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BIOL 2421 - Cellular Biochem > 2. Weak acids and bases > Flashcards

2. Weak acids and bases Flashcards

1
Q

what does water ionize into

A

H+ and OH-

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2
Q

do free protons exist in solution? explain

A

no, any free proton upon water dissociation is hydrated to from H3O+, but we will usually see it as just H+

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3
Q

what is Keq

A

a fixed and dimensionless constant for a given chemical reaction. The starting concentrations do not matter

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4
Q

what is the Keq formula

A

Keq= [products] at equilibrium/[reactants] at equilibrium

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5
Q

in regards to amount of water ionization, what does a high Keq mean?

A

high Keq=high amount of water ionization

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6
Q

what is the formula for Kw

A

Kw= Keq x [H2O]

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7
Q

what is Kw

A

the ion product of water

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8
Q

what type of solution do we have when [H+] is high

A

acidic

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9
Q

what type of solution do we have when [H+] is low

A

alkaline (basic)

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10
Q

what is the formula for pH

A

pH= -log[H+]

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11
Q

what is the relationship between pH and [H+]

A

high pH=low [H+]

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12
Q

what does one unit jump of pH represent in regards to number of H ions

A

one jump represents a 10x difference

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13
Q

T or F: strong acids and strong bases ionize completely in water

A

true

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14
Q

describe a conjugate acid-base pair

A

when a weak acid loses its proton, it becomes the corresponding base pair (or proton acceptor), and together they make the conj. acid-base pair

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15
Q

which donates a proton: acid or base?

A

acid

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16
Q

which accepts a proton: acid or base

A

base

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17
Q

what is Ka

A

the acid dissociation constant. It is an equilibrium constant for ionization reactions of acids

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18
Q

what is the formula for pKa

A

pKa= -log(Ka)

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19
Q

what does pKa measure

A

the strength of the acid (the tendency it has to dissociate into a proton and its conj. base)

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20
Q

what does it mean when you have a low pKa

A

low pKa=high Ka= high level of ionization

21
Q

T or F: the weaker the acid the weaker the conjugate base

A

false. The weaker the acid the stronger the conj. base

22
Q

__ acids have a pKa less than one

A

strong acids

23
Q

__ acids have a pKa greater than one

A

weak acids

24
Q

what is a titration curve?

A

a curve showing the pH of an acidic solution when a strong base has been added

25
Q

how is pH measured on a titration curve

A

in increments

26
Q

what can a titration curve tell us about the given acid?

A

pKa

27
Q

how can we determine the pKa of an acid using a titration curve

A

at the midpoint, pH=pKa

28
Q

what happens as the base is added to the acid in a titration?

A

new OH combines with the free H+ in the solution = H2O (the free H+ was due to acid ionization)

next, the acid further ionizes to produce the H+ that was lost (shifts right), and slowly [HA] will fall and [A-] will rise as equilibrium is reached

29
Q

T or F: shapes of titration curves are consistant

A

true, because all weak acids have the relationship: pH=pKa at the midpoint

30
Q

what does the midpoint of a titration curve represent

A

the midpoint is where the system is 50% titrated

31
Q

will a strong acid’s titration curve start lower or higher on the x axis (pH axis)

A

it will start lower, since strong acids have lower pH

32
Q

how many inflection points will a triprotic acid have?

A

3

33
Q

how do you deal with the 3 midpoints for a triprotic acid on a titration curve?

A

each midpoint represents the point where pH=pKa for that weak acid compound. (As protons are lost, each acid will have a different pKa)

34
Q

how do cells keep their pH values relatively stable

A

they use buffer systems

35
Q

what does the curve look like in the buffering region

A

it’s flat

36
Q

how does a buffer system work

A

the conj acid HA has a reserve of bound protons that can be released to neutralize an addition of OH- into the system, which allows the solution to resist pH changes when small amounts of OH- or H+ are added

37
Q

what is the range of a buffer system

A

+/- 1 pH value away from the pKa

38
Q

what does the Henderson-Hasselbalch equation help us do

A

it allows us to connect pH, pKa, [A-], and [HA] together and descrive the shape of a weak acid titration curve

39
Q

what is the Henderson-Hasselbalch equation

A

pH= pKa + log([A-]/[HA])

40
Q

in regards to buffers, what biological importance does histidine have?

A

His has an amine group with pKa=6, so proteins with His residues can serve as buffers

41
Q

describe the bicarbonate buffer system and how it’s useful

A

we have carbonic acid (H2CO3) in blood plasma which can dissociate into bicarbonate (HCO3-), and there is CO2 in the air space of the lungs. Blood often accepts excess H+ produced during exercise, so we shift toward carbonic acid. CO2 levels in blood rise, transfer to lungs, and extra is exhaled. Blood can also lose H+ from protein breakdown in the body. We shift toward bicarbonate, so CO2 from lungs dissolves into blood plasma

42
Q

how is respiration rate altered (hint: think brain stem)

A

the brain stem is able to detect increases in blood pH or CO2 to alter respiration rate. Too much H= in blood=breathing faster and deeper to expel CO2 and adjust the equilibrium

43
Q

in regards to enzyme function, why is maintaining your body’s pH important

A

many enzymes have a maximal activity at pH 7.4, so changes in pH can decrease enzyme activity and greatly slow essential metabolic reactions in the body

44
Q

how are stored fats impacted when someone has uncontrolled diabetes (high blood sugars)

A

the stored fats are broken down into large amounts of ketone bodies

45
Q

T or F: two of the ketone bodies that are formed during diabetes are weak acids

A

true

46
Q

what is the issue of the two ketone bodies (produced due to diabetes) being weak acids

A

the acids can dissociate into their conjugate bases, which lowers blood pH and causes acidosis

47
Q

describe symptoms of acidosis

A

drowsiness, nausea, vomiting, stupor, convulsions, and coma

48
Q

what are 4 other causes of acidosis other than diabetes

A

starvation (cells=lacking in glucose=fat stores broken down to ketone bodies)

very heavy exercise (high buildup of lactic acid in the blood)

kidney problems (unable to regulate bicarbonate levels in the blood)

lung problems (unable to expel enough CO2)

BIOL 2421 - Cellular Biochem (21 decks)

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