Carbonic Anhydrase

how does delta G change

by changing the concentration of substrates or products

can enzymes change delta G?

no, they change the rate of the reactiom

true or false: enzymes can catalyze any reaction

false! in the case of the blood buffering system, spontaneous dissociation in an aqueous solution cannot be catalyzed by an anzyme

define Le Chatelier’s Principle

if a dynamic equilibrium is disturbed by changing the conditons (temp or concentration for example), the position of equilibrium moves to counteract the change

what is the relationship between the rate of the forward and the rate of the reverse reaction at equilibrium

they are equal

for any system ____ (at or not at) equilibrium, there is a driving force toward the equilibrium state

NOT—the reaction usually wants to get to equilibrium

what is the pH of human blood? does it change/fluctuate often?

the pH is 7.4, and a deviation as big as ± 0.5 can result in a death or a coma

why is it so vital to maintain proper blood pH

any alteration in pH can change the internal electrostatic environment of an organism, weakening the bonds (ex: preventing ionic bonds from forming) that maintain biochemical structures=change or loss in function

how do strong and weak acids behave in water

completely ionize in solution (really affects pH)

what is a common way to easily change in pH

add strong acids (increase [H+]) or strong base (increases [OH-])

what is a buffer/how do they work

a weak acid (HA) and a conjugate base (A-) OR weak base on conjugate acid. they basically help resist changes to pH

ex: buffer of weak acid and conjugate base

• add base/OH-, the weak acid will react with it to A- to keep pH from really increasing

• adding acid/H+, conj base will react to form HA and keep pH from really decreasing (aka prevents H from reacting with H2O to form hydronium)

what is the buffer range (ratio terms)

1:10 or 10:1 of (weak acid:conjugate base)

what is pH buffer range? what happens if we go beyond this?

where pKa=pH is the optimal buffer (equal concentration of weak acid and conjugate base), and the range extends ± 1 of that pH. outside of the range, one component of the buffer will be depleted

what is the common blood buffer formula we are thinking of? is that the only one?

but another one is with phosphates (as sodium dihydrogen phosphate=weak acid and sodium monohydrogen phosphate= weak base)

what body parts help with the carbonic anhydrase blood buffer system

lungs being able to remove CO2 and kidneys removing bicarbonate (connected to the carbonic anhydrase)

if carbon anhydrase (not in membrane) is a soluble protein, where would you find arginine (polar) and glycine (nonpolar)

carbon anhydrase is a soluble protein (not in membrane)→polar

arginine is polar too so it will be on the surface of the protein

glycine will be in the interior (hydrophobic effect)

what is the function of osteoclasts?

break down and remove bone tissue/dissocve the fibers and matrix of bone

what is the pH of osteoplasts?

4

what is the sign of delta G during spontaneous reactions

delta G is negative

what is delta G dependent of? what is it independent of?

dependent of energy difference between substrate and product

independent of path or molecular mechanism (aka not transition state or activation energy)

true or false: delta G gives us insight into the rate of reaction

FALSE it gives us no insight into the rate of the reaction because it is only dependent of the substrate and the product

what are the standard conditions?

pH 7, 298 K, and 1M reactants (before reaction)

what is the formula for delta G’

what is K’ eq? conceptual and formula

conceptual: the equilibrium constant at standard conditions

formula: [products]/[reactants]

what are the three relationship between K’ eq and delta G’ (0, <1, >1)

when K’ eq = 0 we assume delta G’ is also 0 (at equilibirum)

when K’ eq > 1 we assume delta G’ is negative (forward reaction favored)

when K’ eq < 1 we assume delta G’ is positive (reverse favored)

when we reverse a reaction, how do we find the new delta G’?

just flip the sign

how much faster is the reaction with carbonic anhydrase vs without carbonic anhydrase

with carbonic anhydrase the reaction is 10^7 times faster

what does carbonic anhydrase require (cofactor)

a cofactor of Zn2+

what are the two models of substrate binding that we refer to?

• lock and key (less accurate)

• induced fit (more used)

compare lock and key vs induced fit substrate binding models

lock and key: substrate is very specific for enzyme, and the ES complex is made before moving forward in the reaction. very sensitive to shape changes

induced: enzyme is made for the transition state form of the substrate, so the transition state gets stabilized (aka ES complex gets formed at transition state). the shape of substrate/bonds weaken when binding with enzyme

do enzymes change thermodynamics

no, they do not change thermodynamics bc they do not affect the substrate and product state. we can say they change kinetics (rate of reaction)

what do we infer about this graph?

we can say that enzymes help get the reaction to its equilibrium state faster (got there in seconds vs hours)

when something is not at equilibrium can we go in either direction?

no, one direction is favored and will keep going in that direction until equilibrium

how do enzymes speed up reactions? (5)

1. orientation substrates correctly

2. straining substrate bonds

3. providing a favorable microenvironment

4. forming weak interactions with the substrate (energy is released when bonds form)

5. lowers Ea

the essence of catalysis is the stabilization of the ____

transition state

do enzymes change equilibrium position?

Nope! just affects how fast you get there

how does enzyme stickase support induced fit?

• if it is at lock and key, it will stabilize before the transition state and results in a greater Ea →slows the reaction

• if it is induced fit, the ES complex is made, it is at transition state, so it will result in the stabilization of the transition state and a lower Ea

what determines if delta G’ and delta G will the equal?

the concentration of the reactants and products (changes as T, pH, and obviously molarity change)

what is Q? formula? is it the same as K’ eq

reaction quotient not at equilibrium

formula: [products]/[reactants]

no, K’eq is reaction quotient at equilibrium + standard conditions

how do you find delta G from delta G’

is every reaction always at standard conditions/is that always the best?

no, it is not always the best. osteoplasts favor H2CO3 even if delta G’ does not support that, so not every reaction needs to the at standard conditions

what is the delta G for osteoplasts? delta G’?

delta G: negative

delta G’: positive

will osteoplasts ever reach equilibrium?

nope!

what is the definition of steady state

the homeostatic condition in which net concentrations remain constant over time, thus requiring a constant input of energy (not equilibrium)