BOTANY WITH THE BASICS OF HYDROBOTANY (AQUATIC PLANTS OF UKRAINE) - B.Ye. Yakubenko - 2011

V. CYTOLOGY. THE CONCEPT OF THE CELL

Structure of the Plant Cell

Ribosomes

These are microscopic spherical to elongated Organelles up to 26 nm long and 19 nm wide. They lack a Membrane Structure. In The plant Cell, there are three groups of Ribosomes: cytoplasmic, chloroplast, and mitochondrial.

Cytoplasmic ribosomes are larger (80S) than plastid and mitochondrial ones (70S), which in this property are more similar to prokaryotic ribosomes. Cytoplasmic ribosomes consist of two unequal

subunits (60S and 40S) joined by Mq2+ ions. The smaller subunit contains a single rRNA molecule and about 30 protein molecules. The larger subunit is built of three rRNA molecules and 45-50 protein molecules. Between the subunits, There is a channel that can accommodate mRNA and tRNA bound to an amino acid.

The rRNA molecules of cytoplasmic ribosomes are produced by the nucleolus, while mitochondrial and plastid rRNAs result from the METABOLISM/31.html">Transcription of DNA genes of nucleoids located within these organelles. The Proteins of cytoplasmic ribosomes are encoded by nuclear DNA genes and synthesized in the Cytoplasm. Proteins of mitochondrial and plastid ribosomes are encoded by the DNA of their own nucleoids as well as nuclear chromosome DNA, but they are also synthesized in the cytoplasm.

Cytoplasmic ribosomes occur free in the cytoplasmic matrix or are located On the surface of rough Endoplasmic reticulum membranes. They may be single or aggregated into Polysomes.

The function of ribosomes is Protein Biosynthesis.



Last update: 07/08/2026

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