Lecture 10 - pH

Question 1

Body ….. is tightly regulated

Answer 1

H+

Question 2

What is the normal pH in the body ?

Answer 2

the normal pH in the body is 7.35-7.45

Question 3

What is the extreme range that is compatible with life in regards to pH?

Answer 3

6.8-8.0

Question 4

What are some of the acid inputs?

Answer 4

• CO2 production
• metabolic intermediates
• lactic acid

Question 5

what is a basic input?

Answer 5

-some natural sources

Question 6

What is the most important kind of pH for the body?

Answer 6

the msot important kind of pH for the body is ICF pH/

Question 7

In the assessment for pH what do we use ?

Answer 7

we use the ECF pH to make inferences about the ICF conditions.

Question 8

what is the intracellular pH maintained at and why?

Answer 8

6.8 at 37 degrees celcius because this is the point at which metabolites are all charged and trapped inside the cell.

Question 9

what is extracellular pH usually at and why?

Answer 9

it is usually higher than ICF pH by 0.5 or 0.6 which is about a 4 fold increase which favours a gradient that reults in the exit of H+ from cells.

Question 10

What are the lines of defence when it comes to a stable intracellular pH?

Answer 10

1. ) buffering
2. ) pCO2
3. ) acids removal

Question 11

What is the benefit of buffer systems?

Answer 11

• they are instantaneous

Question 12

what are buffers?

Answer 12

they are solutions which can resist the changes in pH when acid or alkali is added.

Question 13

How much of the buffering capacity is in cells?

Answer 13

52%

Question 14

how much of buffering capacuty is in `RBC?

Answer 14

5 %

Question 15

how much of buffering capacity is in the extracellular space?

Answer 15

43 %

Question 16

What are some kinds of buffers?

Answer 16

1. ) phosphate
2. ) ammonia
3. ) proteins

Question 17

Where is phosphate important as a buffer?

Answer 17

they are important as renal tubular buffers

Question 18

Where is ammonia important as a buffer?

Answer 18

they are important as renal tubular buffers

Question 19

Where are proteins important as a buffer?

Answer 19

they are important intracellular and plasma buffers

Question 20

what is the most important buffer system in the body under normal circumstances?

Answer 20

the most importnat buffer system in the body udner normal circumstances is the bicarbonate buffer system

Question 21

what is the bicarboante buffer system physiollogically regulated by?

Answer 21

• the lungs (PCO2)
• the kidneys (HCO3-)

Question 22

What is the bicarboante buffer system catalysed by?

Answer 22

It is catalysed by carbonic anhydrase

Question 23

Equation for the bicarbonate buffer system?

Answer 23

Question 24

Changes in ……. or …… alter ECF pH

Answer 24

HCO3- or PCO2

Question 25

In relation to acid base regulation what are the two functions of the kidneys?

Answer 25

1. ) reabsorption of HCO3- 2. ) excretion of H+

Question 26

Why is HCO3- reabsorption vital?

Answer 26

it is vital due to large filtered load

Question 27

How is acid excretion and bicarbonate reabsorption achieved?

Answer 27

it is achieved by tubular H+ secretion

Question 28

What are some of the urinary buffers?

Answer 28

phospahte and ammonium

Question 29

How much HCO3 is reabsorbed in the proximal tubule?

Answer 29

80 %

Question 30

How much HCO3 is reabsorbed in the thick ascending limb of the loop of henle?

Answer 30

5 %

Question 31

How much HCO3 is reabsorbed in the distal tubule?

Answer 31

5 %

Question 32

Reabsorption is ......

Answer 32

transcellular

Question 33

Reabsorption involves ... secretion

Answer 33

H+

Question 34

What are the steps for reabsorption of HCO3 in the proximal tubule?

Answer 34

1. powered by the Na+ gradient 2. Apical H+ secretion by the Na-H-antiporter 3. secreted H+ binds to filtered HCO3- 4. Complex dissociates to CO2 and H2O 5. CO2 and H2O reassociate inside of cell 6. Reformed HCO3- transported into interstitium

Question 35

What are the steps for reabnsorption of HCO3 in the distal tubule?

Answer 35

1. not powered by the Na+ gradient 2. powered by apical H+ pumps - K-H-ATPase and H-ATPase 3. Secreted H+ binds to filtered HCO3 4. Complex dissociates to CO2 and H2O 5. CO2 and H2O re associate inside cell 6. Reformed HCO3 transported into interstitium

Question 36

What are the steps for H+ secretion and phosphate in the distal tubule?

Answer 36

1. Secreted H+ binds to the phosphate and is not filtered as HCO3 2. Bound H+ is excreted in the urine 3. H+ secretion results in HCO3 formation inside the tubular cell 4. the new HCO3 is transported into the interstitium

Question 37

Explain the steps of H+ secretion with ammonium?

Answer 37

1. ammonium NH4 is produced by H binding to ammonia NH3 2. The proximal tubule creates ammonia only if it is needed, when we need to get rid of acid 3. NH3 and HCO3 are produced from the amino acid glutamine 4. the new HCO3 is transported into the interstitium 5. NH3 diffused into tubular lumen and binds to a secreted H+

Question 39

acidosis, metabolic vs respiratory ?

Answer 39

1. metabolic - decreased HCO3 2. respiratory - increased pCO2

Question 40

alkalosis, metabolic vs respiratory ?

Answer 40

1. metabolic - increased HCO3 2. respiratory - decreased PCO2

Question 41

How does the kidney comopensate for acidosis?

Answer 41

intercalated cells will secrete more acid into the tubular lumen and make new bicarbonate and raise the pH back to its set point

Question 42

How does the kidney compensate for alkalosis?

Answer 42

proximal convoluted cells will not reabsorb filtered bicarbonate and will elimante it formt he body to lower the pH back to the normal.