Ch. 2: Water, Acids, Bases, Buffers Flashcards Preview

Medical Biochemistry > Ch. 2: Water, Acids, Bases, Buffers > Flashcards

Flashcards in Ch. 2: Water, Acids, Bases, Buffers Deck (43):
1

What types of bonds make up a water molecule?

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

2

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

Important in what function of water?

Hydrogen bonds

Thermoregulation

3

How is water transported across cell membranes?

1) simple diffusion

2) aquaporins

4

How are micelles stabilized?

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

5

What do colligative properties depend on?

Number of particles of solvent & solute molecules

6

What are the 4 types of colligative properties?

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

7

Measuring colligative properties is useful for?

Estimating [solute] in biological fluids

8

Is water an acid or base?

Both (donates & accepts H+)

9

Do H+ exist free in solution?

No ➡️ exist as hydronium (oxonium) ions
(H+ very mobile in water via proton jumping)

10

Equation for equilibrium constant for dissociation of water?

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

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

11

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

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

12

Function of buffers?

Resist changes in pH when acid or base added

13

What do most buffers consist of?

Weak acid + its conjugate base

14

Why are strong acids & bases poor buffers?

Completely dissociate ➡️ no buffering capacity

15

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

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

16

What is the Henderson-Hasselbach equation?

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

17

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

Exist in ionic form

18

Death occurs if plasma reaches what pH?

pH 6.8 or 7.8

19

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

Affects charged regions of molecular structures ➡️ alters physiological activity

20

3 main buffer systems in the body?

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

21

Equation for bicarbonate-carbonate acid system?

H+ + HCO3- ↔️ H2CO3 ↔️ H2O + CO2

22

What is the Bohr affect?

Effect of pH on O2 binding to hemoglobin

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

23

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

Zinc (Zn2+ held by 3 His residues)

24

What is the most prevalent type of carbonic anhydrase?

CA I

25

3 important functions carbonic anhydrase is involved in?

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

26

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

CA II

27

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

H+ + HCO3- ↔️ H2CO3

28

What is the pK' for formation of bicarbonate?

pK' = 6.1

29

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

What does this indicate about bicarbonate system as a buffer?

20/1

Good buffer toward acid, poor buffer toward base

30

How does the body buffer against ⬆️ in alkalinity?

Blood H2CO3 in equilibrium w/large amt of cellular CO2

31

Equation for calculating pH from [CO2] and Pco2?

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

32

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

Hypoventilation ➡️ ⬆️ Pco2

Hyperventilation ➡️ ⬇️Pco2

33

Why are proteins buffers in the blood?

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

34

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

2nd pKa = 7.21

H2PO4- + OH- ↔️ (HPO4)2- + H2O

35

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

McArdle's syndrome (pH changes)

Creatine deficiency syndrome (lactate produced)

36

Which a.a. are needed to make creatine?

Arg, Gly, Met

37

Enzyme that converts phosphocreatine ➡️ creatine + ATP?

Function?

Creatine kinase

Quick supply of ATP in muscle

38

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

Lipids = bright
Water = dark

39

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

Lipids = dark
Water = bright

40

What disease can be diagnosed with MRI?

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

41

Mathematically, what is pH?

pH = -log[H+]

42

What is normal range of pH?

pH = 7.36-7.44

43

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

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