Anatomy 25 organelles endoplasmic reticulum

Rough endoplasmic reticulum / granular endoplasmic reticulum are the same thing, can be referred to as r.e.r. or g.e.r.

"endoplasmic reticulum" means "network with in the cytoplasm".

Rer is folds of unit membrane with spaces between called "cisternae".

The rer borders on and connects to the nuclear membrane and also connects to the ser, smooth endoplasmic reticulum.

Process...

• Functioning ribosomes with mRNA bond to the rer.
• The protein being built enters the cisterna.
• The protein elongates and is modified ( lipids or sugar groups added on, folding occurs ).
• The ribosome detaches.
• The protein is released into the cisterna and encapsulated by the rer membrane which forms a bubble around it.
• The protein in the unit membrane bubble is transported through the rer to the Golgi Apparatus.

Rer produces:

• Unit membrane proteins - the proteins that make up the rer itself as well as proteins for the lipid bi-layer.
• Hydrolases - enzymes that are found in lysosomes which break down things in the body.
• Secretory proteins - secreted proteins that are ejected outside of the cell entirely and carried to other parts of the body, like mucus ( snot ) proteins.

Smooth endoplasmic reticulum ( ser ) / agranular endoplasmic reticulum is a system of interconnected unit membrane tubules. It connects to the rer in places and to cytoplasm.

Ser does not receive ribosomes or synthesize / transport proteins. It performs different functions in differenet cells.

• Functions-
• Lipid processing - takes in lipids from food and processes them.
• Steroid production - synthesizes steroids in adrenal cortex, sex hormones in reproductive organs.
• Detoxification - Ser in liver cells takes toxins in and tries to detoxify them ( like when you go drinking ). Too much alcohol can wear out the ser in liver cells.
• Storage of calcium ions - Both smooth and rough ER can store calcium ions which are used in signaling cells to do different things like telling muscle cells to contract and secretory cells to secrete secretions.

Gogli apparatus is similar to the endoplasmic reticulums in that it is made of folds of unit membrane with spaces in between called "cisternae".

The golgi apparatus has a convex "cis face" facing towards the nucleus and a convex "trans face" which faces away from the nucleus.

• Transport vescicles full of proteins from the rer make their way to the Golgi apparatus. They attach to the cis face and release their contents
• into the cis-Golgi-network. The Golgi apparatus then sorts and packages the different proteins, sometimes modifying them by adding carbohydrates or phosphates. Once sorted, the apparatus creates a sacule filled with proteins which then detaches and is released into the cytoplasm and sent off to 1 of 3 places.

Some transport vescicles simply attach to and become part of the cell membrane. This happens in all cells.

Some secretory vesicles make their way to the cell membrane and release their contents to the outside of the cell, "exocytosis". This happens in secretory cells.

Some transport vesicles are actually lysosomes which cary a digestive enzyme called acid hydrolase, the lysosomes break down worn out bits of cells, food particles, carbohydrates, lots of stuff.