Class 11 Biology Chapter 14 Breathing and Exchange of Gases – Revision Notes

Quick revision notes for Class 11 Biology Chapter 14 (Breathing and Exchange of Gases). These Class 11 Biology Chapter 14 notes are ideal for quick revision just before exams.

Respiratory Pathway

• Nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

Breathing Mechanism

• Inspiration: diaphragm contracts, thoracic volume up, pressure down.
• Expiration: diaphragm relaxes, volume down, pressure up.

Gas Transport

• O₂: ~97% via haemoglobin (oxyhaemoglobin).
• CO₂: ~70% as bicarbonate, ~20-25% carbaminohaemoglobin.

Regulation

• Respiratory rhythm centre (medulla oblongata); primarily CO₂-sensitive.

One-Line Summary

Breathing moves air through the respiratory tract to the alveoli, where O₂ and CO₂ are exchanged by diffusion and transported in blood, with breathing rate regulated mainly by blood CO₂ levels via the medulla oblongata.

Written by Satish

NCERTBooks.org is an independent educational resource run by a small team focused on making official NCERT textbooks easy to find, read, and download for students, parents, and teachers across India. We are not affiliated with NCERT or the Ministry of Education -- we organise publicly available NCERT content by class and subject, verify links against official sources, and build tools (like our in-browser reader) that make studying more convenient. Every guide we publish is written and reviewed by our team based on the actual NCERT curriculum and syllabus.