The Night of the Living Dead
While much of the focus in the study of anatomy is on the structure, function, and metabolism of organic molecules (molecules containing carbon), some inorganic compounds are essential for human existence and for life in general.
One way to think of the difference between organic and inorganic molecules (other than organic molecules being carbon-based) is that organic molecules are generally synthesized by living organisms, whereas inorganic molecules are not (they are usually produced by other means, such as geologic processes).
Water
While most life on the planet is carbon-based, water, which is not carbon-based, is a compound without which life would not be possible. The human body, for instance, is considered to be composed of between 50 and 65 percent water.
This water exists within your cells (about two-thirds of your water content) with the remainder outside of the cells in your tissues or blood stream. Your brain is about 85 percent water while your bones are about 10 percent water.
Water is the universal solvent because it is composed of polar molecules—that is, molecules that contain a charge—that are capable of ionizing many molecules (e.g., NaCl). A solvent is used to form a solution when another substance is dissolved in it. A universal solvent is one that can dissolve a wide range of substances. Lemonade is an example of a solution. So is saline (which is water in which NaCl has been dissolved). Both of these solutions use water as the solvent. Water in the human body is used as a solvent for elements such as chloride. Proteins and other molecules also use water as a solvent.
Anatomy of a Word
ionizing
Ionizing means any process that changes a neutral (noncharged) atom (or molecule) into one that carries a charge.
Water is an essential substrate for many processes in the human body. A substrate is a molecule on which enzymes act to catalyze, or cause, biochemical and other essential reactions. So water is the basis upon which many biological processes take place.
The connection between water pressure and blood pressure
In the blood stream, the amount of water pressure has a large impact on blood pressure and heart activity. The kidneys respond to changes in the amount of water and water pressure in the body. For example, the kidneys will excrete more water and salt if the blood pressure increases to help reduce it.
The body uses water for many functions, including:
· regulating body temperature
· lubricating joints and moistening tissues
· flushing waste (preventing constipation and reducing demand on the kidneys)
· aiding in the transport of materials and gases in the blood stream
· dissolving molecules (such as minerals) so the body can use them
The Role of Salts
Your body uses a number of inorganic compounds in the form of salts. (Calcium phosphate salts, described in the following section, are an example.) A salt is an ionic compound formed when a base reacts with an acid, which means it has net neutral charge despite being made up of charged parts (positively charged ions and negatively charged ions).
Because of the properties of salts, in the body they can dissolve to become electrolytes (free ions that are conductive), making it possible for them to carry an electrical charge through a solution. Sodium chloride, for example, helps transmit neural impulses and is necessary for your muscles to contract. It is also used to aid digestion and to help regulate the amount of fluid in your body.
Calcium Phosphates
Calcium phosphates, a type of salt, make up much of the inorganic material in the bones and teeth. These body parts are essential for support, movement, and eating, but they also play the important bodily function of storing calcium as phosphates.
Calcium is an essential ion for muscle contraction, nerve signaling, and protein activation, among other activities. If blood calcium levels decrease, calcium can be recruited from storage in the bones to maintain homeostasis of cellular activity. Endocrine glands secrete hormones that closely regulate blood calcium levels.
Acids and Bases
Your body uses acids and bases for a number of functions as well. Your body produces hydrochloric acid to digest food in the stomach. However, the hydrochloric acid must be neutralized once it is mixed with food and leaves your stomach or it would destroy other tissues, so your body produces a base, bicarbonate, to reduce the acidity.
Your body also produces buffers that can make small changes in the base or acidity of a substance in your body to help keep your bodily fluids the proper pH.
Minerals
Your body needs other inorganic substances in the form of minerals to function. Minerals are naturally occurring solids that help your body with various processes. For example, iron helps bind oxygen to red blood cells and transport it throughout your body. Someone without enough iron in her body will be anemic, and suffer from fatigue and occasionally serious, life-threatening disorders. Other minerals are used to create hormones and to regulate your heartbeat. Minerals your body needs for proper functioning include:
· magnesium
· manganese
· iodine
· zinc
· potassium
· fluoride