Lecture 11 Review

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of SNAREs in membrane trafficking?

They facilitate the fusion of vesicles with target membranes. (correct)

They transport proteins from the Golgi to the lysosomes.

They assist in the budding of vesicles.

They modify proteins in the Golgi apparatus.

Which of the following is NOT a component involved in vesicular transport?

Coat proteins

Tethering factors

Rab proteins

Transcription factors (correct)

What mechanism do cells use to uptake large particles through endocytosis?

Receptor-mediated endocytosis

Phagocytosis (correct)

Pinocytosis

Exocytosis

Where do proteins synthesized in the rough endoplasmic reticulum primarily go next?

To the Golgi apparatus Signup and view all the answers

What is the main function of the Golgi apparatus in the context of membrane trafficking?

Modification and sorting of proteins Signup and view all the answers

What is the significance of coat proteins in vesicle transport?

They facilitate the budding process of vesicles. Signup and view all the answers

Which of the following correctly describes receptor-mediated endocytosis?

It allows specific uptake of molecules, such as LDL, via receptors. Signup and view all the answers

How does vesicular transport maintain the asymmetry of the lipid bilayer?

Through selective insertion of lipids during vesicle formation. Signup and view all the answers

What is the primary function of the Golgi apparatus?

Elaboration of N-linked oligosaccharide chains Signup and view all the answers

Which component is directly involved in selective transport to the Golgi complex?

COPII vesicles Signup and view all the answers

What does the trans Golgi Network (TGN) sort traffic for?

Sorting to various destinations Signup and view all the answers

In which pathway is the Golgi apparatus involved when sorting secretory components?

Exocytic pathway Signup and view all the answers

Where does the modification and sorting of proteins mainly occur?

Golgi apparatus Signup and view all the answers

Which organelle is known for containing digestive enzymes?

Lysosomes Signup and view all the answers

Which process does NOT occur at the Golgi apparatus?

Protein synthesis Signup and view all the answers

What type of sacs comprise the Golgi apparatus?

Cisternae Signup and view all the answers

What role do Rab GTPases serve in cellular transport?

They recruit tethering proteins for vesicle transport. Signup and view all the answers

Which statement about SNAREs in membrane fusion is accurate?

SNARE bundle disassembly occurs after membrane fusion. Signup and view all the answers

What is the primary function of the molecular motors in vesicle transport?

To move vesicles along microtubules. Signup and view all the answers

What happens to v-SNAREs after they participate in membrane fusion?

They are recycled back to the donor compartment. Signup and view all the answers

What role do ATP-hydrolysis play in the functioning of SNAREs?

It is essential for the formation of the SNARE complex. Signup and view all the answers

Which process is primarily driven by SNARE proteins?

Membrane fusion of transport vesicles. Signup and view all the answers

What is the result of Rab GTPase activation?

It recruits tethering proteins to the transport vesicles. Signup and view all the answers

Which of the following is NOT a function of the Rab GTPases?

Facilitating the disassembly of SNARE bundles. Signup and view all the answers

What role do lysosomal enzymes play in the cell?

They break down biological molecules. Signup and view all the answers

Why is the lumen of lysosomes acidic?

Due to the presence of a proton pump. Signup and view all the answers

At what pH do lysosomal enzymes function optimally?

pH 5.0 Signup and view all the answers

What is one way endocytosis is exploited by viruses?

It enables the virus to bind and enter host cells. Signup and view all the answers

Which of the following is NOT a virus that utilizes endocytosis for entry into cells?

Rhinovirus Signup and view all the answers

What is the term used for the enzymes found in lysosomes that break down biological molecules?

Acid hydrolases Signup and view all the answers

What is a key function of membrane transporters in lysosomes?

To enable reuse of degradation products. Signup and view all the answers

What do viruses like the coronavirus and HIV have in common regarding entry mechanisms?

They both exploit endocytosis. Signup and view all the answers

What role does the LDL receptor play in endocytosis?

It binds LDL and facilitates its internalization. Signup and view all the answers

What occurs if the endosome’s pH is neutralized to 7?

Both LDL and the receptor remain trapped inside the endosome. Signup and view all the answers

Which component is critical for the formation of clathrin-coated pits during receptor-mediated endocytosis?

AP-2 cargo adaptor Signup and view all the answers

What is the primary purpose of endocytosis in cellular processes?

To uptake materials and nutrients from the extracellular environment. Signup and view all the answers

What is the typical pH range found in early endosomes?

Acidic, around pH 6.0 Signup and view all the answers

What happens to receptors after they have internalized particles such as LDL?

They can be recycled back to the plasma membrane. Signup and view all the answers

Endocytosis can be specifically characterized by which of the following mechanisms?

Receptor-mediated endocytosis. Signup and view all the answers

Which of the following describes the process of receptor-mediated endocytosis (RME)?

It requires specific receptors for targeted uptake. Signup and view all the answers

What is the primary function of cargo adaptors in vesicle transport?

To bind to and capture transmembrane proteins Signup and view all the answers

Which coat protein is associated with vesicles that transport cargo from the Endoplasmic Reticulum to the cis-Golgi?

COPII Signup and view all the answers

What role do coat proteins play in vesicle formation?

They bind adaptors to shape the membrane into a vesicle Signup and view all the answers

Which of the following transport pathways involves the recycling of cargo receptors back to the Endoplasmic Reticulum?

COPI pathway Signup and view all the answers

Cargo that travels from the plasmic membrane to the early endosome is primarily associated with which coat proteins?

Clathrin / Adaptin-2 Signup and view all the answers

What defines the protein composition of transport vesicles in cellular transport?

Cargo receptors and their sorting signals Signup and view all the answers

What does the term ‘COP’ signify in the context of cargo and adaptation mechanisms?

Coat Protein Signup and view all the answers

Why might many cargos have more than one sorting signal?

To direct them to multiple locations Signup and view all the answers

Study Notes

Membrane Trafficking: Secretory and Endocytic Pathways

Proteins synthesized on the endoplasmic reticulum (ER) have specific destinations
Vesicle transport moves materials between membrane-bound compartments
Coat proteins, adaptors, SNARES, tethers, and Rab proteins are crucial for membrane trafficking
The Golgi apparatus plays a role in protein processing and sorting
Receptor-mediated endocytosis is a mechanism for taking up specific molecules, like LDL
Phagocytosis allows cells to take up large particles
Vesicle transport is selective, only certain specific proteins are incorporated into transport vesicles
The asymmetry of the lipid bilayer is preserved during vesicle transport, as is the orientation of membrane proteins
The lumen of the ER, the lumen of transport vesicles, and the lumen of the Golgi correspond topologically to the outside of the cell
Regions of proteins with N-linked glycosylation are on the lumenal side and therefore topologically on the outside of the cell
Topics include overview of membrane trafficking pathways, mechanisms of vesicle budding, movement, tethering and fusion, the Golgi apparatus, endocytosis, and lysosomes and autophagy
Proteins destined for secretion, delivery to the lysosome, or to be resident proteins have an ER signal sequence

Vesicle Transport: Budding and Fusion

Vesicles bud from donor compartments, move, fuse with acceptor compartments
Cargo proteins are selectively moved from one membrane to another
Coat proteins, adaptors, vesicle tethers, and motor proteins play a role in budding, movement, tethering, fusion

Vesicle Budding: Cargo Selection and Membrane Shaping

Lumenal cargo selection is mediated by cargo receptors
Cargo adaptors bind to sorting signals in cargo receptor cytoplasmic tails and capture transmembrane protein cargos, including receptors
Coat proteins bind to adaptors, shaping the membrane into a vesicle
Vesicle formation involves pinching from membrane

"Coated" Vesicle Transport Pathways

Coats and their associated adaptors define the protein composition of transport vesicles
COPII vesicles transport materials from the ER to the Golgi
COPI vesicles recycle cargo receptors to the ER

Movement

Vesicles and organelles move along microtubules using molecular motors like cytoplasmic dynein and kinesins

Tethering

Rab GTPases recruit tethering proteins, mediating docking, and positioning vesicles for fusion

Fusion

SNAREs (v-SNAREs and t-SNAREs) drive the fusion of transport vesicles with target membranes
"Tethering" and "zipper formation" of SNAREs occur
SNARE disassembly is ATP-dependent

The Golgi Apparatus

The Golgi apparatus (Golgi complex) is a stack of flattened, membrane-enclosed sacs called cisternae
It functions in protein modification, glycosylation (N-linked oligosaccharides), and sorting of proteins to various destinations
Sorting occurs in the trans Golgi network (TGN)

Secretory Pathways (Constitutive and Regulated)

Newly synthesized proteins and membrane lipids are sorted in the trans Golgi network (TGN) for constitutive or regulated exocytosis
Constitutive secretion is a continuous process
Regulated secretion depends on signals triggered by extracellular factors
"Secretory granules" are vesicles storing concentrated secretory proteins
The TGN sorts traffic to multiple destinations

Endocytosis

Endocytosis is the taking-in of materials from the extracellular space via membrane invagination
Receptor-mediated endocytosis is a process utilizing specific receptors for uptake of materials
Low-density lipoprotein (LDL) receptor-mediated endocytosis (RME) is an example of how cholesterol is transported

Lysosomes

Lysosomes are membrane-bound organelles containing acid hydrolases optimally functioning at an acidic pH.
Lysosomes break down biological molecules; their acidic lumen is essential for their function
Membrane transporters in lysosomes recycle products of degradation

Mutations in membrane trafficking proteins can lead to various diseases affecting different body systems

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the complex processes involved in membrane trafficking, focusing on secretory and endocytic pathways. This quiz covers key concepts such as vesicle transport, Golgi apparatus function, and mechanisms like receptor-mediated endocytosis and phagocytosis. Test your understanding of how proteins are synthesized and sorted within cellular environments.