Exam I Flashcards
What is thermodynamics?
Energy change and heat transfer
What is free energy?
Measure of how a reaction will proceed via enthalpy and entropy (delta G)
What is Enthalpy?
Heat content (delta H)
What is entropy?
Randomness of disorder (stats, delta S)
1st law of thermodynamics states that ….
Energy isn’t created or destroyed, potential —> kinetic
2nd law of thermodynamics states…
Entropy always increases, spontaneous not instantaneous
Exergonic free energy is …
(-) delta G gives off energy, spontaneous, enthalpy, heat content, decreases or entropy, disorder, increases or both
Endergonic free energy is …
(+) delta G absorbs energy, non-spontaneous, energy required, enthalpy increases or entropy decreases
Delta G balances out with equal…
Exergonic and endergonic free energy
Standard free energy is…
Delta G constant value with reactants and products = 1mol/L
K=eq is…
Product/reactant
Activation energy is…
Energy required to initiate chemical reaction
Larger activation energy proceeds more _____.
Slowly
Does larger activation energy increase/decrease with heat/catalyst?
Increases with heat
Decreases with catalyst
Enzymes are…
Protein catalysts that Increase rate of reaction, -ase suffix
There are how many classes of enzymes?
6
Oxidoreductase, Transferase, Hydrolase, Lyase, Isomerase, Ligase
Oxidoreductase is a catalyst for what?
Oxidation, reduction
Transferase is a catalyst for what?
Transfer of C-, N-, P-
Hydrolase is a catalyst for what?
Cleavage of bonds by adding H2O
Lyase is a catalyst for what?
Cleavage of C-C, C-S, and some C-N bonds, cuts or decarbonates
Isomerase is a catalyst for what?
Racemitation of optical or geometric isomers, rearranges
Ligase is a catalyst for what?
Formation of bonds between C and O, S, N coupled to hydrolysis of high energy phosphates, glues together
Allosteric enzymes are regulated by what?
Molecules called effectors (modifiers) that bind non-covalently at a site other than the active site
Allosteric enzymes are usually composed of ______ subunits.
Multiple
The regulatory site that binds the allosteric enzyme may be located on a subunit that is not itself _______.
Catalytic
The presence of an allosteric effector _____ alter the affinity of enzyme for its substrate and/or _____ modify the max catalytic activity.
Can do either or both
Effectors that inhibit enzyme activity are termed _____ effectors, whereas those that decrease enzyme activity are called _____ effectors.
Negative, positive
Allosteric enzymes frequently catalyze the commuted step ____ in a pathway.
Early
Which effectors have substrates serving as their own effector?
Homotrophic
Which effectors may be different from their substrate?
Heterotrophic
The active site contains ____ side chains that participate in substrate binding and catalysis.
Amino acids
What is thought to cause conformational change in the enzyme that allows catalysis?
Enzyme-substrate
Enzyme-substrate is converted to ____ that subsequently dissociates to ____ and ____.
Enzyme-product, enzyme and product
Energy of activation is…
Energy difference between reactants and a high-energy intermediate that occurs during product formation.
High free energy of activation leads to ____ rates of uncatalyzed reactions.
Slow
Factors affecting reaction velocity include:
Substrate concentration, temperature, and pH
Max velocity and hyperbolic shape of enzyme kinetics curve dictate the ____.
Substrate concentration
____ enzymes do not follow Michaelis-Menten kinetics and show a sigmoid curve.
Allosteric
The reaction velocity increases with temperature until a ____ velocity is reached.
Peak
Too much heat may cause a temperature-induced ___ of the enzyme.
Denaturation
Reaction velocity is affected by pH’s effect on ____, ____, and ____.
The ionization of the active site, enzyme denaturation, enzyme specific optimum pH level
The structure of the catalytically active protein molecule depends on the ____ of the amino acid side chains.
Ionic character
Catalytic activity may require that a(n) ____ of the enzyme be in the probated form.
Amino group
Line Weaver-Burk Plot
Calculates Km (Michaelis constant) and maximum velocity, as well as to determine the mechanism of action of enzyme inhibitors.
Enzyme inhibition consists of ____ and ____ inhibition.
Competitive and noncompetitive
Competitive inhibition occurs when the inhibitor binds to the ____ site that the substrate would normally occupy.
Active
Competitive inhibition effects ____, ____, ____, and ____.
Maximum velocity, Michaelis constant, Lineweaver-Burk Plot, and cholesterol levels (synthetically)
Maximum velocity effect reversed by ____ substrate levels.
Higher
In the ____ of a competitive inhibitor, more substrate is needed to achieve 1/2 maximum velocity.
Presence
Michaelis constant is ____ in the presence of the competitive inhibitor.
Increased
____ is the most common type of noncompetitive inhibition.
Allosteric inhibition
An increased concentration of substrate cannot overcome noncompetitive inhibition leads to a decreased ____.
Maximum velocity
Michaelis constant ____ in the presence of a noncompetitive inhibitor and ____ in the absence of a noncompetitive inhibitor.
Stays the same, Stays the same
In regards to the Lineweaver-Burk plot when looking at a noncompetitive inhibitor has an apparent maximum velocity ____, with the Michaelis constant ____.
Decreases, unchanged
Some noncompetitive inhibitors act by forming ____ with specific groups of enzymes.
Covalent bonds
Ionic or hydrogen bonding, or even covalent bond bound ions and cations are ____.
Cofactors
Subset of cofactors that are organic molecules with dietary vitamins being very common molecules are called ____.
Coenzymes
____ is an energy carrier with a high activation energy.
ATP
Many coupled reactions use ATP to generate a common ____.
Intermediate
Large (-) free energy (delta G) has a ____ energy phosphate compound.
High
Keq = 1 and free energy (delta G) = 0 relationship is ____.
At equilibrium
Keq > 1 and free energy (delta G) < 0 relationship is ____.
Favors products
Keq < 1 and free energy (delta G) > 0 relationship is ____.
Favors reactants
Coupled reactions are often ___ with 1st reaction without 2nd reaction coupled with the 1st reaction.
Not favorable
The double coupled reactions usually have ____ and ____.
Slower step, faster step
2-multi step coupled reactions often have ____.
Intermediates
For coupled reactions, when there is more than ____ step, overall process is calculated by adding the energy from all steps.
One
____ has the ability to donate protons to an acceptor.
Acid
Strong acids dissociate ____ to their respective ions
Completely
Diprotic acids have ____ protons to donate.
Sulfuric acid
2
With diprotic sulfuric acid, step ____ is nonreversible and step ____ is reversible.
1, 2
Triprotic acids have ____ acids to donate.
Phosphoric acid
3
Weak acids ____ dissociate completely into hydrogen acids and conjugate bases.
Don’t
Strong ____ dissociate completely to their ions.
Bases
Weak ____ do not dissociate completely.
Bases
Ka, dissociation constant, measures…
How much of the acid will dissolve into its hydrogen ions and conjugate base ions
For Ka, (H20) concentration is ____ because molarity (concentration) of H20 is very high compared to other species.
Held constant
PKa= ____
A/B Amino Acid
Lower pKa = ____
Higher acid
Higher Hydrogen levels = ____ pH
Lower
____ Resists pH change following the addition of an acid or a base.
Buffers
Mixing weak acid with conjugate base yields ____.
Buffer
Max buffering capacity occurs when pH ____ pKa.
Equals
Conjugate acid/base pair can still serve as an effective buffer when pH is within ____ pH of the pKa.
Give or take 1
