Structure and Function of Large Biological Molecules: Study Guide

Chapter 5: Structure and Function of Large Biological Molecules

Introduction

This chapter explores the major classes of biological macromolecules, their structure, and their functions in living organisms. Understanding these molecules is fundamental to the study of biology, as they form the basis of cellular structure and function.

Macromolecules: Monomers and Polymers

Monomers and Polymers

• Monomer: A small, repeating molecular unit that can join with others to form a polymer.

• Polymer: A large molecule composed of many repeated subunits (monomers) linked together by covalent bonds.

• Example: Glucose (monomer) forms starch (polymer).

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis (Condensation Reaction): A chemical reaction in which two monomers are joined by removing a water molecule. End product: A polymer and water.

• Hydrolysis: A chemical reaction that breaks a polymer into monomers by adding water. End product: Monomers.

• Equation for Dehydration Synthesis: $\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + \text{H}_2\text{O}$

• Equation for Hydrolysis: $\text{Polymer} + \text{H}_2\text{O} \rightarrow \text{Monomer}_1 + \text{Monomer}_2$

Major Classes of Biological Macromolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Carbohydrates

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

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

• Examples:

  • Monosaccharide: Glucose

  • Disaccharide: Sucrose (glucose + fructose)

  • Polysaccharide: Starch, cellulose, glycogen

• Bond: Glycosidic linkage (joins two monosaccharides)

Lipids

• Not true polymers (do not consist of repeating monomers)

• Main components: Glycerol and fatty acids

• Types: Fats, phospholipids, steroids

• Fat molecule: Composed of one glycerol and three fatty acids (triglyceride)

• Unique property: Hydrophobic (insoluble in water)

• Saturated vs. Unsaturated Fatty Acids:

  • Saturated: No double bonds, solid at room temperature (e.g., butter)

  • Unsaturated: One or more double bonds, liquid at room temperature (e.g., olive oil)

• Phospholipids: Major component of plasma membranes

• Steroids: Lipids with a carbon skeleton of four fused rings (e.g., cholesterol)

Proteins

• Monomer: Amino acid

• Polymer: Polypeptide (protein)

• Bond: Peptide bond (joins amino acids)

• Functions: Enzymes (catalysts), structural support, transport, signaling, movement, defense

• Levels of Protein Structure:

  1. Primary: Sequence of amino acids

  2. Secondary: Alpha helix or beta sheet (hydrogen bonding)

  3. Tertiary: 3D folding due to side chain interactions

  4. Quaternary: Association of multiple polypeptides

• Denaturation: Loss of protein structure and function due to environmental changes (e.g., heat, pH)

• Amino Acid: Contains an amino group, carboxyl group, hydrogen atom, and R group (side chain)

• What makes amino acids different: The R group (side chain)

Nucleic Acids

• Monomer: Nucleotide

• Polymer: Polynucleotide (DNA or RNA)

• Components of a Nucleotide:

  1. Phosphate group

  2. Pentose sugar (deoxyribose in DNA, ribose in RNA)

  3. Nitrogenous base (adenine, guanine, cytosine, thymine [DNA], uracil [RNA])

• Difference between DNA and RNA:

  • DNA: Double-stranded, deoxyribose sugar, bases A, T, C, G

  • RNA: Single-stranded, ribose sugar, bases A, U, C, G

Table: Comparison of Macromolecules

Macromolecule	Monomer	Polymer	Bond Type	Main Function
Carbohydrate	Monosaccharide	Polysaccharide	Glycosidic linkage	Energy storage, structure
Lipid	Glycerol & Fatty acids	Triglyceride, phospholipid, steroid	Ester linkage	Energy storage, membranes, signaling
Protein	Amino acid	Polypeptide	Peptide bond	Catalysis, structure, transport
Nucleic Acid	Nucleotide	Polynucleotide	Phosphodiester bond	Genetic information storage

Additional info:

• Some questions in the original file are phrased as prompts for short answers or definitions. The above notes expand on these with academic context and examples.