BIO 202L Lab 15 Worksheet Electrolytes Water Acid & Bases
Actual Exam 2026/2027 – Complete 30 Questions with
Detailed Rationales | 100% Verified | Pass Guaranteed – A+
Graded
SECTION A: Water Balance & Compartmental Distribution (Q1–Q6)
Q1: Which body fluid compartment contains the largest volume of water in a healthy
adult male?
A. Plasma (approximately 3 L)
B. Interstitial fluid (approximately 11 L)
C. Intracellular fluid (approximately 25 L — about two-thirds of total body water)
[CORRECT]
D. Extracellular fluid as a whole (approximately 14 L)
Correct Answer: C
Rationale: The intracellular compartment holds roughly two-thirds (≈25 L of 40 L) of
total body water, making it the largest single compartment. Interstitial fluid is the largest
ECF subdivision but is far smaller than the ICF, and plasma is only ~3 L.
Q2: A marathon runner loses 2 L of hypotonic sweat during a race without drinking.
What osmotic shift occurs in her body as a result?
A. Water moves from the ECF into the cells, causing them to swell
B. Water shifts from the intracellular compartment into the ECF by osmosis, causing
cellular shrinkage [CORRECT]
C. Water remains evenly distributed because total volume is unchanged
D. Sodium actively pumps water into the plasma compartment
Correct Answer: B
Rationale: Losing hypotonic fluid raises ECF osmolarity, so water leaves cells by
osmosis, shrinking them — which also drives thirst and ADH release. Option A reverses
the direction of flow (that occurs with hyponatremia), and the osmotic gradient
guarantees redistribution despite any total-volume change.
Q3: Which statement about antidiuretic hormone (ADH) is correct?
A. ADH is synthesized in hypothalamic neurons, released by the posterior pituitary, and
increases water reabsorption by inserting aquaporins in the collecting ducts [CORRECT]
, B. ADH is produced by adrenal cortex cells and promotes sodium excretion
C. ADH acts on the proximal tubule to reabsorb glucose and sodium
D. ADH secretion decreases whenever plasma osmolarity rises above 300 mOsm
Correct Answer: A
Rationale: ADH is made in the supraoptic/paraventricular nuclei, stored in the posterior
pituitary, and makes collecting ducts water-permeable to concentrate urine. ADH is not
adrenal in origin, does not act on proximal glucose handling, and its secretion increases
— not decreases — with rising osmolarity.
Q4: A patient with advanced cirrhosis has a serum albumin of 2.1 g/dL and develops
significant pitting edema of the ankles and abdomen. Which mechanism best explains
this fluid accumulation?
A. Increased capillary hydrostatic pressure from venous obstruction
B. Obstruction of lymphatic drainage trapping fluid in the interstitium
C. Increased plasma sodium concentration pulling fluid into vessels
D. Decreased plasma colloid osmotic (oncotic) pressure, allowing fluid to filter into the
interstitial space [CORRECT]
Correct Answer: D
Rationale: Albumin normally holds water in the plasma; hypoalbuminemia lowers
oncotic pressure, so capillary filtration exceeds reabsorption and edema develops.
Hydrostatic pressure and lymph obstruction are alternative edema mechanisms not
present here, and sodium concentration does not correct a protein deficit.
Q5: A hospitalized adult's 24-hour intake/output record shows: intake — oral 1,400 mL +
IV fluids 1,200 mL (total 2,600 mL); output — urine 1,500 mL, insensible losses (skin and
lungs) 900 mL, feces 100 mL. What is this patient's net fluid balance?
A. A negative balance of −100 mL
B. A positive balance of +100 mL [CORRECT]
C. A positive balance of +500 mL
D. A perfectly balanced net of 0 mL
Correct Answer: B
Rationale: Total output = 1,500 + 900 + 100 = 2,500 mL; net balance = 2,600 − 2,500 =
+100 mL (slight positive). Option A reverses the sign, C ignores the actual output total,
and 0 mL would require output equal to intake.
Q6: A patient hiking in hot weather has not drunk water for several hours, and his
plasma osmolarity rises to 305 mOsm/kg. Which physiologic response is triggered
FIRST to restore water balance?
A. Aldosterone secretion by the adrenal cortex
B. Release of atrial natriuretic peptide from the heart
Actual Exam 2026/2027 – Complete 30 Questions with
Detailed Rationales | 100% Verified | Pass Guaranteed – A+
Graded
SECTION A: Water Balance & Compartmental Distribution (Q1–Q6)
Q1: Which body fluid compartment contains the largest volume of water in a healthy
adult male?
A. Plasma (approximately 3 L)
B. Interstitial fluid (approximately 11 L)
C. Intracellular fluid (approximately 25 L — about two-thirds of total body water)
[CORRECT]
D. Extracellular fluid as a whole (approximately 14 L)
Correct Answer: C
Rationale: The intracellular compartment holds roughly two-thirds (≈25 L of 40 L) of
total body water, making it the largest single compartment. Interstitial fluid is the largest
ECF subdivision but is far smaller than the ICF, and plasma is only ~3 L.
Q2: A marathon runner loses 2 L of hypotonic sweat during a race without drinking.
What osmotic shift occurs in her body as a result?
A. Water moves from the ECF into the cells, causing them to swell
B. Water shifts from the intracellular compartment into the ECF by osmosis, causing
cellular shrinkage [CORRECT]
C. Water remains evenly distributed because total volume is unchanged
D. Sodium actively pumps water into the plasma compartment
Correct Answer: B
Rationale: Losing hypotonic fluid raises ECF osmolarity, so water leaves cells by
osmosis, shrinking them — which also drives thirst and ADH release. Option A reverses
the direction of flow (that occurs with hyponatremia), and the osmotic gradient
guarantees redistribution despite any total-volume change.
Q3: Which statement about antidiuretic hormone (ADH) is correct?
A. ADH is synthesized in hypothalamic neurons, released by the posterior pituitary, and
increases water reabsorption by inserting aquaporins in the collecting ducts [CORRECT]
, B. ADH is produced by adrenal cortex cells and promotes sodium excretion
C. ADH acts on the proximal tubule to reabsorb glucose and sodium
D. ADH secretion decreases whenever plasma osmolarity rises above 300 mOsm
Correct Answer: A
Rationale: ADH is made in the supraoptic/paraventricular nuclei, stored in the posterior
pituitary, and makes collecting ducts water-permeable to concentrate urine. ADH is not
adrenal in origin, does not act on proximal glucose handling, and its secretion increases
— not decreases — with rising osmolarity.
Q4: A patient with advanced cirrhosis has a serum albumin of 2.1 g/dL and develops
significant pitting edema of the ankles and abdomen. Which mechanism best explains
this fluid accumulation?
A. Increased capillary hydrostatic pressure from venous obstruction
B. Obstruction of lymphatic drainage trapping fluid in the interstitium
C. Increased plasma sodium concentration pulling fluid into vessels
D. Decreased plasma colloid osmotic (oncotic) pressure, allowing fluid to filter into the
interstitial space [CORRECT]
Correct Answer: D
Rationale: Albumin normally holds water in the plasma; hypoalbuminemia lowers
oncotic pressure, so capillary filtration exceeds reabsorption and edema develops.
Hydrostatic pressure and lymph obstruction are alternative edema mechanisms not
present here, and sodium concentration does not correct a protein deficit.
Q5: A hospitalized adult's 24-hour intake/output record shows: intake — oral 1,400 mL +
IV fluids 1,200 mL (total 2,600 mL); output — urine 1,500 mL, insensible losses (skin and
lungs) 900 mL, feces 100 mL. What is this patient's net fluid balance?
A. A negative balance of −100 mL
B. A positive balance of +100 mL [CORRECT]
C. A positive balance of +500 mL
D. A perfectly balanced net of 0 mL
Correct Answer: B
Rationale: Total output = 1,500 + 900 + 100 = 2,500 mL; net balance = 2,600 − 2,500 =
+100 mL (slight positive). Option A reverses the sign, C ignores the actual output total,
and 0 mL would require output equal to intake.
Q6: A patient hiking in hot weather has not drunk water for several hours, and his
plasma osmolarity rises to 305 mOsm/kg. Which physiologic response is triggered
FIRST to restore water balance?
A. Aldosterone secretion by the adrenal cortex
B. Release of atrial natriuretic peptide from the heart
