Question

The hypothesis that all photosynthetic organisms require a source of hydrogen was given by
A. Hill
B. Ruben and Kamen
C. Van Niel
D. Emerson and Arnold

Answer 1

Hint: All photosynthetic organisms require hydrogen for reducing carbon dioxide into other substances. It was demonstrated by a Dutch-American microbiologist.

Complete answer: C. B. Van Niel, a Dutch-American microbiologist made an introduction of general microbiology studies and made key discoveries about the chemistry of photosynthesis. In 1931, Van Niel suggested a hypothesis which stated that all photosynthetic species need a hydrogen supply. This supply is water in plants and that oxygen is produced by the splitting of water. He was the first scientist to demonstrate by his research on purple sulphur bacteria and green sulphur bacteria, that photosynthesis is a light-dependent redox reaction where hydrogen (usually from an oxidizable compound) can reduce carbon dioxide into cellular materials. In a nutshell, Van Niel found that:
a) Carbon dioxide is fixed by green sulphur photosynthetic bacteria in the presence of hydrogen sulphide.
b) Oxygen was not produced; sulphur globules were formed instead.
So, the correct answer is option C.

Additional information: Photosynthesis occurs in two phases; light-dependent and light-independent phases. In light-dependent reactions, the energy in the form of ATP and NADPH are produced, while in light-independent reactions, ATP and NADPH molecules produced before are utilized to fix carbon dioxide.

Note: The first significant result of Emerson was the quantification of the ratio of chlorophyll molecules to photosynthesis-produced oxygen molecules. The chlorophyll is a green-coloured pigment present in the chloroplasts of plant cells.