Endoplasmic Reticulum & Golgi Apparatus Flashcards
What is the internal space of the ER called?
The ER lumen
What are the two parts of the ER, and why are they called such?
Rough ER - Flattened sheets with ribosomes bound to the outer surface.
Smooth ER - Tubular structure with no ribosomes
What are the four functions of the smooth ER?
- Lipid biosynthesis
- Carbohydrate metabolism
- Calcium storage
- Detoxification of drugs and poisons
What are the three functions of the rough ER?
- Protein biosynthesis
- Protein folding and modification
- Removal of incorrectly folded proteins
What are the three main components of a membrane and where are they made?
- Phospholipids
- Cholesterol
- Glycolipids
All are made in the smooth ER
What is the function of cholesterol?
Important in maintaining membrane structure, and acts to reduce membrane permeability
The sarcoplasmic reticulum in muscles allows for contraction and relaxation by moving calcium in/out of the smooth ER. What happens to the calcium ions during muscle contraction?
Calcium ions released from the ER
The sarcoplasmic reticulum in muscles allows for contraction and relaxation by moving calcium in/out of the smooth ER. What happens to the calcium ions during muscle relaxation?
Calcium ion intake into the ER
What enzymes are found in the smooth ER of liver hepatocytes that detoxify chemicals by adding hydroxyl groups?
Cytochrome P450
How does protein synthesis occur in the rough ER?
Ribosomal sub-units located along the ER and mRNA in the cytoplasm
The ER is a major protein folding site. What two types of molecules in the ER lumen help in the folding and release of the proteins?
Chaperone proteins and folding enzymes
What type of protein is binding immunoglobulin protein (BiP)?
A chaperone protein
Around half of the proteins processed in the ER are glycoproteins. 90% of these undergo what process in the ER lumen?
N-linked glycosylation
What is N-linked glycosylation?
The addition of a pre-formed precursor oligosaccharide (14 sugars) onto the NH2 side-chain of asparagine
Is Endoplasmic Reticulum Quality Control (ERQC) efficient or inefficient?
Very inefficient - more than 80% of proteins never achieve their fully folded state