Following statements are made about the chemical properties and distributions of the respiratory pigments found in animals:

A. Hemoglobins are the most common and widespread respiratory pigments in vertebrates and invertebrates and are always present in blood cells.
B. The heme structure in hemoglobins is an iron (ferrous) porphyrin which varies widely among species, and also varies among the different molecular forms of hemoglobin within any single species. The globin, however, is exactly identical.
C. Hemocyanin contains copper and turns bright blue when oxygenated and it is always dissolved in the plasma.
D. Chlorocruorins are similar to hemocyanin, but have a lower affinity for oxygen binding than hemocyanin present in blood cells of some marine annelid worms.
E. Hemerythrins are non-heme, iron-containing respiratory pigments that have a limited and scattered distribution.

Which one of the following options represents the combination of all INCORRECT statements?

Correct option is B

Correct Answer: (2) A, B and D

 Let's analyze each statement regarding respiratory pigments:

A."Hemoglobins are the most common and widespread respiratory pigments in vertebrates and invertebrates and are always present in blood cells."

Incorrect

• Hemoglobin is widespread in vertebrates, and in some invertebrates, but not always present in blood cells.

• In many invertebrates, hemoglobin is dissolved in plasma (e.g., annelids), not inside cells.

• So, the term “always present in blood cells” is incorrect.

B.The heme structure in hemoglobins is an iron (ferrous) porphyrin which varies widely among species, and also varies among the different molecular forms of hemoglobin within any single species. The globin, however, is exactly identical."

Incorrect

• The heme structure (iron-porphyrin) is highly conserved across species.

• What varies is the globin part, which is encoded by different globin genes (e.g., α, β chains in adult humans vs. γ chains in fetal hemoglobin).

• So, claiming "globin is exactly identical" is incorrect.

C."Hemocyanin contains copper and turns bright blue when oxygenated and it is always dissolved in the plasma."

Correct

• Hemocyanin is a copper-containing pigment, present in arthropods and molluscs.

• It is colorless when deoxygenated and blue when oxygenated.

• It is not inside blood cells, but dissolved in plasma.
   This statement is correct.

D."Chlorocruorins are similar to hemocyanin, but have a lower affinity for oxygen binding than hemocyanin present in blood cells of some marine annelid worms."

Incorrect

• Chlorocruorins are actually related to hemoglobins, not hemocyanin.

• They are iron-containing, heme-based pigments, not copper-based.

• Also, hemocyanin is not present in annelids — this is factually wrong.

E."Hemerythrins are non-heme, iron-containing respiratory pigment that have a limited and scattered distribution."

Correct

• Hemerythrins are non-heme, iron-containing pigments found in a limited range of invertebrates (e.g., sipunculids, priapulids, brachiopods).

• Their distribution is indeed scattered.
   This statement is correct.