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.
The answer is guard cells.
Guard cells are cells surrounding each stoma. They help regulate the rate of transpiration by opening and closing the stomata. They are specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stomatal pore (stoma).
It must be durable and available
Answer:
The bond between the _second_________ phosphate group and the third__phosphate group is a high energy bond.
Explanation:
Adenosine triphosphate is a nucleotide with three phosphate groups. The second and third phosphate groups are bonded by high energy covalent bonds to the rest of the ATP molecule, which consists of a sugar, which is ribose, the first phosphate group, and the nitrogenous base which is adenine. All of the phosphate groups are negatively charged and repel each other, so a high energy covalent bond is necessary to attach these phosphate groups together and keep the forces from pulling them apart.
