Module 2: Lesson 1 Flashcards
Even if cells have different functions, what do they all have the same of?
Membrane-enclosed organelles
What allows for cellular specialization?
Cellular compartmentalization
What dominates cellular mass?
Proteins
What are the different mechanisms by which proteins move from one compartment to the other?
Gated transport, transmembrane transport using protein translocators, and vesicular transport
How do cytosolic proteins know where to go in the cell?
Proteins are dispatched to their specific destination because proteins have specific amino acid sequences in their structure.
What recognizes sorting signals? What is another term for sorting signals?
Complementary sorting receptors that guide proteins to their appropriate destination. Sorting signals are also called signal sequences.
What happens to proteins that lack sorting signals?
They remain in the cytosol.
What terminus are sorting signals found on? What direction does synthesis occur?
A sorting signal is found on the N-terminus, and synthesis proceeds in the Nā to Cā direction.
What happens to the N-terminus when a protein is finished?
It is removed.
What are recombinant DNA techniques to change the destination of two proteins?
The signal sequence is removed from the organelle protein and attached to the cytosolic protein. Both proteins are reassigned to the expected, inappropriate location.
What are the characteristics of the inner nuclear membrane?
The inner membrane consists of nuclear lamins, providing structural support and anchoring sites for NPCs and chromosomes.
What are the characteristics of the outer nuclear membrane?
The outer membrane is contiguous with the ER and penetrated with nuclear pores.
What kind of transport does the NPC use?
Gated transport.
What is/are the type(s) of GTP-binding proteins?
Monomeric GTPases or trimeric GTP-binding proteins.
Nuclear protein is powered by what?
GTP hydrolysis by the small molecule, GTPase Ran.
What are the conformations of GTPase Ran?
One carries GTP, the other carries GDP.
What is the accessory protein that triggers GTP hydrolysis, and where is it found?
The protein is called Ran-GAP (GTPase activating protein) and is found in the cytosol. It converts Ran-GTP to Ran-GDP.
Which conformation of Ran has a higher concentration in the nucleus?
Ran-GTP
What must happen to the proteins transported to the mitochondria or ER?
They must be unfolded to get through the membrane.
What aids protein folding?
Chaperone proteins
Signal sequences that direct proteins to the mitochondrial matrix space have the potential to form what?
An amphiphilic alpha protein, which is recognized by specific receptor proteins on the mitochondrial surface.
Translocation into the mitochondria depends on what?
Signal sequences and protein translocators.
What encloses the ER lumen, and how much cell space does it take up?
The ER and nuclear membrane forming a continuous sheet, taking up around 10% of cell space.
The ER serves as what for proteins destined for other organelles and exocytosis?
An entry point.
What is the co-translation translocation process?
The process of proteins being moved into the ER lumen for import before the polypeptide chain is completely synthesized. This occurs in mammalian cells.
What organelles have post-translation translocation?
Mitochondria and peroxisomes.
What types of proteins are synthesized in membrane-bound ribosomes?
Water-soluble proteins and prospective transmembrane proteins.
