Chemistry for Physiology

The intracellular compartment contains about 27 of the body’s 42 L or so of solution. The next largest is the extracellular with about 15 L. The other two are subsets of the extracellular compartment.

Any hydronium and hydroxide ions present will react with one of the two components of the buffer. So the amount of buffer component (viz. their ratio) governs the concentration of these ions and hence the pH of the solution.

The slightly positive H atom in one molecule is attracted to the adjacent slightly negative O (or N).

2% = 2 g/100 ml = 20 g/L. Mass of 1 mol of Na⁺Cl− = 23 + 35.5 = 58.5 g. Number of moles of Na⁺Cl− required for 1 L of 2% solution = 20 g/58.5 g per mol = 0.34 mol. Sodium chloride is an ionic substance so dissociates into ions when dissolved. This would produce 0.34 mol of Na and 0.34 mol of Cl = 0.68 osmoles of dissolved particles in the 1 L. 0.68 osmol/L = 680 mosmol/L

O symbolises oxygen, element number 16.

Primary structure refers to the order in which amino acids are attached to each other.

Only this choice must be true. The others are just possible.

“Hyper-” refers to greater (tonicity) than inside a RBC. Hence water would move from the less concentrated solution (within the RBC) to the exterior.

The kidneys have the ability to reabsorb and secrete ions and water as required. Aldosterone causes the kidney tubules to reabsorb sodium ions while promoting the secretion of potassium ions.

Choices A and B are both hypertonic. Four percent glucose contains 4/5 of the concentration of dissolved particles that are in (isotonic) 5% glucose. 0.18% sodium chloride contains 1/5 of the concentration of dissolved particles that are in 0.9% sodium chloride (0.18/0.9 = 0.2). One fifth plus four fifths add to five fifths of the number of particles that are required for an isotonic solution.