A student uses iodine to visualize cells under the light microscope. Iodine stains starch deep blue and glycogen granules dark brown.
Observation of the cells reveals the presence of cell walls, dark brown granules, mitochondria, and a prominent nucleus. If the chemical composition of the cell wall is determined, which of the following molecules would MOST likely be the major constituent?
A.
cellulose ****
B.
chitin
C.
lignin
D.
peptidoglycan
1 answer
The answer is B. Chitin. Peptidoglycan is present in bacteria and bacteria do not have mitochondria so you can cross that off. Cellulose and lignin are present in plants and they generally store their energy (glucose) in the form of starch rather than glycogen. Lastly, chitin is present in the exoskeleton of animals like lobsters and crickets, and fungi, but since animals do not possess cell walls it would be fungi and therefore B. Chitin.