Biology study guide 2


Organic Compunds

Carbon containing compounds, usually with hydrogen and sometimes oxygen.


Long chains or rings of carbon that serve as a skeleton backbone. 4 types: carbohydrates, lipids, proteins and nucleic acids.

Polymer principles

Polymers have many molecules, monomers only have one. Molecules are linked by dehydration synthesis (-1 water) and separated by hydrolysis (+1 water).


1) Monosaccharide--simple sugar with 3-7 carbons in the skeleton backbone. Example: glucose (C6H12O6). C=O--carbonyl group, O-H--hydroxyl group.

2) disaccharides--double sugar. Sucrose = glucose + fructose, Lactose = glucose + galactose, Maltose = glucose +glucose. Glycosidic linkage=dehydration synthesis.

3) polysaccharide--complex carbohydrates--starch and cellulose.

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Hydrophobic--little or no affinity for water. Includes fats, phospholipids and steroids.

1) fats--assembled by dehydration. Glycerol + fatty acid. Triglyceride--three fatty acids join glycerol. Structure of tail determines the type--saturated=animal fat, unsaturated=plant/fish oil. Major function energy storage, more compact and more fuel than starch.

2)phospholipids--glycerol + 2 fatty acids + phosphate group. Variety of phospholipids created by what bonds to phosphate group. Main function=cell membrane.

3)steroids--carbon skeleton: four fused rings. Different steroids have different functional groups attached to their rings.

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50% of dry weight of cell. Functions: structural support, storage, transport, communication, movement, defense and enzymes. Proteins structurally sophisticated, all constructed from 20 amino acids. Polymers of amino acids=polypeptides. Amino acids=symmetric carbon with amino group (NH2), carbonyl group, hydrogen and R functional group. Amino acids linked by dehydration synthesis, carbonyl to amino, resulting covalent bond peptide bond. Each polypeptide has unique sequence of amino acids. Four levels of protein structure: primary (amino acid sequence), secondary (alpha helix/beta sheet), tertiary (bending between adjacent amino acids--active form of protein) and quaternary (several polypeptides combine).

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nucleic acids

Informational polymers--amino acid sequence of polypeptide programmed by units of inheritance (genes). Gene consists of DNA, polymer of nucleic acids.

Two types of nucleic acids: RNA (ribonucleic acid) and DNA (deoxyribonucleic acid).


DNA provides direction for own replication. Controls RNA synthesis and thru RNA, protein synthesis. Long molecule with 100s-1000s of genes. Genetic program implemented by proteins. DNA ➡ genes ➡ RNA ➡ protein. DNA=2 nucleotides spiraling around imaginary axis to form double helix (J. Watson and F. Crick at Cambridge University in 1953). Sugar-phosphate backbone on outside with nitrogenous bases on the inside linked by hydrogen bonds between paired bases and other forces between stacked bases.

DNA = 1000s-1,000,000s of complimentary base pairs. A+T, C+G (U replaces T in RNA)


Nucleic acids are polymers, nucleotide is the monomer. Nucleotide has three parts: 1) organic nitrogenous base (5 types), 2) Pentose (5-carbon sugar), and phosphate group.

Covalent bond between phosphate of one nucleotide and pentose of the next (phosphodiester linkage). Result is alternating backbone of sugar and phosphate.

pentose sugar

Connected to nitrogenous base. Ribose in RNA and deoxyribose in DNA. Deoxyribose lacks 1 oxygen on carbon 2. Phosphate added to carbon 5, nitrogenous base added to carbon 1.

nitrogenous bases

Pyrimidines--6-member ring and nitrogen: cytosine (C) in DNA and RNA, thymine (T) in DNA only and uracil (U) in RNA only.

Purines--6-member ring, 5-member ring and nitrogen: adenine (A) in both, guanine (G) in both.

Nitrogenous bases branch off of pentose like appendages. Sequence unique for each gene. Because DNA so long, possible base sequence limitless. Order of bases specifies amino acid order of proteins (primary sequence).

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two strands are complimentary

In cell division (precise copying of genes), strands separate and each strand serves as template to order nucleotides into new complimentary strand. 2 identical copies then made from 1.


I would like to thank my biology teacher for making the PowerPoint from which I took all the material for this study guide.