Lecture 07

• What is the primary function of the nucleus in protein transport?

  DNA is transcribed into mRNA
• How does the endomembrane system relate to the secretory pathway?

  It facilitates protein sorting and secretion

  
• What is the role of ribosomes in protein synthesis?

  They translate RNA to protein

  
• What modifications occur in the rough endoplasmic reticulum?

  Post-translational modifications like disulfide bridges
• What is synthesised in the smooth endoplasmic reticulum?

  Lipids including steroids
• What is the function of the Golgi apparatus?

  Modifies, sorts, and sends proteins
• What do ribosomes consist of?

  Small and large ribosomal subunits

  
• What is the primary structure of a protein?

  A chain of amino acids
• What is an example of a protein with a primary structure?

  Insulin
• What characterises the secondary structure of proteins?

  Local folding patterns like alpha helices
• What is an example of a secondary structure?

  Alpha-helix in keratin
• What defines the tertiary structure of a protein?

  Three-dimensional arrangement of secondary structures
• What is an example of a protein with tertiary structure?

  Myoglobin
• What is the quaternary structure of a protein?

  Multiple polypeptide chains forming a complex
• What is an example of a protein with quaternary structure?

  Hemoglobin
• What is co-translational import?

  Proteins imported as they are translated

  
• What is post-translational import?

  Proteins imported after translation is complete

  
• How does co-translational import occur?

  mRNA moves to ribosome on ER

  
• What happens to proteins after they leave the Golgi apparatus?

  They may go to lysosomes or outside the cell

  
• What is the role of the signal peptide in co-translational translocation?

  Directs proteins into the rough ER

  
• What occurs during simultaneous translation and translocation?

  Polypeptide chain synthesised into ER lumen
• What modifications occur inside the ER?

  Post-translational modifications and folding
• What is the function of chaperones in protein folding?

  Assist in folding and assembly of proteins
• How do chaperones recognise misfolded proteins?

  By identifying exposed hydrophobic regions
• What role do chaperones play in stabilising proteins?

  Prevent aggregation of misfolded proteins
• How do chaperones facilitate correct protein folding?

  Provide a protected environment for folding
• What energy source do some chaperones use for folding?

  ATP
• What happens if a protein cannot reach its correct structure?

  Chaperones may facilitate its degradation
• What are heat shock proteins (HSPs)?

  Well-known types of chaperones
• What is the function of the Golgi apparatus in protein transport?

  Processes and sorts proteins for secretion

  
• What is the Cis face of the Golgi apparatus?

  The receiving side of the Golgi apparatus

  
• What happens when vesicles fuse with the Golgi apparatus?

  Contents are emptied into the Golgi lumen
• What is the targeting sequence for lysosomes?

  GlcNAc phosphotransferase recognition site
• What is the targeting sequence for mitochondria?

  N-terminal amphipathic helix, 20-50 amino acids
• What is the receiving side of the Golgi apparatus called?

  Cis face

  
• How do proteins move through the Golgi apparatus?

  They move from the Cis face to the Trans face

  
• What happens when vesicles formed from the endoplasmic reticulum fuse with the Golgi apparatus?

  They empty their contents into the lumen

  
• What are signal sequences in proteins?

  They direct proteins to their cellular destination
• What is the process of budding?

  Forming small vesicles from a donor membrane

  
• What is fusion in cellular processes?

  Merging two membrane-bound structures