Cell 5

Question 1

Describe the transport of lysosomal hydrolases.

Answer 1

lysosomal hydrolase precursor is first tagged with mannose in the cis face of Golgi. The mannose is then phosphorylated as it moves through the Golgi. In the trans face of the Golgi, it it binds to mannose-6-phosphate receptor and is packaged into a vesicle. The vesicle is then directed to the endosomal compartment.

Question 2

Will a defect in M6P synthesis or receptor lead to a disease? Why or why not?

Answer 2

Yes, lysosomal hydrolase will not get to the lysosome where it is needed

Question 3

What is the most acidic organelle in a cell?

Answer 3

lysosome

Question 4

What kind of molecules do lysosomes degrade?

Answer 4

nucleic acids, lipid material, proteins, and carbohydrates

Question 5

How do you reduce the additional membrane that is no longer needed?

Answer 5

macroautophagic pathway

Question 6

What are some types of autophagic pathways?

Answer 6

macroautophagy, microautophagy and chaperone-mediated autophagy

Question 7

What is microautophagy?

Answer 7

eliminates smaller material such as proteins

Question 8

What is a heterophagosome?

Answer 8

endocytic pathway in which bacterium is phagocytized.

Question 9

How do heterophagosome different from autophagosomes?

Answer 9

heterophagosome contains material from the external environment whereas autophagosome contains material from internal environment

Question 10

Describe the pathway in which bacterium is degraded.

Answer 10

bacterium is phagocytized into a heterophagosome, which meets with a primary lysosome. the two structures fuse to form a secondary lysosome. degradation result in the excretion of the degraded material or the formation of a residual body (partially digested material)

Question 11

What is accumulation of residual bodies called? In which cells does that occur?

Answer 11

lipofuscin, inside long-lived cells (cardiac and nerve cells)

Question 12

What kind of dyes do lysosomes attract?

Answer 12

lysosomes are acidophilic (pos. charged) thus are attracted to acid dyes such as eosin

Question 13

What is the function of osteoclasts?

Answer 13

degradation of bones

Question 14

Defect in the delivery of lysosomal hydrolases to the lysosome can lead to what kind of disorder?

Answer 14

glycogen storage disorder (note that the type of material that accumulates is dependent on the enzyme that is absent from the lysosome)

Question 15

What is deficient in Tay-Sachs disease?

Answer 15

hexosaminidase A is deficient, which is needed for the breakdown of sphingolipids (type of lysosomal disorder)

Question 16

Where can you normally find gated transport mechanism within a cell?

Answer 16

between the nucleus and cytosol

Question 17

What transport mechanism would you find in between membranes of various organelles?

Answer 17

translocons embedded in membranes

Question 18

What is the function of COP II in membrane trafficking?

Answer 18

directs vesicles to cis face of Golgi network (anterograde movement)

Question 19

What is the function of COP I in membrane trafficking?

Answer 19

directs vesicles at the Golgi back to ER (retrograde movement)

Question 20

What is the function of clathrin in membrane trafficking?

Answer 20

1) at plasma membrane to direct traffic into the cell

2) at Golgi to direct material into endosomal compartment or help form secretory vesicles

Question 21

What are coating proteins?

Answer 21

They direct movement from one compartment to the next. (COP I, COP II, clathrin)

Question 22

What is the function of SNARE proteins?

Answer 22

a SNARE protein (v-SNARE) is incorporated into vesicles and it will recognize a specific target SNARE (t-SNARE) on the outside of a compartment. This is how vesicles know where to go.

Question 23

Describe how coating proteins and SNAREs work in trafficking.

Answer 23

vesicle leaves rER with SNARE proteins embedded on the membrane and coated with COP II. the vesicle is uncoated and the SNARE of the vesicle binds with the SNARE of Golgi. Contents are released. In the opposite direction (Golgi back to ER), COP I coats the vesicle along with SNAREs that is already embedded into the membrane of the vesicle. the vesicle loses its coat and the SNARE proteins bind at the surface of the ER.

Question 24

Why do we need retrograde movement?

Answer 24

1) to maintain membrane balance. if we keep taking membrane from the ER and inserting it to the Golgi, the membrane of the Golgi will keep growing while the membrane of the ER keep shrinking.
2) recycle SNAREs.
3) deliver mis-packaged or mis-sorted contents back to the ER for re-delivery

Question 25

How does botulinum toxin disrupt neurotransmission?

Answer 25

the docking mechanism for the release of neurotransmitter is the same as before (vesicles, coating proteins, SNAREs). Botulinum toxin interferes with this docking mechanism. It destroys the target SNARE, thus not allowing the vesicle and its contents (neurotransmitters) to dock and release. this leads to muscle paralysis

Question 26

What two organelles have two membranes?

Answer 26

mitochondria and nucleus

Question 27

Where will you find the enzymes of oxidative phosphorylation and ATP synthase within the mitochondria?

Answer 27

cristae of the inner membrane

Question 28

What does the amount of cristae tell you about the cell?

Answer 28

cell that is in need of a lot of ATP has a lot of cristae

Question 29

At what level do CO and cyanide poisoning interfere?

Answer 29

enzymes of inner membrane (disrupt ox. phos. and ATP synthase)

Question 30

What does palisade arrangement refer to?

Answer 30

the appearance of acidophilic striations seen in the mitochondria. resemble a picket fence

Question 31

What does the presence of tubular cristae indicate?

Answer 31

steroid hormone synthesizing cells (ovaries/testes/adrenal cortex)