Answer the following question given this paragraph: Q: What type of structure between the esophagus and the stomach normally opens only when a bolus arrives? Choices: - larynx - intestine - gland - sphincter A:
sphincter

Answer the following question given this paragraph: Abnormally high activity of the parathyroid gland can cause hyperparathyroidism, a disorder caused by an overproduction of PTH that results in excessive calcium reabsorption from bone. Hyperparathyroidism can significantly decrease bone density, leading to spontaneous fractures or deformities. As blood calcium levels rise, cell membrane permeability to sodium is decreased, and the responsiveness of the nervous system is reduced. At the same time, calcium deposits may collect in the body's tissues and organs, impairing their functioning. In contrast, abnormally low blood calcium levels may be caused by parathyroid hormone deficiency, called hypoparathyroidism, which may develop following injury or surgery involving the thyroid gland. Low blood calcium. Q: Abnormally high activity or low activity of the parathyroid gland can cause disorders related to levels of what bone mineral? Choices: - potassium - collagen - magnesium - calcium A:
calcium

Answer the following question given this paragraph: Small nonpolar molecules can easily diffuse across the cell membrane. However, due to the hydrophobic nature of the lipids that make up cell membranes, polar molecules (such as water) and ions cannot do so. Instead, they diffuse across the membrane through transport proteins. A transport protein completely spans the membrane, and allows certain molecules or ions to diffuse across the membrane. Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion. Q: Due to the __________ nature of the lipids that make up cell membranes, polar molecules (such as water) and ions cannot easily diffuse across the cell membrane. Choices: - hydrophylic - saturated - catalytic - hydrophobic A:
hydrophobic