Protein Sorting and Transport Quiz

Ribosomes and Protein Synthesis

• Ribosomes are found in the cytoplasm, either free or attached to the rough endoplasmic reticulum (ER).
• The small subunit of ribosomes contains ribosomal RNA (rRNA) and is crucial for decoding mRNA.
• Ribosomal proteins assist in the assembly of rRNA and play key roles in the initiation and elongation phases of protein synthesis.

Smooth Endoplasmic Reticulum (ER)

• The smooth ER is primarily responsible for lipid synthesis, including phospholipids and cholesterol.
• It also plays roles in detoxification processes and metabolism of carbohydrates.

Protein Targeting and Processing

• Signal sequences are short peptide chains located at the N-terminus of the protein, guiding it to cellular compartments.
• The signal recognition particle (SRP) facilitates the targeting of proteins to the ER by recognizing and binding to the signal sequences.
• Glycosylation is the process of adding carbohydrates to proteins, critical for protein folding, stability, and cell signaling.

Golgi Apparatus Functions

• The Golgi apparatus modifies, sorts, and exports proteins received from the rough ER, preparing them for their final destinations.
• Specific signals on the proteins direct their incorporation into the correct transport vesicles for transport to cellular locations.

Transport Vesicles and Quality Control

• Transport vesicles function to transport proteins and lipids between cellular compartments, maintaining proper cellular organization.
• The quality control system in the ER ensures that only properly folded and assembled proteins proceed to the Golgi apparatus.

Lysosomes and Cell Membranes

• Lysosomes contain hydrolytic enzymes for breaking down waste materials and cellular debris.
• Phospholipids are the main component of cell membranes, providing structure and fluidity.

Translocon Function

• The translocon is a protein complex in the ER membrane that facilitates the translocation of newly synthesized proteins into the ER lumen.