Lysosomes

Question 1

what is a lysosome?

Answer 1

an organelle of the endomembrane system that contains digestive enzymes capable of degrading all of the major classes of biological macromolecules

Question 2

What does a lysosome look like?

Answer 2

0.5 um

single membrane - the lumenal side of membrane proteins is highly glycosylated which protects membrane proteins from lysosomal proteases

Question 3

What type of environment is inside the lysosome - in terms of pH?

Answer 3

Acidic environment of 4.0-5.0

This favors enzymatic digestion of macromolecules both by activating acid hydrolases and by partially denaturing the macromolecules targeted for degradation

Question 4

What types of acid hydrolases lie within the lysosome?

Answer 4

5 phosphatases, 14 proteases and peptidases, 2 nucleases, 6 lipases, 13 glycosidases and 7 sulfatases

Question 5

Where do lysosomal enzymes come from?

Answer 5

synthesized by ribosomes, go from ER to Golgi for processing and packaging, from there they are endosomes and mature into lysosomes by the activation of acid hydrolases

Question 6

what are heterophagic lysosomes?

Answer 6

lysosomes containing substances of extracellular origin (come from outside the cell)

Question 7

What are autophagic lysosomes

Answer 7

lysosomes that contain materials of intracellular origin (from inside the cell)

Question 8

How do the digested pieces of nucleic acids, proteins, carbohydrates etc, get across the membrane and into the cytosol?

Answer 8

some cross by faciliated diffusion while others need active transport to cross into the cytosol

the acidity of lysosomal lumen contributes to an electochemical proton gradient across the lysosomal membrane

Question 9

what is a residual body?

Answer 9

indigestable material in the lysosome that remains as digestion ceases

Question 10

What is autophagy?

Answer 10

the digestion of old or unwanted organelles or other cell structures

Question 11

what is macrophagy?

Answer 11

a type of autophagy that begins when an organelle or other structure becomes wrapped in a double membrane derived from the ER

Question 12

what is an autophagic vesicle?

Answer 12

a vesicle that resulted from macrophagy

Question 14

What happens when there are lysosomal storage diseases?

Answer 14

skeletal deformaties, muscle weakness and mental retardation

Hurler syndrome and Hunter syndrome - both arise from defects in the degradation of glycosaminoglycans