Proteins And Enzymes Flashcards
Describe the structure of proteins.
- polymer of amino acids
- joined by peptide bonds
- formed by condensation reactions
- primary structure is number and order of amino acids
- secondary is folding into alpha-helix or beta-pleated by hydrogen bonds
- tertiary interactions between r groups, ionic bonding and disulphide bridges
- active site in enzymes or complimentary shapes
- quaternary is interactions between polypeptides
Describe how monomers join to form primary structure of a protein.
- condensation reaction between amino acids
- forms peptide bonds
- specific sequence/order of amino acids
How is a peptide bond formed between two amino acids?
- condensation reaction
- between amine and carboxyl group
Describe how an enzyme-substrate complex increases rate of reaction.
- reduces activation energy
- due to bending bonds
Describe how a change in the base sequence of the DNA coding for an enzyme may result in a non-functional protein.
- change in primary structure changes amino acid sequence
- hydrogen bonds and ionic bonds and disulphide bridges form in diff positions
- alters tertiary structure
- no enzyme-substrate complexes can be formed
What is the proteome of a cell.
- range of different protein a cell is able to produce
Biuret test to distinguish a solution of lactase from a solution of lactose.
- add biuret reagent to both solutions
- lactase will give purple as is a protein
Sucrase does not hydrolyse lactose. Why?
- lactose has a different shape
- does not bind to active site
Describe the induced-fit model.
- active site not complimentary
- active site has conformational change
- substrate fits
- forms enzyme-substrate complex
- reduces activation energy
How is induced-fit different to lock and key?
- active site is fixed shape
- substrate already complimentary before binding
Why can insulin not be taken orally?
- broken down by enzymes
- insulin no longer functional
Effect of substrate concentration on the rate of an enzyme controlled reaction.
- increases then plateaus
- as all sites occupied
- maximum number of ESC’s per second
Explain how a competitive inhibitor works.
- inhibitor is a similar shape to substrate
- inhibitor enters active site
- less substrate binds as active site occupied
Explain how a non-competitive inhibitor works.
- not similar shape to active site
- binds to allosteric site
- causes conformational change in active site
- substrate no longer complimentary
- less ESC’s formed per second
