
|
|
Dictionary » R » Ribosomes RibosomesDefinition noun, singular: ribosome Small round particles in a cell made up of RNA and protein that are primarily involved in the assembly of proteins by translating messenger RNA (a process called translation).
Ribosomes, being entirely particulate, are not considered organelles when the term organelle is strictly used to refer to membraned structures. Although in some literature they are referred to as "non-membranous organelles". Ribosomes are typically composed of two subunits: the large and small subunits. They join as one during translation; together, they catalyze the translation of mRNA into a polypeptide chain during protein synthesis, and since their active sites are made of RNA, ribosomes are also referred to as "ribozymes." Ribosomes are formed in the cytoplasm of prokaryotic cells. In eukaryotic cells, they are formed most often in the nucleolus. Another difference between ribosomes of prokaryotes and eukaryotes is the structure of the ribosomes. Prokaryotes have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit. Eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit. However, the organelles like chloroplasts and mitochondria that are present only in eukaryotic cells also consist of 70S ribosomes resembling those in prokaryotes (e.g. bacteria), indicating that these eukaryotic organelles have descended from their ancestral bacteria (see Endosymbiotic theory). In eukaryotes, the ribosomes may be classified as either ‘free’ or ‘bound’. Free ribosomes may be found suspended in the cytosol whereas bound ribosomes are attached to endoplasmic reticulum (as such called rough endoplasmic reticulum). Free ribosomes are involved in the synthesis of proteins that will function in the cytosol while bound ribosomes in the synthesis of proteins that are to be exported or used within the cell membrane. The two types of ribosomes have similar function and structure, and in fact, are interchangeable.
Related forms: ribosomal (adjective).
![]()
Please contribute to this project, if you have more information about this term feel free to edit this page ![]()
Results from our forumExplain protein transport plzRough ER means that ribosomes are attached to the ER. Ribosomes are what takes the mRNA and translates it into proteins/enzymes. If the protein is bound for the outside (extracellular) or even if it can not touch the cell's own cytoplasm, ...
See entire post
Re: Which compartments of cell are associated with the followingThank you for your help thus far, however I am still stuck on e. I know that bound signal recognition particles are associated with ribosomes, however what about unbound signal recognition particles... would it be correct to assume that they are associated with just cytoplasm???!?!? Thank ...
See entire post
The Colin Leslie Dean species paradox... bacteria[13]; Bacteria belong to the kingdom Protoctista. Typical features include; Circular DNA, Plasmids, Meurin Cell walls, Mesosomes, and 70S Ribosomes. Bacteria have many feeding behaviours - Saprophites, Parasites, Patogens, Mutualites, Autotrops and Heterotrophs. Bacteria reproduce by binary ...
See entire post
The Colin Leslie Dean species paradox... bacteria[13]; Bacteria belong to the kingdom Protoctista. Typical features include; Circular DNA, Plasmids, Meurin Cell walls, Mesosomes, and 70S Ribosomes. Bacteria have many feeding behaviours - Saprophites, Parasites, Patogens, Mutualites, Autotrops and Heterotrophs. Bacteria reproduce by binary ...
See entire post
The Colin Leslie Dean species paradox... bacteria[13]; Bacteria belong to the kingdom Protoctista. Typical features include; Circular DNA, Plasmids, Meurin Cell walls, Mesosomes, and 70S Ribosomes. Bacteria have many feeding behaviours - Saprophites, Parasites, Patogens, Mutualites, Autotrops and Heterotrophs. Bacteria reproduce by binary ...
See entire post
This page was last modified 11:00, 28 October 2008. This page has been accessed 17,236 times. |
© Biology-Online.org. All Rights Reserved.
Register | Login
| About Us | Contact Us | Link to Us | Disclaimer & Privacy
Science Network - Braintrack.com - University Directory | Chemicool.com - Chemistry