PSL301: Water 7 Flashcards Preview

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Flashcards in PSL301: Water 7 Deck (54):
1

Acid can ___ H+

donate

2

Base can ___ H+

accept

3

conversion between pH and [H]

pH = -log[H]

[H] = 10^(-pH)

4

normal pH in blood

7.4
(7.35 - 7.45 range)

5

most acidic part of body

stomach (1.5 pH)

6

most basic part of body fluid

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

7

effect of diet on pH

protein - acidic
- sulfur-containing AA are metabolized to H2SO4

8

sulfur containing AA

- cysteine
- methionine

9

1 Met or 1 Cys generates ___ H2SO4

1 mol

10

what prevents severe acidosis when we eat proteins?

buffers

11

BUFFERS

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

12

Buffers found in humans

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

13

the bicarbonate buffer system is catalyzed by...

carbonic anhydrase (CA)

14

Why is the bicarb system so good?

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

15

Kidney has 2 effects on bicarb

1. make new bicarb
2. reabsorb filtered bicarb

16

New bicarb is generated by excretion of...

H+, buffered by ammonia or phosphate
- NH4+
- H2PO4

17

How does kidney make new bicarb?

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

18

Where does the phosphate we use to buffer come from?

- filtered from plasma
- diet

19

Mechanism of ammonia buffer system, from start to finish

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

20

What is the more important urinary buffer? Why?

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

21

ammonium is a weak ___

acid

22

___ freely diffuses across cell membranes & blood vessels

ammonia

23

___ does not readily cross cell membranes

ammonium

24

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

ammonium

25

How does ammonia buffer H+?

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

26

ammonia is synthesized by the...

proximal tubular cells from Glutamine

27

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

1

28

How is H+ secreted by the CD?

H+-ATPase

29

Which AA makes ammonia?

glutamine

30

What regulates ammonium excretion?

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

31

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

cell receptors;
normalize pH

32

When is ammonium excretion increased?

- metabolic & respiratory acidosis
- higher protein intake

33

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

5-10;
3-5

34

reabsorption of bicarb happens at...

proximal tubule

35

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

proximal tubule

36

main proximal tubule Na transporter

Na-H exchanger (NHE3)

37

for every 1 H+ secreted, ___ bicarb is reabsorbed

1

38

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

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

39

Difference in mechanism between bicarb reabsorption & regeneration?

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

40

most common acid-base disorder is...

metabolic acidosis

41

3 ways which metabolic acidosis can occur

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

42

Which acids cause metabolic acidosis?

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

43

excess lactic acid may be the result of...

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

44

formic acid can't be metabolized to...

CO2 and H2O

45

ethylene glycol is very dangerous because...

it forms poisonous metabolites

46

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

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

47

Why might cardiac shock result in anaerobic respiration?

not enough O pumped by heart

48

causes of lactic acidosis

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

49

site of lactate metabolism

liver

50

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

then there is also respiratory acidosis / alkalosis

51

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

hemodialysis (has to be early enough)

52

main role of kidney in acid-base balance

maintain normal blood bicarbonate

53

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

ammonium

54

the body responds to acid load by...

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