MCAT Biochemistry Flashcards
To get 132 on the final section of the MCAT
What is the first law of thermodynamics?
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
What is the second law of thermodynamics?
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.
What two factors determine whether a reaction will occur spontaneously in the cell?
- The intrinsic properties of the reactants and products (Keq)
- The concentrations of reactants and products (RT lnQ)
What 3 things identify an oxidation reaction?
- GAIN of oxygen atoms
- LOSS of hydrogen atoms
- LOSS of electrons
What 3 things identify a reduction reaction?
- Loss of oxygen atoms
- GAIN of hydrogen atoms
- Gain of electrons
Give the definitions of a Bronsted-Lowry Acid and Base
- Acids are proton donors
- Bases are proton acceptors
Give the definitions of a Lewis Acid and Base
- Lewis acids are electron-pair acceptors
- Lewis bases are electron-pair donors
What happens to the pH of your blood as you hold your breath?
THe CO2 concentration in your blood increases, this increases the formation of carbonic acid, H2CO3, in your bloodm which will decrease the pH
The hydroxyl groups of __,___, and ____ residues are often modified by the attachment of a phosphate group by a regulatory enzyme called___
serine, threonine, tyrosine
Kinase
What amino acid has a sulfhydryl/thiol side chain
Cysteine
What amino acid has a thioether side chain?
Methionine
How are peptide bonds formed and maintained inside a cell even though they are thermodynamically unfavorable?
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
Hydrolysis of a protein by another protein is called___
proteolysis or proteolytic cleavage
Disulfide bridges between two cysteine molecules to form cystine are found where?
Only in extracellular environments becasue the inside of cells are known reducing environmnets
What is denaturation?
DEnaturation refers to the disruption of a proteins shape WITHOUT breaking peptide bonds
What 4 things cause denaturation?
- urea (disrupts hydrogen bonding)
- extreme pH changes
- extreme temperature
- change in salt concentration (TONICITY)
How is the H-bonding different in B-pleated sheets?
In B-pleated sheets, H-bonding occurs between residues distant from each other in the chain or on separate polypeptide strands.
What is the tertiary structure of a polypeptide considered? what forces are involved?
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
This class of enzyme hydrolyzes chemical bonds
Hydrolase
ATPase and protease are this type of enzyme
hydrolase
___rearanges bonds within a molecule to form an isomer
Isomerase
__forms a chemical bond
Ligase
___breaks chemical bonds by means other than oxidation or hydrolysis
Lyase
Pyruvate decarboxylase is an enzyme that breaks chemical bonds by means other than oxidation or hydrolysis
Lyase
___transfers a phosphate group to a molecule from a high energy carrier, such as ATP
Kinase
___runs a redox reaction
Oxidoreductase
Oxidase, reductases, and dehydrogenases are part of this class of enzyme
oxidoreductase
____enzymes are involved in the addition of nucleotides to the leading strand of DNA )
Polymerase aka polymerization enzymes
___removes a phosphate group from a molecule
Phosphatase
___transfers a phosphate group to a molecule from inorganix phosphate
Phosphorylase
___hydrolyzes peptide bonds (breaks em
Proteases
Trypsin, chymotrypsin, and pepsin are ___enzymes
proteases
In the lab the free energy for the hydrolysis of one phosphate group from ATP is ___
-7.3 kcal/mol
What configuration of amino acids are found in animals?
L-amino acids
What configuration of sugars are found in animals?
D-sugars
What is a cofactor?
An inorganic molecule that associates non-covalently with an enzyme, it is required for the proper functioning of the enzyme
What is a coenzyme?
An organic molecule that associates non-covalently with an enzyme required for the proper functioning of the enzyme
___is an organic molecule that associates with an enzyme for proper functioning___is an inorganic molecule that does the same thing
Coenzyme is organic
Cofactor is inorganic
What are the 4 ways that key enzymes in the metabolic pathway are regulated?
- Covalent modifications
- Proteolytic cleavage
- Association with other polypeptides
- Allosteric regulation
What is the difference btween a phosphorylase and a kinase?
- Kinase phosphorylates using ATP
- Phosphorylase uses free-floating inorganic phosphate in the cell instead of ATP
What is proteolytic cleavage?
Many enzymes and other proteins are synthesized in inactive forms (zymogens) that are activated by cleavage by a protease
A smaller Kd (dissociation constant) means_
HIGHER AFFINITY
Thicker bands in Western blot indicate__
more proteins
A measurement is precise (reliable) if__
similar results are obtained on repeated trials`
__ is an enzyme complex composed of 3 subunits. IT catalyzes the oxidative decarboxylation of pyruvate to form acetyl-CoA
Pyruvate dehydrogenase complex
___ requires lipoic acid for activity
Pyruvate dehydrogenase complex
Fatty acids with an odd number of carbons produce __ and __ during B-oxidation
propionyl acid and acetyl-CoA
Carbohydrates with multiple stereocenters are given L or D designation based on the configuration of __
highest numbered stereocenter
__ is required for fatty acids to enter the mitochondria
L-carnitine
For membrane phospholipids, ___ yield the highest fluidity because they participate in the fewest hydrophobic interactions with neighboring lipids
Short chains with double bonds
__forms covalent bonds with enzymes and becomes more potent in its effects given sufficient time to react
Irreversible inhibitors
___quickly form non-covalent bonds with target enzymes and do not require much time to reach their full effect
Reversible inhibitors
__bind only free enzymes and prohibit substrate from binding. This form of inhibition leads to an
INCREASED KM and NO CHANGE TO Vmax
Competitive inhibitor
__ bind only enzyme-substrate complexes. Formation of ES complex leads to:
DECREASED KM and a proportional DECREASE to Vmax
Uncompetitive inhibitor
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__
The Cori cycle
The Cori cycle connects the metabolic pathways of __ and __
gluconeogenesis and glycolysis
