Chemistry for Physiology

The number of atoms immediately follows the symbol for the element as a subscript. A number following a parenthesis multiplies the atoms inside the parenthesis. Hence there are six atoms of carbon (including two inside the parenthesis). By the same reasoning, there are 13 atoms of hydrogen (including 6 inside the parenthesis). An amino acid always has an atom of nitrogen.

Dissolved ions must be present for electrical conduction to occur.

The number of moles of a substance is determined by dividing the mass of substance by the mass of 1 mol of substance. One mole of sodium has a mass of 23 g: 140 mmol/L = 0.140 mol/L = mass of Na dissolved in 1 L (in gram) ÷ 23. Hence mass of Na = 23 × 0.14 = 3.22 g/L

A carbohydrate is composed of carbon, hydrogen and oxygen atoms. Usually there are twice as many H atoms as C atoms. Choice D, having relatively few O atoms, is typical of a lipid.

Osmosis involves water molecules (not solutes) moving down their concentration gradient into a solution of lower concentration of water molecules.

Choice A is an enzyme (“-ase”), B is a hormone and C is a monosaccharide.

An electron so far is immeasurably small, while a molecule must have at least two atoms, and the proton is a subatomic particle.

A buffer must destroy acid, by accepting a hydrogen atom from a hydronium ion and thus converting it to water. This means that monohydrogen phosphate must appear on the left of the arrow and dihydrogen phosphate on the right. So choices B and D are wrong. There must be equal numbers of H atoms (4) on each side of the arrow, but choice B has 5H on one side and 3H on the other.

7.4 is in the healthy range for blood. Being greater than 7.0 indicates alkaline.

As both atoms are non-metals, the bonding is covalent. As the atoms differ in their attraction for the bonding electrons, the bond is polar (the electrons are more closely attracted to O).