enzymes

Question 1

induced fit theory (4)

Answer 1

1. substrate binds with enzyme active site - forming ESC
2. binding of substrate induces a change in the shape of enzymes active site
3. change in specific 3D tertiary structure of AS stresses and distorts substrate bonds - lowering activation energy
4. when products released, active site returns to original shape

Question 2

lock and key theory (5)

Answer 2

1. active site rigid, doesnt change shape
   2.substrate is complementary to enzymes AS
2. bind to form ESC
3. substrate broken down into products, no longer fit AS so released
4. enzyme unchanged can be reused

Question 3

affect of temp on enzyme action

Answer 3

• as temp increases, kinetic energy increases, more successful collisions, more ESC from, inc rate of reaction
• optimum pH, maximum number ESC formed
• past optimum - weak H bonds break, change tertiary structure of enzyme, AS no longer complementary, no ESC can form

Question 4

affect of pH on enzyme action

Answer 4

• as pH moves away from optimum, H and ionic bonds in tertiary structure altered, changing shape AS, no longer complementary, no ESC form

Question 5

pH affect on enzyme R groups

Answer 5

• optimum = complementary charges - attract
• low pH = positive charges - repel
• high pH = negative charges - repel

(between enzyme AS and substrate)

Question 6

complementary inhibitors function

Answer 6

similar structure to substrate, binds to AS, prevents substrate from binding, less ESC formed

Question 7

non- competitive inhibitors

Answer 7

not similar structure to substrate, binds to allosteric site ( other AS), changing shape of active site, no longer complementary, less ESC formed

Question 8

how can competitive inhibitors be overcome

Answer 8

increase substrate concentration

Question 9

charges on R groups on active site and substrate depending on pH

Answer 9

• optimum pH= complementary charges attract
• low pH= positive charges repel
• high pH= negative charges repel

Question 10

draw formation of a peptide bond and a peptide bond

Answer 10

Question 11

name and explain 4 types of structure of proteins

Answer 11

Structure is determined by (relative) position of amino acid/R group/interactions

Primary structure is sequence/order of amino acids

Secondary structure formed by hydrogen bonding (between amino acids)

Tertiary structure formed by interactions between R groups. Creates active site in enzymes

Quaternary structure contains >1 polypeptide chain