Endoplasmic Reticulum

endoplasmic reticulum

• made of membranous sheets

• cisternae, flattened folds

• space in cisternae is called cisternal space

• made of ser and rer

Rough endoplasmic reticulum

• composed of cisternae

• pebbly surface

• ribosomes synthesize proteins, proteins enter the cisternal space via a channel and modified

• proteins are

  • exported from cell

  • lysosomes or vacuoles proteins

  • embedded in plasma membrane

how are proteins on the rer modified

• polypeptide enter

• made into glycoprotein

• then a transport vesicle is formed

smooth endoplasmic reticulum

• formed of vesicles and tubules

• no ribosomes/very rarely

functions of smooth endoplasmic reticulum

• contain enzymes to synthesize carbs, steroids hormones and lipids

• hydrolysis of glycogen

• chemical modification of proteins synthesized on the rer

• stores Ca2+ signaling molecule

• modifies foreign substances to make them less toxic

ratio of rer to ser

• cells needs

  • eg liver cells will have more ser as their function is to detoxify

  • cells that carry out lipid synthesis such as brain and testes will have more ser

  • exocrine pancreatic cells (secrete proteins) have more rer then ser