Lysosomes

Question 1

What is the function of a lysosome?

Answer 1

The site of intracellular digestion

Question 2

What is the structure of a lysosome?

Answer 2

Membrane bound compartments containing hydrolytic enzymes

Question 3

How many types of hydrolytic enzymes are found in lysosomes?

Answer 3

40

Question 4

What types of hydrolases are found in lysosomes? Give 3 examples

Answer 4

Acidic hydrolases
Proteases
Nucleases
Glycosidases

Question 5

What is the internal pH of lysosomes and how is it maintained?

Answer 5

pH = 5

Maintained by H+ pumps on the lysosomal membrane which use ATP

Question 6

Name the three ways in which cells protect themselves from the hydrolytic enzymes found in lysosomes?

Answer 6

Lysosomal membrane
Acid hydrolases do not work at the cells pH
A high degree of glycosylation protects hydrolases from each other

Question 7

What is an early endosomes?

Answer 7

A vesicle carrying substances the cell has taken in via endocytosis

Question 8

What are late endosomes?

Answer 8

Vesicles whose contents is to be degraded

Question 9

What do late endosomes mature into?

Answer 9

Lysosomes

Question 10

What are macromolecules digested into and how are those products used within the cell?

Answer 10

Digested into smaller components which are used to make new molecules

Question 11

What molecule is released when LDL is degraded?

Answer 11

Cholesterol

Question 12

What are recycling endosomes?

Answer 12

Vesicles whose contents was originally from early endosomes which is now being directed back to the plasma membrane

Question 13

Give an example of a process which involves recycling endosomes.

Answer 13

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

Question 14

Hydrolase transport to lysosome - 1

A __________ directs the synthesis of lysosomal proteins into the _______ via ______________

Answer 14

Signal peptide
ER
N-linked glycosylation

Question 15

Hydrolase transport to lysosome - 2
The signal peptide directs the ___________ of the terminal __________ on the N-linked ___________ in the _______ golgi network

Answer 15

Phosphorylation
Mannose
Oligosaccharide
Cis

Question 16

Hydrolase transport to lysosome - 3

________________ receptors bind M6P-labelled ________________ and ___________ in the ________ golgi network

Answer 16

Mannose-6-phosphate
Lysosomal hydrolases adaptins
Trans

Question 17

Hydrolases transport to lysosome - 4

Hydrolases are packed into _____________ coated transport vesicles

Answer 17

Clathrin

Question 18

Hydrolases transport to lysosome - 5

Transport vesicles fuse with a _______________

Answer 18

Late endosome

Question 19

Hydrolases transport to lysosome - 6

_____________ pH causes M6P receptors to dissociate from ______________

Answer 19

Acidic

M6P labelled hydrolases

Question 20

Hydrolase transport to lysosome - 7

A signal in the ________________ of the M6P receptor targets it into a ____________ which returns it to the ____________

Answer 20

Cytoplasmic tail
Vesicle
Golgi network

Question 21

Hydrolase transport to lysosome - 8

_______________ is removed from the _______________ on hydrolases in the __________ endosome

Answer 21

Phosphate
Mannose sugars
Late

Question 22

Hydrolase transport to lysosome - 9

_______ pumps ________ the pH and _____________ begin to digest macromolecules delivered from ___________ endosomes

Answer 22

H+
Lower
Acidic hydrolases
Early

Question 23

Why is phosphate removed from mannose sugars on hydrolases in late endosome?

Answer 23

To ensure it is not returned to the golgi

Question 24

At what point does a late endosome mature into a lysosome?

Answer 24

When H+ pumps lower the pH and acidic hydrolases begin to digest macromolecules