Macromolecules

Introduction to Macromolecules

Macromolecules are large, complex molecules that are fundamental to the structure and function of living organisms. They are primarily organic compounds, meaning they contain carbon atoms and are found in all living things.

• Organic compounds are molecules that contain carbon. An exception is carbon dioxide (CO2), which is considered inorganic.

• All living things are composed of carbon-based molecules.

• Inorganic compounds do not contain carbon-hydrogen bonds.

Biomolecules

Definition and Importance

Biomolecules are the molecules that make up living organisms. They are essential for life and perform a wide range of functions, including energy storage, structural support, and information storage.

• Four major classes: Carbohydrates, Lipids, Proteins, and Nucleic Acids.

• Each class has unique building blocks and functions.

Biomolecule Building Blocks

Each type of biomolecule is made from smaller units called monomers, which join together to form polymers.

Monomers and Polymers

Definitions

• Monomer: A single, small molecule that can join with others to form a polymer.

• Polymer: A large molecule made up of repeating monomer units.

For example, amino acids (monomers) link together to form proteins (polymers).

Types of Biomolecules and Their Functions

Overview

• Carbohydrates: Store quick energy for cells.

• Lipids: Store long-term energy and make up cell membranes.

• Proteins: Build and repair tissues, act as enzymes, and perform many cellular functions.

• Nucleic Acids: Store and transmit genetic information (DNA and RNA).

Carbohydrates

Structure and Elements

Carbohydrates are sugars and starches composed of carbon (C), hydrogen (H), and oxygen (O), typically in a 1:2:1 ratio.

• Monomer: Monosaccharide (e.g., glucose, fructose)

• Polymer: Polysaccharide (e.g., starch, cellulose, glycogen)

General formula for simple carbohydrates:

Examples:

• Glucose: A simple sugar used for energy.

• Starch: A storage polysaccharide in plants.

• Cellulose: A structural polysaccharide in plant cell walls.

Testing for Carbohydrates

• Iodine (Lugol's) Test: Detects the presence of starch. A positive result turns blue/black.

• Benedict's Test: Detects the presence of simple sugars (monosaccharides). A positive result changes from blue to orange.

Lipids

Structure and Elements

Lipids are fats, oils, and waxes composed mainly of carbon (C), hydrogen (H), and oxygen (O), but with a much lower proportion of oxygen compared to carbohydrates.

• Monomers: Glycerol and Fatty Acids

• Polymer: Triglyceride (three fatty acids bonded to one glycerol molecule)

Fatty acids can be saturated (no double bonds between carbon atoms) or unsaturated (one or more double bonds).

• Saturated fatty acids: Solid at room temperature (e.g., butter).

• Unsaturated fatty acids: Liquid at room temperature (e.g., olive oil).

Formation of triglycerides involves a dehydration synthesis reaction, releasing water:

Testing for Lipids

• Solubility Test: Lipids are insoluble in water but soluble in nonpolar solvents.

• Sudan III/IV Test: Lipids will dissolve in the dye and turn red/pink. If not present, the dye will sink to the bottom.

Proteins

Structure and Elements

Proteins are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes sulfur (S). They are made from amino acid monomers linked by peptide bonds to form polypeptides.

• Monomer: Amino Acid

• Polymer: Polypeptide/Protein

Proteins serve many functions, including acting as enzymes, antibodies, and structural components.

Testing for Proteins

• Biuret Test: Uses copper sulfate and sodium hydroxide. A positive result (presence of peptide bonds) turns violet.

Nucleic Acids

Structure and Elements

Nucleic acids, such as DNA and RNA, are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P). They store and transmit genetic information.

• Monomer: Nucleotide (composed of a sugar, phosphate group, and nitrogenous base)

• Polymer: DNA or RNA

Example: DNA encodes the instructions for building proteins in cells.

Summary Table: Biomolecules

Additional info:

• Some details about nucleic acids were inferred for completeness.

• Testing methods for biomolecules are standard in introductory biology labs.