Which of the following structures is present in both prokaryotic and eukaryotic cells

Helper T cells are important cells that stimulate the action of other immune cells. For instance, they not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.

A gene is a segment of DNA that codes for a specific protein or polypeptide.

Crushing a solid reactant into powder increases the surface area of the reactant, thereby increasing chemical reaction. This is because more of the reacting molecules or ions are exposed to the other reactant, which increases the chance of particles colliding and leads to more successful collisions per second.

The kidneys are the primary organs involved in the excretion of nitrogenous wastes. Nitrogenous wastes are mostly products of protein metabolism in the liver. One of the common nitrogenous waste products is urea, which is excreted through the kidneys.

The digestive system breaks down complex food substances into small and less complex absorbable compounds. Proteins, for instance, are broken down to constituent amino acids through a digestion process that combines mastication and enzymatic breakdown.

The endocardium lines the interior structures of the heart. It is a thin, innermost layer of the heart wall that lines the heart chambers and valves. It is composed of subendocardial connective tissue and endothelial cells that are continuous with blood vessel endothelium.

Melanocytes are specialized skin cells that produce melanin, which is the protective skin-darkening pigment. They are found mainly in the epidermis, though they occur elsewhere, such as in the hair.

Water has a high specific heat capacity, which means it can absorb and store a large amount of heat energy without significantly changing in temperature. This helps moderate the temperature fluctuations of the air near the coast, as water can store heat during the day and release it at night, or vice versa.

The inner lining of the uterus is the source of blood and mucosal tissue that is shed during menstruation.

Both prokaryotic and eukaryotic cells have a cell membrane. The cell membrane is a barrier that surrounds the cell and separates its internal environment from the external environment.