A&P Module 2

Within our body, countless chemical reactions are occurring at all times to ensure homeostasis.

Because we cannot see the many chemical reactions that take place daily in our bodies, it is sometimes difficult to comprehend the principles involved in initiating them. Chemicals are responsible for directing virtually all of our bodily functions. It is, therefore, important to understand the basic chemical reactions that occur in the body and to master the fundamental concepts of biochemistry.

• Chemists use the terms elements or compounds to describe all of the substances known as matter in and around us.
• Elements are pure substances, composed of only one kind of atom.
• A compound is made up of two or more elements and has the ability to be broken down into the elements that form it; substances whose molecules have more than one element in them.
• Matter is any substance that occupies space and has mass.

Matter is anything that occupies space and has mass. Because this statement is so broad, matter has been classified into various levels to make the study of biochemistry easier.

• Beginning with the simplest level, an atom is a unit of matter that makes up a chemical element. Atoms are composed of subatomic particles known as:
• Protons
• Electrons
• Neutrons

Elements are pure substances that are composed of only one kind of atom. Some important elements in the body are oxygen, carbon, hydrogen, and nitrogen.

Did you know that if an electron weighed the same as a dime, a proton would weigh the same as a gallon of milk?!

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• Molecules are particles of matter that are composed of one or more atoms.
• A molecule may be formed by the combination of two or more atoms from the same element. For example, two atoms from the element oxygen (O) may combine to form a molecule of oxygen gas (O2).
• A molecule may also be formed by the combination of two or more different kinds of atoms. These molecules are called compounds. For example, two atoms of hydrogen combine with one atom of oxygen to form water (H2O). Water is considered both a molecule and a compound.
• It is essential to understand the basic unit of matter—the atom—and basic levels of chemical organization before progressing to the more complex chemical composition of our body.

• Remember the following facts about elements:
• An element is a substance that is composed of only one kind of atom.
• Elements are represented by symbols.
• It is important to be familiar with the major elements, their symbols, and their role in the human body, as you will use them throughout your study of anatomy and physiology.
• H
• Na
• Mg
• K
• Ca
• C
• N
• O
• P
• S
• Cl

Chemical bonds form to make atoms more stable. Atoms have a tendency to share or transfer electrons to achieve stability in the outermost energy shell. Two types of bonding occur frequently throughout the body:

• Two types of bonding occur frequently throughout the body:
• Ionic bonding occurs when one or more electrons are transferred from one atom to another.
• Covalent bonds are formed when two atoms share a pair of electrons.

Hydrogen bonds are a kind of weak attraction that helps hold your body's substance together. Hydrogen bonds do not form new molecules, but instead provide subtle forces that help a large molecule stay in a particular shape.

• Chemical compounds can be separated into two major classifications:
• Organic
• Inorganic

Inorganic compounds do not contain carbon-carbon bonds or carbon-hydrogen bonds. Water, the most abundant compound in the body, is an example of an inorganic compound.

Organic compounds contain carbon and include carbon-carbon bonds and/or carbon-hydrogen bonds. They are important to survival and include such examples as carbohydrates, lipids, proteins, and nucleic acids.

• There are many inorganic compounds that are essential to homeostasis in our body.
• Besides water, acids and bases are responsible for many of the chemical reactions that take place on a daily basis.
• Acids are compounds that produce an excess of hydrogen (H+) ions, and bases are compounds that produce an excess of hydroxyl (OH-) ions or a decrease in H+ ions.

• The relative concentration of H+ ions is a measure of how acidic or basic a solution is considered. This is expressed in units of pH, with 7 being neutral.
• pH values lower than 7 indicate an acidic solution.
• pH values greater than 7 indicate a basic or alkaline solution.

Organic compounds are more complex than inorganic compounds. Carbohydrates, lipids (fats), proteins, and nucleic acids are the major types of organic compounds found in the body.

Carbohydrates are the body's preferred energy source and are composed of monosaccharide units that can be broken apart to yield energy.

• Monosaccharides
• Glycogen
• Starch
• Lactose
• Polysaccharides — glycogen and starch

• Lipids are a secondary source of energy that is stored in the body in many forms. They are fat molecules composed mainly of glycerol and fatty acids.
• Corn oil
• Triglycerides — Lipid molecules formed by a glycerol unit joined to three fatty acids
• Cholesterol

• Proteins are composed of amino acids and are responsible for proper growth, development, and maintenance of health.
• Collagen
• Enzymes
• Amino acids

Nucleic acids are involved in the determination and transmission of genetic characteristics. Nucleic acids (DNA and RNA) are composed of nucleotides. These nucleotides serve as a code for assembling proteins.

A substance that, when dissolved in water, contributes to an excess of OH- ions

the pH scale and will help to neutralize the "acid indigestion" that Karsten is experiencing. Orange juice, lemon juice, and black coffee are acid on the pH scale and might intensify the condition.

Buffers maintain pH balance by preventing sudden changes in the H+ ion concentration. LDL is low-density lipoprotein, or “bad” cholesterol; amino acids are the building blocks of protein; and enzymes are functional proteins.

Correct!Coffee is an acid with a pH of 5.0.

Correct!Berries are acid and have a pH similar to that of orange juice.