BackMacromolecules: Structure, Function, and Biological Importance
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Macromolecules
Introduction
Macromolecules are large, complex molecules essential to life, forming the structural and functional basis of cells. This study guide covers the composition of cells, the chemical reactions involved in macromolecule assembly and disassembly, and the four major classes of biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
Cell Composition
Water and Organic Molecules
Cells are composed mainly of water (~70–95%).
The remainder consists primarily of organic molecules containing carbon (C) and hydrogen (H), often with other elements.
Macromolecules: Classes and Properties
The Four Major Classes
Carbohydrates
Lipids
Nucleic acids
Proteins
Polymers and Monomers
Three of these classes (carbohydrates, proteins, nucleic acids) are polymers: long molecules made from repeating units called monomers.
Lipids are not true polymers.
Polymerization Reactions
Condensation (Dehydration) Reactions: Monomers are covalently joined by removing a water molecule.
Hydrolysis Reactions: Polymers are broken down into monomers by adding water.
Monomer-Polymer Relationships
If the monomer is... | The polymer is... |
|---|---|
A monosaccharide (e.g., glucose, fructose) | A polysaccharide (e.g., starch, glycogen, cellulose) |
An amino acid (e.g., arginine, leucine) | A polypeptide or protein |
A nucleotide (sugar, phosphate, base) | A nucleic acid (e.g., DNA, RNA) |
Carbohydrates
Structure and Properties
Carbohydrates are sugars and their polymers.
General formula:
Typical C:H:O ratio is 1:2:1 (e.g., ).
Contain polar covalent bonds, form hydrogen bonds, and are hydrophilic (interact favorably with water).
Roles of Carbohydrates
Short-term energy storage: Monosaccharides (simple sugars) such as glucose, fructose, galactose, and ribose are readily burned for energy.
Longer-term energy storage: Polysaccharides like starch (plants) and glycogen (animals) store energy for later use.
Structural roles: Cellulose (plant cell walls) and chitin (fungal cell walls, arthropod exoskeletons) provide structural support.
Cell communication: Glycoproteins and glycolipids on cell surfaces are involved in cell signaling.
Examples and Applications
Honey contains mainly glucose and fructose (monosaccharides).
Disaccharides (e.g., sucrose, lactose, maltose) are two monosaccharides linked by condensation reactions and can be hydrolyzed to release energy.
Lactose Tolerance and Intolerance
Biological Basis
Infants produce lactase, an enzyme that hydrolyzes lactose into glucose and galactose.
Most adults experience a decline in lactase production, leading to lactose intolerance (symptoms: nausea, cramps, bloating, gas, diarrhea).
Genetic mutations in some populations allow continued lactase production into adulthood, conferring lactose tolerance.
Evolutionary and Cultural Context
Domestication of cattle and dairy farming led to increased lactose tolerance in populations where milk was a major food source.
Frequency of lactose intolerance varies globally due to genetic and cultural factors.
Additional info:
Further details on lipids, proteins, and nucleic acids are covered in subsequent slides and notes, including their structure, function, and biological significance.
