Lysosomes and Peroxisomes

Question 1

Primary vs secondary lysosomes

Answer 1

secondary lysosomes have eaten something and are digested it

Question 2

How can you identify lysosomes?

Answer 2

Multivesicular bodies, contain recognizable debris, or undigested material, use histochemistry against acid phosphatase

Question 3

How is acidic pH of lysosome maintained?

Answer 3

proton pump, actively transports H+ ion into lysosome to lower pH and activate enzymes

Question 4

Proteins destined for the lysosomes come from where?

Answer 4

Trans golgi after being tagged with mannose-6-phosphate N-terminus bind to receptor and are ferried to lysosomes

Question 5

What do lysosomes eat?

Answer 5

Heterophagy, autophagy, crinophagy

Question 6

Types of Heterohpagy

Answer 6

Phagocytosis (fuse with lysosomes)
Pinocytosis (nonspecific uptake of fluid)
Receptor-mediated endocytosis (rq. clathrin coat)

Question 7

Autophagy

Answer 7

Digestion of cells own organelles that are no longer needed, microautophagy, macroautophagy, chaperone-mediated direct transport

Question 8

Crinophagy

Answer 8

Degrade cells own products

Question 9

Fates of endocytosed material

Answer 9

recycle, transported, degraded (early endosomes, multivesicular body, late endosomes that matures into lysosome

Question 10

Multivesicular bodies

Answer 10

pinching off of endocytoses vesicle

Question 11

Microautophagy

Answer 11

cytoplasmic proteins are continuously engulfed by lysosomes

Question 12

Macroautophagy

Answer 12

sER surrounds cytoplasmic material destined for autophagy such as mitochondrian, then fuse with lysosomes

Question 13

Chaperone-mediated direct transport

Answer 13

Activated during nutrient deprivation, requires chaperone protein

Question 14

Exocytosis of lysosomes

Answer 14

Lysosomal secretion is rare but occurs when the cell is stressed which can be identified by an increase in intracellular Ca++

Question 15

Lysosomal storage diseases

Answer 15

mutations affecting specific lysosomal enzymes, transport of enzymes, or signaling proteins (ex proton pump)

Niemann-Pick disease - three types A, B, C, accumulation of things that should be degraded in the lysosomes

Question 16

Proteasomes

Answer 16

digest misfolded proteins that are signaled by ubiquitin tags

Question 17

Peroxisomes

Answer 17

morphologically homogeneous, degrade lipids and toxins, oxidize long-chain FAs and ethanol and catalyze first step in biosynthesis of plasmalogen (most abundant phospholipid in myelin)

Question 18

Formation of peroxisome and how to proteins get there?

Answer 18

Formed by budding off the ER, de novo or fission, enzymes are synthesized on free polyribosomes and transferred to peroxisomes, entry of proteins depends on targeting signal that can be on N or C-terminus

Question 19

Disorder of peroxisomal enzymes

Answer 19

1) lacks essential pathway involving both N- and C-terminus targeting signal
2) lacks only N-terminus targeting signal
3) single peroxisomal enzyme is mutated

Question 20

Peroxisomal proliferators

Answer 20

Certain drugs, diets, chemicals can cause peroxisomes to proliferate through binding of Peroxisome proliferator-activated receptors (PPAR), broad biological effects, however peroxisome catalase content does not always proportionally increase