Protein Cotranslational Targeting to the ER

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What is the final product of the conversion of diacylglycerol to phosphatidylcholine?

Phosphatidic acid

Phosphocholine (correct)

Phospholipid flippase

Phosphatase

Where are phospholipids synthesized in relation to the ER membrane?

On the luminal side of the ER membrane

In the Golgi apparatus

On both sides of the ER membrane simultaneously

On the cytosolic side of the ER membrane (correct)

What facilitates the transfer of phospholipids to the lumenal half of the ER bilayer?

Flippases (correct)

Mitochondria

Ribosomes

Golgi apparatus

Where are large amounts of smooth ER typically found?

Steroid-producing cells Signup and view all the answers

What is the primary function of smooth ER in the liver?

Detoxification of compounds Signup and view all the answers

Which process occurs at the smooth ER?

Synthesis of steroid hormones Signup and view all the answers

What is the role of the signal recognition particle (SRP) in cotranslational targeting of secretory proteins to the ER?

Binds to the signal sequence emerging from the ribosome Signup and view all the answers

What happens after the signal recognition particle (SRP) escorts the complex to the ER membrane?

The SRP binds to the translocon Signup and view all the answers

Which step involves the insertion of the signal sequence into the translocon during cotranslational targeting of secretory proteins to the ER?

Step 3: Release of SRP and ribosome binding to translocon Signup and view all the answers

What drives the translocation of the growing polypeptide chain across the membrane during cotranslational targeting to the ER?

Continued translation process Signup and view all the answers

Which enzyme is responsible for cleaving the signal sequence during cotranslational targeting of secretory proteins to the ER?

Signal peptidase Signup and view all the answers

Where are glycolipids and sphingomyelin synthesized?

Golgi apparatus Signup and view all the answers

How are proteins transported from the Golgi apparatus to their final destinations?

In vesicles Signup and view all the answers

What is one function of the Golgi apparatus besides processing glycoproteins?

Synthesizing glycolipids Signup and view all the answers

Where are ceramide, cholesterol, and glycerol phospholipids synthesized?

Endoplasmic Reticulum Signup and view all the answers

What is the process known as when proteins are targeted to late endosomes that develop into lysosomes?

Autophagy Signup and view all the answers

In polarized epithelial cells, how are plasma membranes divided?

Apical and basolateral domains Signup and view all the answers

What is the role of Arf/GTP in vesicle formation?

Recruits an adaptor protein for cargo selection and coat assembly Signup and view all the answers

Where are lysosomes formed?

From late endosomes and transport vesicles Signup and view all the answers

What happens when Dynamin constricts the neck of a vesicle?

Membrane fission occurs Signup and view all the answers

What is one major function of lysosomes?

Digesting material taken up by endocytosis Signup and view all the answers

Where are active drugs processed in the cell?

Lysosomes Signup and view all the answers

What leads to the formation of lysosomes?

Fusion of transport vesicles with trans-Golgi network Signup and view all the answers

What is the final destination for transmembrane proteins after they are inserted into the ER membrane?

Golgi apparatus Signup and view all the answers

Where are the portions of polypeptide chains that are translocated into the ER exposed following transport to the plasma membrane?

Cytosolic side Signup and view all the answers

How are membrane proteins with internal transmembrane sequences inserted in the ER membrane?

Its amino (N) terminus is exposed on the cytosolic side Signup and view all the answers

Which region of a protein directs the insertion of a polypeptide chain into the ER membrane?

20-25 hydrophobic amino acids Signup and view all the answers

What happens to a polypeptide chain after its transmembrane sequence exits the translocon during insertion into the ER membrane?

It anchors in the lipid bilayer Signup and view all the answers

What is the topological equivalence between the lumens of the ER and Golgi apparatus?

They are equivalent to the exterior of the cell Signup and view all the answers