Enzymes Flashcards

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1
Q

Do enzymes impact the thermodynamics of a biological reaction?

A

No, delta H_rxn and the equilibrium position do not change

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2
Q

What do enzymes do?

A
  1. Lower the activation energy
  2. Increase the rate of the reaction
  3. Are not changed or consumed in the reaction (will appear in the reactants and the products)
  4. Are pH and temperature sensitive, optimal activity at specific pH ranges and temperatures
  5. Do not affect the overall deltaG of the reaction
  6. Are specific for a particular reaction or class of reactions
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3
Q

Oxidoreductases?

A

Catalyze oxidation-reduction reactions, transfer electrons between biological molecules, often have cofactors that serve as electron carriers, like NAD+ or NADP+; electron donor = reductant; electron acceptor = oxidant

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4
Q

transferases?

A

catalyze the movement of a functional group from one molecule to another, ex. kinases

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5
Q

kinases?

A

catalyze the transfer a phosphate group, generally from ATP, to another molecule

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6
Q

Hydrolases?

A

Catalyze the breaking down of a compound into two molecules using the addition of water, ex. phosphatase, cleaves a phosphate group from another molecule

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7
Q

Lyases?

A

Catalyze the cleavage of a single molecule into two products, don’t require water, don’t act as oxidoreductases, can also catalyze the reversal (two molecules into a single molecule), in that case would be called a synthase

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8
Q

LIL’HOT

A

Major enzyme classifications

  1. Ligase
  2. Isomerase
  3. Lyase
  4. Hydrolase
  5. Oxidoreductase
  6. Transferase
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9
Q

Isomerases?

A

Catalyze the rearrangement of bonds within a molecule, can catalyze reactions between stereoisomers as well as constitutional isomers

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10
Q

Ligase?

A

Catalyze addition or synthesis reactions, generally between large similar molecules and often require ATP, often with nucleic acid synthesis and repair on Test Day

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11
Q

Endergonic reaction?

A

One that requires energy input, deltaG>0

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12
Q

Exergonic reaction?

A

One where energy is given off, deltaG< 0

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13
Q

If a reaction is spontaneous, deltaG is

A

negative

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14
Q

How do catalysts impact activation energy?

A

They lower it

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15
Q

The molecule upon which an enzyme acts is known as its…?

A

Substrate

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16
Q

The location where the substrate is held during its chemical reaction is known as the

A

active site

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17
Q

Lock and Key Model

A

suggests that the enzyme’s active site is already in an appropriate conformation for the substrate (key) to bind

18
Q

Induced Fit Model

A

More scientifically accepted theory, substrate and enzyme active site don’t seem to fit, but then they do

19
Q

Enzymes without their cofactors are called

A

apoenzymes

20
Q

Enzymes with cofactors are called…

A

holoenzymes

21
Q

Tightly bound cofactors or coenzymes that are necessary for enzyme function are called…

A

prosthetic groups

22
Q

A rate of reaction can’t go faster once it has reached

A

Saturation, max velocity= v_max

23
Q

What does K_m represent?

A

The substrate concentration at which half of the enzyme’s sites are full, 1/2 V_max

24
Q

cofactors

A

small, metal cations

25
Q

coenzymes

A

small, organic molecules

26
Q

temp. impact on enzymatic reactions?

A

tend to double in velocity for every 10 degrees C, eventually will denature at higher temps

27
Q

pH impact on enzymatic reactions?

A

body works best at certain pHs

28
Q

salinity impact on enzymatic pHs?

A

altering the concentration of salt can change enzyme activity in vitro, can change conformation of the enzyme, sometimes cause denaturation

29
Q

negative feedback

A

helps maintain homeostasis, once we have enough of a given product, we turn off the pathway that created that product

30
Q

feed-forward regulation

A

enzymes may be regulated by intermediates that precede the enzyme in the pathway

31
Q

competitive inhibition?

A

involves occupancy of the active site, doesn’t alter V_max, because if enough substrate is added, it will outcompete the inhibitor and be able to run the reaction at max velocity, K_m increases

32
Q

noncompetitive inhibitors?

A

bind to an allosteric site instead of the active site, which induces a change in enzyme conformation, decreases V_max, doesn’t change Km

33
Q

Mixed inhibition?

A

inhibitor can bind to enzyme or the enzyme-substrate complex, different affinity for each, bind at the allosteric site, decrease V_max, can increase or decrease Km

34
Q

Uncompetitive inhibtion?

A

bind only to the enzyme-substrate complex, decrease Km and decrease vmax

35
Q

allosteric activator?

A

an activator will result in a shift that will make the active site more available for binding to the substrate by binding to the allosteric site

36
Q

allosteric inhibitor?

A

will make the active site less available for binding to the substrate by binding to the allosteric site

37
Q

allosteric sites

A

a site that can regulate the availability of the active site that’s not the active site

38
Q

Glycosylation

A

the covalent attachment of sugar moieties, another covalent enzyme modification

39
Q

enzyme can be activated or deactivated by…

A

phosphorylation or dephosphorylation (covalent modification with phosphate)

40
Q

zymogens

A

inactive forms of enzymes (like ones for the stomach), often have the suffix -ogen

41
Q

irreversible inhibtion

A

alters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently; new enzyme must be synthesized for the reaction to occur again

42
Q

cooperative enzymes

A

display a sigmoidal curve bc of the change in activity with substrate binding