Ch 5: Cytoplasmic membrane system: Structure, Function, and Membrane Trafficking Flashcards
What are the two types of secretory (biosynthetic) pathway?
constitutive and regulated
What is the difference between the constitutive®ulated?
constitutive secretion, materials are transported in secretory vesicles from their sites of synthesis and discharged into the extracellular space
During regulated secretion, materials are stored as membrane-bound packages and discharged only in response to an appropriate stimulus.
Why various types of proteins can be selected and transported to the right destinations?
by specific sorting signals that are encoded in the amino acid sequence of the proteins or in the attached oligosaccharides
By which way, cells uptake proteins or other big molecular groups?
By the endocytic pathway, materials move from the outer surface of the cell to compartments
What are the functions of Smooth Endoplasmic Reticulum
①synthesis of steroid hormones in the endocrine cells of the gonad and adrenal cortex,
②detoxification in the liver of a wide variety of organic compounds,
③Release of glucose from glucose 6-phosphate in liver cells
What are the functions of Rough Endoplasmic Reticulum?
1) synthesize, process, glycosylate and quality-control certain proteins, includes: ①proteins secreted from the cell, ②integral membrane proteins, ③soluble proteins that reside within compartments of the endomembrane system; (2) synthesize most membrane lipids and membranes
Why do ribosomes attached to the cytosolic surface of the RER membranes?
Certain polypeptides are synthesized on ribosomes attached to the cytosolic surface of the RER membranes. These proteins contain a signal sequence at their N-terminus that directs the emerging polypeptide and ribosome to the ER membrane.
What is the detailed process of signal hypothesis?
(1) Secretory proteins contain a signal sequence at their N-terminus that directs the emerging polypeptide and ribosome to the ER membrane.
(2) The polypeptide moves into the cisternal space of the ER through a protein-lined, aqueous channel in the ER membrane.
(3) The polypeptide moves through the membrane as it is being synthesized, that is, cotranslationally.
What is the structure of a Golgi Complex?
The Golgi complex has a characteristic morphology consisting primarily of flattened, disklike, membranous cisternae with dilated rims and associated vesicles and tubules.
What are the defferences of glycosylation between Golgi Complex with rER?
The synthesis of N-linked oligosaccharides begins in the ER, those attached to proteins by O-linkages are assembled entirely within the Golgi complex.
What are the three types of vesicles transporting between cell organelles and cell membrane?and their functions?
COPII-coated vesicles mediate transport from the ER to the ERGIC and Golgi complex.
COPI-coated vesicles return proteins from the ERGIC and Golgi complex to the ER, also transport Golgi enzymes between cisternae in a retrograde direction.
Clathrin-coated vesicles mediate transport from the TGN to endosomes and lysosomes
What is the retrieval signals of ER proteins maintaining them staying in the ER lumen?
“lys-asp-glu-leu” (or KDEL).
What’s the sorting signal of Lysosomal proteins in Golgi complex?
phosphorylated mannose residues
What is the character of all enzymes inside lysosomes?
all have their optimal activity at an acid pH and thus are acid hydrolases.
How can lysosomes maintain low pH?
proton pump
Why lysosomal enzymes could not digest lysosomal membrane?
Lysosomal membranes contain a variety of highly glycosylated integral proteins, those carbohydrate chains form a protective lining that shields the membrane from attack by the enclosed enzymes.
What are the functions of lysosomes?
(1) breakdown materials brought into the cell from extracellular environment, resulting nutrients into the cytosol;
(2) ingest debris and potentially dangerous microorganisms
(3) role in organelle turnover, regulate destruction of the cell’s own organelles.
How does a cell uptake macromolecules high efficiently?
Receptor-mediated endocytosis provides a means for selective and efficient uptake of macromolecules
