What is Mineral matter and organic matter? — Biology

Definition 1.5 High School Biology · Chapter 1 — The Chemical Makeup of Living Things

The molecules of a living thing fall into two groups. Mineral matter is made of molecules that also exist outside living things: water and the dissolved mineral salts (ions such as $\mathrm{Na^+}$ , $\mathrm{K^+}$ , $\mathrm{Ca^{2+}}$ , $\mathrm{Cl^-}$ , phosphate and bicarbonate). Organic matter is made of molecules built on a skeleton of carbon atoms bonded to hydrogen, and usually to oxygen and nitrogen — molecules that, on Earth, are made only by living things or from their remains.

A fresh apple slice and the same slice after drying: what remains is the dry matter, a sixth of the original mass. The rest was water.

Examples

Example 1.7 (Drying an apple slice)

A slice of fresh apple of mass $24.0\,\mathrm{g}$ is dried until its mass settles at $3.6\,\mathrm{g}$ . Water lost: $24.0 - 3.6 = 20.4\,\mathrm{g}$ , i.e. $20.4/24.0 = 0.85$ , or 85% of the fresh mass. The $3.6\,\mathrm{g}$ that remain are the dry matter: organic molecules plus mineral salts. Burn that dry matter and about $0.1\,\mathrm{g}$ of pale ash — the mineral salts — survives; the rest, the organic part, has left as carbon dioxide and water vapour.

Example 1.9 (Mineral salts you can name)

Calcium phosphate stiffens bone and teeth (calcium is 1.5% of body mass, almost all in the skeleton). Sodium and chloride ions set the salinity of blood, close to $9\,\mathrm{g}/\mathrm{L}$ ; potassium ions are concentrated inside cells; iron sits at the heart of haemoglobin; iodine is needed to make the hormone of the thyroid gland. A mineral salt is never a source of energy, but a body deprived of one of them fails at a precise task.

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