Ribosomes are non-membranous bounded strOctures. Ribosomes are the sites where the cell synthesizes proteins according to genetic instructions. A bacterial cell may have a few thousand ribosomes.But a human liver cell has a few million ribosomes. Cells hat have high protein synthesis have a particulaly great number of ribosome. Cells active in protein synthesis also have prominent nucleoli.These nucleoli synthesize the ribosomes.
They colitain equal amount of proteins and rRNA So they are also known as
Types of ribosomes
Ribosornes function in two cytoplasmic locations.
- Free ribosomes: They are suspended in the cytoplasm. Most of proteins synthesized by the free ribosomes will function within the cytosol. The free ribosomes are abundant in the cells growing by the addition of cytoplasm.
- Bound ribosomes: They are attached to the outside of the endoplasmic
reticulum. The proteins of bound ribosomes are stored in the inclusion of mem manes. Or these proteins are exported from the cell. Some cells specialize in protein secretion like pancreas and other glands. These cells secrete digestive enzymes. They have a high proportion of bound ribosomes.
Structure of ribosomes
Bound and free ribosomes are structurally identical and interchangeable. The cells car adjust the numbers of ribosome. Each ribosome has two subunits. The ribosomal subunits are constructed in the nucleolus from RNA in eukaryotes. The rRNA is produced in the nucleus. Protein is imported from the cytoplasm. The subunits join to form functional ribosomes.
Functions of ribosomes
The ribosome plays a key role in translating the genetic message. This genetic message is carried by mRNA from the nucleus to the cytoplasm. This message sequence) of a.polypeptide chain.
The ribosomes of prokaryotes are smaller than eukaryotes. They are different in their molecular composition. This dissimilarity in a structure is fundamental. It differentiates the prokaryotes from eukaryotes. The difference in ribosomes is also medically significant. Certain drugs (antibiotics) can affect the prokaryotic ribosomes. But they do not affect the eukaryotic ribosomes.
STRUCTURES AND FUNCTIONS OF CELLULAR COMPONENTS
||Located within microtubule-
organizing center. Contains
nine triple microtubules
|Forms basal body of cilia an
flagella; functions in mitotii
||Organelle that contains
chlorophyll and is involved in
|Traps, transforms, and use
tight energy -to convert carbor dioxide and water into glucose and oxygen
||Made up of nucleic acid (DNA) and protein
||Controls heredity- and pellula activities
||Thread like structures
||Cilia and flagella move smal
particles through fixed cellE
and are a major form o.
locomotion in some cells.
||The endoplasmic reticulum,
Golgi apparatus,, vacuoles, vesicles
|Organelles functioning as a
system, to modify, package.
and distribute newly formec
proteins and lipids