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MCAT Flashcards > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What is an enzyme?

A

A specific protein that speeds up the rate of a reaction by lowering the activation energy of a reaction.

  • They are not changed or consumed in the reaction
  • are sensitive to temperature and pH
  • do not affect equilibrium
  • do not change thermodynamic parameters (G, S, H)
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2
Q

What is the structure of an enzyme?

A
  • scaffolded for support and position the active site

- then the active site has a binding site and a catalytic site

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3
Q

Catalytic site

A

Part of enzyme that is very specific and where the reaction is catalyzed

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4
Q

Binding site

A

Where the substrate interacts with enzyme through intermolecular interactions
Positions the substrate so it is properly in the catalytic site

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5
Q

Substrate

A

What is being changed by the enzyme

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6
Q

Ligand

A

Any Substance enzyme interacts with - encompasses both substrate and regulatory molecules

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7
Q

Orthosteric Regulatory Elements

A

Interact with enzyme at its active site

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8
Q

Allosteric Regulatory Elements

A

Bind/interact with enzyme at some other place, other than the active site

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9
Q

Induced fit model

A

Enzyme and substrate affect each other

-initial binding undergoes conformational shifts that allow closer binding and more efficient catalyst

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10
Q

Lock and key

A

Substrate fits into enzyme like a key to a lock - perfect fit with no changes in structure to get a better fit
This is inadequate to explain enzymes interactions with their substrates

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11
Q

Oxidoreductases

A

Catalyze oxidation/reduction reactions

Ex: alcohol dehydrogenase, superoxide dismutase

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12
Q

Transferases

A

Transfer fictional group between molecules
Ex: aspartame transaminase
Creatine kinase
DNA polymerase

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13
Q

Hydrolases

A

Catalyze hydrolysis
Ex: angiotensin converting enzyme
Pancreatic lipase
Lactase

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14
Q

Isomerases

A

Catalyze isomerization

Ex: Ribose-5-phosphate isomerase

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15
Q

Ligases

A

Join molecules together with covalent bonds
Ex: aminoacyl tRNA synthetase
Glutamine synthetase
Pyruvate carboxylase

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16
Q

Kinase

A

Adds a phosphate group to a molecule (phosphorylates

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17
Q

Phosphatase

A

Removes a phosphate

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18
Q

Name the different types of enzyme regulation

A

Negative feedback
Positive feedback
Feed forward regulation
Cooperativity

19
Q

Negative feedback

A

Downstream products inhibit the pathways to the products
Stimulus —> sensor —> control —> effector
If you have negative inhibition of an enzyme, the products of the reaction end up inhibiting the enzyme upstream in the pathway

20
Q

Positive feedback

A

Downstream products amplifies initial stages of a reaction

21
Q

Feed forward regulation

A

Products at an earlier step in the pathway regulate the enzyme

22
Q

Cooperativity

A

Where the binding of one substate makes it easier to bind the next
Characterized by a sigmodal curve

23
Q

Hill coefficient

A

Expresses the degree of cooperativity of an enzyme or protein
>1 is positively cooperative
<1 is negatively cooperative
=1 non-cooperative

24
Q

What is the vmax?

A

The maximum rate of reaction

When X is fully saturated and rate of reaction can’t increase

25
Q

What is Km

A

Concentration of the substate that corresponds to 1/2 vmax

Can be used to measure the affinity and enzyme has for a substrate

26
Q

Michaelis-menten plot

A

Reaction rate on y axis
Substrate concentration on x axis
1/2 vmax = rate where substrate conc = km

27
Q

Lineweaver-Burk plot

A 
Double-reciprocal transformation of Mich-Men, 
1/v is on the y 
1/Conc. of substate is on the x axis
Y intercept = 1/vmax
X intercept = -1/km
28
Q

Competitive inhibitors

A

Bind at active site
Increase Km
Vmax stays the same
You can out compete them with more substrate

29
Q

Non competitive inhibitor

A

Bind allosterically
Lower Vmax
Km stays same

30
Q

Uncompetitive inhibitor

A

Prevent enzyme from letting go of substate
Vmax decreases
Km decreases

31
Q

Mixed inhibition

A

Inhibitor binds at the allosteric site or binds the enzyme substrate complex
Vmax is always decreased
Km depends on if the mixed prefers binding the free enzyme or if it prefers the complex
Km increases if it prefers free
Km decreases if it prefer complex

32
Q

Glycosytion

A

Form of regulating/modifying enzymes by adding carbohydrate moieties

33
Q

Zymogens

A

Aka proenzymes

Enzymes that need to be cleaved to be active

34
Q

Cofactors

A

Chemical compounds that help enzyme carry out its biological function
Ex: Mg2+, cu2+, coenzymes (if it’s a cofactor that acts in an enzyme), vitamins

35
Q

Prosthetic groups

A

When a coenzyme is very tightly bonded to its enzyme

Ex: heme

36
Q

Holoenzyme

A

Enzyme together with its coenzyme and/or metal

37
Q

Apoenzyme

A

Enzyme without the coenzymes needed for to function

38
Q

Primary Structure

A

amino acids held together by covalent bonds (the peptide bonds holding each one together). These are strong, hard to break, so primary structure resilient

39
Q

Secondary Structure

A

formed by hydrogen bonds between the amine and carboxylic acid groups of the amino acid backbone
ex: alpha helices, beta sheets

40
Q

Tertiary Structure

A

formed by hydrogen bonding and interactions between the side chains of the amino acids to form a 3D structure
environment plays role in how the side chains will behave
ex: hydrophobic side chains moving the protein so they are enclosed by hydrophilic proteins when in an aqueous environment
-oxidizing environments that cause formation of disulfide bonds
-reducing environments (often by a reagent, such as 2-mercaptoethanol) to break those bonds
disulfide bridges contribute heavily to tertiary structure b/c covalent
ex: hydrogen bonding, van der waals, disulfide bridges, salt bridges

41
Q

Quaternary Structure

A

At least two subunits (full tertiary structure of a protein = 1 subunit) coming together via intramolecular bonds

42
Q

Common Denaturing Agents

A

temperature
high and low pH extremes (this would interfere with charges, or break disulfide bridges if reducing environment)
once you remove the denaturing conditions, proteins are able to fold/reassemble again

43
Q

What breaks primary structures?

A

proteases

these target specific amino acid residues

MCAT Flashcards (23 decks)

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