Lysosomes and Peroxisomes Flashcards
Primary vs secondary lysosomes
secondary lysosomes have eaten something and are digested it
How can you identify lysosomes?
Multivesicular bodies, contain recognizable debris, or undigested material, use histochemistry against acid phosphatase
How is acidic pH of lysosome maintained?
proton pump, actively transports H+ ion into lysosome to lower pH and activate enzymes
Proteins destined for the lysosomes come from where?
Trans golgi after being tagged with mannose-6-phosphate N-terminus bind to receptor and are ferried to lysosomes
What do lysosomes eat?
Heterophagy, autophagy, crinophagy
Types of Heterohpagy
Phagocytosis (fuse with lysosomes)
Pinocytosis (nonspecific uptake of fluid)
Receptor-mediated endocytosis (rq. clathrin coat)
Autophagy
Digestion of cells own organelles that are no longer needed, microautophagy, macroautophagy, chaperone-mediated direct transport
Crinophagy
Degrade cells own products
Fates of endocytosed material
recycle, transported, degraded (early endosomes, multivesicular body, late endosomes that matures into lysosome
Multivesicular bodies
pinching off of endocytoses vesicle
Microautophagy
cytoplasmic proteins are continuously engulfed by lysosomes
Macroautophagy
sER surrounds cytoplasmic material destined for autophagy such as mitochondrian, then fuse with lysosomes
Chaperone-mediated direct transport
Activated during nutrient deprivation, requires chaperone protein
Exocytosis of lysosomes
Lysosomal secretion is rare but occurs when the cell is stressed which can be identified by an increase in intracellular Ca++
Lysosomal storage diseases
mutations affecting specific lysosomal enzymes, transport of enzymes, or signaling proteins (ex proton pump)
Niemann-Pick disease - three types A, B, C, accumulation of things that should be degraded in the lysosomes
Proteasomes
digest misfolded proteins that are signaled by ubiquitin tags
Peroxisomes
morphologically homogeneous, degrade lipids and toxins, oxidize long-chain FAs and ethanol and catalyze first step in biosynthesis of plasmalogen (most abundant phospholipid in myelin)
Formation of peroxisome and how to proteins get there?
Formed by budding off the ER, de novo or fission, enzymes are synthesized on free polyribosomes and transferred to peroxisomes, entry of proteins depends on targeting signal that can be on N or C-terminus
Disorder of peroxisomal enzymes
1) lacks essential pathway involving both N- and C-terminus targeting signal
2) lacks only N-terminus targeting signal
3) single peroxisomal enzyme is mutated
Peroxisomal proliferators
Certain drugs, diets, chemicals can cause peroxisomes to proliferate through binding of Peroxisome proliferator-activated receptors (PPAR), broad biological effects, however peroxisome catalase content does not always proportionally increase
