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MCAT > MCAT Biochemistry > Flashcards

MCAT Biochemistry Flashcards

To get 132 on the final section of the MCAT

1
Q

What is the first law of thermodynamics?

A

Also known as the law of conservation of energy, states that energy of the universe is constant.

-When the energy of the system decreases, the energy of the rest of the univrse (the surroundings) must increase and vice versa

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2
Q

What is the second law of thermodynamics?

A

Second law of thermodynamics states that the disorder or entropy of the universe tends to increase.

-Spontaneous reactions tend to increase the disorder of the universe.

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3
Q

What two factors determine whether a reaction will occur spontaneously in the cell?

A
  • The intrinsic properties of the reactants and products (Keq)
  • The concentrations of reactants and products (RT lnQ)
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4
Q

What 3 things identify an oxidation reaction?

A
  1. GAIN of oxygen atoms
  2. LOSS of hydrogen atoms
  3. LOSS of electrons
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5
Q

What 3 things identify a reduction reaction?

A
  1. Loss of oxygen atoms
  2. GAIN of hydrogen atoms
  3. Gain of electrons
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6
Q

Give the definitions of a Bronsted-Lowry Acid and Base

A
  • Acids are proton donors

- Bases are proton acceptors

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7
Q

Give the definitions of a Lewis Acid and Base

A
  • Lewis acids are electron-pair acceptors

- Lewis bases are electron-pair donors

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8
Q

What happens to the pH of your blood as you hold your breath?

A

THe CO2 concentration in your blood increases, this increases the formation of carbonic acid, H2CO3, in your bloodm which will decrease the pH

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9
Q

The hydroxyl groups of __,___, and ____ residues are often modified by the attachment of a phosphate group by a regulatory enzyme called___

A

serine, threonine, tyrosine

Kinase

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10
Q

What amino acid has a sulfhydryl/thiol side chain

A

Cysteine

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11
Q

What amino acid has a thioether side chain?

A

Methionine

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12
Q

How are peptide bonds formed and maintained inside a cell even though they are thermodynamically unfavorable?

A

During protein synthesis, stored energy is used to force peptide bonds to form. Once the bond is formed, even though its destruction is thermodynamically favorable, it remains stable because of the activation energy for the hydrolysis reaction is so high. Hydrolysis is THERMODYNAMICALLY favorable, but kinetically slow

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13
Q

Hydrolysis of a protein by another protein is called___

A

proteolysis or proteolytic cleavage

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14
Q

Disulfide bridges between two cysteine molecules to form cystine are found where?

A

Only in extracellular environments becasue the inside of cells are known reducing environmnets

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15
Q

What is denaturation?

A

DEnaturation refers to the disruption of a proteins shape WITHOUT breaking peptide bonds

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16
Q

What 4 things cause denaturation?

A
  • urea (disrupts hydrogen bonding)
  • extreme pH changes
  • extreme temperature
  • change in salt concentration (TONICITY)
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17
Q

How is the H-bonding different in B-pleated sheets?

A

In B-pleated sheets, H-bonding occurs between residues distant from each other in the chain or on separate polypeptide strands.

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18
Q

What is the tertiary structure of a polypeptide considered? what forces are involved?

A

Tertiary structures concern interactions between amino acids more distant on the polypeptide chain:

  • Van der Waals forces between nonpolar side chains
  • H-bonds between polar side chains
  • Disulfide bonds between cysteine residues
  • electrostatic interactions between acidic and basic side chains
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19
Q

This class of enzyme hydrolyzes chemical bonds

A

Hydrolase

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20
Q

ATPase and protease are this type of enzyme

A

hydrolase

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21
Q

___rearanges bonds within a molecule to form an isomer

A

Isomerase

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22
Q

__forms a chemical bond

A

Ligase

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23
Q

___breaks chemical bonds by means other than oxidation or hydrolysis

A

Lyase

24
Q

Pyruvate decarboxylase is an enzyme that breaks chemical bonds by means other than oxidation or hydrolysis

A

Lyase

25
Q

___transfers a phosphate group to a molecule from a high energy carrier, such as ATP

A

Kinase

26
Q

___runs a redox reaction

A

Oxidoreductase

27
Q

Oxidase, reductases, and dehydrogenases are part of this class of enzyme

A

oxidoreductase

28
Q

____enzymes are involved in the addition of nucleotides to the leading strand of DNA )

A

Polymerase aka polymerization enzymes

29
Q

___removes a phosphate group from a molecule

A

Phosphatase

30
Q

___transfers a phosphate group to a molecule from inorganix phosphate

A

Phosphorylase

31
Q

___hydrolyzes peptide bonds (breaks em

A

Proteases

32
Q

Trypsin, chymotrypsin, and pepsin are ___enzymes

A

proteases

33
Q

In the lab the free energy for the hydrolysis of one phosphate group from ATP is ___

A

-7.3 kcal/mol

34
Q

What configuration of amino acids are found in animals?

A

L-amino acids

35
Q

What configuration of sugars are found in animals?

A

D-sugars

36
Q

What is a cofactor?

A

An inorganic molecule that associates non-covalently with an enzyme, it is required for the proper functioning of the enzyme

37
Q

What is a coenzyme?

A

An organic molecule that associates non-covalently with an enzyme required for the proper functioning of the enzyme

38
Q

___is an organic molecule that associates with an enzyme for proper functioning___is an inorganic molecule that does the same thing

A

Coenzyme is organic

Cofactor is inorganic

39
Q

What are the 4 ways that key enzymes in the metabolic pathway are regulated?

A
  • Covalent modifications
  • Proteolytic cleavage
  • Association with other polypeptides
  • Allosteric regulation
40
Q

What is the difference btween a phosphorylase and a kinase?

A
  • Kinase phosphorylates using ATP

- Phosphorylase uses free-floating inorganic phosphate in the cell instead of ATP

41
Q

What is proteolytic cleavage?

A

Many enzymes and other proteins are synthesized in inactive forms (zymogens) that are activated by cleavage by a protease

42
Q

A smaller Kd (dissociation constant) means_

A

HIGHER AFFINITY

43
Q

Thicker bands in Western blot indicate__

A

more proteins

44
Q

A measurement is precise (reliable) if__

A

similar results are obtained on repeated trials`

45
Q

__ is an enzyme complex composed of 3 subunits. IT catalyzes the oxidative decarboxylation of pyruvate to form acetyl-CoA

A

Pyruvate dehydrogenase complex

46
Q

___ requires lipoic acid for activity

A

Pyruvate dehydrogenase complex

47
Q

Fatty acids with an odd number of carbons produce __ and __ during B-oxidation

A

propionyl acid and acetyl-CoA

48
Q

Carbohydrates with multiple stereocenters are given L or D designation based on the configuration of __

A

highest numbered stereocenter

49
Q

__ is required for fatty acids to enter the mitochondria

A

L-carnitine

50
Q

For membrane phospholipids, ___ yield the highest fluidity because they participate in the fewest hydrophobic interactions with neighboring lipids

A

Short chains with double bonds

51
Q

__forms covalent bonds with enzymes and becomes more potent in its effects given sufficient time to react

A

Irreversible inhibitors

52
Q

___quickly form non-covalent bonds with target enzymes and do not require much time to reach their full effect

A

Reversible inhibitors

53
Q

__bind only free enzymes and prohibit substrate from binding. This form of inhibition leads to an
INCREASED KM and NO CHANGE TO Vmax

A

Competitive inhibitor

54
Q

__ bind only enzyme-substrate complexes. Formation of ES complex leads to:
DECREASED KM and a proportional DECREASE to Vmax

A

Uncompetitive inhibitor

55
Q

During anaerobic exercise, pyruvate is reduced to lactate to regenerate NAD+. Lactate that builds up in muscles is sent to the liver to get converted back to glucose and returned to muscles. This process is called__

A

The Cori cycle

56
Q

The Cori cycle connects the metabolic pathways of __ and __

A

gluconeogenesis and glycolysis

MCAT (45 decks)

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