Question

Which among the following is not a prokaryote?
A. Nostoc
B. Saccharomyces
C. Oscillatoria
D. Mycobacterium

Answer 1

Prokaryotes are microscopic organisms. They are single-celled organisms and lack well defined nuclei. Prokaryotes are more primitive than eukaryotes. They reproduce asexually mostly by binary fission.

Complete answer:
Prokaryotes are microscopic single-celled organisms. They lack well defined nuclei. The DNA in prokaryotes is contained in a nucleoid which is not membrane-bound. They also lack membrane-bound organelles.
In the given options, Saccharomyces is not a prokaryote as it is a fungus and hence a eukaryote. They have a well-defined nucleus and membrane-bound nucleus. Their cell structure is more complicated than a prokaryotic cell. Nostoc and Oscillatoria are cyanobacteria; they are a group of photosynthetic and nitrogen-fixing bacteria, and Mycobacterium comes under true bacteria. Therefore, Nostoc, Oscillatoria, and Mycobacterium are prokaryotes.

Understanding more about Saccharomyces.
It is a single-celled eukaryote which is used in baking and brewing and thus called baker’s yeast. They have a globular shape, are yellow-green in colour, and belong to kingdom Fungi. It is a model organism for the study of genetic, biochemistry, microbiology due to its rapid growth rate and is easy to modify genetically. These fungi have both a stable haploid and diploid state.
Commercial applications of Saccharomyces cerevisiae
They are used in baking as they release carbon dioxide on fermentation which makes the bread rise and fluffy.
It is used in brewing beer and wine-making and thus, also called top-fermenting or to-cropping yeast.
It is used in biomedical research in drug research and drug maintenance.

The correct answer to this question is option B.

Note: In contrast to prokaryotes, eukaryotes have well-defined nuclei which are enclosed in the nuclear envelope. Eukaryotic cells have membrane-bound organelles. Eukaryotic cells are much larger than prokaryotic cells and are much more complicated. Animals, plants, fungi fall under eukaryotes.