Review for Exam 3 - Enzymes

Question 1

Vmax

Answer 1

• highest velocity of the enzyme (maximum rate of reaction)

- achieved when all the enzyme active sites are filled with substrate (i.e. saturated)

Question 2

Km

Answer 2

• substrate concentration at which the rate of the reaction is 1/2 its maximum (i.e. the [S] at which 1/2 the enzyme active sites are filled w/substrates
• measurement of rate of reaction
• affected by substrate concentration, pH, temp & ionic strength

Question 3

cofactors

Answer 3

help activate enzymes

can be inorganic or organic

Question 4

organic cofactors

Answer 4

coenzyme A
NAD+
FAD
NADP+

Question 5

inorganic cofactors

Answer 5

Zn
Fe
Cu

Question 6

regulation of enzyme activity:

competitive inhibitors

Answer 6

• competes w/substrate for same active site on enzyme
• a higher concentration of substrate can be added to overcome competition
• Vmax is not altered, but Km increases

Question 7

regulation of enzyme activity:

non-competitive inhibitor

Answer 7

• bind to protein at some place other than active site, which changes the shape of the enzyme & makes it less active or inactive
• adding more substrate does not overcome inhibition
• Vmax decreases & Km remains the same (won’t happen as quickly; less effective)
  e. g. DDT

Question 8

regulation of enzyme activity:

irreversible inhibitor

Answer 8

bind to site & make enzyme permanently inactive
e.g. penicillin binds to a bacterial cell wall synthesizing enzyme / cyanide binds to respiratory protein & irreversibly inactivates them

Question 9

regulation of enzyme activity:
allosteric regulation
feedback regulation
chemical modification

Answer 9

allosteric - have active and inactive sites / complex enzymes
feedback -
chemical -

Question 10

Factors that affect enzyme activity

Answer 10

temperature
pH
salt concentration
substrate concentration
co-factors

Question 11

Examples of EXERGONIC reactions

Answer 11

-∆G
osmosis
respiration
ice melting
burning fossil fuels

Question 12

Examples of ENDERGONIC reactions

Answer 12

\+∆G
photosynthesis
active transport
amino acid biosynthesis
ATP synthesis

Question 13

examples of EXOTHERMIC reactions

Answer 13

–∆H
respiration

burning fossil fuels
burning methane

Question 14

examples of ENDOTHERMIC reactions

Answer 14

+∆H
photosynthesis
melting ice

Question 15

Keq equals ____?`

Answer 15

reactants

• higher the #, more quickly reaction took place = spontaneous

Question 16

energy coupling

Answer 16

use of an exergonic process to drive an endergonic one
ex. using ATP to phosphoylate glucose, which then combines w/fructose to make sucrose = exergonic rxn. W/o ATP, glucose + fructose = endergonic rxn.
ATP + H2O —> ADP + Pi + 7.3 kcal
(exergonic & exothermic)