Foundations — Vitamins — fat-soluble (A, D, E, K) vs water-soluble (B-complex, C)

Before you can read the parent note Vitamins, you need a small toolbox. This page builds every word and symbol it quietly assumes, from absolute zero. Nothing here is memorisation — each tool is earned with a picture and a reason.

1. Molecule — the thing everything is made of

The picture: think of atoms as coloured beads and bonds as short springs joining them. A vitamin molecule is one particular bead-and-spring shape. Change the shape and you change the vitamin.

Why the topic needs it: every vitamin is a molecule, and its shape — long oily tail vs small watery cluster — is what makes it fat- or water-soluble. If you don't picture molecules, "solubility" is just a word.

Related building blocks in the vault: Biomolecules, Carbohydrates, Lipids.

2. Chemical formula & the symbols in it

So ${\text{H}}_2\text{O}$ reads as two hydrogens and one oxygen (no subscript = one). You'll meet groups written the same way:

Why the topic needs it: the parent note claims the B vitamins are water-soluble because they carry lots of these groups. To believe that, you must first read the groups. Coming up next: why these particular groups love water.

3. Polar vs non-polar — the master concept

This is the single most important idea on the whole page, so we build it slowly with a figure.

The Greek letter $\delta$ (delta) just means "a little bit of", so $\delta +$ reads "a little bit positive."

Read the figure: on the left, water has a red (minus) oxygen end and blue (plus) hydrogen ends — clearly two-sided, so polar. On the right, a long chain of carbons and hydrogens shares evenly — no coloured ends — so non-polar and "oily."

Why the topic needs it: "fat-soluble" means non-polar; "water-soluble" means polar. Every consequence in the parent note starts here. The polar groups from section 2 ($-\text{OH}$ etc.) are exactly the parts that make a molecule polar.

4. Solubility & "like dissolves like"

The picture: polar molecules cling to other polar molecules because their plus-ends stick to minus-ends (little magnets snapping together). Non-polar molecules have no ends to grab water, so they huddle among themselves — that's why oil and water separate into layers.

Read the figure: water and oil refuse to mix (two layers). A polar vitamin joins the water layer; a non-polar vitamin joins the oil layer. This one picture is the classification of vitamins.

Why the topic needs it: see Solubility — like dissolves like. This rule converts molecule shape → where the vitamin goes in the body. Fat-soluble → into fat stores; water-soluble → into watery blood.

5. The body's two environments

Read the figure: follow the arrows. A non-polar vitamin (coral) travels to fat storage → it stays → not needed daily, but can pile up (toxic). A polar vitamin (lavender) stays in watery blood → not stored → excess leaves in urine → needed often, deficiency comes fast.

Why the topic needs it: this is the exact "logic chain" the parent note asks you to derive rather than memorise. Storage, toxicity, and how often you eat it are all consequences of which home the vitamin picked.

6. Coenzyme, metabolism & micronutrient

The picture: imagine an enzyme as a workbench and a coenzyme as a special tool clipped onto it — without the tool, the bench can't do that particular job.

Why the topic needs it: the parent note says B vitamins are coenzymes working inside watery cytoplasm — which is why they must be water-soluble. And "micronutrient" explains the parent's phrase "required in small amounts."

7. A quick note on ions & ${\text{Ca}}^{2+}$

Why the topic needs it: the parent note says vitamin D controls ${\text{Ca}}^{2+}$ (calcium) absorption for bones. You just need to read the symbol, not compute with it.

Prerequisite map

Each box on the left must be solid before the box it points to makes sense. The whole page pours into the bottom node — the parent topic.

Equipment checklist

Cover the right side and test yourself. If you can answer all, you're ready for the parent note.