General Biology: Biomolecules, Functional Groups, and Cellular Compounds Study Guide

Biological Molecules and Functional Groups

Overview of Biomolecules

Biological molecules are essential compounds that form the structure and carry out the functions of living cells. They include carbohydrates, lipids, proteins, and nucleic acids, each with distinct properties and roles.

• Carbohydrates: Organic compounds composed of carbon, hydrogen, and oxygen. Serve as energy sources and structural materials.

• Lipids: Hydrophobic organic compounds, including fats, oils, and phospholipids. Function in energy storage, insulation, and cell membrane structure.

• Proteins: Polymers of amino acids that perform structural, enzymatic, and regulatory functions.

• Nucleic Acids: Macromolecules (DNA and RNA) that store and transmit genetic information.

Functional Groups in Biomolecules

Functional groups are specific groups of atoms within molecules that determine their chemical properties and reactions.

• Hydroxyl: –OH group, found in alcohols and carbohydrates.

• Amine: –NH2 group, found in amino acids and proteins.

• Ketone/Carbonyl: C=O group, found in sugars and other organic molecules.

• Phosphate: –PO4 group, important in nucleic acids and energy transfer.

• Aldehyde: –CHO group, found in some sugars.

• Sulfhydryl: –SH group, found in some amino acids.

Key Chemical Reactions

• Condensation/Dehydration: Joins two molecules to form a larger molecule, releasing water. $\text{A} + \text{B} \rightarrow \text{AB} + \text{H}_2\text{O}$

• Hydrolysis: Breaks down a compound by adding water. $\text{AB} + \text{H}_2\text{O} \rightarrow \text{A} + \text{B}$

Carbohydrates

Types and Functions

Carbohydrates are classified based on the number of sugar units.

• Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose).

• Disaccharides: Two monosaccharides joined by a covalent bond (e.g., sucrose, lactose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen).

Polysaccharides serve as energy storage (starch, glycogen) or structural components (cellulose).

Lipids

Types and Functions

• Fats: Composed of a glycerol molecule bonded to three fatty acids. Used for energy storage.

• Fatty Acids: Long hydrocarbon chains with a carboxyl group at one end.

• Triglycerides: Three fatty acids bonded to glycerol.

• Phospholipids: Major component of cell membranes, with hydrophilic heads and hydrophobic tails.

• Steroids: Lipids with a four-ring structure (e.g., cholesterol).

Proteins

Structure and Function

Proteins are polymers of amino acids linked by peptide bonds. They perform a wide range of functions, including catalysis, transport, and structural support.

• Amino Acids: Building blocks of proteins, each with an amino group, carboxyl group, and side chain (R group).

• Peptide Bond: Covalent bond linking amino acids. $\text{Amino acid}_1 + \text{Amino acid}_2 \rightarrow \text{Dipeptide} + \text{H}_2\text{O}$

• Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Local folding (alpha helix, beta sheet).

  • Tertiary: Overall 3D shape.

  • Quaternary: Multiple polypeptide chains.

Nucleic Acids

Structure and Function

Nucleic acids store and transmit genetic information. They are polymers of nucleotides.

• Nucleotide: Consists of a phosphate group, five-carbon sugar, and nitrogenous base.

• DNA: Stores genetic instructions for development and function.

• RNA: Involved in protein synthesis and gene expression.

• ATP: Nucleotide that serves as the cell's energy currency.

Table: Major Cellular Organic Compounds

The following table summarizes the major types of cellular organic compounds and their functions.

Type	Example	Function
Lipids	Phospholipids	Cell membranes
Proteins	Enzymes	Catalyze reactions
Proteins	Weapons against bacteria	Defense
Nucleic Acids	DNA and RNA	Genetic information
Nucleic Acids	ATP	Energy currency
Lipids	Triglycerides	Energy storage
Lipids	Steroids, oils, waxes	Structural and signaling
Carbohydrates	Glucose, sucrose	Energy source
Carbohydrates	Glycogen, starch, cellulose	Storage and structure

Enzymes and Chemical Reactions

Role of Enzymes

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy. They are essential for metabolism and cellular function.

• Example: The enzyme acts as a catalyst to speed up the reaction between substrates.

Short Answer Explanations

Condensation and Hydrolysis Reactions

• Condensation: The hydroxyl group from one amino acid and hydrogen from another combine, forming water and a peptide bond.

• Hydrolysis: Water is added to break the peptide bond, separating the amino acids.

Formation of Triglycerides

• Triglyceride Formation: Glycerol combines with three fatty acids, forming three covalent bonds and releasing three water molecules.

Phospholipid Structure and Function

• Phospholipids: Main component of cell membranes, forming a bilayer with hydrophilic heads and hydrophobic tails. Functions include transport, signaling, and enzymatic activity.

Multiple Choice Concepts

• Lipids: Fats are broken down into fatty acids and glycerol; triglycerides serve as energy sources.

• Amino Acids: Linked by peptide bonds to form proteins.

• DNA: Contains genetic instructions and is composed of nucleotides.

• Carbohydrates: Serve as structural materials and energy storage.

• Carbon: Forms four covalent bonds, allowing for diverse molecules.

• Protein Structure: Folding leads to secondary, tertiary, and quaternary structures.

• Hydrolysis: Involves breaking a compound by adding water.

Additional info:

• Some diagrams and chemical structures were referenced but not fully visible; explanations are based on standard textbook representations.

• Functional group labeling and matching exercises reinforce recognition of key chemical groups in biomolecules.