Prokaryotic vs Eukaryotic Ribosomes
The difference between the prokaryotic and eukaryotic organisms is the difference of the location that DNA exists as the name implies (Taylor, 1998). Eukaryotes have a membrane bound nucleus, which contains DNA, but prokaryotes lack a membrane bound nucleus (true nuclei).
Eukaryotes contain other membrane bound organelles too. Chloroplast in plant cells, mitochondria, and nucleus are enveloped from two membranes. Golgi bodies, lysosomes, vacuoles, endoplasmic reticulum (ER) are covered with one membrane.
Ribosomes can be found in both eukaryotic and prokaryotic organisms. In eukaryotes, ribosomes are not bound by a membrane, although it has been described as an organelle. They are dispersed in the cytoplasm, and which are called free ribosomes. Ribosomes on the membrane of the nucleus and on the membrane of endoplasmic reticulum are called bound ribosomes. Chloroplasts in plant cells and mitochondria in all eukaryotic cells have ribosomes, which resembles prokaryotic ribosomes. In prokaryotes, ribosomes are scattered in the cytoplasm.
Either eukaryotic or prokaryotic, ribosomes are made from protein and ribosomal RNA (rRNA). Ribosomes are involved in translation in protein synthesis where genetic code of DNA translates into a protein. Translation is the process, in which transcripted mRNA is translated into a sequence of amino acids that occur on the ribosomes. Therefore, cells that have a higher rate of protein synthesis have a higher amount of ribosomes such as in brain cells and pancreas cells. Ribosomes are made up of two subunits. When the protein synthesis does not occur, the two subunits are separated.
Generally prokaryotic ribosomes are called 70S ribosomes, which are smaller than eukaryotic ribosomes (Taylor, 1998). Ribosomes consist of two subunits, and these two subunits are called 30S and 50S, the smaller unit and the larger unit respectively. These ribosomes units are denoted by Svedberg (S) values depending on the rate of the sedimentation in the centrifugation . In prokaryotes, rRNA is organized into three strands in ribosomes .
Smaller subunit and larger subunit of eukaryotic ribosomes are described as 40S and 60S respectively, and the whole ribosome is 80S. This is lager than the prokaryotic ribosome. The rRNA in ribosomes has four strands. Ribosomes are produced in the nucleolus, in a special position in nucleus.
What is the difference between Eukaryotic and Prokaryotic Ribosomes?
• Prokaryotic ribosomes are smaller (70S) than eukaryotic ribosomes (80S).
• Prokaryotic ribosomes consist of 30S and 50S, the smaller unit and the larger unit respectively whereas eukaryotic ribosomes have smaller subunit and larger subunit as 40S and 60S respectively.
• In eukaryotes, rRNA in ribosomes has four strands whereas, in prokaryotes, rRNA is organized into three strands in ribosomes .
• In eukaryotic cells, ribosomes are in free and bound form, whereas prokaryotic cells have only free form.
• Eukaryotic cells have chloroplasts and mitochondria as organelles and those organelles also have ribosomes 70S. Therefore, eukaryotic cells have different types of ribosomes (70S and 80S), whereas prokaryotic cells only have 70S ribosomes.
• Eukaryotic ribosome consists of eight kinds of protein and five kinds of rRNA, and prokaryotic ribosomes are made of three types of rRNA and fifty kinds of protein.
Taylor, D.J., Green N.P.O., Stout, G.W., (1998), Biological Science. Cambridge University Press, Cambridge