Lecture17-Unit5-Endocytosis-student - Lysosomes Figure 15...

Lysosome’in’the’liver’
cell’of’a’rat.’
Lysosomes’
Figure’15-35’(15-34’2
nd
’edi>on)’

Lysosomes’
Figure’15-35’(15-34’2
nd
’edi>on)’
Vacuoles’in’plant’cells’also’
func>on’as’lysosomes’

Clicker Q: Put’the’events’in’this’list’in’the’correct’order’
1. Vesicles’fuse’with’late’ endosomes’with’a’lower’pH’environment’-’where’
the’cargo’dissociates’from’the’receptor’and’the’receptor’is’recycled.’
2. Lysosomal’proteins’have’a’core’sugar’transferred’to’them’from’ dolichol.’
This’is’trimmed’and’processed’so’that’it’consists’primarily’of’mannose’
sugars.’
3. An’enzyme’transfers’a’phosphate’to’the’mannose’sugars’so’that’they’
become’mannose-6-P.’
4. Phosphate’is’removed’from’the’ lysosomal’protein’by’another’enzyme’
(phosphatase)’before’the’protein’can’become’func>onal.’
5. The’receptors’for’M6P’bind’to’all’the’proteins’containing’M6P’and’gather’
them’together’into’a’vesicle’–’with’ clathrin’coat.’
A. 2,’5,’3,’4,’1’
B. 2,’3,’5,’1,’4’
C. 4,’1,’5,’3,’2’
D. 5,’4,’3,’2,’1’

Inclusion-cell (I-cell) disease
’
In patients with I-cell disease, fibroblasts do not digest material in
their lysosomes, undigested material accumulates as “ inclusions ” .
• The lysosomal enzymes are found in the patients blood.
• A single gene defect is found in the enzyme which adds
phosphate to mannose-6-phosphate oligosaccharides in Golgi .
1. Why are the lysosomal enzymes in the blood?
A. Undigested material accumulates and leaks.
B. Lysosomal enzymes lack oligosaccharides.
C. Lysosomal enzymes are secreted by accident.
D. The mannose-6-phosphate receptor is defective.
E. All of the above

Inclusion-cell (I-cell) disease
’
In patients with I-cell disease, fibroblasts do not digest material in
their lysosomes, undigested material accumulates as “ inclusions ” .
• The lysosomal enzymes are found in the patients blood.