Enzyme kinetics

Question 1

What is enzyme kinetics?

Answer 1

It is a way to study how fast a reactions occurs based on the enzyme involved.

Question 2

What are the six types of enzymes and their function?

Answer 2

1. Transferanse: transfer a chemical groups from one molecule to another ( kinases - move phosphate)
2. Isomerase: transfer of a chemical group within the same molecule. ( isomerase, mutase, racemase)
3. lyases: break a molecule into 2 pieces by using something else than water
4. Hydrolyses: uses water to break the molecule into two pieces (often on the peptide bond)
   
   1. Nuclease: break nucleotide
   2. Protease: break protein
   3. Esterase: break fat
5. ligase: combine two things ( synthase + synthase)
6. Oxidoreductase: Biological redox reaction ( add electrons)
   
   1. oxidoreductase:
   2. dehydrogenase:
   3. peroxidase
   4. oxidase
   5. reductase

Question 3

How are reaction rate measured?

Answer 3

1. Increase in the concentration of products per unit of time of M/s
2. or decrease of concentration of reactant per unit of time (usually has a negative)

Question 4

what is the relationship between the rate of an enzyme and the reactant?

Answer 4

1. The rate will always depends on the concentration of one or more reactant in some way.

Question 5

what is the reactions order?

Answer 5

1. It tells us the relationship between a rate and a particular concentration;
2. the reactions order gives us info with respect to a particular substance.

Question 6

Reactions orders

Answer 6

This allows you to analyze the number of reactan in the rate-limiting step of a reaction.

1. First order reaction: is dependend on the cencentration of ONLY one reactant. ​if you double that reactant and the reactant double than we call this a first order reactant with respect with the reactant in question.
   
   1. The rate is dependent on one substrate.
2. Second order reaction: is dependend on two reactant so if you double the concentration of reactant and the rate quadrupled, this is a second order reactant.
   
   1. The rate is dependent on two substrate.
3. Zero order: the reaction moves at a constant rate regardelss of the substrate concentration.
   
   1. The rate is not dependent on any substrate.

Question 7

what type of graphs can we get from the different 1/2 rate orders?

Answer 7

​Integrated rate law expression equations: these equations can let us determine the amount of reactant or product present after a period of time or to estimate the time needed for the reaction to take place.

1. zeroth order: [A] final = -Kt + [A] initial
   
   1. similar to y =mx + b
   2. slope = -k linear and indicates a constant slope decay
   3. y intercept = initial concentration
2. ln [A final] = -kt + ln [A initial]
   
   1. y =mx + b
   2. slope = -k
   3. b = ln [ A initial)
3. zeroth order: rate is con

Question 8

What is the rate determining step?

Answer 8

1. It is the only thing that we care about in kinetics, this is a species that is involved in determining the rate of the reaction.
   2.

Question 9

What is a rate Law: how to determine the reaction order?

Answer 9

1. if you double the concentration the impact that the doubling has on the rate lets us know the reactions order
   
   1. if the rate doesn’t change = zero order
   2. if the rate doubles = first order
   3. if it quadruples= second order
   4. 1/2 = then it has a negative order

Question 10

Write down the rate equations for each rate law

Answer 10

1. Zero order: rate =k ( is not dependent on any concentration)
2. 1st order: rate =K [A] ^ 1
   
   1. if you double the concentration of A the rate is 2^1= 2
   2. if you trilple 3^1 = 3
   3. KEY HERE IS THAT IT IS RAISED TO THE 1
3. Second order: rate = K [A] ^ 2
   
   1. if you double concentration of A 2^2= 4
   2. if you tripple concentration A 3^2 =9
   3. KEY HERE IS THAT IT IS RAISED TO THE 2
4. The rate of a chemical reaction is more affected by a reactant that is 2nd order than the rest

Question 11

What are the units of rate in kinetics?

Answer 11

1. zero order: (M^1)(t ^-1)
2. first order reaction (M^ 0)(t ^-1)
3. second order reaction (M ^-1) (t^-1)

Molarity decrease by one

1. (M^ n-1) * (t ^-1) : units of K for any order
   
   1. n= which order you looking at

Question 12

What is the 1/2 life? and what are the 1/2 equations for rate orders?

Answer 12

1. In kinetics 1/2 represent the time that it takes for the concentration of reactant to decrease by 1/2 ( due to the enzyme)

Equations

1. Zero order: [A] initial / 2k
   
   1. 1/2 depends on the initial concentation
   2. increase initial concentration 1/2 increase
2. First order: ln 2 or (0.7) / K
   
   1. 1/2 does not depend on the initial concentration
   2. increase initial concentration: doesn’t matter
3. Second order reactions: 1/ k[A] initial
   
   1. 1/2 depends on initial concentration
   2. increase initial concentraton 1/2 decreases (inversely related)

In all cases the 1/2 life depends on rate k, and it is always at the bottom thus it is invertly related to the 1/2 life therefore K increase as 1/2 life time decrease

Question 13

what type of order would we have if we are given more than two reactants?

Answer 13

1. Rate= k [A][B] (second order) because if you recall the definition is that it depends on 2 reactant to give you a rate. can also be given as 2 moles of a products.
2. However if they become specific about the one reactant than the equation follow the 1st order.

Question 14

what does the Arrhenius equation tells us?

Answer 14

1. Tells us how does the temperature affect the rate of the specific chemical reaction?
2. General rate law : rate = k [concentration] ^ power n
3. Temperature is not really relevant to concentration so to make sense of it we figure that the rate constant gives us the answer of how temperature affects reaction

K (rate) = Ae (arrhenius constant) ^ [(eact ( activation energy))/ R(ideal gas constant)( temp in kalvin)]

Variables relationship:

1. K decrease as Eact increase: logic the enzyme role is to decrease this
2. K increase as R increase ( ideal gas constant) 8.314 S/ mol* K logic: this is in the denominator therfore an increase in due to an increase in gas would also increase the rate
3. K increases as temperature increase: logic in dominator as well so inversely elated to K
4. K increase as arrhenius constant increase: look into molecular collision frequency of collition ( the more they collide the higher the rate)
   5.

Question 15

how do we determine rate order?

Answer 15

IT CAN ONLY BE GIVEN EXPERIEMENTALLY

(They will gie you a table (trials)

you will use that table to solve for k and obtain your order from it.

Question 16

what is the general way to solve for problems given a rate order?

Answer 16

1. General equation: Rate=k [A]^x [B] ^y
2. Set up the ratio of data
   
   1. rate of Trial 2/ rate trial 1 (or which ever one gives you a goof whole number) to sove for the overall rate of the two equations
   2. Then solve for x ( or the rate order n) by trying to figure out what number the rate was raise to which will give you your 1st rate order
      
      1. ex 2=2 (reactants) ^ to the n (rate order)
      2. you use the rate equation
   3. do this for all the trials to find out the rate

Strategy:

1. Idenify the reactant (x) and y
2. pick one of the reactant as a changing reactant so you can keep the other one constant and solve for on the changing reactant.
3. look at the rate of two trial and divide it
4. use the rate law equation to determine rate law
5. do step 3-4 for the other two reactant left

Find over all order: if A is first order and B is first order that means the overal reaction is 2nd order. if only one of them is 1st order and the second one is constant then you have 1st order.

to find k use rate= k[A] [B]

Question 17

what are 4 things that can affect the rate of a reaction?

Answer 17

1. Temperature (arrhenius equations)
2. concentration if it is 1st order or second order
3. catalyst: an enzyme
4. adding volume and dilluting the cencentration decrease the rate

Question 18

What is the rate limiting step?

Answer 18

1. The step that takes longer ( has the highest activation energy)
   
   1. To determine : you look at which one has the highest activation energy

Question 19

when does an increase in temperature not affect the a rate of reaction

Answer 19

1. when we are dealing with an enzyme: enzymes can degrade to high temperature therefore temperature can actually stop the rate of the reaction.
2. but the rule of thumb is that at a high temperature the molecules have a higer kinetic energy and therefore react the activation energy barrier faster.