Question

Describe the structure and function of ribosomes. Where are they made and where are they found in the cell?

Answer 1

• There are large numbers of minute granular particles are attached to the outer surface of the endoplasmic reticulum(ER) , which are called ribosomes. Where ribosomes are present , the ER is called the granular ER .
• Ribosomes can also be present freely in the cytosol .
• Ribosomes are made in both the cell cytoplasm and nucleolus in the eukaryotes . And in bacterial cell the are synthesized in the cytoplasm through the transcription of ribosome gene operons.

Structure and function: The ribosome in eukaryotes measure approximately 22×32 nm . They are made up of a large and a small subunit called the 60S and 40S subunits , on the basis of their rates of sedimentation in the centrifuge. Ribosomes are complex structures, mostly composed of a mixture of RNA and proteins.

They are the sites of protein synthesis. Ribosomes attached to the ER synthesized all transmembrane proteins, most secreted proteins, and protein stored in the Golgi apparatus, lysosomes . The free ribosomes synthesize cytoplasmic proteins like hemoglobin and proteins found in peroxisomes and mitochondria.