B. the salad is wilted because it lost water in a hypertonic solution
The correct answer is B. Natural selection occurs through generations and is in which organisms best suited to their environment survive.
Answer: A
Explanation:The Trp operon is responsible for synthesis of the amino acid trytophan when it is not available in the cellular environment.
When the tryptophan is plentiful, a repressor protein binds to two molecules of tryptophan.
Thiss repressor-tryptophan complex binds to the trp operator. This binding prevents the binding of RNA polymerase, so the operon is not transcribed, and no new trptophan is produce.
On the other hand, when tryptophan levels are reduced, the inactive repressor will not bind the tryptophan operator so the operon is transcribed.
Regulation of the trp operon is determined by the concentration of tryptophan; when adequate tryptophan is present in the growth medium, there is no need for tryptophan biosynthesis.
Transcription is turned off when a high concentration of tryptophan is present, and is turned on when tryptophan is absent. The regulatory signal is the concentration of tryptophan itself.
Therefore in the absence of tryptophan, the inactive repressor cannot bind trpO, so operon gene transcription occurs.
Answer:
Cell walls prevent cells from dying in hypertonic conditions.
Explanation:
The cell wall is a rigid structure, essential for the survival of fungi, and knowledge of its composition may be useful for the development of new antifungal drugs. This wall does not alter the characteristics of the fungus, it stimulates and presses the fungus to flourish.
The fungal cell walls are similar in function to the cell walls of many protists, bacteria and plants. They prevent cells from bursting in hypotonic environments, but are unable to prevent cells from dying in hypertonic conditions. These cell walls also provide the cell with a degree of physical environmental protection and differ in the molecular composition of plant cell walls, as the fungal cell walls are chitin, while the plant cell walls are formed by cellulose.
