General Science • Topic 3 of 4

Biology & Human Body

The cell is the basic unit of life; the mitochondrion is its 'powerhouse'. Humans have 206 bones and the heart has four chambers. Blood group O is the universal donor and AB the universal recipient.

The cell — the basic unit of life

Nucleus Mitochondrion ("powerhouse") cell membrane
The mitochondrion is the cell's "powerhouse" — it releases energy. The nucleus controls the cell.

Human-body numbers worth memorising

  • 206 bones in the adult body; the heart has 4 chambers.
  • Blood groups: O = universal donor, AB = universal recipient.
  • Photosynthesis uses chlorophyll + sunlight + CO₂ + water to make food and release oxygen.
Vitamin deficiencies (a guaranteed question). Vitamin C → scurvy · Vitamin D → rickets · Vitamin A → night blindness · Vitamin B1 → beri-beri.

✅ Solved examples

1. What is called the powerhouse of the cell?
The mitochondrion.
2. How many bones are there in the adult human body?
206.
3. Which blood group is the universal donor?
Blood group O.
4. Deficiency of which vitamin causes scurvy?
Vitamin C.

✏️ Practice — try these, take hints as needed

1. The human heart has how many chambers?
Even number.
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—
Four
2. The green pigment used in photosynthesis is?
In leaves.
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—
Chlorophyll
3. Deficiency of Vitamin D causes?
Bone disease in children.
—
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Rickets
4. The universal recipient blood group is?
Two letters.
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—
AB
5. The basic structural unit of life is the?
Discovered by Hooke.
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—
Cell

📝 Topic test — 8 questions

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