Q. Rough endoplasmic reticulum (RER) looks rough under the microscope because of the attachment of which one of the following cell organelles to its surface?
- Centrioles
- Plastids
- Lysosomes
- Ribosomes
Answer: Ribosomes
The surface of the rough endoplasmic reticulum is attached with protein-manufacturing ribosomes giving it a "rough" appearance (hence its name). The binding site of the ribosome on the rough endoplasmic reticulum is the translocon. However, the ribosomes are not a stable part of this organelle's structure as they are constantly being bound and released from the membrane. A ribosome only binds to the RER once a specific protein-nucleic acid complex forms in the cytosol.
The surface of the rough endoplasmic reticulum is attached with protein-manufacturing ribosomes giving it a "rough" appearance (hence its name). The binding site of the ribosome on the rough endoplasmic reticulum is the translocon. However, the ribosomes are not a stable part of this organelle's structure as they are constantly being bound and released from the membrane. A ribosome only binds to the RER once a specific protein-nucleic acid complex forms in the cytosol.
Endoplasmic Reticulum (ER)
The endoplasmic reticulum (ER) is a cellular organelle. It is the transport network for molecules going to specific places, as compared to molecules that float freely in the cytoplasm. The endoplasmic reticulum is in cells that have a nucleus: in eukaryote cells but not in prokaryote cells.
It takes these forms:
- Rough endoplasmic reticulum (RER), so-called because it is studded with ribosomes, and secretes proteins into the cytoplasm.
- Smooth endoplasmic reticulum (SER). Among its functions is the production of proteins and steroids, the maintenance of plasma membranes, and a pathway for molecules to move along.
1 Nucleus 2 Nuclear pore 3 Rough endoplasmic reticulum (RER) 4 Smooth endoplasmic reticulum (SER) 5 Ribosome on the rough ER 6 Proteins that are transported 7 Transport vesicle 8 Golgi apparatus 9 Cis face of the Golgi apparatus 10 Trans face of the Golgi apparatus 11 Cisternae of the Golgi apparatus
Similar to the ER is the sarcoplasmic reticulum (SR) found only in muscle cells. The SR stores and pumps calcium ions. The SR contains large stores of calcium, which it releases when the muscle cell is stimulated. Another type of cytoplasmic network is the plate-like Golgi apparatus.
The lacey membranes of the endoplasmic reticulum were first seen in 1945 by scientists using an electron microscope.
The lacey membranes of the endoplasmic reticulum were first seen in 1945 by scientists using an electron microscope.
The ER was observed with light microscope by Garnier in 1897, who coined the term "ergastoplasm". With electron microscopy, the lacy membranes of the endoplasmic reticulum were first seen in 1969 by Keith R. Porter, Albert Claude, and Ernest F. Fullam. Later, the word "reticulum", which means "network", was applied by Porter in 1953 to describe this fabric of membranes.
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