Acid/Base Balance & Anion Gap

Question 1

What is the relationship between acid strength and its conjugate base?

Answer 1

A strong acid has a weak conjugate base; a weak acid has a strong conjugate base.

Question 2

What are the three main buffer systems in the body?

Answer 2

Bicarbonate (HCO₃⁻), phosphate (HPO₄²⁻), and proteins (especially hemoglobin).

Question 3

What is the isohydric principle?

Answer 3

Multiple buffer systems act on the same pool of protons, making buffering more effective than any single buffer alone.

Question 4

Why is bicarbonate an effective buffer despite a pKa of 6.1?

Answer 4

It’s present in high concentrations and is supported by respiratory and renal compensation.

Question 5

What is the pKa of the bicarbonate buffer system?

Answer 5

6.1

Question 6

Which protein plays a dominant role in intracellular buffering?

Answer 6

Hemoglobin (inside red blood cells)

Question 7

What does a steeper buffer line on a nomogram indicate?

Answer 7

Better buffering capacity — more bicarbonate change for a given pH shift.

Question 8

What causes a flatter buffer line?

Answer 8

Low protein (e.g., low hemoglobin) → weaker buffering and greater pH changes.

Question 9

Why is hemoglobin more important than albumin in acid-base buffering?

Answer 9

Hemoglobin is much more abundant in blood and exists in high concentrations inside RBCs.

Question 10

What causes acute respiratory acidosis?

Answer 10

Sudden drop in ventilation → ↑CO₂ → ↓pH

Question 11

How do kidneys compensate for chronic respiratory acidosis?

Answer 11

Increase bicarbonate reabsorption and acid excretion.

Question 12

What causes respiratory alkalosis?

Answer 12

Overventilation → ↓CO₂ → ↑pH

Question 13

What limits compensation for respiratory alkalosis?

Answer 13

Hypoxemia risk from reduced ventilation.

Question 14

What are causes of metabolic acidosis with ↑ anion gap?

Answer 14

MUDPILES: Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates.

Question 15

What are causes of metabolic acidosis with normal anion gap?

Answer 15

Diarrhea, pancreatic fistula, renal tubular acidosis.

Question 16

5 conditions listed

What are causes of metabolic alkalosis?

Answer 16

Vomiting, gastric fistula, diuretics, aldosterone excess, excessive antacids/bicarb.

Question 17

How does the body respond to metabolic acidosis?

Answer 17

Hyperventilation (↓CO₂) via brainstem chemoreceptors.

Question 18

How is the anion gap calculated?

Answer 18

Na⁺ - (Cl⁻ + HCO₃⁻)

Question 19

What is a normal anion gap?

Answer 19

~12 ± 4 mEq/L

Question 20

What does an increased anion gap suggest?

Answer 20

Presence of unmeasured anions (e.g., lactate, ketones, toxins).

Question 21

What does a normal anion gap acidosis suggest?

Answer 21

Bicarbonate loss replaced by chloride (e.g., diarrhea).

Question 22

What are the most common unmeasured anions?

Answer 22

Albumin, phosphate, sulfate, organic acids.

Question 23

How do kidneys compensate for acidosis?

Answer 23

Secrete H⁺ and generate/reabsorb HCO₃⁻.

Question 24

What limits respiratory compensation for metabolic alkalosis?

Answer 24

Hypoxemia risk if ventilation is reduced too much.

Question 25

How quickly does the respiratory system begin compensating for metabolic disorders?

Answer 25

Within seconds to minutes (textbook: 3 minutes).

Question 26

How quickly does the kidney compensate for respiratory acid-base disturbances?

Answer 26

Hours to days.

Question 27

What are common causes of respiratory acidosis?

Answer 27

CNS depression (opioids, anesthetics), COPD, neuromuscular disorders.

Question 28

# 5 conditions listed What are some conditions that can lead to respiratory alkalosis?

Answer 28

Anxiety, pregnancy (progesterone), high altitude, early sepsis, aspirin toxicity.

Question 29

What toxins increase the anion gap?

Answer 29

Methanol, ethylene glycol, salicylates.

Question 30

What is the effect of ethylene glycol ingestion?

Answer 30

High anion gap metabolic acidosis.

Question 31

Why are children more vulnerable to acid-base disturbances?

Answer 31

Immature kidneys and poor compensatory reserve.

Question 32

What is the normal arterial pH range in humans?

Answer 32

7.35–7.45 (with 7.4 being the average baseline)

Question 33

What determines the acidity of a body fluid?

Answer 33

The concentration of free hydrogen ions (H⁺), also referred to as proton activity.

Question 34

What is a volatile acid and what is the main one in the body?

Answer 34

A volatile acid can transition to the gas phase; CO₂ is the primary volatile acid.

Question 35

How is CO₂ related to acid production in the body?

Answer 35

CO₂ combines with water to form carbonic acid (H₂CO₃), a weak acid that can dissociate into H⁺ and HCO₃⁻.

Question 36

What happens when a strong acid dissociates?

Answer 36

It fully separates into H⁺ and a weak conjugate base (e.g., HCl → H⁺ + Cl⁻).

Question 37

What happens when a weak acid dissociates?

Answer 37

It only partially dissociates and produces a stronger conjugate base (e.g., H₂CO₃ → H⁺ + HCO₃⁻).

Question 38

What is the significance of bicarbonate (HCO₃⁻) in acid-base physiology?

Answer 38

It is the conjugate base of carbonic acid and serves as a major buffer in the extracellular fluid.

Question 39

What is the formula for calculating pH?

Answer 39

pH = –log[H⁺]

Question 40

How does a change of 1 in pH affect [H⁺]?

Answer 40

It changes [H⁺] by a factor of 10 (logarithmic scale).

Question 41

What is the [H⁺] concentration at pH 7.4?

Answer 41

Approximately 40 nanomoles/L

Question 42

What happens to [H⁺] at pH 7.7?

Answer 42

It decreases to about 20 nanomoles/L (cut in half)

Question 43

What pH values are considered incompatible with life?

Answer 43

Below 6.9 or above 7.8

Question 44

What are the 3 primary buffer systems in the body?

Answer 44

Bicarbonate, proteins (especially hemoglobin), and phosphate.

Question 45

Why is hemoglobin a good buffer?

Answer 45

It is abundant and can bind or release H⁺ depending on tissue needs (Bohr effect).

Question 46

How do proteins act as buffers?

Answer 46

They bind excess H⁺ ions, reducing proton activity and stabilizing pH.

Question 47

What happens to buffer effectiveness with low protein levels?

Answer 47

Buffering capacity decreases, especially for bicarbonate.

Question 48

How do the lungs help regulate pH?

Answer 48

By excreting or retaining CO₂, which alters the H⁺ concentration.

Question 49

What happens in respiratory acidosis?

Answer 49

CO₂ retention → ↑H⁺ → ↓pH (e.g., CNS depression, COPD)

Question 50

What happens in respiratory alkalosis?

Answer 50

CO₂ loss → ↓H⁺ → ↑pH (e.g., anxiety, pain, high altitude)

Question 51

What is the renal compensation for respiratory acidosis?

Answer 51

Increased HCO₃⁻ reabsorption and H⁺ excretion (over time)

Question 52

Name some common non-volatile acids.

Answer 52

Lactic acid, sulfuric acid, phosphoric acid, hydrochloric acid.

Question 53

What are some abnormal acids produced in disease states?

Answer 53

Acetoacetic acid (ketoacidosis), butyric acid (poorly controlled diabetes or alcoholism).

Question 54

How are non-volatile acids removed from the body?

Answer 54

Primarily through the kidneys (some are modified in the liver).

Question 55

Why is pH important for drug action?

Answer 55

pH affects drug ionization, absorption, and receptor binding.

Question 56

What can happen to a drug’s efficacy in a low-pH (acidotic) environment?

Answer 56

Reduced efficacy due to altered dissociation and impaired protein binding.

Question 57

Why are many IV drugs packaged as hydrochloride salts?

Answer 57

To improve solubility and absorption by modulating pH.

Question 58

How does acidosis affect the sodium-potassium pump?

Answer 58

Protons bind to the pump protein, disrupting its structure and slowing function.

Question 59

What does acidosis do to intracellular K⁺ levels?

Answer 59

Causes potassium to leak out of cells → hyperkalemia.

Question 60

How does acidosis affect ATP production?

Answer 60

Proton overload disrupts mitochondrial enzymes → ↓ ATP synthesis.