Ch. 2: Water, Acids, Bases, Buffers

Question 1

What types of bonds make up a water molecule?

Answer 1

Polar, covalent H-O bonds (contains dipole moment)

Question 2

What types of bonds are involved in intermolecular bonding between water molecules?

Important in what function of water?

Answer 2

Hydrogen bonds

Thermoregulation

Question 3

How is water transported across cell membranes?

Answer 3

1) simple diffusion

2) aquaporins

Question 4

How are micelles stabilized?

Answer 4

1) H bonds (via water)
2) Van der Waals forces
3) Hydrophobic interactions

Question 5

What do colligative properties depend on?

Answer 5

Number of particles of solvent & solute molecules

Question 6

What are the 4 types of colligative properties?

Answer 6

1) vapor pressure depression
2) boiling point elevation
3) melting point depression
4) osmotic pressure (osmosis)

Question 7

Measuring colligative properties is useful for?

Answer 7

Estimating [solute] in biological fluids

Question 8

Is water an acid or base?

Answer 8

Both (donates & accepts H+)

Question 9

Do H+ exist free in solution?

Answer 9

No ➡️ exist as hydronium (oxonium) ions

H+ very mobile in water via proton jumping

Question 10

Equation for equilibrium constant for dissociation of water?

Answer 10

Keq = [H+][OH-] / [H2O]

Rearranged: Keq x [H2O] = Kw = 1.0 x 10^-14

Question 11

In neutral solution, what is the concentration of acid and base (of water)?

Answer 11

[H+] = [OH-] = 1.0 x 10^-7

Question 12

Function of buffers?

Answer 12

Resist changes in pH when acid or base added

Question 13

What do most buffers consist of?

Answer 13

Weak acid + its conjugate base

Question 14

Why are strong acids & bases poor buffers?

Answer 14

Completely dissociate ➡️ no buffering capacity

Question 15

When is max buffering capacity achieved? (Buffer responds equally to added acid or base)

Answer 15

Molarity of salt = molarity of acid (pH = pK’)

Question 16

What is the Henderson-Hasselbach equation?

Answer 16

pH = pKa + log10([A-] / [HA])

Question 17

At a certain pH, what can happen to certain medications?

Answer 17

Exist in ionic form

Question 18

Death occurs if plasma reaches what pH?

Answer 18

pH 6.8 or 7.8

Question 19

Changes in [H+] have what affect in the body?

Answer 19

Affects charged regions of molecular structures ➡️ alters physiological activity

Question 20

3 main buffer systems in the body?

Answer 20

1) Bicarbonate-carbonic acid system
2) Proteins (hemoglobin, albumin)
3) phosphate buffer

Question 21

Equation for bicarbonate-carbonate acid system?

Answer 21

H+ + HCO3- ↔️ H2CO3 ↔️ H2O + CO2

Question 22

What is the Bohr affect?

Answer 22

Effect of pH on O2 binding to hemoglobin

H+ binds to Hb ➡️ ⬇️ Hb affinity for O2 ➡️ O2 released

Question 23

What metal is involved in structure of carbonic anhydrase? What a.a. residues hold this metal?

Answer 23

Zinc (Zn2+ held by 3 His residues)

Question 24

What is the most prevalent type of carbonic anhydrase?

Answer 24

CA I

Question 25

3 important functions carbonic anhydrase is involved in?

Answer 25

1) form H+ in stomach parietal cells
2) bone resorption via osteoclasts
3) reclaim HCO3- in renal tubule cells

Question 26

Deficiency of which CA type is involved in osteopetrosis (marble bone disease)?

Answer 26

CA II

Question 27

Which part of the bicarbonate-carbonate acid system is an acid-base reaction? (Other part is NOT)

Answer 27

H+ + HCO3- ↔️ H2CO3

Question 28

What is the pK’ for formation of bicarbonate?

Answer 28

pK’ = 6.1

Question 29

At blood pH 7.4, [HCO3-] / [H2CO3] = ?

What does this indicate about bicarbonate system as a buffer?

Answer 29

20/1

Good buffer toward acid, poor buffer toward base

Question 30

How does the body buffer against ⬆️ in alkalinity?

Answer 30

Blood H2CO3 in equilibrium w/large amt of cellular CO2

Question 31

Equation for calculating pH from [CO2] and Pco2?

Answer 31

pH = pK + log ( HCO3- / 0.03 x Pco2)

Question 32

How does changes in respiration affect Pco2 & [H2CO3]? (2 affects)

Answer 32

Hypoventilation ➡️ ⬆️ Pco2

Hyperventilation ➡️ ⬇️Pco2

Question 33

Why are proteins buffers in the blood?

Answer 33

1) Hemoglobin, albumin: pK’ of His imidazolium group = 6.5 (can accept/donate H+)
2) pK’ of alpha-amino group of N terminal = 7.8-10.6

Question 34

Which of the 3 pKa of the titration curve of phosphoric acid serves as buffer for the body?

Answer 34

2nd pKa = 7.21

H2PO4- + OH- ↔️ (HPO4)2- + H2O

Question 35

P13-NMR used to determine pH (Pi resonance varies w/changes in pH) ➡️ which hereditary defects can be diagnosed with this?

Answer 35

McArdle’s syndrome (pH changes)

Creatine deficiency syndrome (lactate produced)

Question 36

Which a.a. are needed to make creatine?

Answer 36

Arg, Gly, Met

Question 37

Enzyme that converts phosphocreatine ➡️ creatine + ATP?

Function?

Answer 37

Creatine kinase

Quick supply of ATP in muscle

Question 38

MRI: what do T1 (relaxation time) weighted images look like?

Answer 38

Lipids = bright
Water = dark

Question 39

MRI: what do T2 (relaxation time) weighted images look like?

Answer 39

Lipids = dark
Water = bright

Question 40

What disease can be diagnosed with MRI?

Answer 40

Multiple sclerosis (MS): scattered lesions of myelin sheath of axons

Question 41

Mathematically, what is pH?

Answer 41

pH = -log[H+]

Question 42

What is normal range of pH?

Answer 42

pH = 7.36-7.44

Question 43

Equation to calculate [H+] from Pco2 & [HCO3-]?

Answer 43

[H+] = 24 x (Pco2 / [HCO3-])