protein group attached)
- each of the 4 polypeptide chains have a prosthetic group called Haem
- Haem contains iron which oxygen bind sto
Insulin
- hormone secreted by pancreas
- regulated blood glucose levels
- soluble so transports to the tissues where it acts via blood
- consists of 2 polypeptide chains held together by disulfide bonds
amylase
- enzyme that catalyses the breakdown of starch in digestive system
- made of a single chain of amino acids
- secondary structure has both alpha helix and beta pleated sections
