pH = -log[H+] 10 fold increase in [H+] = 1 unit change in pH

Lect 9 Flashcards by Alex Steinmann

What are the three main components of the homeostatic mechanisms that regulate [H+] in the body

buffers: bicarb, phosphates, etc
respiratory compensation: alters CO2 levels
renal compensation: alters HCO3- levels

How well did you know this?

Not at all

Perfectly

what is the plasma concentration of H+

40 nEq/L

How well did you know this?

Not at all

Perfectly

equation for pH

pH = -log[H+]

10 fold increase in [H+] = 1 unit change in pH

How well did you know this?

Not at all

Perfectly

normal blood pH level

7.4
normal range: 7.37-7.42

How well did you know this?

Not at all

Perfectly

what is volatile acid

source of H+ that is produced from respiratory CO2 and handled by the lungs

How well did you know this?

Not at all

Perfectly

what are some examples of non-volatile or fixed acid (50 mEq/day)

degradation of certain amino acids
- sulfuric acid from methionin and cysteine
- phosphoric acid from phospholipid
exercise (lactate)
diabetic ketosis
ingestion of acids

**acid load that kidney must eliminate

How well did you know this?

Not at all

Perfectly

differentiate between acid and base in terms of donor and acceptor

acid: H+ donor
base: H+ acceptor

How well did you know this?

Not at all

Perfectly

in HA <-> H+ + A-, which is the conjugate base

A-
The conjugate base of an acid is formed when the acid donates a proton

How well did you know this?

Not at all

Perfectly

with this equation in mind HA <-> H+ + A-, how can it be rearranged to make a constant

K = [A-][H+] / [HA]

How well did you know this?

Not at all

Perfectly

what is the henderson-hasselbalch equation

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

How well did you know this?

Not at all

Perfectly

with this equation in mind pH = pK + log ([A-] / [HA]), when does pH = pK?

when [A-] = [HA]

How well did you know this?

Not at all

Perfectly

describe strong acids. do they have a lower or higher pK?

lower affinities for hydrogen ions -> will dissociate easily from conjugate base
lower pKs

How well did you know this?

Not at all

Perfectly

describe weak acids. do they have a lower or higher pK?

have higher affinities for hydrogen ions -> will not dissociate easily from conjugate base
higher pKs

How well did you know this?

Not at all

Perfectly

buffers are the first line of defense against pH changes. effectiveness of a buffer is proportional to?

its concentration
its pK

How well did you know this?

Not at all

Perfectly

what is the most important buffer system in the ECF?

bicarbonate buffer system
- due to high concetration and both CO2 and HCO3- are tightly regulated
CO₂ + H₂O <-> H₂CO₃ <-> H+ + HCO₃-

How well did you know this?

Not at all

Perfectly

what do buffers consist of

acid and conjugate base pairs

ex: HA/A^-

what are the most effective buffers in terms of pH

most effective buffering is +/- one pH unit from pK

what are the acid/conjugate base pairs form bicarb and phosphate buffer systems

HCO₃-/H₂CO₃
HPO₄^2-/H₂PO₄^-

Bicarbonate accounts for 53% of total buffering capacity. Why is it effective

pK is low (6.1) but effective due to its concentration and because both the acid (H2CO3) and base (HCO3-) are regulated

Hemoglobin accounts for 35% of total buffering capacity. What is the buffer?

Hb ^- + H⁺ <-> HHb
Imidazole groups on histidine and alpha amino groups are the primary buffer sites on all proteins

What are the four buffers in blood

bicarbonate
hemoglobin
proteins (7%): low conc.
phosphate (5%): very important in urine

what are the primary intracellular buffers?

proteins (pK close to 7.4)
phosphate

how can bone act as a buffer

takes up H+ in exchange for Na+ and K+
helps during acute acid load

what are the normal ranges for pH, PCO2, and HCO3-

pH = 7.4
PCO2 = 40 mmHg
HCO3- = 24 mEq/L

what is the equation that determines pH (values inserted for HH equation)

pH = 6.1 + log [HCO3-] / (0.03 x PCO₂)

pH = 6.1 + log [HCO3-] / (0.03 x PCO2); decreased bicarbonate or increased PCO2 will give what state

acidosis

pH = 6.1 + log [HCO3-] / (0.03 x PCO2); increased bicarbonate or decreased PCO2 will give what state

alkalosis

buffers can't return pH to normal, lungs and kidneys regulate CO2 and HCO3- respectively such that the ration of [HCO3-] to dissolved CO2 = X

changes in [HCO3-] are considered metabolic or respiratory disturbances? What organs can compensate?

* loss or gain of HCO3- = metabolic disturbance * compensated for by both kidneys and lungs

which is quicker, metabolic or respiratory compensation?

respiratory

changes in [CO2] are considered metabolic or respiratory disturbances? What organs can compensate?

* respiratory disturbances * must be compensated for by the kidney

what happens in metabolic acidosis

1. plasma HCO3- decreases 2. respiratory system responds by increasing ventilation to expel CO2; kidneys synthesize new HCO3-

what happens in metabolic alkalosis

1. plasma HCO3- increases 2. respiratory system responds by reducing ventilation to retain CO2; kidneys excretes excess HCO3-

what happens in respiratory acidosis

1. plasma PCO2 increases * caused by decreased ventilation (drug overdose, airway obstruction) 2. kidneys will synthesize new HCO3- and excrete H+ in the urine to raise blood pH

what happens in respiratory alkalosis

1. plasma PCO2 decreases * caused by hyperventilation (stress, high altitude) 2. kidneys will excrete HCO3- causing urine to become alkaline; blood HCO3- and pH will decrease