Chapter 1 Study Guide: Biological Macromolecules and Their Properties

Biological Macromolecules

Introduction to Macromolecules

Biological macromolecules are large, complex molecules essential for life. They include carbohydrates, lipids, proteins, and nucleic acids, each with unique structures and functions in cells.

• Macromolecule: A large molecule formed by the joining of smaller molecules, usually by a condensation (dehydration) reaction.

• Monomer: A small molecule that can join with other similar molecules to form a polymer.

• Polymer: A long molecule consisting of many similar or identical building blocks linked by covalent bonds.

• Example: Starch is a polymer made of glucose monomers.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically with a ratio of 1:2:1. They serve as energy sources and structural components in cells.

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

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

• Function: Energy storage (starch, glycogen), structural support (cellulose in plants)

• Example: Glucose is a monosaccharide; starch is a polysaccharide.

Identifying Sugars

Sugars can often be identified by their names, which typically end in "-ose" (e.g., glucose, fructose).

• Key Point: The suffix "-ose" is commonly used for sugars.

Dehydration vs. Hydrolysis

Dehydration and hydrolysis are chemical reactions involved in the formation and breakdown of polymers.

• Dehydration Reaction: Joins two monomers by removing a water molecule.

• Hydrolysis: Breaks a polymer into monomers by adding a water molecule.

• Equation: $\text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{dehydration}} \text{Polymer} + \text{H}_2\text{O}$

• Equation: $\text{Polymer} + \text{H}_2\text{O} \xrightarrow{\text{hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2$

Lipids

Structure and Properties

Lipids are hydrophobic molecules, including fats, oils, and phospholipids. They are not true polymers and are characterized by nonpolar bonds.

• Monomer: Fatty acid and glycerol

• Polymer: Not a true polymer, but triglycerides are formed from three fatty acids and one glycerol.

• Function: Energy storage, insulation, cell membrane structure

• Example: Triglyceride, phospholipid

Saturated vs. Unsaturated Fatty Acids

Saturated and unsaturated fatty acids differ in the presence of double bonds.

• Saturated Fatty Acid: No double bonds between carbon atoms; solid at room temperature.

• Unsaturated Fatty Acid: One or more double bonds; liquid at room temperature.

• Example: Butter (saturated), olive oil (unsaturated)

Phospholipids and Cell Membranes

Phospholipids are major components of cell membranes, forming a bilayer that allows cells to exist in aqueous environments.

• Structure: Hydrophilic (polar) head and hydrophobic (nonpolar) tails

• Function: Forms the lipid bilayer of cell membranes

• Example: Phospholipid bilayer in animal cells

Nucleic Acids

DNA and RNA Structure

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

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

• Polymer: DNA, RNA

• Function: Genetic information storage (DNA), protein synthesis (RNA)

• Example: DNA double helix, mRNA

Nitrogenous Bases

DNA and RNA contain five nitrogenous bases: adenine (A), thymine (T), cytosine (C), guanine (G), and uracil (U).

• DNA: A, T, C, G

• RNA: A, U, C, G

Pentose Sugar and Backbone

The sugar in nucleotides is a pentose (five-carbon) sugar: deoxyribose in DNA and ribose in RNA. The sugar-phosphate backbone forms the structural framework of nucleic acids.

• Phosphate Sugar Backbone: Alternating sugar and phosphate groups

Base Pairing and Chargaff's Rules

Chargaff's rules state that in DNA, the amount of adenine equals thymine, and the amount of cytosine equals guanine.

• Base Pairing: A pairs with T, C pairs with G

• Equation: $\%A = \%T$, $\%C = \%G$

DNA vs. RNA

DNA and RNA differ in several ways:

• Sugar: DNA has deoxyribose; RNA has ribose.

• Bases: DNA uses thymine; RNA uses uracil.

• Structure: DNA is double-stranded; RNA is single-stranded.

Proteins

Structure and Function

Proteins are polymers of amino acids and perform a wide variety of functions in cells, including catalysis, structure, and transport.

• Monomer: Amino acid

• Polymer: Polypeptide

• Function: Enzymes, structural support, transport, signaling

• Example: Hemoglobin, enzymes

Polypeptide vs. Protein

A polypeptide is a single chain of amino acids; a protein may consist of one or more polypeptides folded into a functional shape.

• Key Point: All proteins are polypeptides, but not all polypeptides are functional proteins.

Amino Acid Structure

There are about 20 different amino acids, each with a unique side chain (R group) that determines its properties.

• Bond: Peptide bond joins amino acids together.

• Equation: $\text{Amino acid}_1 + \text{Amino acid}_2 \xrightarrow{\text{dehydration}} \text{Dipeptide} + \text{H}_2\text{O}$

Protein Structure Levels

Proteins have four levels of structure:

• Primary: Sequence of amino acids

• Secondary: Local folding (alpha helix, beta sheet) stabilized by hydrogen bonds

• Tertiary: Overall 3D shape, stabilized by various bonds (hydrogen, ionic, disulfide)

• Quaternary: Association of multiple polypeptide chains

Enzymes and pH

Enzymes are proteins that catalyze biochemical reactions. pH can affect enzyme activity by altering the enzyme's shape and function.

• Key Point: Extreme pH levels can denature enzymes, reducing their activity.

Summary Table: Macromolecules

Type	Monomer (including illustration)	Polymer Name (if applicable)	Purpose or Function	Example of Macromolecule
Carbohydrates	Monosaccharide (e.g., glucose)	Polysaccharide (e.g., starch, cellulose)	Energy storage, structural support	Starch, cellulose
Lipids	Fatty acid and glycerol	Triglyceride (not a true polymer)	Energy storage, cell membrane structure	Phospholipid, lipid bilayer
Nucleic Acids	Nucleotide	DNA, RNA	Genetic information storage, protein synthesis	DNA double helix, mRNA
Proteins	Amino acid	Polypeptide	Catalysis, structure, transport	Enzyme, hemoglobin

Additional info:

• Some content was expanded for clarity and completeness, including definitions and examples.

• Illustrations referenced in the table are described textually due to format limitations.