Topic 2.1 · Core
Specialised Cells and Their Functions
New cells only ever come from cells that already exist, and in a multicellular organism some of those new cells develop features suited to one particular job. Cambridge tests two separate things here — the plain function of each named cell, and, when a question asks for it, the structural feature that makes that function possible.
New cells come from existing cells
Before specialisation can happen at all, new cells have to exist in the first place, and they are produced only by the division of cells that already exist — nothing in biology generates a new cell out of non-living material. In a multicellular organism, that steady production of new cells is what supports growth, repair and replacement, and it is worth being precise about why: an organism gets bigger mainly because it ends up with more cells, not because individual cells keep swelling in size. You are not expected to describe the mechanism of division at this stage — the detailed stages of nuclear division belong to a later chapter — the Chapter 2 requirement is simply the statement itself: new cells arise from the division of existing cells.
Specialised animal cells
| Cell | Function | Feature that helps it perform that function |
|---|---|---|
| Ciliated cell | Moves mucus in the trachea and bronchi | Hair-like cilia beat in a coordinated way to move the mucus along the airway |
| Neurone | Conducts electrical impulses | A long extension carries impulses over distance; branched endings connect with other cells |
| Red blood cell | Transports oxygen | Contains haemoglobin; a biconcave shape gives a large surface area; in mammals, no nucleus leaves more space for haemoglobin |
| Sperm cell | Reproduction — delivers the male nucleus to the egg cell | A tail enables movement; the nucleus carries the genetic material |
| Egg cell | Reproduction — carries the female nucleus | A large cell with cytoplasm that supports the earliest stage of development after fertilisation |
Specialised plant cells
| Cell | Function | Feature that helps it perform that function |
|---|---|---|
| Root hair cell | Absorbs water and mineral ions from the soil | A long hair-like projection gives a large surface area for absorption |
| Palisade mesophyll cell | Carries out photosynthesis | Contains many chloroplasts to absorb light |
Sperm and egg cells are usually presented together under the single function “reproduction” because they are both gametes, but that is still two distinct named cell types, not one — an answer that only mentions one of them when a question asks about gametes is incomplete.
Function versus adaptation — read the command word first
These two question types look similar but want completely different answers, and mixing them up is where most of the marks in this unit are actually lost. If a question asks you to state the function, the job alone is the full answer — “red blood cells transport oxygen” is a complete response, and adding haemoglobin or the biconcave shape is not required and earns nothing extra. If a question instead asks you to explain how a cell is adapted or suitedto its function, naming the cell is not an explanation on its own — you have to name a specific structural feature andstate what that feature achieves. “It is a root hair cell, so it absorbs water” explains nothing; “a root hair cell has a long projection, which gives it a large surface area for absorbing water” does.
The process by which a cell becomes specialised in the first place is called differentiation — useful vocabulary to recognise, though the underlying logic that matters for an exam answer is always the same sentence pattern: a structural feature makes a particular job easier or possible.
Where marks are actually lost
Red blood cells transport oxygen, not carbon dioxide — carbon dioxide transport is a separate idea covered later, mainly carried in the plasma, and confusing the two costs a mark that should be straightforward. Root hair cells absorb; they do not photosynthesise, because they grow underground and contain no chloroplasts — a common mistake is assuming any plant cell might contain chloroplasts by default. And a feature with no linked benefit, or a benefit with no named feature, is only ever a half answer to an “explain how it is adapted” question, however confidently it is written.
Once each function and feature is secure, the next step is placing these cells inside the bigger structural picture — see levels of organisation, which is where individual specialised cells like these start building tissues, organs and organ systems.