Questions: In nature, which pigment gives red algae its color? A. phycoerythrin B. fucoxanthin C. chlorophyll D. peptidoglycan E. chitin

The answer is the first one (A): phycoerythrin.

Explanation for each option:

A. Phycoerythrin - This is the correct answer. Phycoerythrin is a red pigment found in red algae, which gives them their characteristic color. It is a type of phycobiliprotein that absorbs light, particularly in the blue-green spectrum, and reflects red light.

B. Fucoxanthin - This is incorrect. Fucoxanthin is a brown pigment found in brown algae and diatoms, not red algae.

C. Chlorophyll - This is incorrect. Chlorophyll is a green pigment found in all photosynthetic organisms, including red algae, but it does not give red algae their red color.

D. Peptidoglycan - This is incorrect. Peptidoglycan is a structural molecule found in the cell walls of bacteria, not a pigment.

E. Chitin - This is incorrect. Chitin is a structural polysaccharide found in the exoskeletons of arthropods and the cell walls of fungi, not a pigment.

In summary, the pigment responsible for the red color in red algae is phycoerythrin.