🫁 10.3 – Respiratory Pigments
🧪 Proteins that carry or store oxygen in the body
🔷 What Are Respiratory Pigments?
Let’s start with the basics.
🧠 Definition:
Respiratory pigments are special proteins found in blood or tissues that help:
- Carry oxygen from lungs to the body
- Store oxygen in muscles
- Transport carbon dioxide
- Sometimes, carry other substances too
Think of them as oxygen couriers and oxygen banks in your body!
🔹 Why Do We Need These Pigments?
Here’s a real-life example:
🏃♂️ When you run or exercise, your muscles need more oxygen to make energy. If oxygen only traveled dissolved in blood, it wouldn’t be enough. That’s why we need oxygen-carrying proteins — to quickly deliver or store oxygen where it’s needed.
🔷 Two Important Respiratory Pigments
The two most well-known respiratory pigments in humans are:
- Haemoglobin (in blood – carries oxygen)
- Myoglobin (in muscles – stores oxygen)
Let’s understand each in detail.
🩸 1. Haemoglobin
📍 Where is it found?
- Haemoglobin is present in red blood cells (RBCs).
🧬 Structure of Haemoglobin
Imagine haemoglobin like a four-seater car:
- It has four polypeptide chains:
- 2 alpha (α) chains (141 amino acids each)
- 2 beta (β) chains (146 amino acids each)
Each chain has a special seat called a haem group.
🔸 What is a Haem Group?
- A haem group contains:
- A porphyrin ring (ring-like structure)
- In the center of this ring is an iron (Fe²⁺) ion
- The iron can attach to one oxygen (O₂) molecule
So, 1 haemoglobin = 4 haem groups = Can carry 4 oxygen molecules.
🧠 Real-Life Example:
Think of haemoglobin as a delivery truck with 4 baskets. Each basket can carry 1 oxygen molecule — so 4 oxygen molecules total per truck!
🌬️ Oxygen Binding and Release
- In the lungs, where oxygen level (partial pressure of O₂) is high, oxygen binds to haemoglobin.
- In the tissues, where oxygen level is low, haemoglobin releases the oxygen.
🧪 Partial Pressure:
This means how much oxygen is available in a certain area (measured in mm Hg).
Higher pressure → more oxygen available, Lower pressure → less oxygen available.