rough & smooth endoplasmic reticulum

illustration of cell structure: rough endoplasmic reticulum

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animal cell structure diagram

Generalised Animal Cell Structure Diagram

DIAGRAM In this picture, the rough endoplasmic reticulum is seen as stack of golden cisternae connected by bridges. It is sectioned to reveal the interior space or "lumen" which appears purple. At lower left, the lumen is seen to be continuous with the lumen of thenuclear envelope. The surface (golden) is covered by ribosomes, which impart the "rough" appearance. Proteins synthesised by these attached ribosomes pass into the lumen. At upper right, small transitional vesicles can be seen budding from the roughER. These carry proteins destined for processing by theGolgi. As well as connecting to the nuclear envelope, the rough ER is continuous with thesmooth endoplasmic reticulum. SUMMARY name(s): rough endoplasmic reticulum, rough ER location: throughout cytoplasm appearance: sacs size: about 100nm in depth function: used in protein synthesis.

This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. A series of membrane bound chambers within a cell which plays an important part in the synthesis of lipids and proteins which are destined to be inserted in the cell membrane. There are two types of ER: smooth and rough. Smooth ER is the site of synthesis and digestion of fatty acids and phospholipids. In the liver it is used to modify dangerous chemicals such as pesticides ready for excretion. Rough ER is the site of manufacture of secretory proteins as well as proteins destined to be inserted in the cell membrane. It is rough because of the vast numbers of ribosomes which stud its surface. As these ribosomes build an amino acid chain, it is injected through the ER into the vesicle, as shown in this diagram. Once the amino acid chain enters the vesicle it is folded, often with the help of other enzymes. There are several "quality control" mechanisms to ensure that incorrectly folded proteins do not leave the vesicle. There are special proteins called "chaperones" which stick to mis-formed proteins and ensure they do not leave the ER. Life could not function well without these mechanisms. However genetic mutations can cause some diseases which affect these quality control chaperones. For example cystic fibrosis is caused by a build up of misformed proteins, together with their chaperones, inside ER vesicles. The proteins made in the ER are packaged into vesicles and passed on the Golgi complex for further processing.

illustration of cell structure: smooth endoplasmic reticulum

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Picture by Russell Kightley Media, all rights reserved.

Generalised Animal Cell Structure Diagram
DIAGRAM In this picture, the smooth endoplasmic reticulum is seen as a tangle of pink interconnected tubules. Unlike therough ER, it lacks ribosomes. The smooth ER is continuous with therough ERbut has different functions. SUMMARY name(s): smooth endoplasmic reticulum, smooth ER, tubular endoplasmic reticulum, agranular endoplasmic reticulum location: in cytoplasm appearance: interconnected and ramifying tubules; no ribosomes size: tubules are about 150nm in diameter (variable) function: used in lipid synthesis, detoxification and other metabolic processes.