Enzymes, Mechanisms, Hemoglobin Flashcards
Tells us whether a reaction will occur spontaneously
System at equilibrium
Thermodynamics
Tells us what the speed (rate) of a reaction will be
System not at equilibrium
Kinetics
How does an enzyme increase the rate of a reaction?
They recognize a substrate S (the reactant) and speed up its conversion to product P
The standard free energy change under standard conditions
ΔG°
What is the equation for Keq?
A + B ↔ C + D.
K’eq = [C][D]
[A][B]
so ΔG°’ = -RT lnK’eq
What is the equation for Ka?
Ka = H+ [A −]
[HA]
What is the relationship between Ka and pKa?
pKa = -logKa
What is the equation for pH?
pH = pKa + log ([A −] / [HA])
What is the opposite of a log?
10log number
What additional equation is necessary for finding specific concentration of the acid?
[HA] = M – A
What will a Ka equation look like given only M?
Ka = (x)(x)
(M − x)
What two equations do you need when adding a strong base?
[A-] = Mof given base
[HA] = Mof solution − Mof given base
In physical terms, how do enzymes lower the activation energy?
All enzymes will lower the activation energy by providing energy derived from weak interactions (H-bonds, hydrophobic interactions, ionic interactions, and Van der Waals forces). This occurs through formation of the ES complex and is called binding energy.
An enzyme conforms to the shape of a substrate
Induced fit
Pocket or cleft on the enzyme where the catalytic reaction occurs
Active Site
Molecule that binds in the active site and is chemically transformed
Substrate
Catalytically active version of an enzyme
Holoenzyme
Catalytically inactive version of an enzyme
Apoenzyme
Affinity for processing S to P
larger kcat/Km
Affinity for binding
Small Km
Affinity for processing the fastest
large kcat
Best overall substrate
large kcat/Km
Change the equilibrium between the T and R states
Effector molecules
The enzyme-substrate transition-state complex
Enzymes (typically proteins) are biological catalysts
[E] + [S] → [ES] → [E] + [P]
ES
What is the y-intercept when looking at a Km Vmax graph?
1/Vmax
Nucleophile in the active site temporarily forms a covalent bond
Covalent Catalysis
An amino acid sidechain acts as a proton donor/acceptor
Acid-Base Catalysis
Can work in multiple ways, electrophile, nucleophile, acid/base etc.
Metal ion catalysis
Act of bringing two substrates into close proximity at a reactive surface
Catalysis by approximation
Inhibitor resembles the substrate and binds to the active site thereby preventing binding of the substrate
Competitive
Inhibitor binds to the enzyme substrate complex created only when substrate binds to enzyme
Uncompetitive
Inhibitor binds at different site on enzyme (like allosterism).
Noncompetitive
What type of inhibition is this?
Competitive
What type of inhibition is this?
Uncompetitive
What type of inhibition is this?
Noncompetitive
What type of inhibition is this?
Competitive
What type of inhibition is this?
Uncompetetive
What type of inhibition is this?
Non-competitive
Carries O2 from lungs to tissue Hb-O2 and CO2 and H+ from tissues to lungs HB-CO2/H+.
Hemoglobin
Where is myoglobin found?
Muscles, not RBCs
The low oxygen affinity state of the oxygen carrier
T-state
The oxygen-bound state of the oxygen carrier
R-State
An increase in blood CO2 concentration leads to a decrease in blood pH and will result in hemoglobin proteins releasing their load of oxygen. Conversely, a decrease in carbon dioxide provokes an increase in pH, which results in hemoglobin picking up more oxygen
The Bohr Effect
What makes hemoglobin allosteric?
multimeric state, sigmoidal V vs S curve, cooperativity
Hb can bind __ O2 while Myoglobin can bind __
4
1
Found in RBCs
Active form is a tetramer
Hemogloblin
Found in muscle tissue
Active form is a monomer
Myoglobin
Would equilibrium would be shifted towards the T state or R state of hemoglobin with an increase in O2 concentration?
R-State
Would equilibrium would be shifted towards the T state or R state of hemoglobin with an increase in CO2 concentration?
T-State
Would equilibrium would be shifted towards the T state or R state of hemoglobin with a decrease in 2,3-DPG concentration?
R-State
Would equilibrium would be shifted towards the T state or R state of hemoglobin with an increase in cellular pH (decrease in H+)?
R-State
