1103 Chapter 2. The Chemical Level of Organization
1103 Chapter 2. The Chemical Level of Organization
2.5 Organic Compounds Essential to Human Functioning
Learning Objectives
By the end of this section, you will be able to:
- Describe the composition of organic molecules
- Specify two characteristics of organic molecules that make them useful to living organisms
- Name and describe specific examples of organic molecules
- Specify the major elements that make up carbohydrate molecules
- Describe three major groups of carbohydrates, using specific examples and specifying one function in the human body served by each group
- Specify the major elements that make up lipid molecules
- Specify a function for each of the following groups of lipids: triglycerides, phospholipids, and steroids
- Describe the structural components of a typical phospholipid molecule
- Distinguish between the polar “head” and non-polar “tail” ends of a phospholipid molecule
- Distinguish between saturated, unsaturated, and polyunsaturated fats
- Specify the major elements that make up protein molecules
- Describe, using examples, eight major functional groups of proteins
- Specify the major elements that make up nucleic acids
- Describe the structure and function of the two types of nucleic acids
- Describe the general structure and importance of adenosine triphosphate
Organic compounds typically consist of groups of carbon atoms covalently bonded to hydrogen, usually oxygen, and often other elements as well. Created by living things, they are found throughout the world, in soils and seas, commercial products, and every cell of the human body. The four types most important to human structure and function are carbohydrates, lipids, proteins, and nucleotides. Before exploring these compounds, you need to first understand the chemistry of carbon.
The Chemistry of Carbon
What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via covalent bonds.
Commonly, carbon atoms share with other carbon atoms, often forming a long carbon chain referred to as a carbon skeleton. When they do share, however, they do not share all their electrons exclusively with each other. Rather, carbon atoms tend to share electrons with a variety of other elements; in organic compounds, one of these elements is always hydrogen. Carbon and hydrogen groupings are called hydrocarbons. If you study the figures of organic compounds in the remainder of this chapter, you will see several with chains of hydrocarbons in one region of the compound.
Many combinations are possible to fill carbon’s four “vacancies.” Carbon may share electrons with oxygen or nitrogen or other atoms in a particular region of an organic compound. M