Pretty confusing AS Biology question:

Question

A scientist carried out an experiment to separate the organelles in an animal cell by mass.

The scientist mixed the cells with a buffer solution which had the same water potential as the cells. He then broke the cells open with a blender to release the organelles.

The extracted mixture was filtered and then spun in a centrifuge at a speed to separate the heaviest organelle. This sank to the bottom, forming a solid pellet, 1.

The liquid above pellet 1 was poured into a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest organelle. This organelle sank to the bottom, to form a solid pellet, 2.

He repeated this procedure twice more to obtain pellet 3 and pellet 4, each containing a single organelle.

What is the function of the organelle extracted in pellet 3?

A digestion of old organelles
B production of ATP
C synthesis of mRNA
D synthesis of protein

The answer is A, but I'm not sure why, thanks for helping me out!

Answer 1

This is according to the cell fractionation. These organelles separate according to their mass, the heaviest that is the nucleus in the bottom as pellet 1, mitochondria as pellet 2, lysosomes as pellet 3 and ribosomes as pellet 4. So the question asks for pellet 3 and lysosomes digest old organelles.

Answer 2

Please, I don't understand why it is lysosome since Endoplasmic reticulum is larger than lysosome, why is lysosome the answer(A)?

Answer 3

Endoplasmic reticulum is not in the options. The only options are nucleus, mitochondria, lysosomes and ribosomes. Arranging them according to descending order of sizes: nucleus>mitochondria>lysosomes>ribosomes