Which of the following are not membrane-bound?

Which of the following are not membrane-bound?
  1. Ribosomes
  2. Lysosomes
  3. Mesosomes
  4. Vacuoles

Solution

Ribosomes were first observed under an electron microscope by George Palade (1953). Ribosomes are composed of RNA and proteins.  STRUCTURE:
The eukaryotic ribosomes are 80S, while the prokaryotic ribosomes are 70S. In this case, ‘S’ stands for sedimentation coefficient or Svedberg’s Unit. It is an indirect measure of the density and size of the ribosome. Both 70S and 80S ribosomes are composed of two subunits. It has two subunits. Small sub-unit and large sub-unit.
Prokaryotic Ribosome: 70S; Small subunit: 30S; Large subunit: 50S.
Eukaryotic Ribosome: 80S; Small sub-unit: 40S; Large subunit: 60S.FUNCTIONS:
It is mainly involved in protein synthesis. Ribosomes are known as protein factories of the cell.

Asked in: NEET 2015 (Phase 2)

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