2025.2.12+BIOL+170+Organelles_+Lysosomal+Targeting_POST

Game Time and Polling Setup

  • Event Details:

    • Join @ slido.com

    • Session #: 8607384

    • Starts: 12:00PM

Secretory Proteins and the Endoplasmic Reticulum

  • True or False: The translation of secretory proteins begins at the rough endoplasmic reticulum.

N-terminal Signal Peptide Recognition

  • Question: The emergence of an N-terminal signal peptide during translation of a secreted protein is recognized by which protein complex?

SRP Receptors and Organelles

  • Question: The SRP receptor is found on the membranes of which organelle?

Types of Transmembrane Proteins

  • Question: Which type of transmembrane protein possesses a typical N-terminal signal sequence for SRP recognition?

Protein Modifications in RER Lumen

  • Question: Which protein modification does NOT occur in the rough endoplasmic reticulum lumen?

Protein Folding Quality Control

  • Question: Which quality control mechanism assists proteins to fold properly in the rough endoplasmic reticulum?

Muddiest Points Summary

  • Themes: Most to Least Frequent:

    1. Types of Membrane Proteins & Their Differences (9 mentions)

      • Difference between Type II and III membrane proteins.

      • Characteristics of protein types 1-4.

      • GPI-anchored proteins.

    2. Signal Sequences & Anchoring Mechanisms (4 mentions)

      • Confusion about signal anchors on RER.

      • Peripheral proteins' transition to fatty acids.

Recap of Membrane Protein Types

  • Types:

    • Type I: N-terminal signal sequence for SRP recognition.

    • Type II: Second hydrophobic region as a stop-transfer anchor.

    • Type III: One internal hydrophobic region as both signal sequence and stop-transfer anchor.

    • Type IV: Multiple hydrophobic regions that alternate as signal-anchor and stop-transfer sequences.

Endoplasmic Reticulum Quality Control

  • Key Terms:

    • Endoplasmic reticulum-associated degradation (ERAD) pathway.

    • Misfolded proteins are exported to the cytoplasm.

Ubiquitin-Proteasome System

  • Components:

    • E1, E2, E3, and E4 enzymes activate and transfer ubiquitin.

    • Proteasome degrades polyubiquitinated proteins.

Background on Ubiquitin Proteasome System

  • Question: Which component ligates a ubiquitin molecule to a protein fated for degradation?

    • Correct: E3 ligase.

Proteins' Pathway Analysis in the Cytoplasm

  • Key Terms:

    • Glycosidase, ubiquitination, misfolded proteins.

    • Retrotranslocon, 26S proteasome for degradation.

Vesicular Traffic: Basics

  • Coat Protein Assembly: Important in shaping vesicles from membranes.

Membrane Targeting and Fusion

  • Mechanisms:

    • Rab proteins contribute to specificity.

    • v-SNAREs (vesicle) and t-SNAREs (target) for membrane fusion.

SNARE Protein Recycling

  • Process: SNARE complexes are disassembled by NSF to allow recycling.

Golgi Apparatus Overview

  • Regions:

    • cis Golgi: Where vesicles arrive.

    • trans Golgi: Where sorting occurs.

N-linked Glycosylation

  • Process: Transferring oligosaccharide units to asparagine residues for protein stability and targeting.

Golgi Apparatus Modifications

  • Key Processes:

    • Trimming and additional modifications in the Golgi.

    • Different types of glycosylation (O-linked, phosphorylation).

Anterograde vs. Retrograde Transport

  • Key Points:

    • Anterograde (RER to Golgi) vs. Retrograde (Golgi to RER).

    • Importance of retrograde transport for SNARE recycling.

Lysosomal Targeting

  • Enzyme Dynamics: Targeting and function of lysosomal enzymes under study.

Endosomes: Sorting Vesicles

  • Functions: Formed during endocytosis, crucial for internalized material processing.

Types of Endocytosis

  • Categories:

    • Phagocytosis: Engulfing large particles.

    • Clathrin-dependent vs. Clathrin-independent.

Receptor-Mediated Endocytosis Examples

  • LDL Uptake: Mechanism of dietary cholesterol delivery involving clathrin-coated vesicles.

List of Lysosomal Storage Diseases

  • Examples: I-cell disease, Tay-Sachs disease, Pompe disease, Gaucher’s disease, and their impacts.

Pathways for Protein Degradation Comparison

  • ERAD vs. Lysosomal: Analysis of degradation pathways, highlighting similarities and differences.

Mitochondria Overview

  • Features:

    • Number changes based on cell metabolic needs.

    • Symbiotic theory of origin.

Peroxisomes Functionality

  • Roles: Oxidation of fatty acids, breakdown of purines, biosynthesis related processes.

Targeting of Proteins to Organelles

  • Process: Recognition of signals for transport.

Journal Club Activity Overview

  • Goals: Understanding experimental design and analyzing scientific data from assigned articles and figures.