Lysosomes Flashcards
What is the function of a lysosome?
The site of intracellular digestion
What is the structure of a lysosome?
Membrane bound compartments containing hydrolytic enzymes
How many types of hydrolytic enzymes are found in lysosomes?
40
What types of hydrolases are found in lysosomes? Give 3 examples
Acidic hydrolases
Proteases
Nucleases
Glycosidases
What is the internal pH of lysosomes and how is it maintained?
pH = 5
Maintained by H+ pumps on the lysosomal membrane which use ATP
Name the three ways in which cells protect themselves from the hydrolytic enzymes found in lysosomes?
Lysosomal membrane
Acid hydrolases do not work at the cells pH
A high degree of glycosylation protects hydrolases from each other
What is an early endosomes?
A vesicle carrying substances the cell has taken in via endocytosis
What are late endosomes?
Vesicles whose contents is to be degraded
What do late endosomes mature into?
Lysosomes
What are macromolecules digested into and how are those products used within the cell?
Digested into smaller components which are used to make new molecules
What molecule is released when LDL is degraded?
Cholesterol
What are recycling endosomes?
Vesicles whose contents was originally from early endosomes which is now being directed back to the plasma membrane
Give an example of a process which involves recycling endosomes.
LDL receptors in early endosomes release LDL into cells
The LDL receptors are then returned to the plasma membrane in recycling to ‘pick up’ more LDL
Hydrolase transport to lysosome - 1
A __________ directs the synthesis of lysosomal proteins into the _______ via ______________
Signal peptide
ER
N-linked glycosylation
Hydrolase transport to lysosome - 2
The signal peptide directs the ___________ of the terminal __________ on the N-linked ___________ in the _______ golgi network
Phosphorylation
Mannose
Oligosaccharide
Cis
Hydrolase transport to lysosome - 3
________________ receptors bind M6P-labelled ________________ and ___________ in the ________ golgi network
Mannose-6-phosphate
Lysosomal hydrolases adaptins
Trans
Hydrolases transport to lysosome - 4
Hydrolases are packed into _____________ coated transport vesicles
Clathrin
Hydrolases transport to lysosome - 5
Transport vesicles fuse with a _______________
Late endosome
Hydrolases transport to lysosome - 6
_____________ pH causes M6P receptors to dissociate from ______________
Acidic
M6P labelled hydrolases
Hydrolase transport to lysosome - 7
A signal in the ________________ of the M6P receptor targets it into a ____________ which returns it to the ____________
Cytoplasmic tail
Vesicle
Golgi network
Hydrolase transport to lysosome - 8
_______________ is removed from the _______________ on hydrolases in the __________ endosome
Phosphate
Mannose sugars
Late
Hydrolase transport to lysosome - 9
_______ pumps ________ the pH and _____________ begin to digest macromolecules delivered from ___________ endosomes
H+
Lower
Acidic hydrolases
Early
Why is phosphate removed from mannose sugars on hydrolases in late endosome?
To ensure it is not returned to the golgi
At what point does a late endosome mature into a lysosome?
When H+ pumps lower the pH and acidic hydrolases begin to digest macromolecules
