Question 1

Which of the following best describes the correct sequence of events for the localization of a hydrolase protein from its gene to the lumen of the lysosome?

Accepted Answer

Transcription in the nucleus → mRNA exits nucleus → translation begins in cytoplasm and continues on rough ER → protein enters ER lumen → vesicle buds off ER and fuses with Golgi → Golgi modifies protein → vesicle buds off Golgi and matures into lysosome

Question 2

During the targeting of a hydrolase to the lysosome, which cellular structure is responsible for the initial translation of the hydrolase mRNA?

Accepted Answer

Cytoplasmic ribosomes (free ribosomes)

Question 3

What is the primary function of the signal peptide in the synthesis of lysosomal hydrolase proteins?

Accepted Answer

To direct the ribosome to the rough endoplasmic reticulum for co-translational import

Question 4

Which of the following modifications is most likely to occur to a hydrolase protein as it passes through the Golgi apparatus?

Accepted Answer

Glycosylation (addition of carbohydrate groups)

Question 5

A mutation prevents vesicles from budding off the Golgi apparatus. What is the most immediate consequence for lysosomal hydrolase proteins?

Accepted Answer

They will accumulate in the Golgi and not reach the lysosome

Question 6

Which of the following equations correctly represents the surface area to volume ratio ($$SA:V) $$for a spherical cell of radius $$r$$?

Accepted Answer

$$SA:V = \frac{4\pi r^2$}{\frac{4}{3}\pi r^3$}$$

Question 7

Why are ribosomes on the rough endoplasmic reticulum (RER) necessary for the synthesis of lysosomal hydrolases?

Accepted Answer

They ensure the hydrolase is inserted into the ER lumen for proper targeting

Question 8

Which of the following best explains why a hydrolase protein must be localized to the lysosome?

Accepted Answer

Hydrolases are digestive enzymes that function optimally at the acidic pH found in lysosomes

Question 9

If a hydrolase protein lacks a mannose-6-phosphate tag in the Golgi, what is the most likely fate of the protein?

Accepted Answer

It will be secreted from the cell

Question 10

Which of the following steps occurs immediately after the translation of a hydrolase protein is completed on the rough ER?

Accepted Answer

The protein is folded and modified in the ER lumen

Question 11

Which of the following best describes the role of vesicles in the endomembrane system?

Accepted Answer

They transport proteins between organelles such as the ER, Golgi, and lysosome

Question 12

A scientist observes that a hydrolase protein is present in the cytoplasm instead of the lysosome. Which step in the targeting pathway most likely failed?

Accepted Answer

Translation on free ribosomes without ER targeting

Pathway of Hydrolase Protein Targeting to the Lysosome: Cell Biology Study Notes

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