Question
A student is asked: “Name the three types of blood cells and state one function of each.”
This is a 3-mark question from NCERT Class 10 Chapter 6 (Life Processes). It appears almost every year in CBSE board exams — either as a direct question or embedded in a diagram-based question. NEET often pairs it with a structural detail like “which cell lacks a nucleus?”
Solution — Step by Step
Blood has three cellular components: Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets (thrombocytes). Remember: these are not all technically “cells” — platelets are cell fragments, which is why they behave differently.
RBCs contain haemoglobin, an iron-containing protein that binds oxygen. One RBC can carry about 250 million haemoglobin molecules — that’s the reason blood can transport far more oxygen than plasma alone ever could.
The key fact examiners want: RBCs lack a nucleus in mature form. This creates space for more haemoglobin.
WBCs (leucocytes) protect the body by engulfing pathogens (phagocytosis) and producing antibodies. Unlike RBCs, WBCs do have a nucleus — they need it to carry out complex immune responses.
There are multiple types (neutrophils, lymphocytes, etc.) but for Class 10 and NEET basics, just knowing their immune function is enough.
Platelets rush to a wound site and trigger clot formation, preventing excessive blood loss. They release chemicals that convert fibrinogen (a plasma protein) into fibrin threads — these threads form the actual clot mesh.
Low platelet count is the reason dengue patients are at risk: dengue destroys platelets, making clotting impossible.
For a 3-mark answer, one line per cell type is sufficient:
| Blood Cell | Also Called | Key Function |
|---|---|---|
| Red Blood Cell | Erythrocyte | Transports oxygen via haemoglobin |
| White Blood Cell | Leucocyte | Immunity — destroys pathogens, produces antibodies |
| Platelet | Thrombocyte | Blood clotting at wound sites |
Why This Works
The three cell types have a clear division of labour. RBCs are optimised purely for transport — they even sacrifice their nucleus to fit more haemoglobin. WBCs are the flexible defenders, capable of changing shape to squeeze out of capillaries and reach infected tissue. Platelets are the rapid-response team, always circulating and ready to aggregate at damage sites.
Understanding why each cell is shaped the way it is helps you remember function. A biconcave disc (RBC) has maximum surface area for gas exchange. An irregular, amoeba-like WBC can move through tight spaces. Tiny, disc-shaped platelets can stack and clump fast.
This also explains disease symptoms. Anaemia (low RBC/haemoglobin) → fatigue. HIV (attacks WBCs specifically, the CD4 T-cells) → weakened immunity. Dengue/leukaemia → platelet problems → bleeding disorders.
Alternative Method
For NEET MCQs, you’re often tested on which is largest/smallest or which lacks a nucleus:
- Largest cell in blood → Monocyte (a type of WBC)
- Smallest cell in blood → Platelets
- Most numerous → RBCs (~5 million per mm³)
- Lacks nucleus → Mature RBC (this is the #1 NEET trap)
- Shortest lifespan → Platelets (~7-10 days); RBCs last ~120 days
Memorise these comparative facts — NEET loves “which of the following is correct” options built around these numbers.
Common Mistake
Students write “WBCs fight infection by destroying bacteria” and leave it at that. Examiners expect two mechanisms: phagocytosis (engulfing) AND antibody production. Writing only one can cost you half a mark. Also, never say RBCs “carry” oxygen without mentioning haemoglobin — the mechanism is what earns the mark, not just the function.
For NEET, the fact that mature RBCs lack a nucleus is asked almost every alternate year. The reason: during maturation, the nucleus is pushed out to maximise haemoglobin content. Platelets also lack a nucleus (they’re cell fragments from megakaryocytes). WBCs are the only blood cells with a proper nucleus — remember this as the exception, not the rule.