Proteins + Enzymes Flashcards
Draw the structure of an amino acid.
- amino group on left of central C
- carboxyl group on right of central C
- H beneath central C
- R (variable group) above central C
Describe how dipeptides form.
- 2 AA join together by a condensation reaction forming a peptide bond + releases water
- involves OH of the 1st AA carboxyl group + the H of the 2nd AA amino group
What are the 4 levels of protein structure?
- primary
- secondary
- tertiary
- quaternary
What is the primary structure of a protein?
- the order/sequence of AA in a polypeptide chain
What is the secondary structure of a protein?
- sequence of AA causes hydrogen bonds to form between AAs in the chain making it coil into an α-helix or fold into a β-pleated sheet
What is the tertiary structure of a protein?
- further folded + coiled to form a unique 3D shape
- held in place by **hydrogen, ionic + disulphide bonds [between AA cysteine] **
What is the quaternary structure of a protein?
- 3D structure resulting from more than 1 polypeptide chain chemically bonded together
- e.g. haemoglobin + collagen
Describe the biochemical test for proteins.
- add sample to a test tube
- add Biuret reagent to the sample (sodium hydroxide + dilute copper (II) sulphate)
- turns purple/lilac in the presence of proteins
What are enzymes?
- tertiary structure globular proteins which lower activation energy of the reactions they catalyse
How do enzymes lower the activation energy?
by forming an enzyme-substrate complex bc:
- holds substrates molecules close together, reducing any repulsion between the molecules so can bond more easily
- catalyse breakdown by putting a strain on bonds in the substrate, so breaks up more easily
What is activation energy?
- the minimum amount of energy needed to activate the reaction
What is the lock + key model?
- suggested that the rigid shape of the active site of the enzyme was a precise fit for the specific shape of the substrate
What is the induced fit model?
- prior to binding, substrate + active site are not completely complementary in shape
- when substrate binds the active site alters shape + moulds around substrate
What factors affect enzyme activity?
- T°C
- pH
- enzyme conc
- substrate conc
- inhibitors
How does T°C affect enzyme activity?
- higher T°Cs inc KE so molecules move faster
- so enzymes more likely to collide w substrate + form enzyme-substrate complexes
- inc ROR until optimum T°C, then the vibration can break bonds + denature the enzyme