General Biology Study Guide: Organic Molecules, Proteins, and Enzymes

Organic Compounds in Biology

Major Groups of Organic Compounds

Organic compounds are essential molecules that form the basis of life. There are four major groups, each with distinct structures and functions.

• Carbohydrates: Composed of carbon, hydrogen, and oxygen (usually in a 1:2:1 ratio). Their main function is to provide energy and structural support. Examples: Glucose, starch.

• Lipids: Made primarily of carbon and hydrogen, with some oxygen. They function in energy storage, insulation, and forming cell membranes. Examples: Fats, phospholipids.

• Proteins: Polymers of amino acids containing carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. They serve as enzymes, structural components, and signaling molecules. Examples: Hemoglobin, enzymes.

• Nucleic Acids: Polymers of nucleotides, containing carbon, hydrogen, oxygen, nitrogen, and phosphorus. They store and transmit genetic information. Examples: DNA, RNA.

Functional Groups

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules. Common functional groups include:

• Hydroxyl (-OH): Found in alcohols and carbohydrates.

• Carboxyl (-COOH): Found in amino acids and fatty acids.

• Amino (-NH2): Found in amino acids.

• Phosphate (-PO4): Found in nucleic acids.

• Methyl (-CH3): Found in many organic molecules.

Additional info: See Table 3.2 in your textbook for a detailed summary of functional groups.

Dehydration Synthesis and Hydrolysis

These are key chemical reactions in the formation and breakdown of biological polymers.

• Dehydration Synthesis: The process of joining two molecules by removing a water molecule. This forms polymers from monomers. Equation: $\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + \text{H}_2\text{O}$

• Hydrolysis: The process of breaking down polymers into monomers by adding water. Equation: $\text{Polymer} + \text{H}_2\text{O} \rightarrow \text{Monomer}_1 + \text{Monomer}_2$

Saturated vs. Unsaturated Fats

Fats are a type of lipid and can be classified based on the presence of double bonds in their fatty acid chains.

• Saturated Fats: Have no double bonds between carbon atoms; solid at room temperature. Example: Butter.

• Unsaturated Fats: Have one or more double bonds; liquid at room temperature. Example: Olive oil.

Nucleotides and Nucleic Acids

Nucleotides are the building blocks of nucleic acids.

• Composition of a Nucleotide:

  • Phosphate group

  • Pentose sugar (ribose or deoxyribose)

  • Nitrogenous base (adenine, thymine, cytosine, guanine, uracil)

• Differences between DNA and RNA:

  1. DNA contains deoxyribose sugar; RNA contains ribose sugar.

  2. DNA uses thymine as a base; RNA uses uracil.

  3. DNA is double-stranded; RNA is single-stranded.

Protein Structure

Proteins have four levels of structure that determine their function.

• Primary Structure: Sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha-helices and beta-sheets, stabilized by hydrogen bonds.

• Tertiary Structure: Overall three-dimensional shape of a polypeptide, formed by interactions among side chains.

• Quaternary Structure: Association of multiple polypeptide chains into a functional protein.

Enzymes and Biochemical Reactions

Key Terms and Definitions

Enzymes are biological catalysts that speed up chemical reactions in cells.

• Enzyme: A protein that accelerates a specific chemical reaction.

• Substrate: The reactant molecule upon which an enzyme acts.

• Active Site: The region of the enzyme where the substrate binds and the reaction occurs.

• Reactant: A starting material in a chemical reaction.

• Product: The molecule(s) produced by a chemical reaction.

Enzyme-Catalyzed Reaction Parts

Enzyme-catalyzed reactions involve specific steps and components.

• Step 1: Substrate binds to the enzyme's active site, forming an enzyme-substrate complex.

• Step 2: The enzyme catalyzes the conversion of substrate to product.

• Step 3: Product is released, and the enzyme is free to catalyze another reaction.

Component	Description
Enzyme	Protein catalyst
Substrate	Molecule acted upon
Active Site	Region of enzyme for substrate binding
Product	Resulting molecule(s)

Example: The enzyme sucrase catalyzes the breakdown of sucrose into glucose and fructose.

Additional info: These notes expand upon the study guide questions by providing definitions, examples, and context for each topic, suitable for exam preparation in a General Biology course.