Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCAT Biochem > Ch 2 - Enzymes > Flashcards

Ch 2 - Enzymes Flashcards

You may prefer our related Brainscape-certified flashcards:
MCAT flashcards
1
Q

What are enzymes?

A

biological catalyst that are unchanged by the reactions they catalyze and are reusable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do oxidoreductase do?

A

catalyze oxidation-reduction reactions that involve the transfer of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do transferases do?

A

move a functional group fro one molecule to another molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do hydrolases do?

A

catalyze cleavage with the addition of water

- breaking of compound into 2 products with water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do lyases do?

A

catalyze cleavage without the addition of water and without the transfer of electrons

  • the reverse reaction (synthesis) is often more important biologically
  • cleavage of small molecules into 2 produces or synthesis of small organic molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do isomerases do?

A

catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers
- rearrangement of bonds within a compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What do ligases do?

A

responsible for joining two large biomolecules, often often of the same type

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the difference between exergonic and endergonic reactions?

A
  • ex: release energy; delta G is negative

- end: requires energy; delta G > 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do enzymes affect activation energy?

A

they lower the activation energy necessary for biological reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do enzymes affect free energy and enthalpy?

A
  • enzymes do not alter free energy (G) or enthalpy (H) change that accompanies the reaction nor the final equilibrium position
  • they change the rate (kinetics) at which equilibrium is reached
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do enzymes act?

A
  • by stabilizing the transition state
  • providing a favorable microenvironment
  • bonding with the substrate molecules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where is the site of catalysis?

A

the active site on an enzyme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is binding to the active site explained?

A
  • lock and key theory: the enzyme and substrate are exactly complementary
  • induced fit theory: the enzyme and substrate undergo conformational changes to interact fully
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do some enzymes require to be active?

A

metal cation factor or small organic coenzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is saturation kinetics?

A

as substrate concentrations increases, the reaction rate does as well until a maximum value is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What do Michaelis-Menten and Lineweaver-Burk plots represent?

A

the relationship of saturation kinetics as a hyperbola and line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How can enzymes be compared?

A

on the basis of their Km and Vmax values

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do cooperative enzymes display?

A

a sigmoidal curve because of the change in activity with substrate binding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What can affect enzyme activity in vivo?

A
  • temperature and pH
  • changes in temp and pH can result in denaturing of the enzyme and loss of activity due to loss of secondary, tertiary, or, if present, quaternary structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What can affect enzyme activity in vitro?

A

salinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is feedback inhibition?

A

regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway
- helps maintain homeostasis: as product levels rise, the pathway creating that product is appropriately downregulated

22
Q

What is reverse inhibition?

A

characterized by the ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment

23
Q

What is competitive inhibition? How can it be overcome and what happens to Km and Vmax? Binding site?

A
  • type of reverse
  • results when the inhibitor is similar to the substrate and binds at the active site
  • can be overcome by adding more substrate
  • Vmax is unchanged and Km increases
  • binding: active site
24
Q

What is noncompetitive inhibition? What happens to Km and Vmax? Binding site?

A
  • type of reverse
  • results when the inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex
  • Vmax decreases, Km is unchanged
  • binding: allosteric site
25
Q

What is mixed inhibition and how is Km and Vmax affected? Binding site?

A
  • type of reverse
  • results when the inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex
  • Vmax is decreased
  • Km is increased or decreased depending on if the inhibitor has higher affinity for the enzyme of enzyme-substrate complex
  • binding: allosteric site
26
Q

What is uncompetitive inhibition an dhow is Km and Vmax affected? Binding site?

A
  • type of reverse
  • results when the inhibitor binds only with the enzyme-substrate complex
  • Km and Vmax both decrease
  • binding: allosteric site
27
Q

What is irreversible inhibition?

A
  • the prolonged or permanent inactivation of an enzyme, such that it cannot be easily renatured to gain function
28
Q

What can occupy allosteric sites causing what?

A

can be occupied by activators, which increases either affinity or enzymatic turn over

29
Q

How are zymogens secreted and activated?

A
  • secreted in an inactive form

- activated by cleavage

30
Q

What are the key features of enzymes?

A
  • lower activation energy
  • increase the rate of the reaction
  • do not alter the equilibrium constant
  • are not changed or consumed in the reaction (appear in both reactants and products)
  • are pH and temperature sensitive
  • do not affect the overall delta G
  • are specific for a particular reaction or class of reactions
31
Q

What are the major enzyme classifications?

A

LIL HOT

  • Ligase
  • Isomerase
  • Lyase
  • Hydrolase
  • Oxidoreductase
  • Transferase
32
Q

How do catalysts exert their effect?

A
  • by lowering the activation energy

- they make it easier for the substrate to reach the transition state

33
Q

What are cofactors and coenzymes and how do they differ?

A
  • they are activators that induce conformational changes in the enzyme to promote activity
  • cofactors are inorganic (minerals)
  • coenzymes are organic (vitamins)
34
Q

What are prosthetic groups?

A

tightly bound cofactors and coenzymes that are necessary for enzyme function

35
Q

What is Km?

A
  • michaelis constant used to measure enzyme affinity for substrates
  • concentration of S where enzyme is functioning at half of Vmax
  • high Km has a low enzyme affinity for substrate
36
Q

What is Michaelis-Menten equation?

A

v = Vmax[S]/Km + [S]

37
Q

What are the effects of increasing [S] on enzyme kinetics?

A
  • if [S] is low, increasing it will drastically increase the enzyme activity
  • if [S] is already high, increasing will not have any effect
38
Q

What are the effects of increasing [E] on enzyme kinetics?

A

increase Vmax

39
Q

What is the difference between Michaelis-Menten and Lineweaver-Burk plot”

A
  • michaelis: v v. [S] –> hyperbolic curve

- lineweaver: 1/v v. 1/[S] (-1/Km v. 1/Vmax) –> linear curve

40
Q

What is enzyme cooperativity?

A
  • cooperativity refers to the interactions between subunits in a multsubunit enzyme or protein
  • the binding of substrate to one subunit induces a change in the other subunits from the T (tense) state to the R (relaxed) state, which encourages binding of substrate to the other subunits and vice versa
41
Q

What are the effects of temperature on the function of enzymes and what is the ideal temperature?

A
  • increased temperature generally increases enzyme activity
  • once body temperature reached, activity drops fat as enzyme is denatured
  • ideal temp: 37 C, 98.6 F, 310 K
42
Q

What are the effects of pH on the function of enzymes and what is the ideal pH in most enzymes, gastric enzymes, and pancreatic enzymes?

A
  • enzymes are maximally active within small pH range
  • outside of this range, activity drops quickly with changes in pH as the ionization of the active site changes and the protein is denatured
  • most: 7.4
  • gastric: 2
  • pancreatic: 8.5
43
Q

What are the effects of salinity on the function of enzymes?

A
  • changes in salinity can disrupt the bonds of enzyme, causing disruption of tertiary and Quaternary structure, which leads to loss of enzyme function
44
Q

Of the 4 types of reversible inhibitors, which could potentially increase Km?

A
  • competitive increases Km because the substrate concentration has to be higher to reach the half maximum velocity in the presence of the inhibitor
  • a mixed inhibitor will increase Km only if the inhibitor preferentially binds to the enzyme over the ES complex
45
Q

What are examples of transient modifications?

A

allosteric activation or inhibition

46
Q

What are examples of covalent modifications?

A

phosphorylation and glycosylation

47
Q

Why are some enzymes released as zymogens?

A
  • they are precursors of active enzymes

- critical that certain enzymes remain inactive until arriving at their target site

48
Q

What determines an enzymes specificity?

A

the 3D shape of its activation site

49
Q

Are enzymes altered during catalysis?

A

No. A molecules that breaks intramolecular bonds to provide activation energy would not be able to be reused.

50
Q

How does the ideal temperature for a reaction change with or without an enzyme catalyst?

A

ideal temperature is generally lower with a catalyst than without

MCAT Biochem (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions