Acid Base Physiology

Question 1

What are the 3 main components that regulate H+ in the body?

Answer 1

Buffers- bicarbonate, proteins, phosphates, etc

Respiratory compensation- alters CO2 leverls

Renal compensation-alters HCO3- levels

Question 2

Can buffers correct pH?

Answer 2

No, they can “blunt” changes to pH

Question 3

Which faster: respiratory compensation or metabolic compensation

Answer 3

Respiratory

Question 4

What is the normal plasma concentration of H+

Answer 4

40nEq/L

4x10-8 moles

Question 5

What is the normal blood pH range?

Answer 5

7.35-7.45

Question 6

What is normal blood pH?

Answer 6

7.4

MUST memorize

Question 7

What is “volatile” acid?

Answer 7

CO2 that is produced in the lungs.

THIS IS THE ONLY VOLATILE ACID IN OUR BODY IF YOU SEE IT ON AN EXAM IT’S CO2

Question 8

What are non-volatile or fixed acids?

Answer 8

Acids that arise from normal and abnormal processes:

• degradation of amino acids
• lactic acid
• ketones in DKA

Etc

Question 9

We produce ______mEq/day of fixed acid

Answer 9

50mEq

Due to gluconeogenic utilization of AA’s in the liver,

Sulfuric acid from methionine etc

Question 10

What is the Henderson-hasselbalch equation?

Answer 10

pH=pK + log [A-]/[HA]

Question 11

When [A-]=[HA], then what is the pH

Answer 11

pH=pK

Think about it if [a]/[ha] =1, and you take the log of 1, you get 0

Question 12

What are strong acids?

Answer 12

Have lower affinities for hydrogen ions which easily dissociate from the conjugate base and have LOW pKs

Question 13

What are weak acids?

Answer 13

Acids that have higher affinities for H+ and do not dissociate as easily from the conjugate base. Have HIGHER pKs

Question 14

Where are buffers located?

Answer 14

ECF, ICF, bone

Question 15

What is our first line defense against pH changes?

Answer 15

Buffers

Question 16

What is the most important buffer in the ECF?

Answer 16

Bicarbonate

Due to its high concentration

Question 17

What 2 things contribute to a buffer’s effectiveness?

Answer 17

Its concentration

Its pK

Question 18

Buffers consist of a pair of:

Answer 18

Acid and conjugate base

HA/A-

Question 19

At low pHs, which will be higher: [HA] or [A-]

Answer 19

[HA]

Question 20

At high pHs, which will be higher: [HA] or [A-]

Answer 20

[A-]

Question 21

At what pHs are buffers most effective

Answer 21

+/- one pH unit from their pK

Question 22

What is the acid/conjugate base pair for the bicarbonate buffer system?

Answer 22

HCO3-/H2CO3

Question 23

What is the acid/conjugate base pair for the phosphate buffer system?

Answer 23

HPO42-/H2PO4-

Question 24

At a pH of 7.4, which will be a better buffer:

Phosphate: pK 6.8

Bicarbonate: pK 6.1

Answer 24

Technically phosphate would be a better buffer since its pK is closer to 7.4, but bicarbonate is more important in the blood

Question 25

What are the 4 buffers in the blood?

Answer 25

1. Bicarbonate (53% of total buffering capacity) 2. Hemoglobin (35%) 3. Proteins (7%) 4. Phosphate (5%)

Question 26

How does hemoglobin act as a buffer?

Answer 26

Imidaizole groups on histidine and α amino groups are the primary buffer sites on ALL proteins

Question 27

Why is phosphate unimportant in blood?

Answer 27

It is at a low concentration

Question 28

What are the 3 intracellular buffers?

Answer 28

Proteins- high conc, pK close to 7.4 Phosphate-same as proteins Bicarb (less important because concentration is low)

Question 29

How does bone act like an intracellular buffer?

Answer 29

It takes up H+ in exchange for Na+ and K+ May account for a significant amount of buffering capacity during acute acid load

Question 30

What is the normal range for pCO2?

Answer 30

35-45

Question 31

What is the normal range for HCO3-?

Answer 31

22-26

Question 32

Why do we use CO2 to calculate pH if the the equation uses log[A-]/[HA]

Answer 32

Because CO2 drives the formation of H2CO3 [HCO3] pH= pK + log ____________ .03(CO2) Can you see how that is [A-]/[HA]

Question 33

Lungs and kidneys regulate CO2 and HCO3 so that the [HCO3]/[CO2] remains near________

Answer 33

20

Question 34

Can the kidneys AND the lungs compensate for metabolic disturbances (changes in [HCO3])?

Answer 34

Yes, but NOT if the kidneys caused the metabolic defect in the first place

Question 35

What organ must compensate for respiratory disturbances?

Answer 35

Kidneys only Compensation takes days

Question 36

If you go into metabolic acidosis by eating acid or through the formation of metabolic acids, what will happen?

Answer 36

1. Plasma HCO3 decreases when you eat acid(causes the acidosis) 2. Respiratory system responds by increasing ventilation to expel CO2 3. Kidneys synthesize new HCO3

Question 37

What can cause respiratory acidosis?

Answer 37

Decreased ventilation (drug overdose, airway obstruction)

Question 38

How will the kidneys respond to respiratory acidosis?

Answer 38

They will synthesize new HCO3 and excrete H+

Question 39

What can cause respiratory alkalosis?

Answer 39

Hyperventilation (stress, high altitude, etc)

Question 40

How will the kidneys respond to respiratory alkalosis?

Answer 40

They will excrete HCO3 causing the urine to become alkaline, while the blood pH will decrease

Question 41

How do you calculate pH using HCO3 and PCO2?

Answer 41

[HCO3] pH= pK + log ___________ (0.3)(PCO2)