Red blood cells carry oxygen using a pigment called:

## The Reasoning **Haemoglobin** is the iron-containing protein found in red blood cells that binds to oxygen molecules. Here's how it works: When blood flows through your lungs, haemoglobin picks up oxygen (forming oxyhaemoglobin, which gives blood its bright red color). It then travels through your bloodstream to deliver that oxygen to tissues and organs throughout your body. This is called **oxygen transport** — one of blood's most vital functions. The iron in haemoglobin is what actually grabs onto the oxygen, which is why iron deficiency causes anemia (not enough oxygen delivery). ## Why the Wrong Options Tempt You **Chlorophyll (A)** — This is the green pigment in plants that captures sunlight for photosynthesis. Students sometimes confuse "pigments" and think all biological pigments do similar jobs. **Melanin (B)** — This pigment gives color to your skin, hair, and eyes. It protects against UV rays but has nothing to do with oxygen. **Keratin (D)** — This is a structural protein in your hair and nails, not a pigment at all. ## Quick Takeaway Remember: **Haem** (iron) + **globin** (protein) = the oxygen taxi in your blood. No haemoglobin, no oxygen delivery!