Term
| What are the major types of internalization events? |
|
Definition
| endocytosis, early endosome, pinosomes, phagosomes, pinocytosis, phagocytosis. |
|
|
Term
| what are the molecules that can enter by receptor mediated endocytosis? |
|
Definition
toxins, antibodies, viruses, hormones, growth factors, serum transport proteins
LDL |
|
|
Term
|
Definition
| allow lipids to be carried through the bloodstream. |
|
|
Term
| what are the steps of receptor mediated endocytosis? |
|
Definition
ligand binds to the receptor
receptor/ligand will complex or patch.
receptor ligand is concentrated in clathrin coated pit |
|
|
Term
| what is the importance of ligand binding? |
|
Definition
| causes activation of second messenger that can eventually affect cells in good or bad way |
|
|
Term
| what is the importance of concentrating the receptor/ligand in patches? |
|
Definition
| it allows entry of fluids, stops overflow from occurring, which would make more work for the cell. |
|
|
Term
| what is the importance of the clathrin coated pits? |
|
Definition
| they collect the receptor ligand complex and concentrate them. |
|
|
Term
| what effect does temperature play on clathrin coated pits. |
|
Definition
| the higher the temperature, the more patching and internalization; although some may still occur in low temperatures |
|
|
Term
| how do clathrin coated pits form? |
|
Definition
the clathrin coat subunits assemble on the membrane and bud formation.
they then begin to form a coated pit, which then forms the vesicle. |
|
|
Term
| how are pits organized on the membrane? |
|
Definition
|
|
Term
| what is the name of the protein that assists in the guiding of the receptors to the pits? |
|
Definition
|
|
Term
| what do receptors have that recognize the pits |
|
Definition
| signal sequence at the end of their cytoplasmic domain |
|
|
Term
| what happens when receptor binds to the pits? |
|
Definition
| the signal sequence binds to adaptin molecules in the coat (AP-2) which stops and concentrates the receptor. |
|
|
Term
| what other effects does the signal sequence have on pits |
|
Definition
| they will stimulate more clathrin to accumulate |
|
|
Term
| how does the pit become a vesicle? |
|
Definition
pit is bound to the PM by a narrow stem
dynamin associates w/the stem.
hydrolysis of GTP provides energy to free connection and formation of the vesicle carrying cargo away from cell.
the clathrin coated vesicle then loses its coat and then fuses, by a specific sorting signal, with other vesicles to form the early endosome |
|
|
Term
| what is the composition of the signal complex? |
|
Definition
| tyrosine arginine phenylalanine |
|
|
Term
| what is the receptor signal complex present for? |
|
Definition
| binda adaptin in clathrin coated pit. |
|
|
Term
| what does the genetic defect in LDL receptors cause? |
|
Definition
| inability of receptors to bind to adaptin 2 |
|
|
Term
| what does the genetic defect in not being able to take in cholesterol cause? |
|
Definition
|
|
Term
| what is hypercholesteolemia? |
|
Definition
| mutation in LDL receptor that binds cholesterol but never enters the cell |
|
|
Term
| how do vesicles lose their clathrin coat and fuse to form early endosomes |
|
Definition
| they carry a rab5 sorting signal linked to GDP |
|
|
Term
| what happens to early ribosomes |
|
Definition
they release some receptors at a ph of 6.
the receptors are then recycled back to the PM. |
|
|
Term
| why are endosomes called recycling endosomes |
|
Definition
| the endosome recycles the receptors back to the membrane in the form of vesicles. |
|
|
Term
| are all receptors recycled? |
|
Definition
|
|
Term
| what are the characteristics of a late endosome? |
|
Definition
pH will lower to 5-6
the rab sorting signal changes to rab 7 GDP
it is distinguished by LBPA |
|
|
Term
| what organelles communicate with the late endosome? |
|
Definition
| golgi complex and the lysosome |
|
|
Term
| what is the role of the Golgi complex in late endosome function? |
|
Definition
they deliver acid hydrolases, which are bound to mannose 6 phosphate receptors.
this prompts the late endosome to become a lysosome |
|
|
Term
| what is the eventual fate of late endosomes? |
|
Definition
some may be degraded and release free cholesterol.
some are recycled to the Golgi complex and the mannose 6 phosphate receptor goes back |
|
|
Term
| What do late endosomes usually do if not recycle to Golgi? |
|
Definition
|
|
Term
| how might you distinguish a late endosome from a lysosome? |
|
Definition
|
|
Term
| are mannose 6 phosphate receptors present in late endosomes and lysosomes? |
|
Definition
| present ONLY in late endosomes |
|
|
Term
| what is the importance of lysosomes? |
|
Definition
| regulate celluar stores by enzymatically degrading them. |
|
|
Term
| what happens when the lysosomes fail to degrade material? |
|
Definition
| products will build up in cell causing damage |
|
|
Term
| neiman pick disease type A and B involve a deficiency in what? |
|
Definition
|
|
Term
| what does a deficiency in ASM lead to? |
|
Definition
|
|
Term
| where is deficiency in ASM seen |
|
Definition
|
|
Term
| what is type a neiman pick disease characterized by? |
|
Definition
| neurological tissues causing death w/in 2-3 years |
|
|
Term
| What are the symptoms of neiman pick type B disease? |
|
Definition
| enlarged spleen, respiratory problems, cardiovascular. |
|
|
Term
| what is the mode of inheritance of neiman pick disease? |
|
Definition
|
|
Term
| what is importance of the NPC1 protein |
|
Definition
|
|
Term
| what happens as a result in the mutation of the NPC1 protein |
|
Definition
| cholestrol accumulates in the late endosomes and cant get out |
|
|
Term
| what blocks the retrograde transport of mannose 6 phosphate receptors to the Golgi complex |
|
Definition
| cholesterol accumulation due to the NPC1 mutation |
|
|
Term
| where is the site of traffic blocking in type c disease state? |
|
Definition
| inability to recycle MPR's |
|
|
