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
