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BCM210 > Topic 5 - Enzymes > Flashcards

Topic 5 - Enzymes Flashcards

1
Q

What is an enzyme and what is it’s function?

A

A Catalyst. Speed up reactions w/out being used up or changed

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2
Q

Most enzymes are what kind of protein?

A

globular => soluble in H20, hydrophobic outside, hydrophilic inside

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3
Q

To bind to an enzyme and cause a reaction the substrate’s structure and stereochemistry must fit the entire active site exactly. T or F?

A

True

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4
Q

Enzyme function is determined by their….?

A

primary aa sequence

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5
Q

What is a simple enzyme?

A

all protein, no cofactor

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6
Q

What is a complex enzyme?

A

protein and cofactor/coenzyme

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7
Q

What is a holoenzyme?

A

A complete complex enxyme

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8
Q

What is a Apoenzyme?

A

Protein component of holoenzyme. Require a cofactor or prosthetic group for activity

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9
Q

What is a cofactor?

A

one or more weakly bound metal ions, or a weakly bound organic (e.g. NADH) or metalloorganic molecule

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10
Q

What is a prosthetic group?

A

tightly or covalently bonded cofactor (e.g. heme)

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11
Q

What is a metallo-enzyme?

A

metal always bound to active site

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12
Q

What is a metal-activated enzyme?

A

metal not part of native structure, but required for activity.

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13
Q

What is the main difference b/w a cofactor and a prosthetic group?

A

A prosthetic G is tightly bound

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14
Q

Are coenzymes consumed during a reaction?

A

yes

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15
Q

Are coenzymes a substrate?

A

yes

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16
Q

What is an isozyme? What do they allow?

A

different enzymes that catalyse the same reaction. Can have related aa sequence or very different. allow metabolic pathways to follow different courses in different cells: same metabolites, different fates

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17
Q

How do enzymes act, what do they induce and what does this allow

A

Enzymes act by binding substrates, allowing development of kinetic equations. Induce transition state.

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18
Q

What is the transition state?

A

midway b/w substrate & product

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19
Q

PLEASE READ SLIDES 44-56 FOR TRANSITION STATE INFO

Draw transition state graph

A

PLEASE PLEASE PLEASEE!!!

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20
Q

State the equilibrium constant (Keq) equation for products & substrates

A

Keq = [P]/[S] for multiple: Keq = ([C].[D])/([A].[B])

21
Q

State the equation which describes the direct relationship b/w Keq and the free energy change (ΔG) => answer gives how much energy is given off changing a substrate into a product

A

ΔG = -RT R= universal gas constant (1ap) T = absolute temp (298K=25C) PLEASE SEE TRANSITION SLIDES 44-56

22
Q

Enzymes do not bind transition states better than substrates. T or F?

A

False

23
Q

Enzymes do not effect equilibrium (ΔG). T or F?

A

True

24
Q

Define enzyme specificity.

A

The ability of an enzyme to selectively bind to and catalyse a specific substrate(s) is termed enzyme specificity.

25
Q

Catalytic reactions @ active site: What is general acid-base catalysis?

A

A number of aa side chains can act as H+ donors or acceptors (Glu, Asp, Lys, Arg, His)

26
Q

Catalytic reactions @ active site: What is covalent catalysis?

A

A transient bond is formed b/w substrate & enzyme. Requires a nucleophile

27
Q

Catalytic reactions @ active site: What is metal ion catalysis?

A

can electrostatically polarise atoms, or change oxidation state to donate/receive electrons (H+). Involves a metal ion bound to enzyme. -stabilisies -ve charges -participates in oxidation reactions

28
Q

Define enzyme activity?

A

rate of enzyme catalysed reaction

29
Q

Define specific enzyme activity?

A

measure of enzyme purity = number of enzyme units per mg of total protein i.e. the purer, the higher the specific activty

30
Q

List the factors that influence enzyme activity.

A

enzyme [] -linear relationship pH -can denature enzyme; have optimal pH Temp. -see pH Substrate [] inhibitors

31
Q

What is the study of enzyme kinetics?

A

study of rate of enzyme catalysed reactions -how rates are affected by enviro -[] of substrate

32
Q

FOR ENZYME KINETICS, LINEWEAVER-BURKE PLOT, MICHAELIS-MENTEN EQUATION AND ENZYME INHIBITION PLEASE REVISE HAND WRITTEN NOTES

A

DO IT DO IT DO IITTT!!!

33
Q

Qrite the equation for the reaction where substrate (S) is converted into product (P) by enzyme (E)

A
34
Q

For the enzyme-substrate complex reaction, what is:

k1?

k-1?

k2?

A
35
Q

Where does the transition state occur within the enzyme-substrate complex reaction?

A

within the ES complex

(not E or P or S)

36
Q

What is Vmax? When does it occur?

A

maximum rate of enzyme-catalysed reactions

Occurs when all enzyme exists as ES complex => when E is saturated

37
Q

Write the Michaelis-Menten Equation and what it describes and what it allows us to determine.
Draw the graph it reciprocates

A
38
Q

Low km = ?

(km=michaelis constant)

A

E has higher affinity for S & vice versa

39
Q

What is Kcat? Write the equation.

A

Measures enzyme efficiency (catalytic production of product)

Kcat= number of substrate molecules converted per enzyme molecule per second

Kcat = Vmax/[E]

40
Q

Kcat & Km together determine rate of catalysis.

High Kcat, low Km =?

A

reactions catalysed the fastest

41
Q

Draw the Lineweaver-Burke Plot

A
42
Q

FOR ENZYME INHIBITION ALSO READ NOTES

A

PLEASE PLEASE PLEASE!!!!!!

43
Q

Describe irreversible enzyme inhibitors

A

react w/ enzyme

One inhibitor molecule can permanently shut off one enzyme molecule

44
Q

Describe reversible inhibitors

A

bind to & can dissociate from enzyme

-prevent reaction or binding of substrate

45
Q

Describe competitive inhibition, its affects on Vmaz and Km. Draw it’s LWB plot.

A

Competes w/ substrate for binding

  • binds active site
  • does NOT affect catalysis

No change in Vmax, apparent increase in Km

LWB lines intersect y axis

46
Q

Describe uncompetitive inhibition, its affects on Vmax and Km. Draw it’s LWB plot.

A

Only binds to ES complex

  • does not affect S binding
  • Inhibits catalytic function

Decrease in Vmax, apparent decrease in Km

in LWB lines are parallel

47
Q

Describe mixed inhibition, its affects on Vmaz and Km. Draw it’s LWB plot.

A

Binds enzyme w/ or w/out substrate

  • binds regulatory site
  • inhibits both S binding & catalysis

Decrease in Vmax, change in Km

LWB lines intersect left of y axis

48
Q

List the types of enzyme regulation

A

irreversible

reversible

covalent modification

noncovalent mod

BCM210 (18 decks)

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