12.4 Lysosomes

Question 1

() are membrane-enclosed organelles that contain an array of enzymes capable of breaking down all types of biological polymers (e.g. proteins, nucleic acids, carbohydrates, lipids) as well as obsolete cell components

Answer 1

lysosomes

Question 2

() are a series of genetic diseases that result in the accumulation of material in cells

Answer 2

lysosomal storage diseases

Question 3

most lysosomal storage diseases result from deficiencies in ()

Answer 3

single lysosomal enzymes

Question 4

Gaucher disease results from a mutation in the gene that encodes a lysosomal enzyme called () required for the breakdown of glycolipids; results in the accumulation of lipid molecules in organs

Answer 4

glucocerebrosidase

Question 5

most lysosomal enzymes are ()

Answer 5

lysosomal acid hydrolases

Question 6

lysosomal acid hydrolases are active ata pH of about ()

Answer 6

5

Question 7

how is the low pH maintained in lysosomes?

Answer 7

low pH is maintained by a proton pump in the lysosomal membrane; powered by energy from ATP hydrolysis

Question 8

inactivity of lysosomal enzymes at cytosol pH ensure protection against ()

Answer 8

uncontrolled digestion of cytosolic contents

Question 9

lysosomes are formed when transport vesicles from the trans-Golgi network fuse with a (), which contains molecules taken up by endocytosis at the plasma membrane

Answer 9

late endosome

Question 10

() represent an intersection between the secretory pathway (where lysosomal proteins are processed) and the endocytic pathway (where extracellular molecules are taken up at the cell surface)

Answer 10

endosomes

Question 11

() separate molecules targeted for recycling back to the plasma membrane from those destined for degradation in lysosomes (transported to late endosomes)

Answer 11

early endosomes

Question 12

molecules targeted for recycling back to the plasma membrane are transported to ()

Answer 12

recycling endosomes

Question 13

molecules destined for degradation are transported to ()

Answer 13

late endosomes

Question 14

late endosomes develop into lysosomes as they receive () from the Golgi

Answer 14

a complete set of lysosomal enzymes

Question 15

() is the turnover (degradation) of the cell’s own components

Answer 15

autophagy

Question 16

give an overview of the process of autophagy

Answer 16

1. enclosure of a small area of cytoplasm or cytoplasmic organelle in a membrane derived from the ER
2. the resulting vesicle (autophagosome) fuses with a lysosome
3. contents of autophagosome are digested

Question 17

autophagy can also be regulated during (1) and (2)

Answer 17

1. development
2. in response to stress

Question 18

why is autophagy activated when the cell is deprived of nutrients

Answer 18

nonessential macromolecules are degraded so their components can be reutilized

Question 19

generally, uptake of proteins into autophagosomes is ()

Answer 19

nonselective

Question 20

some organelles (e.g. damaged mitochondria) can be selectively targeted for autophagic degradation, usually as a result of ()

Answer 20

ubiquitylation