proteins and enzymes

Question 1

what is a protein?

Answer 1

a polymer made of monomers (amino acids)

Question 2

what are the functional groups of an amino acid?

Answer 2

• carboxylic acid (COOH)
• amine group (H₂N)

Question 3

what differs in all amino acids and why?

Answer 3

the R group which represents a side chain so that there are different types of amino acids

Question 4

how many types of amino acids are there?

Answer 4

20

Question 5

what type of bond forms when a condensation reaction occurs when forming a dipeptide?

Answer 5

a peptide bond between an amine group and a hydroxyl group from another amino acid

Question 6

what are different levels of structures of proteins?

Answer 6

1. primary structure
2. secondary structure
3. tertiary structure
4. quaternary structure

Question 7

describe the primary structure

Answer 7

the order and sequence of amino acids joined by a condensation reaction forming peptide bonds which determine the tertiary structure

Question 8

describe the secondary structure

Answer 8

• contains hydrogen bonds which are between amino acids
• forms an alpha helix structure or beta pleated sheets
• this makes the structure stable by forming a polypeptide

Question 9

describe the tertiary structure

Answer 9

• contains hydrogen, ionic and disulphide bridges bonds between the R groups
• which forms 3D structure by the polypeptide chain folding

Question 10

describe the quaternary structure

Answer 10

made up of many polypeptide chain forming a complex 3D structure

Question 11

describe a method to test for proteins

Answer 11

1. crush up food in a pestle and mortar
2. add water to form a solution
3. add biuret solution which detects a peptide bond present.
4. shake and leave for 2 mins
5. if proteins are present, it should turn from a blue –> lilac

Question 12

what type of test is the biochemical test for protein?

Answer 12

qualitative

Question 13

what are enzymes?

Answer 13

enzymes are made of proteins which lowers activation energy to speed up chemical reactions
- enzymes are used as catalysts

Question 14

what do enzymes catalyse?

Answer 14

enzymes catalyse specific metabolic reactions at an intercellular level and a n extracellular level

Question 15

what is an example of a intercellular reaction?

Answer 15

aerobic respiration

Question 16

what is an example of an extracellular reaction?

Answer 16

digestion

Question 17

what is the induced fit model?

Answer 17

• where the substrate collides with a enzyme
• then the active site changes shape to fit around the substrate
• which then forms an enzyme substrate complex

Question 18

what does inhibitors do?

Answer 18

prevents the substrate to bind to the enzyme

Question 19

what does non competitive inhibitors do?

Answer 19

• they have a different shape to the substrate.
• so they bind to the allosteric site
• this changes the shape of the active site
• so the substrate can no longer bind to the active site as they are no longer complementary
• no more ES complexes formed

Question 20

what does competitive inhibitors do?

Answer 20

• they have a similar shape to the substrate
• they compete with the substrate to bind to the active site of the enzyme
• the CI binds to the enzyme’s active site instead of the substrate
• no more ES complexes formed

Question 21

what would increasing substrate conc do to an competitive inhibitor?

Answer 21

increasing the substrate conc will reverse effects of a competitive inhibitor as substrate out competes the CI

Question 22

what are the effects of rate of enzyme controlled reactions?

Answer 22

temperature, pH, enzyme concentration and substrate concentration

Question 23

what does temperature do to rate of enzyme controlled reactions?

Answer 23

• the ke of the molecules increase
• more enzyme substrate collisions
• which increases the rate of reaction
• so more ES complexes are formed
  optimum temperature
• enzyme will denature
• no substrate wouldn’t bind to enzyme as the active site changes shape
• no ES complex formed
• the reaction stops which is irreversible

Question 24

what does pH do to the rate of enzyme controlled reactions?

Answer 24

• most enzymes work best at pH 7
• when enzymes are above or below optimum pH, H and OH ions disrupt the tertiary structure (the bonds)
• if the pH is extremely high, the enzyme denatures so the active site changes shape so no ES complex formed as substrate doesn’t fit

Question 25

what does enzyme concentration do to the rate of enzyme controlled reactions?

Answer 25

- by increasing enzyme concentration, it increases the number of active sites - so more ES complexes can be formed - rate of reaction increases until substrate becomes the limiting factor (more enzyme than substrate) - by increasing enzyme conc even more, it won't affect rate as no more ES complex formed

Question 26

what does substrate concentration do to the rate of enzyme controlled reactions?

Answer 26

- by increasing substrate concentration, it increases the number of active sites - so more ES complexes can be formed - rate of reaction increases until enzyme becomes the limiting factor (more enzyme than substrate) - by increasing substrate conc even more, it won't affect rate as no more ES complex formed