Biology: Human Body, Cell, Vitamins & Plants

🎯 Learning Objective

Recall the cell, the main human body systems, vitamins and their deficiency diseases, and the basics of plants.

💡 Concept

• The cell is the basic structural and functional unit of life; it was discovered by Robert Hooke (1665) in cork
• The mitochondrion is the 'powerhouse of the cell' as it releases energy (ATP); the nucleus is the control centre and DNA is the genetic material
• Plant cells have a cell wall (of cellulose) and chloroplasts (with chlorophyll) that animal cells lack
• An adult human has 206 bones; the femur (thigh bone) is the longest and the stapes (in the ear) is the smallest
• The skin is the largest organ, the liver is the largest internal organ and gland, and the human heart has four chambers
• Blood has red cells (carry oxygen using haemoglobin), white cells (fight infection) and platelets (help clotting); the universal donor blood group is O and the universal recipient is AB
• Vitamin deficiency diseases: Vitamin A - night blindness, Vitamin B1 - beri-beri, Vitamin C - scurvy, Vitamin D - rickets; iodine deficiency causes goitre and iron deficiency causes anaemia
• Vitamin C is ascorbic acid (found in citrus fruits and amla); Vitamin D is made in the skin from sunlight
• Photosynthesis is how green plants make food from carbon dioxide and water using sunlight and chlorophyll, releasing oxygen
• Malaria is caused by the Plasmodium parasite spread by the female Anopheles mosquito; dengue is spread by the Aedes mosquito

🧮 Key Formulas

Adult bones: 206 | Heart chambers: 4 | Human teeth (adult): 32

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Vit A - night blindness | Vit C - scurvy | Vit D - rickets | Iodine - goitre

✏️ Easy Example

Q. The deficiency of which vitamin causes scurvy? (a) Vitamin A (b) Vitamin C (c) Vitamin D (d) Vitamin K

1. Scurvy causes bleeding gums and is prevented by citrus fruits
2. It is caused by a deficiency of Vitamin C

Answer: (b) Vitamin C

🇮🇳 Real-Life Example

Grandmothers who tell you to sit in the morning sun and eat amla in winter are giving solid biology advice — sunlight makes Vitamin D (against rickets) and amla is packed with Vitamin C (against scurvy).

📝 Exam-Level Example

Q. Which is the largest gland in the human body?

1. It also acts as the largest internal organ and helps digestion
2. The liver is the largest gland

Answer: Liver

📝 Exam-Level Example

Q. Malaria is transmitted by which mosquito?

1. The disease is caused by the Plasmodium parasite
2. It is spread by the bite of the female Anopheles mosquito

Answer: Female Anopheles mosquito

🪄 Memory Trick

Mosquito diseases: 'A for Anopheles - mAlaria', 'Aedes - dengue'. Bones: 206 in adults. Powerhouse of the cell = mitochondria.

⚠️ Common Mistakes

• ❌ Confusing scurvy (Vitamin C) with rickets (Vitamin D)
• ❌ Saying a baby has 206 bones — babies have around 300; adults have 206
• ❌ Mixing up the mosquitoes: Anopheles spreads malaria, Aedes spreads dengue

🏆 Exam Tips

• ✅ Universal donor = O blood group; universal recipient = AB blood group
• ✅ Mitochondria = powerhouse; ribosome = protein factory; chloroplast = only in plant cells

📌 Summary

• Cell discovered by Robert Hooke (1665); mitochondria = powerhouse; DNA = genetic material
• Adult: 206 bones, 4 heart chambers; liver = largest gland, skin = largest organ
• Deficiency: Vit A - night blindness, Vit C - scurvy, Vit D - rickets, iodine - goitre
• Photosynthesis makes food + oxygen; malaria - Anopheles, dengue - Aedes