The dark spots are ribosomes. There are two types of endoplasmic reticulum: rough endoplasmic reticulum rough ER and smooth endoplasmic reticulum smooth ER. Both types are present in plant and animal cells. The two types of ER often appear as if separate, but they are sub-compartments of the same organelle. Cells specialising in the production of proteins will tend to have a larger amount of rough ER whilst cells producing lipids fats and steroid hormones will have a greater amount of smooth ER.
Part of the ER is contiguous with the nuclear envelope. The Golgi apparatus is also closely associated with the ER and recent observations suggest that parts of the two organelles, i. This is an extensive organelle composed of greatly convoluted but flattish sealed sacs, which are contiguous with the nuclear membrane. These are called membrane bound ribosomes and are firmly attached to the outer cytosolic side of the ER About 13 million ribosomes are present on the RER in the average liver cell.
Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus. This process is called translation. Certain cells of the pancreas and digestive tract produce a high volume of protein as enzymes. Many of the proteins are produced in quantity in the cells of the pancreas and the digestive tract and function as digestive enzymes. Proteins are produced for the plasma membrane, Golgi apparatus, secretory vesicles, plant vacuoles, lysosomes, endosomes and the endoplasmic reticulum itself.
Some of the proteins are delivered into the lumen or space inside the ER whilst others are processed within the ER membrane itself. In the lumen some proteins have sugar groups added to them to form glycoproteins. When proteins are destined to be part of the cell membrane or exported from the cell, the ribosomes assembling them attach to the endoplasmic reticulum, giving it a rough appearance.
The endoplasmic reticulum can either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins.
Sometimes, when those proteins are made improperly, the proteins stay within the endoplasmic reticulum. They're retained and the endoplasmic reticulum becomes engorged because it seems to be constipated, in a way, and the proteins don't get out where they're suppose to go.
Its main function is to produce proteins. It is made up of cisternae, tubules and vesicles. The cisternae are made up of flattened membrane disks, which are involved in the modification of proteins. They are held together by the cytoskeleton. The rough endoplasmic reticulum also contains a perinuclear space , which is the space between the inner and outer phospholipid membrane. The membrane is continuous to the nuclear membrane. Proteins are transferred from the Rough endoplasmic reticulum to the Golgi apparatus via membrane-bound vesicles.
The reason why it is rough endoplasmic reticulum is because of the ribosomes attached to the endoplasmic reticulum. These ribosomes are constantly being attached and detached from the ER because they are not part of the stable organelle.
0コメント