How is carbon different from other atoms?
Why is it essential to living things?
2.3 Carbon-based Molecules
Key Concept: Carbon-based molecules are the basis of life.
Carbon atoms have unique
bonding properties.
 Carbon forms covalent bonds (strong bonds) with up to
four other atoms, including other carbon atoms
 Carbon-based molecules have three general types of
structures
 Straight chain
 Branched chain
 Ring
(3-D structures)
Carbon atoms have unique
bonding properties.
 Carbon can form single, double, or triple bonds
 Carbon forms isomers
 Isomers are compounds that have the same chemical
formula, but different structural formulas
 Example: C4H10
 Only carbon has these characteristics
Many carbon-based molecules are made of
many small subunits bonded together.
 Monomers are the individual subunits.
 Polymers are made of many monomers.
Four main types of carbon-based
molecules are found in living things.
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic acids
Carbohydrates
Molecule 
Has Carbon
Carbohydrates
All of the time
Has Hydrogen
All of the time
Has Oxygen
All of the time
Has Nitrogen
-
Has Phosphorus
-
Monomer
Polymer
Examples
Unique
monosaccharide
disaccharide (dimer), polysaccharide
Monosaccharide: glucose, fructose
Disaccharide: sucrose (table sugar)
Polysaccharide: starch & cellulose (cell wall in plants),
glycogen (in animals)
- Provide a quick source of energy
Lipids
Molecule 
Has Carbon
Has Hydrogen
Has Oxygen
Has Nitrogen
Has Phosphorus
Monomer
Polymer
Examples
Unique
Lipids
All of the time
All of the time
All of the time
Some of the time
Some of the time
glycerol & fatty acids; polar heads & fatty acid tails
triglycerides; phospholipids
Fats, oils, cholesterol, steroids, waxes, phospholipids
- Nonpolar
- Broken down to provide energy
- Used to make steroid hormones (control stress,
estrogen, testosterone)
- Phospholipids make up all cell membranes
- Fats and oils contain fatty acids bonded to glycerol
Proteins
Molecule 
Has Carbon
Has Hydrogen
Has Oxygen
Has Nitrogen
Has Phosphorus
Monomer
Polymer
Examples
Unique
Proteins
All of the time
All of the time
All of the time
All of the time
Amino acid
Polypeptide (protein)
Enzymes, hemoglobin (in blood), muscle movement,
collagen
- 3D structure makes them active
- Peptide bonds hold amino acids together
- Have a side group (R) that makes each amino acid (and
therefore protein) different
- Sometimes may contain sulfur
Nucleic acids
Molecule 
Has Carbon
Nucleic acids
All of the time
Has Hydrogen
All of the time
Has Oxygen
All of the time
Has Nitrogen
All of the time
Has Phosphorus
All of the time
Monomer
Polymer
Examples
Unique
Nucleotide (5-carbon sugar, phosphate group, & base)
Nucleic acid
DNA & RNA
- Order of the bases makes every living thing unique
- DNA stores genetic information
- RNA builds proteins
Building & Using Carbon-based
Molecules
 Building (process): dehydration synthesis
 Removal of water to make a new product
 Using (process): hydrolysis
 Breaking apart using water
Dehydration Synthesis
 Two monomers need to join
 One monomer loses (-OH) and one loses (-H)
 The two monomers join and the (-OH) and (-H) join,
forming H2O
 A-OH + B-H  AB + HOH (H2O)
Hydrolysis
 A polymer needs to break apart (the carbs, proteins,
and lipids we ingest are too big for us to use)
 Water breaks apart into (-OH) and (-H) and splits the
polymer into monomers
 The (-OH) and (-H) bond to each monomer to make them
stable molecules
 AB + HOH (H2O)  A-OH + B-H
 What’s in a mixture?
 What’s in a molecule?
 Macromolecules Gone Wild (Bio Style)
 Gangnam parody