Perspective: A group of researchers are responsible for classifying newly isolat

Question

Perspective: A group of researchers are responsible for classifying newly isolated cells as originating from bacteria, plants or animals. After an initial look under the microscope it is noted that the each cell contains a cell wall. Subsequently, a cell fractionation experiment is performed and the presence of a pellet in each fraction was recorded. The experimental design and results are outlined below: Tube # | Visible pellet? medium highy low peed speed resent resent- large resent resent 8 4 Cell homogenate Tube 1 Tube 2 Tube 3 Tube 4 After the cells were lysed (broken open), the cell homogenate was centrifuged at a low speed (Tube 1). The supernatant from Tube 1 was placed in a new tube and centrifuged at medium speed (Tube 2). The supernatant from Tube 2 was placed in a new tube and centrifuged at high speed (Tube 3). Lastly, the supernatant from Tube 3 was placed in a new tube and centrifuged at a very high speed (Tube 4). At the end of the centrifugation, the researchers looked at the bottom of each tube and recorded whether or not they saw a pellet in each tube (table on the right) Writing Assignment: Based on the results provided, are the cells in the original tube bacteria, animal, or plant cells? Explain your reasoning using evidence from the experiments, what you have learned in Chapter 4 and evidence from the literature.

Explanation / Answer

In the given experiment (cell fractionation), the cell homogenates are separated into fractions with the use of centrifugation. In centrifugation with rotation centrifugal force applied on particles/ organelles in the homogenates based on their properties such as mass, density, and shape. The repeated centrifugation with progressively increasing centrifugation speed, fractionate cell homogenates into their components. The larger and denser components of homogenate experience the grater centrifugal force and move more rapidly towards the bottom of the tube (settle in the pellet of the tube). While the smaller and less dense components remain in suspension, require more speed for their settlement in the tubes.

Tube-1; pellet of tube-1, contains heavier/denser component of the cell that is Nucleus and cytoskeletons.

Tube-2; Contains relatively less heavy/denser component of the cell than tube-1, that is mitochondria, lysosomes, peroxisomes.

Tube-3; Contains relatively less heavy/denser component of the cell than tube-1 and tube-2, that is microsomes, vesicles

Tube-4; Contains less heavy/denser component of the cell than that of all tubes, that is ribosomes, viruses, and large macromolecules.

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