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Bsc Sports Biochemistry (year 1) > Enzymes (LOIL 2) > Flashcards

Enzymes (LOIL 2) Flashcards

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1
Q

Enzymes can occur in 2 different forms. State, and explain, what these 2 forms are

A
  1. Holoenzymes - contain a prosthetic group

2. Apoenzymes - don’t contain a prosthetic group

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2
Q

state what it is meant by the key term - co-factors

A

co-factors are non-protein factors which are essential for enzyme activity, can be organic or inorganic (eg - metallic ions)

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3
Q

state what it is meant by the key term - co-enzymes

A

co-enzymes are substances that enhance the action of an enzyme (organic co-enzymes are derived from water soluble vitamins; fat soluble vitamins do no form co-enzymes)

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4
Q

state what it is meant by the key term - co-substrates

A

co-substrates are loosely and transiently bound co-factors

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5
Q

state what it is meant by the key term - prosthetic group

A

a prosthetic group is a non-protein group forming part of, or is combined with, a protein

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6
Q

state 2 facts about prosthetic groups

A
  1. usually a small inorganic molecule or atom

2. usually tightly bound to the enzyme

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7
Q

state 2 facts about co-enzymes

A
  1. large organic molecule

2. loosely bound to the apoenzyme

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8
Q

state the function of the following enzyme - Riboflavin/B2

A

forms part of the coenzyme - FAD (flavin adenine dixnucleortide)

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9
Q

state the function of the following enzyme - Niacin/B3

A

forms part of the coenzyme - NAD (nicotinamide adenine dinucleotide)

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10
Q

state the function of the following enzyme - Pantothenic Acid/B5

A

forms part of the coenzyme - CoEnzyme A

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11
Q

state the function of the following enzyme - Biotin/B7

A

forms part of the - Biotin coenzyme

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12
Q

state the function of the following enzyme - Thiamine/B1

A

forms part of the coenzyme - Thiamine Pyrophosphate TTP

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13
Q

state the function of the following enzyme - Pyridoxine/B6

A

forms part of the coenzyme - Pyridoxal Phosphate

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14
Q

what is the term for a deficiency in Niacin/B3 ?

A

Pellagra

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15
Q

what is the term for a deficiency in Thiamine/B1 ?

A

BeriBeri

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16
Q

state the functions for the following deficiency - Riboflavin/B2 Deficiency

A
  1. itching and burning eyes
  2. sluggishness
  3. oily skin
  4. night blindness
  5. mouth/lip sores
  6. sore throat
  7. skin disorders
  8. fatigue
  9. anaemia
  10. development deformities (eg - cleft lip)
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17
Q

state the functions for the following deficiency - Pellagra (Niacin/B3 deficiency)

A
  1. neurological impairments
  2. skin inflammation
  3. nausea
  4. decreased appetite
  5. watery diarrhoea
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18
Q

state the functions for the following deficiency - Pantothenic Acid/B5 deficiency

A
  1. vomiting
  2. fatigue
  3. stomach pain
  4. irritability
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19
Q

state the functions for the following deficiency - Pyridoxine/B6 deficiency

A
  1. sore glossy tongue
  2. cracked and sore lips
  3. skin rashes
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20
Q

state the functions for the following deficiency - Biotin/B7 deficiency

A
  1. scaly skin
  2. skin lesions
  3. dry and dull hair
  4. scruffy appearance
  5. lethargy
  6. alopecia
  7. reduced growth rate
  8. diarrhoea
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21
Q

state the functions for the following deficiency - BeriBeri (This,ine/B1 deficiency)

A
  1. shortness of breath
  2. swelling of feet
  3. increased heart rate
  4. tingling in hands and feet
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22
Q

when is a steady state of a reaction reached ?

A

a steady state is reached a short time after the initial mixing of an enzyme and a substrate

23
Q

explain what it is meant by the key term - V (velocity)

A

V = the quantity of reactant which disappears in a given time frame

24
Q

explain what it is meant by the key term - activity/velocity

A

umol/min (depends on the amount of protein)

25
Q

explain what it is meant by the key term - specific activity

A

umol/min.mg

26
Q

explain what it is meant by the key term - ‘enzyme unit’

A

amount which gives 1 umol product/min

27
Q

explain what it is meant by the key term - Katal (SI)

A

about which gives 1 Mol/sec

28
Q

what is a first order reaction ? (5 points)

A
  1. A —–> P
  2. reactions that are directly proportional to the reactant concentration
  3. the rate of the reaction is directly related to the concentration of A by a proportionality constant - k (the rate constant)
  4. V = k[A]
  5. units = s-1
29
Q

explain second order reactions (3 points)

A
  1. two reactants: A + B —-> P
  2. V = k[A][B]
  3. units = M-1 s-1
30
Q

state what it is meant by the key term - Pseudo First Order Reactions (2 points)

A
  1. when a second order reaction can appear to be a first order reaction
  2. eg - if B is in excess and A and low conc^, the reaction rate will be 1st order with respect to A and will not appear to depend on [B]
31
Q

how do you measure reaction rate ? (2 points)

A
  1. follow each reaction over time

2. measure [P] or [S] and time

32
Q

what are the two equations for reaction rate ?

A
  1. V = Δ[P] / Δt

2. V = Δ[S] / Δ

33
Q

state the 3 phases of an enzyme reaction

A
  1. Pre-steady state (micro second equilibration, too short to measure)
  2. steady state
  3. substrate depletion
34
Q

state what it is meant by the key term - ‘direct assay’

A

assay has a way of detecting P or S directly due to some property off either - can be measured continuously

35
Q

state what it is meant by the key term - ‘discontinuous direct assay’ (2 points)

A
  1. the reaction is stopped at set time points to measure P or S
  2. the assay to measure P or S may quench the enzyme
36
Q

explain what a ‘Couples Assay’ is (4 points)

A
  1. sometimes P or S can’t be measured
  2. P can be consumed in another reaction
  3. the product of the 2nd reaction can be measured
  4. 2nd enzyme must be in excess to ensure that the rate limiting step is the one to be measured
37
Q

state the 4 factors which effect enzyme rate

A
  1. enzyme concentration - [E]
  2. substrate concentration - [S]
  3. temperature
  4. pH
38
Q

reaction rate is proportional to [E] providing what 2 things ?

A
  1. the substrate is not rate limiting

2. the product is not in excess

39
Q

what is Vo ?

A

Vo is the initial velocity of a reaction at t = 0 (as close as measurable)

40
Q

state 2 introductory facts about Michaelis and Menten

A
  1. in 1913, Leonor Michaelis and Maud Menten proposed a simple method to account for the kinetic characteristics
  2. the critical feature in their treatment in that a specific ES complex is a necessary intermediate in catalysis
41
Q

what is a steady state system ?

A

in a steady state system, the concentrations of the intermediaries stay the same, even though the concentrations of products and substrates are changing

42
Q

finish the sentence:

E + S = ES complex….

A

E + S = ES complex, with a rate constant

43
Q

The ES complex has 2 possible fates. What are they ?

A
  1. it can dissociate to E and S, with a rate constant - k

2. it can proceed to form P, with a rate constant - k2

44
Q

explain what can also occur with the ES complex

A

The ES complex can also be reformed from E and P by the reverse reaction with a rate constant - k-2. However, as before, we can simplify these reactions by considering the rate of reaction at time close to 0 (Vo) when there is negligible product formation, and thus no back reaction (no k-2)

45
Q

state the 3 main assumptions of ‘Michaelis-Menten Kinetics’

A
  1. the step of (ES —-> E + P) is irreversible - no K-2
  2. [ES] is in steady state (K1 = K-1 + K2)
  3. E < km
46
Q

state the ‘Michaelis Menten Equation’

A

Vo = (Vmax[S]) / (km + [S])

47
Q

what enzymes don’t follow MM kinetics, and why ?

A

allosteric enzymes as they consist of multiple sub-units and multiple active sites

48
Q

explain the characteristics of an enzyme with a high km

A

enzymes with a high km have a low affinity for its substrate and requires a greater concentration of substrate to achieve its Vmax

49
Q

km (Michaelis Constant) varies for each enzyme with what 3 things ?

A
  1. Substrate
  2. pH
  3. Ionic Interactions
50
Q

explain what km (Michaelis Constant) is using 3 points

A
  1. provides a measure of the [S] required for significant catalysis to take place
  2. the higher the km of an enzyme, the lower its affinity for its substrate
  3. a higher km means that it takes a lot of substrate before the enzyme gets to Vmax/2
51
Q

what is the reason for the ‘Line-Weaver Burk Plot’ (2 points)

A
  1. linearised data gives straight forward regression analysis to yield kinetic parameters
  2. a line-weaver burk plot is widely used to transform a MM graph into linear form to make it easy to find the km and Vmax
52
Q

explain, using 4 points, what it is meant by the key term - Kcat

A
  1. kcat = rate of catalysis = turnover number
  2. kcat = Vmax / [E]
  3. number of substrate molecules transformed per minute by a single enzyme molecule when the enzyme is the rate limiting factor
  4. units = ms-1
53
Q

what do allosteric enzymes often display ?

A

allosteric enzymes often display ‘Sigmoidal Plots’ of the reaction velocity

Bsc Sports Biochemistry (year 1) (12 decks)

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