Unit 1 - Enzymes

Question 1

What is an enzyme

Answer 1

“biological catalysts” = speed up body rxn

• biological mols that catalyze or speed up rxn wout being consumed
• enzymes = proteins
• each enzyme has its own 3D shape which dictates the rxn it will catalyze.

Question 2

What is an enzyme pt. 2

Answer 2

ends in ase
- often globular
- larger than substate
- has ACTIVE SITES

Question 3

Activation Energy

Answer 3

in order for a rxn to proceed, particles must collide w sufficient energy. if mols collide w not enough energy, they will remain unchanged. the min amt of energy for a rxn to occur is called the AE.

Question 4

Lower The Activation Energy

Answer 4

this means that rxn can occur at lower body temperatures if enzymes r present. this gives cells control over which rxn will occur. Not only that but since enzymes r catalysts they CAN BE REUSED.

Question 5

Binding to an enzyme

Answer 5

• active site interacts w specific mol to catalyze specific rxn
• called a substrate

sucrose = glucose & fructose
starch = sugars
deoxynucleotide triphosphates = DNA

Question 6

Models of enzymes

Answer 6

1) lock and key
2) induced fit model

Question 7

Lock and Key model

Answer 7

• enzyme has an active site that is unchanging (rigid)
• substrates bind = chemical process occurs

Question 8

Induced Fit Model (new)

Answer 8

enzyme change its shape (flexible).

Question 9

IFM 1)

Answer 9

when a substrate enters the active site, it binds to the enzyme through many weak intermolecular bonds.

Question 10

IFM 2)

Answer 10

the enzyme itself slightly changes shape to envelop the substrate

Question 11

IFM 3)

Answer 11

this changes of shape can line up substrate mol and or stress chemical bonds producing the product

Question 12

activation energy can be lowerd in 3 ways?

Answer 12

a) orientation
bring substrates in correct position
b) physical strain
make bonds weaker and easier to rearrange
c) chemical change
+ / - ions to destabilize

Question 13

The catalytic cycle

Answer 13

since enzymes r not used up themselves in a chemical rxn they r reusable
(an enzyme binds to one or more substrate

Question 14

Cofactors and Coenzymes

Answer 14

some enzymes need to bind to additional mols to functions

Question 15

Cofactors

Answer 15

nonprotein inorganic substance (metal ions)

Question 16

Coenzymes

Answer 16

nonprotein organic cofactos that r needed for some enzymes to function (shuttle btw enzymes )
ie. NAD / FAD

Question 17

Apoenzyme

Answer 17

the enzyme without its cofactors or coenzymes

Question 18

Holoenzymes

Answer 18

the active form bound to cofactors and coenzymes

Question 19

Factor affecting enzyme activity

Answer 19

-concentration
-enzyme
-substrate
-temp
-ph

Question 20

enzyme concentration

Answer 20

concentration of both the enzyme and substrate will influence the rate of a catalysis rxn.
so if there is excess substrate present then the rate of rxn is proportional to the enzyme concentration

Question 21

Increasing EC

Answer 21

will speed up the reaction as long as there is a substrate to bind too. once all substrate is bound, the rxn will no longer speed up since there will be nothing for additionl enxymes to bind which limits the rate of rxn.

Question 22

Substrate Concentration

Answer 22

increasin substrate concentration also increase the rate of rxn to a certain point. once all of the enzymes have bound, any substrate incease will have no effect on the rate of rxn, as the avaliable enzymes will be saturated and working at their max rate

Question 23

pH and Temp

Answer 23

changes in pH and temp strognly affect the activity of most enxymes. enzymes usually reach max activity with a narrow range

Question 24

pH

Answer 24

• enzymes also have optimal pH
• normal pH is 7 ; outside of this range will slow enzyme activity
  -dependent on location
  ie. pepsin = ph of 2
  ie. trypins = ph 8 - 12

Question 25

temperature

Answer 25

enzymes catalyzed reaction increase as temp increases
but if temp increase past a certain point, protein structure will be disrupted and enzymes will be denatured

Question 26

Optimal temp

Answer 26

each enzyme has its own best OT.
but for most it is between 40 - 50c
humans = 37c
archaebacteria = 100c

Question 27

regulation of enzyme activity

Answer 27

1) inhibition
2) allosterically
3) feedback inhibition

Question 28

enzyme inhibitors

Answer 28

• lower the rate at which an enzyme catelyzes a rxn
• inhibitors r mols that bind to an enzyme and decreases its activity

Question 29

competitive inhibition

Answer 29

• v similar in shape
• bind to the active site and physically block the correct substrate from binding
• if the concentration of inhibitor is high enough the rxn will stop

Question 30

Non-Competitive inhibition

Answer 30

• substance that attach to a binding site on an enzyme other than active site causing a change in the enzymes shape abd loss of affinity
• may be allosteric
• inhibitor directly affects the enzyme so that it cannot carry out its function

Question 31

Allosteric Regulation (2)

Answer 31

cells must control enzymes to coordinate cellular activities. they may accomplish this in 2 ways
1) restricting the production of a specific enzyme
2) inhibiting the action of an enzyme that had already been produced

Question 32

Allosteric sites

Answer 32

receptor site; some distance from the active site of certain enzymes that bind substances that may inhibit or stimulate an enzymes activity.

Question 33

Effector

Answer 33

substance that binds to the allosteric site may inhibit or stimulate and enzymes activity

Question 34

Feedback inhibitor

Answer 34

the production of a series of enzymes catalyzed rxn acts to allosterically inhibit and enzyme that acts earlier in the series. this is an effective way to stop the synthesis of that product when aq level r produced in a cell.