endocytosis and exocytosis Flashcards

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1
Q

N linked, O linked glycoproteins and proteoglycan synthesis

A

N link glycoproteins - added in ER, modified by glycosyl transferase in golgi. 3 classes: mannose, complex, hybrid

O link glycoproteins - Add OH to threonine and serine. adding sugars one at a time (N linked is added at once then modified). done post translationally

proteoglycan synthesis - 95% carb. must contain glycoaminoglycan (varying amounts)
-protein core made in ER, sugars added in golgi or ER
3 types of glycosylation
1. o linked glycosaminoglycan
2. o linked oligosaccharide
3. N linked oligosaccharide

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2
Q

glycoaminoglycan

A
  • repeating disaccharide 100 sugars long

- negatively charged

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3
Q

degradation of proteoglycans and glycoproteins

A
  • by hydrolases (protease and gllycosidase) in lysosome
    1. glycosidase removes carb
    2. protease cleaves peptide
    3. glycosidase removes sugars in opposite way they were added
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4
Q

ABO blood type

A
  • depends on oligosacchardie portion of glycoprotein on RBC
  • codes for certain glycosyltransferase that delivers:
  • GA1 Nac - A antigen
  • GA1 -B antigen
  • nothing - O antigen
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5
Q

constituitive vs regulated exocytosis

A

constituitive: default. always going on and happens unless signal says otherwise
regulated: proteins from golgi into secretory vesicles and wait by PM for signal to be released

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6
Q

Phagocytosis

A
  • ingest large particles by phagosomes
  • need receptors
  • alternate to pinocytosis which is all the same for small molecules
  • WBC, neutrophils, macrophages
  • when induced extends PM and engulfs to form phagosome, which binds lysosome for degradation
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7
Q

receptor mediated endocytosis

A

-bind receptors on PM to recruit clathrin coated bits and enguld coated vesicles. makes pinocytosis efficient.
LDL example
-need cholesterol for membrane synthesis
-cholesterol is in LDL particles
-LDL receptors on PM associate with clathrin proteins and bring LDL vesicle in
-shed clathrin in endosome, LDL receptor disociates
-LDL frees cholesterol once inside llysosome
-Familial hypercholesterolemia - LDLreceptors are block and build plague in blood. kids get heart attacks

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8
Q

early and late endosome

A

early - near PM. sorting station for endocytosis. pH 6

late - near nucleus. delivers cargo to lysosome or becomes a lysosome

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9
Q

endocytosis pathways

A
  1. recycle- to PM
  2. degrade - in lysosome
  3. transcytosis - in onemembrane domain and out another. like Ab to breast milk from blood
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10
Q

lysosome structure and function

A
  • 40 acid hydrolases
  • ATP pump keeps pH at 5
  • degraded products back to cytosol
  • proteins that make up lysosome are glycosylated to protect themselves from harsh environment
  • lysosomal protein and enzymes made in ER. tagged with M6P msrker and in trans golgi get packed into vesicles that will be transported to lysosome by an endosome

3 paths to lysosome:

  1. endocytosis
  2. phagocytes
  3. autophagy - obsolete cell parts build themselve a membrane and fuse with endosome or lysosome
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11
Q

human lysosomal storage disease

A

defective hydrolases

  • undigested glycoproteins and proteoglycans accumulate
    a. Inclusion cell disease - enzymes for M6P marker missing. hydrolases are secreted. undigested substrate accumulate

b. mucopolysaccharidoses - enzyme for glycosamnoglycan degradation defect. build up in lysosomes, blood, tissues (Hurler syndrome)
c. oligosaccharidoses - cant degrade oligosaccharides. cause facial dysmorphia and mental retardation. Schindler disease
d. sphingolipidoses - cant degrade sphingoliids. build up in macrophages in lver, spleen, bone marrow. Gaucher and Tay Sachs disease

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