Bio-Physical Sciences — the first-year Physiology chapter on the physics inside the body

Water moves across a membrane. A substance spreads out through a liquid. Fluid is pushed through a filter. These are physical processes, the kind you met in school science. Your body uses them every second. Bio-Physical Sciences is the chapter that names them.

The NCH syllabus lists this as chapter two of Physiology and Biochemistry (HomUG-PB). The sheet gives thirteen topics and nothing else. There is no introduction line and no revision line. Each topic is a single word or a short name. This piece gives each one a plain meaning and sorts them into groups, so the list becomes easier to hold.

A caution before we start

The meanings below are first steps, in everyday words. They are not exam definitions. Your textbook has the exact wording, and often a formula or a diagram. Learn those. Use this page to understand what each word is about before you learn it properly.

Group one: things moving through a barrier

Filtration. Fluid is pushed through a barrier with small holes. Small things pass. Larger things stay behind.

Ultra-filtration. Filtration through a very fine barrier, so that only very small particles pass. “Ultra” means beyond.

Dialysis. Separating small particles from large ones by letting the small ones pass through a membrane.

These three are close cousins. A good exercise is to write one line on how each differs from the other two.

Group two: things spreading and water moving

Diffusion. Particles spread from where there are more of them to where there are fewer, until they are evenly mixed.

Osmosis. Water moves across a membrane towards the side with more dissolved substance.

Students often mix these two up. Here is one way to keep them apart. In diffusion, the dissolved particles move. In osmosis, it is the water that moves. Check this against your textbook’s wording.

Donnan equilibrium. A special balance that forms across a membrane when some charged particles cannot cross it. It is a harder idea. Give it extra time, and ask your teachers for a worked example.

Group three: things sticking and dissolving

Adsorption. A substance sticks to the surface of something else. Note the spelling. It is not absorption.

Absorption. A substance is taken in, into the body of something else. In physiology this often means taken in from the gut.

Adsorption and absorption look almost the same on paper. It is an easy mistake to make. Keep them apart with one clear line each: adsorption is on the surface; absorption is taken in.

Hydrotropy. A way of helping a substance dissolve in water when it would not dissolve well on its own. “Hydro” means water.

Colloid. A mixture where very small particles are spread through another substance and do not settle out.

Group four: using and tracing

Assimilation. The body takes what has been absorbed and makes it part of itself.

Tracer elements. Elements that can be followed as they move through the body. They let scientists trace a path that would otherwise be hidden. Your textbook will explain how they are used.

Group five: surfaces

Surface tension. The surface of a liquid behaves a little like a thin, stretched skin. That pull at the surface is surface tension. It matters in the body wherever a liquid meets air.

How the chapter sits in the year

This chapter comes right after General Physiology, and it supports it. General Physiology asked how things cross a cell membrane. Bio-Physical Sciences gives you the physical processes behind that. Many later chapters then use these words. Absorption returns in the Digestive System chapter. Filtration returns in Renal Physiology, where the sheet lists glomerular filtration.

What to take from it

1. Give each of the thirteen words a one-line plain meaning.
2. Keep diffusion and osmosis apart.
3. Keep adsorption and absorption apart.
4. Know how filtration, ultra-filtration and dialysis differ.
5. Give the Donnan equilibrium extra time.

The sheet gives one word per topic and nothing more. It does not say which formulas or experiments are needed. Your textbook and practical classes will.

Where to go next on the platform

This piece sits in the first-year Physiology and Biochemistry room. “General Physiology — the first-year Physiology chapter on how a cell lives” is the chapter before it, and it uses these ideas. “Physiology and Biochemistry in the First Year — how the body works” shows the whole subject at once.