PSL301: Water 7

Question 1

Acid can ___ H+

Answer 1

donate

Question 2

Base can ___ H+

Answer 2

accept

Question 3

conversion between pH and [H]

Answer 3

pH = -log[H]

[H] = 10^(-pH)

Question 4

normal pH in blood

Answer 4

7. 4

7. 35 - 7.45 range

Question 5

most acidic part of body

Answer 5

stomach (1.5 pH)

Question 6

most basic part of body fluid

Answer 6

bile (pH = 8)
alkaline urine (pH = 8)

Question 7

effect of diet on pH

Answer 7

protein - acidic

- sulfur-containing AA are metabolized to H2SO4

Question 8

sulfur containing AA

Answer 8

• cysteine

- methionine

Question 9

1 Met or 1 Cys generates ___ H2SO4

Answer 9

1 mol

Question 10

what prevents severe acidosis when we eat proteins?

Answer 10

buffers

Question 11

BUFFERS

Answer 11

limit the change in [H] when an acid is added/removed from a solution

Question 12

Buffers found in humans

Answer 12

• bicarb (HCO3-)
• phosphate (HPO4^2-)
• ammonia (NH3)

Question 13

the bicarbonate buffer system is catalyzed by…

Answer 13

carbonic anhydrase (CA)

Question 14

Why is the bicarb system so good?

Answer 14

both sides of the equilibrium can be independently regulated; no other buffer system has this quality
- this allows for compensation

Question 15

Kidney has 2 effects on bicarb

Answer 15

1. make new bicarb

2. reabsorb filtered bicarb

Question 16

New bicarb is generated by excretion of…

Answer 16

H+, buffered by ammonia or phosphate

• NH4+
• H2PO4

Question 17

How does kidney make new bicarb?

Answer 17

1. CO2 + H2O -> H+ and bicarb
2. H+ is secreted into lumen, buffered by ammonia/phosphate
3. bicarb is exchanged with Na+, reabsorbed into bloodstream

Question 18

Where does the phosphate we use to buffer come from?

Answer 18

• filtered from plasma

- diet

Question 19

Mechanism of ammonia buffer system, from start to finish

Answer 19

1. NH3 synthesized by proximal tubular cells
2. Binds with H+, secreted into lumen as NH4+
3. Reabsorbed in thick ascending limb
4. NH3 diffuses through medulla
5. Bind with H+ from MCD
6. NH4+ trapped in CD lumen, excreted in urine

Question 20

What is the more important urinary buffer? Why?

Answer 20

Ammonia;

• Phosphate amount is limited and cannot be adjusted
• Kidneys can regulate amount of ammonia 5-10x

Question 21

ammonium is a weak ___

Answer 21

acid

Question 22

___ freely diffuses across cell membranes & blood vessels

Answer 22

ammonia

Question 23

___ does not readily cross cell membranes

Answer 23

ammonium

Question 24

in a more acidic environment, there is more ammonia // ammonium

Answer 24

ammonium

Question 25

How does ammonia buffer H+?

Answer 25

1. Freely cross into lumen 2. Bind H+ inside lumen 3. NH4+ cannot cross back into tubular cell 4. must be excreted

Question 26

ammonia is synthesized by the...

Answer 26

proximal tubular cells from Glutamine

Question 27

For every 1 H+ / 1 NH4+ secreted, ___ bicarb is synthesized

Answer 27

1

Question 28

How is H+ secreted by the CD?

Answer 28

H+-ATPase

Question 29

Which AA makes ammonia?

Answer 29

glutamine

Question 30

What regulates ammonium excretion?

Answer 30

acid/base status | - acidosis = ammonia synthesis & H+ secretion in CD (activate H+-ATPase)

Question 31

Cell pH is recognized by ____, which then alters cell function to _____

Answer 31

cell receptors; | normalize pH

Question 32

When is ammonium excretion increased?

Answer 32

- metabolic & respiratory acidosis | - higher protein intake

Question 33

when there is a large acid load, ammonium excretion can increase ____ fold, but it takes ___ days to reach maximum

Answer 33

5-10; | 3-5

Question 34

reabsorption of bicarb happens at...

Answer 34

proximal tubule

Question 35

the best place to reabsorb large amounts of solute is at...

Answer 35

proximal tubule

Question 36

main proximal tubule Na transporter

Answer 36

Na-H exchanger (NHE3)

Question 37

for every 1 H+ secreted, ___ bicarb is reabsorbed

Answer 37

1

Question 38

What is the drive for excreting H+ at the proximal tubule?

Answer 38

Na-K ATPase keeps intracellular Na+ low, so NHE3 pumps Na+ into cell in exchange for H+ into lumen

Question 39

Difference in mechanism between bicarb reabsorption & regeneration?

Answer 39

regeneration: CO2 is from capillary reabsorption: CO2 is from lumen

Question 40

most common acid-base disorder is...

Answer 40

metabolic acidosis

Question 41

3 ways which metabolic acidosis can occur

Answer 41

1. addition of an acid not normally present 2. kidney can't secrete ammonium 3. loss of bicarb through diarrhea

Question 42

Which acids cause metabolic acidosis?

Answer 42

- lactic acid - diabetic ketoacidosis - methanol poisoning (formic acid) - ethylene glycol poisoning (antifreeze) - salicylate poisoning (aspirin)

Question 43

excess lactic acid may be the result of...

Answer 43

anaerobic glycolysis - exercise - shock (tissue not oxygenated) - liver failure (removes lactate)

Question 44

formic acid can't be metabolized to...

Answer 44

CO2 and H2O

Question 45

ethylene glycol is very dangerous because...

Answer 45

it forms poisonous metabolites

Question 46

Why does lactic acidosis happen when there is not enough oxygen?

Answer 46

- build up of pyruvate - increased glycolysis to supply ATP - increase in NADH that want to be used up (minor effect)

Question 47

Why might cardiac shock result in anaerobic respiration?

Answer 47

not enough O pumped by heart

Question 48

causes of lactic acidosis

Answer 48

- low CO (shock) - hypoxemia - severe anemia - exercise - drugs that interfere w/ mitochondrial action - liver failure

Question 49

site of lactate metabolism

Answer 49

liver

Question 50

what happens if there is no respiratory compensation for metabolic acidosis / alkalosis?

Answer 50

then there is also respiratory acidosis / alkalosis

Question 51

If toxic alcohols are present in blood stream, how do we cure it?

Answer 51

hemodialysis (has to be early enough)

Question 52

main role of kidney in acid-base balance

Answer 52

maintain normal blood bicarbonate

Question 53

kidney excretes ___ in order to make new bicarb lost to buffering

Answer 53

ammonium

Question 54

the body responds to acid load by...

Answer 54

- buffer with bicarb (rapid) - hyperventilating to lower pCO2 (rapid) - excrete more ammonium (slow)