Cells obtained from an organism were homogenized and centrifuged. A test indicated that the cells contained glycogen. If you were asked to find out as quickly as possible whether the cells were from a plant or an animal, you would:

Question

Accepted Answer

The correct option is 3:
answer immediately that the cell were from animal source.

The fundamental concept being tested here is the profound biochemical distinction in energy storage between the two major eukaryotic kingdoms: Plantae and Animalia. You are provided with the critical piece of information that a preliminary biochemical test on the homogenized cells revealed the unmistakable presence of **glycogen**. Glycogen is biologically recognized as the main *storage* polysaccharide for glucose in animal cells, primarily stored in the liver and muscle tissues. Conversely, the primary storage polysaccharide in plant cells is **starch** (composed of amylose and amylopectin). Since the presence of glycogen is a clear, definitive, and highly specific biochemical marker for Animalia (or Fungi, but the comparison in the options is animal vs. plant), the student possessing this basic biological knowledge can make the classification instantly. No further physical work or analytical steps are needed; the answer is derived directly from the already-available test result, making it the *quickest* possible determination.

The incorrect option is 1:
examine the centrifuged sample for the presence of extracts of chloroplasts.

While chloroplasts are indeed a hallmark organelle of plant cells, as they are the site of photosynthesis, attempting to find their "extracts" through further analysis is a less immediate method than using the information you already possess. The proposed action—examining the centrifuged sample for their extracts—is a multi-step process that would require additional time. Following homogenization and centrifugation, the next step would be differential staining, high-resolution microscopy, or a specific pigment (chlorophyll) assay to confirm their identity and integrity. Since the presence of glycogen has already provided a conclusive answer for the *animal* source, choosing a time-consuming organelle analysis would violate the condition of answering "as quickly as possible."

The incorrect option is 2:
examine the centrifuged sample for the presence of centriole.

Centrioles are organelles that participate in cell division and are responsible for forming the basal bodies of cilia and flagella. While they are a characteristic feature of most animal cells, their use as a definitive marker is flawed for two primary reasons. Firstly, centrioles are also found in the cells of lower plants (like mosses, ferns, and most green algae) and many protists, meaning their presence would not unequivocally exclude a plant source. Secondly, centrioles are sub-microscopic structures that would require specific, high-magnification electron microscopy and potentially specific markers to identify them accurately in a cell homogenate, making this a slow and complex procedure. This approach is much slower and less conclusive than the immediate interpretation of the glycogen test result.

The incorrect option is 4:
It is very difficult to answer whether it is from animal or plant.

This statement is simply factually wrong in the context of the question. The difficulty of identification only arises when the distinguishing feature is shared or ambiguous. In this case, the test result—the presence of glycogen—is a highly specific and fundamental biological difference that clearly separates animals from the vast majority of plants, which use starch for storage. The established presence of glycogen is a perfect "quick answer" piece of evidence, negating any claim that the determination is difficult.