Answer:
A <u><em>receptor</em></u> is a protein that recognizes and responds to a signal.
Explanation:
A receptor is a protein molecule present on the cells on which the signalling molecules can bind and generate a physiological response. Some receptor molecules can also respond to Sun and light. Each type of cell has specific receptors molecules and hence can respond to specific signals. The receptor molecules hence tend to receive signals for a cell. Molecules such as hormones bind to the receptors.
Answer:
peptide antigens by MHC class II molecules
Explanation:
Helper T cells are activated by peptide antigens by MHC class II molecules. These antigens express on the surface of antigen-presenting cells (APCs). After activation, the T helper cells divide and secrete cytokines to assist the immune response.
Answer:
if there was no photosynthesis, then we won't have plants. Plants will die out, and we will not get the oxygen needed to survive.
I think the correct answer from the choices listed above is the third option. The DNA is used as a molecular clock in the sense that the <span>percent of carbon in DNA is compared between parent and offspring. Hope this answers the question. Have a nice day.</span>
