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Biomolecules And Metabolism > Enzymes > Flashcards

Enzymes Flashcards

1
Q

By what factorcan enzymes accelerate chemical reactions?

A

10^5- 10^19

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2
Q

What enzyme accelerates reactions the most?

A

Arginine decarboxylase (10^19)

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3
Q

What can enzymes be affected by?

A

Inhibitors and activators

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4
Q

What is a holo enzyme?

A

Enzyme containing non-protein cofactor

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5
Q

What is an apoenzyme?

A

Enzyme that doesn’t contain a non-protein cofactor

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6
Q

What does the group EC1 Oxidoreductases do?

A

Catalyze redox reactions
NADPH oxidation to NADP+ ,molecule reduction

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7
Q

What does the group EC2 Transferases do?

A

Transfer the functional group
tRNA AA is transferred to the created protein

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8
Q

What does the group EC3 Hydrolases do?

A

Hydrolyze bonds
Digestive enzymes split bonds

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9
Q

What does the group EC4 Lyases do?

A

Non-hydrolytic bond cleavage

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10
Q

What does the group EC5 Isomerases do?

A

Molecular isomerization
Isomer is rearranged spatially (molecular weight stays the same)

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11
Q

What does the group EC6 Ligases do?

A

Join 2 molecules covalently

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12
Q

What does the group EC7 Translocases do?

A

Move the molecule around the cell

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13
Q

Name the 4 enzyme regulation processes

A
  1. Bioavailability
  2. Covalent modification
  3. Allosteric regulation
  4. Compartmentation
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14
Q

What does bioavailability do?

A

Cell controls how much of the synthesized enzyme will be used /available by the substrate
Degrades it if too much
Binds to regulatory molecule
Coucuent modification

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15
Q

What is repression in bioavailability

A

Product of a biochemical pathway inhibits synthesis of a key enzyme in the pathway
Feedback inhibition

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16
Q

What is induction in bioavailability?

A

Coulchanges the production of a specific enzyme to stimulate / inhibit activity

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17
Q

What is the issue with bioavailability?

A

It is too slow to control all cell functions

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18
Q

What is covalent modification?

A

Covalently attaching a moleculeto the enzyme to stimulate / inhibit activity
Much faster than genetic control
Uses (de)phosphorylation

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19
Q

What catalyzes phosphorylation?

A

Catalyzed by enzymes kinases
ATP isthe source ofthe phosphate

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20
Q

What catalyzes dephosphorylation?

A

Catalyzed by phosphatase enzymes

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21
Q

What other molecules covalently modify enzymes?

A

Methyl/acetyl groups, sugars, lipids
Less commonly Than phosphate

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22
Q

What are the sites for phosphorylation?

A

The OH side chain of serinine, threonine, tyrosine

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23
Q

What is an example of covalent modification?

A

Proteolytic processing to activate and deactivate enzymes

24
Q

What is allosteric inhibition?

A

Feedback inhibition
Catalyzes the committed step in a metabolic pathway- controls the vote
Doesn’t always follow the Michaelis-Menten kinetics

25
Q

What is an exampleof allosteric regulation?

A

Phospho-fructokinase (step 3 of glycolysis)
ATP is a negative regulator

26
Q

What is compartmentation?

A

Storing enzymes in specific compartments
Keep them from doing damage or provide proper conditions for activity

27
Q

Describe the lock and key model

A

Enzyme and substrate possesses specific complementary shapes that fit exactly into eachother
Doesn’t explain the transition state that ES complex achieve - proven inaccurate model

28
Q

Describe the induced fit model

A

Enzyme slightly changes shape upon substrate binding
Active site forms a complementary shape after substrate binds

29
Q

Describe the substrate in a transition state

A

Short-lived, unstable, requires less activation energy

30
Q

Describe conformational selection

A

Newer model of the induced fit model
Enzyme adapts to substrate dependent on the environment and presence of regulatory molecules

31
Q

How enzymes affect the activation energy?

A

Lower the activation energy of a chemical reaction by the randomness of collisions between molecules
Help bring the substrates together in proper orientation so that the reaction can occur

32
Q

What information enzyme kinetics give?

A

About enzyme catalysis, mechanism, activity regulation, basis of enzyme assays

33
Q

What are enzyme kinetics affected by?

A

By enzyme, substrate, ph, temperature, co-enzymes, activators, inhibitors

34
Q

What is a steady state?

A

When ES builds up initially and then remain constant
Will persist until thesubstrate runs out
takes nearly all of the reaction time

35
Q

Describe 1st order reaction

A

The reaction rate is proportional to the substrate
There is move enzymethan substrate

36
Q

Describe 2nd order reaction

A

More substrate than enzyme
Substrate is not proportional to the reaction rate
Rate depends only on the enzyme

37
Q

Describe michaelis-menten kinetics.

A

Under physiological conditions enzymes are not saturated with substrates
Reaction rate is dependent on substrate concentration

38
Q

What does the Michaelis constant describe

A

The affinity of an enzyme for a substrate
Lower Km = higher affinity

39
Q

What is the turnover number?

A

K cat
Number of substrate molecules cleaved per enzyme molecules per time when enzyme is fully saturated

40
Q

What plots describe the Michaelis-menten kinetics

A

Lineweaver- Burk plot
Hanes-woolf plot
Eddie- hofsteeplot

41
Q

What are inhibitors?

A

Interact with enzymes to reduce their catalytic activity
Structurally similar to natural substrate of an enzyme

42
Q

Features of reversible inhibition

A

Reversibly bind and dissociate from enzyme
Activity of enzyme recovers when inhibitor is diluted out
Non covalent interactions

43
Q

Name reversible inhibition types:

A

Competitive inhibition
Non-competitive inhibition
Uncompetitive inhibition

44
Q

Features of irreversible inhibition

A

Inactivators that irreversibly associate with an enzyme
Activity of enzyme doesn’t recover with dilution
Covalent interactions

45
Q

Describe competitive inhibition:

A

Direct competition between I and S for binding
I binds to active site of S
I only bina to free enzymes
Most common type of inhibition

46
Q

What are examples of competitive inhibition

A

HIV protease inhibitor
Phosphodiester-5 inhibitor

47
Q

Describe the kinetics of competitive inhibition

A

Vmax is unchanged
Km increases as higher S concentration is needed to reach max
Low Ki = higher affinity
Less affinity for S occurs

48
Q

Feature of uncompetitive inhibition

A

Inhibitor binds to ES complex (not free E)
Binds to allosteric site
Common in multi-substrate reactions

49
Q

Example of uncompetitive inhibition

A

Lansoprazole for gastric reflux

50
Q

Kinetics of uncompetitive inhibition

A

Km is lower
Vmax is lower

51
Q

Features of non-competitive inhibition

A

Inhibitor binds to both free enzymes and ES complex
Binds to allosteric site
ESI complex doesn’t react

52
Q

Example of non-competitive inhibition

A

Nifedipine inhibits CYP29 (cytP450 enzyme involved in drug metabolism)

53
Q

Kinetics of non-competitive inhibition

A

Km is unchanged
Vmax is lowered
At high S, the inhibitor is still bound to the enzyme

54
Q

Detailed Features of irreversible inhibition

A

Enzyme inactivated or suicide inhibition
Inhibitors form covalent bonds with their target enzymes leading to permanent inactivation
Used to identify the functional AA within the active site

55
Q

Describe the irreversible inhibition on aspirin

A

Aspirin covalently modifies the enzyme prostaglandin H synthase
Prevents prostaglandin synthesis and lowers inflammation
Occurs vidacetylation of serine-530 at the active site of PGH synthesis

56
Q

Describe the irreversible inhibition on eflornithine

A

Is a suicide inhibitor treating sleeping sickness
Binds irreversibly to cysteine residue on ornithine decarboxylase
Reduces production of polyamides necessary for parasite growth

57
Q

Describe the irreversible inhibition on penicillin

A

Is a irreversible inhibitor of bacterial wall synthesis
Innibits peptidoglycan cell wall synthesis and makes bacteria susceptible to osmosis
Without thePG layer bacteria lyse
Penicillin covalently modifies glycopeptide transpeptidase

Biomolecules And Metabolism (7 decks)

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