Enzymes

Question 1

What is Km?

Answer 1

substrate conc. needed for rate to be half of the max

Question 2

What is Vmax?

Answer 2

maximal velocity
max rate when all active sites are saturated

Question 3

what is Vo?

Answer 3

inital rate

Question 4

what does the x-intercept on the Lineweaver burk plot give?

Answer 4

-1/Km

Question 5

what does the y-intercept on the Lineweaver burk plot give?

Answer 5

1/Vmax

(v looks like y)

Question 6

what does the gradient of the Lineweaver burk plot give?

Answer 6

Km/Vmax

Question 7

how do competitive inhibitors affect the Vmax?

Answer 7

unaffected
- adding enough substrate will eventually over come the inhibitor

Question 8

how do competitive inhibitors affect the Km?

Answer 8

increases
- harder for substrate to bind at the active site > higher conc needed
- lower affinity = high Km

Question 9

what is the relationship between affinity and Km?

Answer 9

reciprocal
higher affinity=lower Km
less substrate needed to reach same rate of reaction

Question 10

how do competitive inhibitors change Vmax and Km?

Answer 10

Vmax unchanged
Km increases

Question 11

how do non-competitive inhibitors change the Vmax?

Answer 11

decreases

Question 12

how do non-competitive inhibitors change the Km?

Answer 12

unaffected

Question 13

what Lineweaver Burk plot of inhibitor + no inhibitor has the lines crossing on y axis?

Answer 13

competitive
y-intercept - Vmax which is unaffected

Question 14

how do non competitive inhibitors affect the Vmax and Km?

Answer 14

Vmax decreases
Km unaffected

Question 15

Key features of active sites

Answer 15

• occupies small part of enzyme
• formed by amino acids
• are clefts or cervices - to stop H2O from interfering
• complementary shape to substrate
• substrate bound by multiple weak bonds