MSK - Biochemistry - Enzymes; Microtubules Flashcards
What are enzymes?
How do they accomplish their function?
Biological catalysts (mostly proteins, but some are RNA);
by lowering activation energy

Do enzymes change the overall thermodynamics of a reaction?
(I.e., can they change equilibrium states?)
No; equilibrium is not changed but the reactions reach equilibrium more quickly
Under what conditions do human enzymes operate?
Very mild conditions
(aqueous environment, fairly neutral pH, body temperature)
How many types of reaction can a single enzyme produce?
With how many substrates can a single enzyme produce its specified product?
One
(reaction specificity);
one, or one class of structurally similar substrates
(substrate specificity)
What type of chemical interactions do enzymes use to bring substrates together in favorable ways towards the product of the reaction?
Weak bonds (I.e., not covalent bonds)
these can be hydrogen bonds, hydrophobic bonds, ionic bonds, or van der Waals (London forces) interactions
If a reaction is thermodynamically stable, the product will always have a ________ ground state than the substrate.
Lower

What is the name of the peak point of the activation energy for a particular reaction?

Transition state energy
What is ΔG in terms of enzymatic reactions and activation energy?
The change in free energy
(i.e. the energy required to reach the transition state energy, aka the peak of the activation energy)

True/False.
Enzymes lower ΔG.
True.

What is ΔG’°?
A favorable reaction will have a __ ΔG’°.
An unfavorable reaction will have a __ ΔG’°.
The total change in free energy for a reaction
(from the transition state energy [peak activation energy] to the product energy);
-
+
Why are transition state analogues useful in binding enzymes?
They tend to bind more forcefully than substrate or product analogues would
What type of analogue tends to bind enzymes more forcefully than either substrate or product analogues?
What are two examples of this?
Transition state analogue;
most HIV protease inhibitors,
Oseltamivir (TAMIFLU) - binds neuraminidase
What enzymatic class transfers electrons from donors to acceptors?
Oxidoreductases
Redox reactions mostly involve what atoms (elemental types) in our cells?
Carbon, nitrogen, sulfur
What two mnemonics can be used to remember which molecule is reduced and which is oxidized in a reaction based on the movement of electrons?
LEO the lion says GER;
OIL RIG
What is velocity in terms of enzyme kinetics?
The rate of appearance of P (product)
What is initial velocity (vi or v<span>0</span>) in terms of enzyme kinetics?
The rate of product appearance at t = 0
(before any loss of substrate or other change in conditions)
(basically, peak velocity for the enzyme in question)
True/False.
Initial velocity (vi or v0) will remain unchanged even if enzyme concentration increases.
False.
Left graph: different initial velocities (dashed line) for different enzyme concentrations
Right graph: linear relationship between initial velocity and enzyme concentration

True/False.
A high concentration of enzyme will reach reaction equillibrium faster than a low concentration of enzyme?
True.
The Y-axis of a Michealis-Menten graph shows:
The X-axis of a Michealis-Menten graph shows:
Velocity (rate of product formation; often mmoles/sec)
Substrate concentration [S]
In Michaelis-Menten enzyme kinetics, the value for Km is __ Vmax.
1/2
Km is:
Vmax is:
the substrate concentration [S] at 1/2 Vmax
the velocity at an infinte amount of [S]
State the Michaelis-Menten equation.

What is the general hypothesis of enzyme kinetics on which the Michaelis-Menten equation builds?
E + S -> ES* -> E + P
OR
E + S <– ES
























