Intracellular Transport (Chapter 10)

Intracellular Transport (Chapter 10)

Distinguishing Features of Eukaryotic and Prokaryotic Cells

• Question: What distinguishes eukaryotic cells from prokaryotic cells?
  Answer: Eukaryotic cells are characterized by the presence of membrane-bound organelles and a complex intracellular organization.

Endomembrane System

• Question: What is the endomembrane system?
  Answer: The endomembrane system is a network of connected organelles that are involved in the processing and transport of proteins and lipids.

Major Components of the Endomembrane System

• Question: Name major components of the endomembrane system.
  Answer: The major components include the Endoplasmic Reticulum (ER), Golgi apparatus, lysosomes, endosomes, and peroxisomes.

Protein Destination Inside the Cell

• Question: What determines the final destination of a protein inside the cell?
  Answer: The final destination of a protein is determined by its signal sequence.

Nuclear Localization Signal (NLS)

• Question: What is a Nuclear Localization Signal (NLS)?
  Answer: A Nuclear Localization Signal (NLS) is a short amino acid sequence that directs proteins specifically to the nucleus.

Proteins Lacking Targeting Signals

• Question: Proteins lacking targeting signals remain where?
  Answer: Proteins that do not have targeting signals remain in the cytosol.

ER Signal Sequence Attachment

• Question: What happens if an ER signal sequence is attached to a cytosolic protein?
  Answer: If an ER signal sequence is attached, the cytosolic protein is directed into the ER.

Nuclear Transport Regulation

• Question: What structure controls transport into and out of the nucleus?
  Answer: The structure that controls transport into and out of the nucleus is the Nuclear Pore Complex (NPC).

Selectivity of the Nuclear Pore Complex (NPC)

• Question: Why is the NPC considered selective?
  Answer: The NPC is selective because it allows specific macromolecules to pass while blocking others.

Protein Conformation and Nuclear Entry

• Question: Can proteins enter the nucleus in their folded form?
  Answer: Yes, proteins can enter the nucleus while in their folded structure.

Energy Source for Nuclear Transport

• Question: What energy source powers nuclear transport?
  Answer: Nuclear transport is powered by GTP hydrolysis.

Molecular Switch for Nuclear Transport

• Question: What molecular switch regulates nuclear import and export?
  Answer: The molecular switch that regulates this process is Ran GTPase.

Distribution of Ran Forms

• Question: Where is Ran-GTP most abundant?
  Answer: Ran-GTP is most abundant in the nucleus.

• Question: Where is Ran-GDP most abundant?
  Answer: Ran-GDP is most abundant in the cytosol.

Importance of the Ran Gradient

• Question: Why is the Ran gradient important?
  Answer: The Ran gradient is important because it provides directionality to nuclear transport.

Protein Synthesis Location

• Question: Where are most proteins synthesized before targeting?
  Answer: Most proteins are synthesized in the cytosol prior to being targeted for specific locations.

Protein Conformation Before Membrane Crossing

• Question: What must happen to many proteins before crossing a membrane?
  Answer: Many proteins must unfold before they can cross a membrane.

Mechanisms for Membrane Crossing

• Question: What structures allow proteins to cross membranes?
  Answer: Protein translocators are the structures that enable proteins to cross membranes.

Entry Point of the Secretory Pathway

• Question: Why is the ER considered the entry point of the secretory pathway?
  Answer: The ER is considered the entry point because proteins destined for secretion or membrane incorporation first enter here.

Role of the Signal Recognition Particle (SRP)

• Question: What particle recognizes ER signal sequences during translation?
  Answer: The Signal Recognition Particle (SRP) recognizes ER signal sequences during translation.

Effect of SRP Binding on Translation

• Question: What effect does SRP binding have on translation?
  Answer: The binding of SRP temporarily pauses translation.

Differences Between Soluble and Membrane Proteins

• Question: What distinguishes soluble ER proteins from membrane proteins?
  Answer: Soluble ER proteins are released into the lumen, whereas membrane proteins remain embedded within the membrane.

Sequence for Membrane Anchoring

• Question: What sequence anchors proteins in the membrane?
  Answer: A hydrophobic stop-transfer sequence is responsible for anchoring proteins in the membrane.

Vesicular Transport Purpose

• Question: What is vesicular transport used for?
  Answer: Vesicular transport is used for moving proteins and lipids between membrane-bound compartments.

Secretory Pathway Definition

• Question: What is the secretory pathway?
  Answer: The secretory pathway refers to the outward transport of proteins and lipids from the ER to the cell surface.

Endocytic Pathway Definition

• Question: What is the endocytic pathway?
  Answer: The endocytic pathway is the inward transport from the plasma membrane to endosomes and lysosomes.

Role of Coat Proteins

• Question: What role do coat proteins play?
  Answer: Coat proteins shape membranes into vesicles and select cargo for transport.

Major Types of Vesicle Coats

• Question: Name major vesicle coat types.
  Answer: The major types of vesicle coats include clathrin-coated vesicles and COP-coated vesicles.

Protein Lattice Formation

• Question: What protein forms a lattice around budding vesicles?
  Answer: Clathrin is the protein that forms a lattice structure around budding vesicles.

Linking Cargo to Clathrin

• Question: What proteins link cargo to clathrin?
  Answer: Adaptins are the proteins that connect cargo to clathrin.

Vesicle Budding Mechanism

• Question: What protein pinches off budding vesicles from membranes?
  Answer: Dynamin is the protein responsible for pinching off budding vesicles from membranes.

Vesicle Docking and Fusion Proteins

• Question: What proteins mediate vesicle docking and fusion?
  Answer: SNARE proteins mediate the processes of vesicle docking and fusion.

Location of v-SNARE and t-SNARE

• Question: Where are v-SNAREs located?
  Answer: v-SNAREs are located on the vesicle membrane.

• Question: Where are t-SNAREs located?
  Answer: t-SNAREs are located on the target membrane.

Mechanism of SNARE Protein Function

• Question: What happens when v-SNAREs bind t-SNAREs?
  Answer: When v-SNAREs bind to t-SNAREs, the membranes are pulled together until fusion occurs.

Result of Vesicle Fusion

• Question: What is the final result of vesicle fusion?
  Answer: The final result of vesicle fusion is the delivery of cargo to the target compartment.