B) Cytosine pairs with guanine.
Unsaturated fats because they have no double bonds and is not saturated with hydrogens.
Water and ions are regulated by antidiuretic hormone (ADH), which is released by lower blood pressure and stretch receptor sensation by heart and large arteries. ADH is released by the hypothalamus and leads to control of the osmolarity of the blood. This release restores the ions and water level, and blood pressure is increased to the required level.
Aldosterone is released by the adrenal cortex and leads to retention of water by regulating sodium and potassium in the blood.
During low blood pressure, enzymes renin is released and causes the formation of angiotensin II, which signals the adrenal cortex to release aldosterone.
Water can cushion and protects the structures of the body because of ITS BUOYANCY.
Water protects the cells and organs in the body from physical trauma by cushioning them. For instance, water cushion the brain within the skull and the fetus inside the womb.
A hydrogen bond is formed when a positively polarized hydrogen atom in one molecule is attracted to a highly electronegative atom in another molecule. In the example of water molecules, the negatively charged oxygen atom in one water molecule attracts the positively charged hydrogen atom in another water molecule. Oxygen atoms tend to steal electrons away from the hydrogen atoms within molecules. When this occurs within a water molecule, the electron loss creates a hydrogen atom with a partial positive charge, which is then attracted to a negatively charged oxygen atom in another water molecule.
The hydrogen bonds that form between water molecules cause them to stick together. This gives water a high boiling point temperature because a greater degree of heat energy is required to break the intermolecular hydrogen bonds. Many organic substances that are required to sustain life, such as nucleic acids and proteins, contain hydrogen bonds. Although these bonds are weaker than the internal ionic or covalent bonds existing between the atoms within molecules, the accumulated strength of hydrogen bonds within living organisms is highly significant and plays an important role in maintaining stability.