Shared Flashcard Set

Details

Microanatomy Lysosomes & Peroxisomes
Abnormal Amnio module - Lysosomes & Peroxisomes
35
Anatomy
Graduate
09/03/2012

Additional Anatomy Flashcards

 


 

Cards

Term
Lysosome structure/content
Definition
contain degradative enzymes (acid hydrolases). Contain proteins for: proton pump to keep pH acidic; transport of digested materials
Term
Safety features of lysosome
Definition
membrane; internal pH optimal for lysosomal enzymes; heavy glycosylation of enzymes/membrane protein inhibit breakdown; membrane contains unusual lipids resistant to degradation
Term
Morphological Identification of lysosomes
Definition
Hard to recognize. But: multivesicular bodies; contain recognizable debris; contain residual bodies (undigested material)
Term
How to accurately identify lysosomes
Definition
histochemistry: acid phosphatase is most common lysosomal enzyme, so organic phosphates and lead salts are added to see where PbPO4 precipitates & then viewed with EM
Term
lysosomal enzyme pathway (synthesis to final destination):
Definition
formed in RER, thru golgi, from trans of golgi to lysosomes via mannose-6-phosphate pathway OR via mannose-6-phosphate independent pathway
Term
mannose-6-phosphate pathway
Definition
transport of lysosomal enzymes from golgi to lysosome: enzymes receive mannose-6-phosphate to N-terminus; M6P binds to receptor in golgi membranes & clathrin-coated vesicles bud off; targeted by receptor complex on lysosome; pH causes M6P to dissociate and can be recycled for further use
Term
heterophagy
Definition
lysosomal digestion of material from outside the cell via endocytosis (phagocytosis or pinocytosis)
Term
autophagy
Definition
lysosomal digestion of parts of cell's own cytoplasm. Occurs more during cell starvation
Term
crinophagy
Definition
lysosomal digestion of secretory material produced by the cell; happens when product is not likely needed for a long time (e.g. lactation)
Term
Endocytosis
Definition
uptake of substrates from the extracellular space (phagocytosis, pinocytosis, receptor-mediated endocytosis)
Term
phagocytosis
Definition
uptake of matter into large vacuoles called phagosomes. Normally fuse w/lysosomes.
Term
How are bacteria engulfed?
Definition
by phagocytic cells like macrophages. To fuse w/lysosomes, TACO protein must be removed & TB bacillus prevents this.
Term
pinocytosis
Definition
nonspecific uptake of macromolecules & fluid into small vesicles (which lack clathrin coat). Occurs in most cells.
Term
receptor-mediated endocytosis
Definition
uptake of specific materials (e.g. LDLs). Requires binding of macromolecules to specific receptors in membrane. Creates clathrin-coated vesicles.
Term
fates of endocytosed materials
Definition
Recylced. Transcytosis (transported & released at different cell surface). Degradation w/lysosomes
Term
pathway of endocytosed materials to lysosome formation
Definition
early endosome. These turn into MVB (multivesicular bodies), which travel alond microtubles. Turn into late endosomes, which receive lysosomal enzymes from golgi. Turn into lysosomes.
Term
pathway of receptor-mediated endocytosis (LDL as example):
Definition
LDL binds receptor-->Receptors cluster & form clathrin-coated pit-->Pinches off to form coated vesicle-->loses clathrin & fuses w/early endosome-->endosome's low pH dissociates ligand & receptors-->leaves endosome & MVBs carry to late endosomes-->fuse w/lysosome to become new lysosome.
Term
Macroautophagy
Definition
cytoplasm/organelles are surrounded by vacuole/sER (autophagosome) and fuses w/lysosome to form autophagolysosome
Term
decreased macrophagy levels leads to
Definition
neurogenerative diseases and cancer
Term
microautophagy
Definition
non-specific: cytoplasmic proteins enter lysosomes via invagination of lysosomal membrane
Term
Chaperone-mediated direct transport
Definition
specific proteins directed to lysosome by chaperone & interacts w/receptors on lysosome. Activated during starvation.
Term
Crinophagy mechanism
Definition
occurs via fusion of membrane of the secretory vesicle w/lysosome
Term
Exocytosis of lysosomes
Definition
eliminates indegestible debris; rarely used, except when cell is stressed; osteoclasts use this
Term
Diseases from defects in gene encoding for a hydrolytic enzyme
Definition
Lysosomal Storage disease: Tay-Sachs, Hurler's, metachromatic leukodystrophy
Term
Tay-Sachs disease
Definition
lysosomal storage disease. Deficiency in Beta-hexosaminidase A, which leads to accumulation of GM2 in lysosomes (forms whorls of membranes in lysosomes)
Term
Diseases from defects in processing that lead to incorrect sorting of lysosomal enzymes
Definition
Lysosomal Storage disease: I-cell disease, which fails to create a M6P marker on lysosomal enzymes (& is therefore excreted from cell)
Term
Proteasome digestion
Definition
proteasomes in the cytoplasm digest damaged/mis-folded proteins marked w/ubiquitin markers
Term
Peroxisome morphology
Definition
single membrane; homogenous; 1-5X bigger than mitochondria
Term
Peroxisome functions
Definition
degrade lipids & toxins via enzymatic oxidation (yielding H2O2); oxidizes long fatty-acid chains (beta oxidation); catalyzes 1st step in plasmalogen formation (abundand phospholipid in myelin in nervous system); oxidizes ethanol
Term
Formation of Peroxisomes
Definition
1) peroxisome fissure or 2) de novo from ER (w/proteins from cytosol)
Term
targeting peroxisomal proteins to peroxisomes
Definition
peroxisomal proteins synthesized on free polysomes w/peroxisomal targeting signal (PTS) bind to cytosol receptors-->transferred to peroxisomes-->binds to docking proteins on peroxisome, which allows enzymes to enter
Term
Class 1 peroxisomal disorder
Definition
patient lacks pathways involving both C & N-terminal targeting sequences, which leads to deficient/empty peroxisomes. Zellweger, NALD
Term
Class 2 peroxisomal disorder
Definition
patient lacks pathway for N-terminal targeting sequence. Rhizomelic chondroplasia.
Term
Class 3 peroxisomal disorder
Definition
enzymatic activity or subcellular location of a single protein is compromised. X-linked adrenoleukodystrophy (ALD).
Term
peroxisome proliferators
Definition
some chemicals can increase # of peroxisomes by up to 10-fold. High-fat diets, aspirin, chemicals, etc. May result in H2O2 accumulation. Could result in cancer thru oxidative damage.
Supporting users have an ad free experience!