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Flashcards in Water And pH Deck (25):
1

Important Water facts

-most abundant cellular component, excellent nucleophile, 70% of our body mass (80% in infants), each molecule is H bonded to 4 more molecules, due to the H bonding between these molecules water has high ST, viscosity, MP, BP, heat of vaporization, etc.

2

What can serve as H acceptors

Oxygen atoms of aldehydes, ketones, and amides

3

What can serve as both H acceptors and donors

alcohols, carboxylic acids and amines

4

Is water amphoteric?

Yes, because it dissociation generates both H+ and OH-

5

What is pH?

The pH is a measurement of the acidity or alkalinity of a solution based on H+ concentration. The pH=-log[H+]

6

What can almost completely dissociate into their ions in aqueous solution?

Strong electrolytes (salts, strong acids and bases)

7

Acid

Substance that donates protons

8

Base

Accepts protons

9

When does pH=pKa?

When the conjugate acid concentration and the conjugate base concentration are equal.

10

Polyprotic acids and bases

Can ionize to form more than one proton or hydroxyl ion per molecule of acid or base.

Carbonic acid
Phosphoric acid

11

Buffer

One that resists a change in pH upon addition of acid or base

Two factors:
Molar conc. And pKa

12

How to know which buffer is best?

The buffer with the pK close to desired pH at the highest possible conc.

13

Buffers 2

Weak acids and its conjugate base mixture, they buffer cells and tissues against pH changes

Carbonate and phosphate buffers are the most important in the body

14

What are the most important organs for both controlling pH and eliminating excess H+?











Lungs and Kidneys

Lungs: reduce pCO2 in blood increasing [HCO3-]/[CO2]

Kidneys: keep [HCO3-] right by retaining it and making more if need be, and eliminate H+ by forming NaH2PO4 and NH4+ (urine)

15

How does the respiratory system control the acidity of blood?

Through regulating the elimination of CO2 and H20

16

Hypoventilation

Lowers [HCO3-]/[CO2] ratio and therefore lowers pH by increasing pCO2

17

Hyperventilation

increases the ratio and therefore increases the pH by decreasing pCO2

18

Isohydric Transport

Transport of CO2 without generating a change in blood pH

19

Chloride exchange

helps maintain electrical neutrality during passage of HCO3- out of and back into red blood cells.

Low [Cl-] and high [HCO3-] in tissues (venous) plasma
High [Cl-] and low [HCO3-] in lung plasma (arterial)

20

How do the kidneys regulate the [HCO3-] in the blood?

- By adjusting the amount reabsorbed in lumen

- make more by the deamination of glutamine by glutaminase in kidney tubule cells and also oxidative deamination of other amino acids

21

Transport of O2

Transported as oxyhemoglobin, Hb's affinity for O2 is reduced by 2,3-bisphosphoglycerate and by decrease in pH and by CO2

22

Transport of CO2

-15% of CO2 transported from tissues to lungs as carbamino Hb in red blood cells, only occurs in uncharged amino groups.

23

Bicarbonate Buffer

-Most important inorganic buffer in body
- volatile acid component: CO2; which has a great affect on pH
- Both H2CO3 and CO2 considered as acid form
- [H2CO3] only 1/200 of [CO2]

24

How to determine [CO2]?

-Concentration of gas proportional to partial pressure
- Measure partial pressure of CO2 (pCO2)
- Multiply pCO2 by conversion factor (.03 mM/ mm Hg)

25

Phosphate Buffer

H2PO4(-) HPO4(-2) are the important forms in the body since pK 6.7 is closest to pH 7.4