It is true that an organism that is asymmetrical can not be divided into identical or mirror images.
Answer:
Helper T cells stimulate B-cells to produce antibodies and killer T cells to destroy the non-self cells. Cytotoxic T cells on the other hand are direct attack cells. They can kill the micro organisms by creating pores on the invader's cell.
Explanation:
T lymphocyte mediated immunity of cell mediated immunity do not secrete antibodies but they help stimulate the B cells to produce them. Immature T cells are produced in bone marrow from where they migrate to thymus via blood. In the thymus maturation of T cells occur and then they migrate to lymphoid tissue and get differentiated into three types:
a. Helper T cells: As the name suggests, they help in activating other immune cells, in other terms they are the regulator of virtually all functions of immune system. Protein mediator called lymphokines are produced by these helper T cells in order to regulate the immune functions. Some examples of these lymphokines are: Interleukin-2 interleukin-3, interferon gamma. T helper cells stimulate the B-cells to produce antibodies.
b. Cytotoxic cells or killer T cells: The lymphokine interleukin-2 is responsible for the growth and proliferation of both cytotoxic T cells and suppressor T cells. With the help of receptor proteins on the surface of killer T cells, they bind to the specific antigen. After binding, they secrete a pore forming protein called perforins which create pores on the invaders cell membrane for water to enter into it thereby cell swells and finally lyse.
c. Suppressor T cells: They suppress the function of above two T cells.
The statement would be considered to be B. False, because genetic drift occurs when different genotypes in smaller populations have a chance of disappearance. This is due to the species either dying off or not reproducing with others, so the genotype doesn't spread to offspring, because the species didn't have offspring.
Answer:
The answer to these questions are the following:
1. sucrose solution (higher concentration of water molecules in the onion cells) >> red onion cells will shrink >> smaller diameter
2. distilled water (higher concentration of water molecules in the surrounding solution) >> red onion cells will become turgid >> higher diameter
Osmosis refers to the movement of a solvent (usually water molecules) across semipermeable biological membranes, which occurs from a region of higher concentration to a region of lower concentration. There are three classes of solutions that have different effects on cells due to the process of osmosis:
1. In a hypotonic solution, the cells will become turgid
2. In an isotonic solution, the cells will become flaccid.
3. In a hypertonic solution, the cells will shrink (plasmolysis)
When plant cells are placed into a hypertonic solution where there is a greater concentration of solute outside the cells (as in this case sucrose solution), water molecules will move from inside the cells to outside the cells, thereby cells will shrink due to water loss
When plant cells are placed into a hypotonic solution that is diluted in comparison to the content of the cell (as in this case plant cells placed in distilled water) water molecules will move from outside the cells to inside the cells, thereby cells will become turgid.
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