Week 6

Question 1

Enthalpy

Answer 1

the total energy in a system

Question 2

Entropy

Answer 2

the tendency for ordered things to become random

Question 3

Free Energy (G)

Answer 3

refers to the amount of energy that is available in a system to use

Question 4

If Product (P) has less free energy than the starting reagents (A and B), the ∆G for this reaction is –

Answer 4

Exergonic which means energy (or heat) is released and the reaction will go forward spontaneous

Question 5

If P has more free energy than A and B, the ∆G is +

Answer 5

endergonic (which means energy need to be added for reaction to occur) and the reaction will not spontaneous occur

Question 6

∆G predicts the…

Answer 6

direction of the reaction but doesn’t affect the rate at which the reaction occurs.

Question 7

Transition state

Answer 7

when the substrate is mid-way through the transition to product

Question 8

when do molecules have the highest potential energy

Answer 8

When in transition state/point

Question 9

Rate of reaction dependent on….

Answer 9

activation energy. The smaller the activation energy the quicker the reaction will occur

Question 10

Function of enzymes

Answer 10

speed chemical reactions by lowering the activation energy

Question 11

what molecule drives endergonic reactions?

Answer 11

ATP

Question 12

energetically favorable reactions

Answer 12

the free energy of the reactants is grater than the free energy of the of the product. Therefore, G is negative and the reaction con occur spontaneously

Question 13

energetically unfavorable reactions

Answer 13

G would be positive if the reaction occurred and the universe would become more ordered. So the reaction can only occur if coupled to a second energetically favorable reaction

Question 14

Active site

Answer 14

Site where chemical reaction takes place

Contains functional groups that are actively involved in the reaction

Question 15

Stabilization of an enzyme

Answer 15

Additional bonds form with the enzyme to stabilize the substrate in its transition state. This is how enzymes lower the activation energy.

Question 16

Substrate binding involves…

Answer 16

formation of non covalent bonds and interactions with amino acids from enzymes or cofactors (hydrophobic, electrostatic, and Hbonds)

Question 17

Enzyme-substrate specificity

Answer 17

extremely high specificity due to the chemical shapes/interactions within the substrate binding site

Question 18

lock and key mechanism

Answer 18

substrate binding site creates a 3-D shape that is complementary to the substrate
Enzyme AAs, cofactors, etc interact with substrate via non-covalent interactions

Question 19

induced fit mechanism

Answer 19

Substrate binding to the enzyme induces a conformational change. Helps to reposition functional groups to promote reaction

Question 20

Activation energy

Answer 20

energy required to raise substrate energy to the transition state

Question 21

Coenzymes

Answer 21

non-protein organic molecules (vitamins).

Question 22

Activation transfer coenzymes

Answer 22

Form covalent bond with substrate then activate it for transfer

Question 23

Oxidation reduction coenzymes

Answer 23

similar to activation-transfer, but no covalent bond is formed. Functional groups accept or donate electrons

Question 24

metal ions

Answer 24

electrophiles. involved in substrate binding, stabilizing anions, donate/accept electrons in redox reactions

Question 25

inhibitors

Answer 25

compounds that decrease the rate of an enzymatic reaction

Question 26

Covalent inhibitors

Answer 26

form covalent bond with functional groups in the active site

Question 27

transition state analogs inhibitors

Answer 27

Bind more tightly to enzyme than substrate to products

Question 28

the velocity of all reaction is dependent on what?

Answer 28

Substrate concentration

Question 29

substrate saturation are found in which reactions?

Answer 29

enzymes catalyzed reactions

Question 30

Michaelis-Menten Equation

Answer 30

E+S ES E+P

Assumes enzyme will let go once the product its formed and will go on to grab more substrate

Question 31

Rate of product formation

Answer 31

is dependent on 2 constants (Km and Vmax) and on the amount of substrate available at that time point

Question 32

Km

Answer 32

1/2 Vmax. allows us to compare affinities

Question 33

Km values for enzymes

Answer 33

are typically just above [S] in the cell, so that the enzyme rate is sensitive to small changes in [S]

Question 34

Catalytic constant/ Turnover number

Answer 34

Kcat = Vmax / [E]total

measured in units per sec

Question 35

irreversible inhibitors

Answer 35

decreases amount of enzyme available

Question 36

Reversible inhibitors

Answer 36

can diffuse away at a significant rate.

Competitive, non competitive, uncompetitive

Question 37

Competitive inhibitors

Answer 37

inhibitor binds to substrate-binding site.

Km is increased. Vmax is the same

Question 38

non-competitive inhibitors

Answer 38

Inhibitor binds enzyme someplace other than s-site. Vmax is lowered. Km is the same

Question 39

uncompetitive inhibitors

Answer 39

inhibitor only binds to the ES complex. both the Vmax and Km will decrease but the slope stays the same.

Question 40

Lineweaver-Burk transformation

Answer 40

plotting the velocity vs substrate concentration gives us hyperbolic curve
Y intercept = 1/Vmax
X intercept = -1/Km
slope is Km/Vmax

Question 41

feedback loops

Answer 41

as product forms, apparent rate of enzymes decreases

Question 42

genetic regulation

Answer 42

Activation of gene expression, increased enzyme (protein) production

Question 43

Allosteric modification

Answer 43

Binding of regulators to sites outside of the active site (allosteric sites) induces conformational. Doesn’t follow Michaelis mention/ yields a sigmoidal shape

Question 44

Cooperativity in allosteric enzymes

Answer 44

Substrate binding in one subunit increases the chance of substrate binding in another

Question 45

Allosteric inhibitors

Answer 45

tend to bind more tightly to T state

Question 46

Allosteric activators

Answer 46

tend to bind more tightly to R state

Question 47

covalent modification

Answer 47

Extremely common way to quickly adjust activity of enzymatic reactions. Usually reversible.