Section E

Question 1

What is the rate of reaction?

Answer 1

Rate at which reagents are used up and products are formed

Question 2

What is the rate equation?

Answer 2

Rate = k[A]^m.[B]^n

Question 3

How do you find overall order from partial order?

Answer 3

Overall order: m + n (if m or n are partial orders)

Question 4

What does the rate constant vary with?

Answer 4

Temperature and the nature of reactants

Question 5

Define a zero order reaction

Answer 5

Rate of the reaction does not depend on concentration

Question 6

What is the equation for a zero order reaction?

Answer 6

[A] = [A0] - kt

Question 7

In a zero order reaction, what decreases linearly over time?

Answer 7

Concentration of reactants

Question 8

What is the equation for first order reactions?

Answer 8

[A] = [A0].e^-kt

Question 9

Define T 1/2

Answer 9

Half life, time required for the concentration to drop to half of its original value

Question 10

What is the equation to find half life from rate constant?

Answer 10

T 1/2 = ln2/k

Question 11

what are the two processes occurring during drug metabolism?

Answer 11

Renal and metabolic elimination

Question 12

What is the equation for drug metabolism kinetics?

Answer 12

-d[drugs]/dt = ae^-k1t + be^-k2t (k1/2 are diff. rate constants, a/b are weighting factors)

Question 13

What form of kinetics is radioactive decay?

Answer 13

First order

Question 14

What is the definition of radioactive activity (Bq)?

Answer 14

number of decay events per second

Question 15

what are the units for radioactive activity?

Answer 15

Becquerels

Question 16

What is 1 curie equivalent to?

Answer 16

3.7 x 10^10 disintegrations per second

Question 17

What are 2 equations to find activity?

Answer 17

Activity = -dN/dt = kN

Question 18

What is the equation for radioactive decay?

Answer 18

N = N0.e^-kt

Question 19

What is an alternative equation for radioactive decay?

Answer 19

N = N0.e^(-ln2.t/t 1/2)

Question 20

What is the half life of Krypton 85 gas?

Answer 20

10.8 years

Question 21

Define a second order reaction

Answer 21

Rate of reaction proportional to square of concentration of the reagent

Question 22

What is the equation for a second order reaction?

Answer 22

1/[A] = 1/[A0] + kt

Question 23

What is the general procedure to measure a rate of reaction?

Answer 23

start reaction, measure property as function of time, convert measurement to concentration, analyse data

Question 24

What spectrophotometric method is used to measure the rate of reaction for very fast reactions?

Answer 24

Flash photolysis

Question 25

What spectrophotometric method is used to measure the rate of reaction for fast reactions?

Answer 25

Stopped flow method

Question 26

How would you determine the order of a reaction experimentally?

Answer 26

diff. [A0] but same [B], plot [A] vs T (if linear then 0 order), plot ln[A] vs T (if linear then 1st order), plot 1/[A] vs T (if linear 2nd order)

Question 27

What is the initial rates/differential method for determining order of a reaction?

Answer 27

keep [B] same, but [B]>>>[A] so [B] constant, run reaction at different [A0], determine initial rate of each, plot against time, then put into equation: log(rate) = log(k obs) + alog[A]

Question 28

What are pseudo-order conditions?

Answer 28

having such a high concentration of a substrate that it’s concentration remains effectively constant throughout the reaction

Question 29

Define an elementary reaction

Answer 29

most reactions require several steps for the reaction to go to completion, reactions go via intermediates, two types e.g. photochemical reactions of alkanes

Question 30

What is a unimolecular reaction?

Answer 30

Single species undergoes a change, type of elementary reaction, e.g. bond cleavage

Question 31

What is a bimolecular reaction?

Answer 31

Two species come together, type of elementary reaction e.g bond formation

Question 32

Define an elementary step

Answer 32

Reaction at molecular level e.g. collision between 2 molecules/bond breaking or formation

Question 33

What is the equation for rate law in a unimolecular step?

Answer 33

Rate = k[A2] assuming reaction: A2 —> A + A

Question 34

What is the equation for rate law in a homonuclear and bimolecular step?

Answer 34

Rate = k[A]^2 assuming reaction: A + A —> A2

Question 35

What is the equation for rate law in a heteronuclear and bimolecular step?

Answer 35

Rate = k[A][B] assuming reaction: A + B —> AB

Question 36

What is the rate determining step?

Answer 36

If reaction is a series of steps, then slowest step governs the rate of reaction,

Question 37

What is the equation for rate constant from temperature?

Answer 37

k = Ae^-Ea/RT OR lnk = lnA - Ea/RT

Question 38

What is the Arrhenius relation?

Answer 38

Rate constant depending on temperature, equation = k = Ae^-Ea/RT OR lnk = lnA - Ea/RT

Question 39

Why do reactions depend on temperature?

Answer 39

depends on collisions, molecules require collision of threshold energy = activation energy

Question 40

What is the Boltzmann distribution?

Answer 40

A distribution of the kinetic energy of molecules within a sample, represented by the equation e^-E/RT

Question 41

What does the equation e^-E/RT represent?

Answer 41

The fraction of molecules at a temperature T which have energy greater than E

Question 42

What is the significance of the pre-exponential factor A?

Answer 42

A usually represents the total number of collisions occurring per second in a reaction (if more complex then important to factor in orientation of collision)

Question 43

Define a catalyst

Answer 43

A substance which takes part in a reaction and changes its rate but which can be recovered unchanged at the end of the reaction

Question 44

Why do catalysts work?

Answer 44

Provides the reaction with a separate mechanism with a lower activation energy

Question 45

What is a homogenous catalyst?

Answer 45

Catalyst in the same phase as the reactants

Question 46

What is a heterogenous catalyst?

Answer 46

Catalyst in different phase as reactants

Question 47

What is an example of an enzyme which shows extreme specificity?

Answer 47

Urease

Question 48

Who proposed the lock and key method in 1958?

Answer 48

Koshland

Question 49

What is the michealas-menten equation to find rate of product formed?

Answer 49

V = k2[E0][S]/(Km+[S])

Question 50

What measure is km?

Answer 50

Measure of how strongly something binds, small Km = strong binding

Question 51

What is the equation for Vmax?

Answer 51

Vmax = limiting rate = k2.[E0}

Question 52

What is the equation for rate (V)?

Answer 52

V = Vmax.[S]/(Km+[S])

Question 53

When does [S]+Km occur?

Answer 53

At very high [S]

Question 54

What is the equation for Kcat?

Answer 54

Kcat = Vmax/[E0]

Question 55

What is the definition of Kcat?

Answer 55

How many substrate molecules can be processed per second by 1mole of catalyst

Question 56

What do you plot on a line weaver burke plot?

Answer 56

1/[S] (x) against 1/V (y)(double reciprocal plot)

Question 57

What does the slope, X=0, Y=0 equal?

Answer 57

slope=Km/Vmax, X=0= -1/Km, Y=0= 1/Vmax

Question 58

What is an Eadie-Hofstee plot?

Answer 58

rearrange v equation to: V = -V/[S].Km + Vmax, plot V against V/[S], Vmax at X=0, slope= -Km

Question 59

What is a competitive inhibitor?

Answer 59

Inhibitor binds reversibly to active site, enzyme retains ability to process enzyme (Vmax same), but cannot bind S (Km changed) - gradient rotates up around 1/Vmax point

Question 60

What is a non-competitive inhibitor?

Answer 60

Inhibitor binds to a remote site, affects its activity not ability to bind substrate so Vmax changes, Km same

Question 61

What is an irreversible inhibitor?

Answer 61

Binds to active site and shuts down activity so [E] decreases