Lecture Notes-10 Biology 1004

North Arkansas College

Topic: Macromolecules

1. All living organisms are composed of 4 major classes of chemical compounds.

1. Proteins
2. Carbohydrates
3. Lipids
4. Nucleotides

2. The individual types of organisms differ in type of these molecules.
3. Major chemical elements that make up those found in the 4 major classes of compounds.
4. What is the chemical backbone of living organisms? How is it formed?

Carbon is the backbone of all living things. Characteristics that make it important to living systems:

1. Carbon has 4 valence electrons.
2. Therefore, carbon can react with 4 other substances, producing a wide variety of chemical compounds.
3. Normally, carbon reacts with hydrogen, oxygen, sulfur, etc.
4. Also, carbon can share electrons with other carbon atoms to form C-C chains.
5. These carbon chains can be several hundred carbons long. This further increases the diversity of the chemical compounds.
6. On some occasions, carbons can share 2 or 3 pairs of electrons to form double or triple bonds. These are reactive and increase the diversity in saturated compounds.
7. Sometimes these carbon chains can form cyclic molecules furthering the variation in the compounds.

1. Isomers are chemical compounds that have the same molecular formula but different structural formula. For example, glucose and fructose have the same numbers of carbons, hydrogens, and oxygens, but they are arranged differently. Both are C₆H₁₂0₆.
2. Isomers further increase the diversity of chemical compounds found in living organisms.

1. Clusters of atoms with a certain pattern and certain function or properties.
2. They allow chemical molecules to take on polarity (+,-).
3. Examples of functional groups:

1. Amino groups –NH₂ found in amino acids and proteins.
2. Hydroxy groups –OH found in sugars and lipids.
3. Carboxylic acid found in fatty acids, lipids and sugars.
4. Aldehyde found in sugars.
5. Ketos found in sugars and ketones.
6. Sulfhydric groups –SH found in amino acids and proteins.

4. Functional groups add to the diversity of compounds found in living systems and their reactivity. Polarity of compounds is important in living organisms.

How do monomers (single molecules) combine to form macromolecules?

Monomers:

1. Amino acids (proteins)
2. Simple sugars (polysaccharides).
3. Glycerol and fatty acids (lipids).
4. Nucleotides (DNA< RNA, vitamins).

1. Monomers combine by a process called dehydration synthesis.
2. Complex molecules can be broken down with hydrolysis (adding H₂0).

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