Proteins Flashcards
What are proteins?
- large molecules, polymers of amino acids
What enzyme catalyses formation of peptide bonds ?
- peptidyl transferase
What are peptides?
- between 2 and 50 amino acids
What are 3 methods of post-translational modification of proteins?
- Proteolysis = polypeptide chain cleaved into fragments
- glycosylation = addition of sugars
- phosphorylation
What kind of hormone is insulin + where is it produced?
- Peptide hormone produced in 𝛃 of pancreas
function of proteins ?
- enzymes
- structural support
- hormones
- cell signaling
what do amino acids form at low and high pH’s ?
- form cations in low pH
- anions in high pH
how many amino acids does a polypeptide chain contain ?
- polypeptide chain between 50 and 2000 amino acids
what is the primary structure of a protein ?
- sequence of amino acids in polypeptide chain
What is the secondary structure of a protein ?
- localized folding patterns within the polypeptide chain
- stabilized by H bonds
- α-helix and β-pleated sheets
What is the α-helix (𝛼-helix), and how is it structured?
- right-handed spiral structure
- each C=O forms a H bond with the NH of the amino acid four residues earlier
What is the β-pleated sheet (𝛃-sheet) ?
- 2 or more lengths of the polypeptide chain lie parallel to each other
- R groups of the amino acids point above and below the sheets
- NH and C=O parts of the peptide bond point towards each other
- H-bonds between these sections
What is the tertiary structure of a protein?
- final 3D shape, which is determined by the interactions between the R-groups
What are the four main types of interactions that stabilize the tertiary structure of proteins?
- Ionic bonds
- Hydrophobic interactions
- Hydrogen bonds
- Disulphide bridges = (covalent)
What is the quaternary structure of a protein?
- two or more polypeptide chains interact
- Forces between these chains, SAME AS TERTIARY structure
which bond is strongest out of disulfide, ionic, H bonds, van der waals ?
- disulfide bonds
what is the role of insulin ?
- lowers blood glucose level
- promotes absorption of glucose from blood into liver +fat + muscle cells
insulin therapy ?
- porcine insulin close to human version
- used to treat type 1 diabetes by injection
why is insulin administered via injection ?
- too big to pass through PLB
difference between structures of human and porcine insulin ?
- only 1 amino acid differs in sequence
- folded and twisted differently
2 Factors affecting insulin activity ?
- folding = correct folding pattern allows protein to bind adequately, makes insulin more stable
- hydration = H2O molecules attached in correct places = affects solubility
- hydrophobic amino acids cluster in interior form hydrophobic protein core
why was insulin measured in IU ?
- impossible to dry and rehydrate into correct 3D structure
process of genetic engineering of insulin ?
- isolate human insulin gene
- plasmid cut by enzyme
- insert human insulin gene into plasmid
- plasmid inserted into new bacterium
- bacterium divides + produces insulin
