Question

Organelle ribosomes occur in
A.Bacteria
B.Blue-green algae
C.Plastids and mitochondria
D.Nucleus

Answer 1

Hint: Ribosomes occur in an organelle which is large membrane-bound and contain pigments. It also occurs in an organelle which is known as the powerhouse of the cell.

Complete answer:
First we should know about ribosomes to answer this question. Ribosomes are non membrane-bound and essential cytoplasmic organelles. The two components which together constitute ribosomes are Ribosomal RNA and Ribosomal proteins. In all living cells, the primary feature of ribosomes involves protein synthesis that ensures the cell's survival. Ribosomes are the primary sites of protein synthesis; they are known as protein factories.
Now, let us find the solution from the options-
Single-celled microbes are bacteria. They have no nucleus or membrane attached organelles, and their cell composition is simpler than that of other organisms. Thus, the option A is incorrect.
Blue-green algae are also said as Cyanobacteria which are a group of photosynthetic bacteria and also refer to as "pond scum." Blue-green algae are refer as blue-green in color, but can also be green, blue, brown or reddish-purple. Thus, the option B is incorrect.
Ribosomes are found in the cytoplasm, plastids, in the mitochondrial matrix, on the rough endoplasmic reticulum membrane. Within mitochondria, the ribosome is responsible for energy transfer and adenosine triphosphate production in eukaryotic cells, therefore ribosome in mitochondria is said as mitochondrial ribosomes (mitoribosomes) that conduct protein synthesis. Just like the mitochondrial matrix, the stroma of chloroplast (plastids) contains 70S ribosomes for the synthesis of proteins.
A double-membraned organelle present in all eukaryotic cells is the nucleus. It is the main organelle that serves as the cellular activity control centre and is the DNA storehouse of the cell. Thus, the option D is incorrect.

Hence, the correct answer is option (C)

Note: In a significant number of cells, ribosomes are present in the form of small particles and are largely consisting of 1/3rd of protein and 2/3rd of RNA. They are referred to as the 70s (observed in prokaryotes) or 80s (observed in eukaryotes). The letter S corresponds to the size and density known as the Unit of Svedberg. Two subunits consist of both 70S and 80S ribosomes.