Chapter 12 (12.6 - 12.7)

Question 1

Enzymes

Answer 1

• known as GLOBULAR PROTEINS
• help SPEED UP biochemical reactions
• can be REUSED
• often end in “ASE”
• goes from SUBSTRATES —-(E)—–> PRODUCTS

Question 2

absolute specificity

Answer 2

the enzyme only accepts ONE specific substrate

Question 3

relative specificity

Answer 3

the enzyme can accept a RANGE of substrates (depending if it has the same functional group or similar structures)

ex. oxidation

Question 4

aldehyde reductase

Answer 4

• an example of RELATIVE SPECIFICITY
• this CATALYZES THE REDUCTION OF AN ALDEHYDE
  (opposite of oxidation)

Question 5

where do substrates bind to?

Answer 5

• the ACTIVE SITE
  1) creation of an enzyme-substrate complex formation
  2) reaction starts
  3) product leaves/enzyme stays in ORIGINAL FORM (repeats cycle!)

Question 6

cofactors

Answer 6

some enzymes need COFACTORS to function
1) inorganic ions/metallic ions
2) organic compounds aka COENZYMES - comes from VITAMINS

Question 7

pH optimum

Answer 7

the pH where enzymes are MOST ACTIVE
*typical around 7 (except pepsin - 1.5)

Question 8

temperature + catalytic activity?

Answer 8

catalytic activity will INCREASE with temperature until the protein DENATURES

Question 9

temperature optimum

Answer 9

the temp. where enzymes are most ACTIVE
*around 37 degrees Celsius

Question 10

Michaelis-Menten enzymes

Answer 10

• can be describe in a 2-step process
• characterized by two parameters:
• Michaelis constant
• Vmax

Question 11

Michaelis constant

Answer 11

the AFFINITY (the tendency to bind) between an enzyme and its substrate

Question 12

Vmax

Answer 12

the maximum velocity or reaction rate

Question 13

inhibitor

Answer 13

reduces an enzyme’s activity

Question 14

irreversible inhibitors

Answer 14

react COVALENTLY with an enzyme
*aspirin - reduce inflam.

Question 15

reversible inhibitors

Answer 15

binds to the enzyme and INTERFERES with the activity
- binding is TEMPORARY
- the inhibitory effect is TEMPORARY

Question 16

competitive inhibitors

Answer 16

• type of REVERSIBLE INHIBITOR
  (compete for that binding active site)
  (substrate similar structure)
• AFFECTS AFFINITY or KM

Question 17

noncompetitive inhibitors

Answer 17

• binds to site in enzyme DIFFERENT than the active site
• binding affects the RATE or VMAX

Question 18

allosteric enzymes

Answer 18

• have MORE THAN ONE POLYPEPTIDE CHAIN
• COOPERATIVE BEHAVIOR:
  binding of substrate to active site effects other substrates and their bindings

Question 19

allosteric enzymes are affected by?

Answer 19

allosteric effectors: change the SHAPE of enzyme and active site

Question 20

positive effectors

Answer 20

ENHANCES binding of substrate and INCREASES RATE OF REACTION

Question 21

negative effectors

Answer 21

REDUCES binding of substrate and SLOWS RATE OF REACTION
- helps prevent its own overproduction - called FEEDBACK INHIBITION

Question 22

covalent modification + zymogens/inactive enzyme precursors

Answer 22

another way allosteric enzymes are controlled
(2 ATP - 2 ADP - covalent mod.)
(“gen” - zymogen)