Chemistry of Carbon

Building Blocks of Life

2007-2008

AP Biology

Why study Carbon?

• All of life is built on carbon
• Cells
• ~72% H₂O
• ~25% carbon compounds
• carbohydrates
• lipids
• proteins
• nucleic acids
• ~3% salts
• Na, Cl, K…

AP Biology

*

Chemistry of Life

• Organic chemistry is the study of carbon compounds
• C atoms are versatile building blocks
• bonding properties
• 4 stable covalent bonds

AP Biology

*

AP Biology

Complex molecules assembled like TinkerToys

*

Hydrocarbons

• Combinations of C & H
• non-polar
• not soluble in H₂O
• hydrophobic
• stable
• very little attraction �between molecules
• a gas at room temperature

AP Biology

methane�(simplest HC)

*

Hydrocarbons can grow

AP Biology

*

Isomers

• Molecules with same molecular formula but different structures (shapes)
• different chemical properties
• different biological functions

AP Biology

6 carbons

6 carbons

6 carbons

*

Form affects function

• Structural differences create important functional significance
• amino acid alanine
• L-alanine used in proteins
• but not D-alanine
• medicines
• L-version active
• but not D-version
• sometimes with�tragic results…

AP Biology

stereoisomers

*

Form affects function

• Thalidomide
• prescribed to pregnant women in 50s & 60s
• reduced morning sickness, but…
• stereoisomer caused severe birth defects

AP Biology

*

Diversity of molecules

• Substitute other atoms or groups around the carbon
• ethane vs. ethanol
• H replaced by an hydroxyl group (–OH)
• nonpolar vs. polar
• gas vs. liquid
• biological effects!

AP Biology

ethane (C₂H₆)

ethanol (C₂H₅OH)

*

Functional groups

• Parts of organic molecules that are involved in chemical reactions
• give organic molecules distinctive properties

■ hydroxyl ■ amino

■ carbonyl ■ sulfhydryl

■ carboxyl ■ phosphate

• Affect reactivity
• makes hydrocarbons hydrophilic
• increase solubility in water

AP Biology

*

Viva la difference!

• Basic structure of male & female hormones is identical
• identical carbon skeleton
• attachment of different functional groups
• interact with different targets in the body
• different effects

AP Biology

*

Hydroxyl

• –OH
• organic compounds with OH = alcohols
• names typically end in -ol
• ethanol

AP Biology

*

Carbonyl

• C=O
• O double bonded to C
• if C=O at end molecule = aldehyde
• if C=O in middle of molecule = ketone

AP Biology

*

Carboxyl

• –COOH
• C double bonded to O & single bonded to OH group
• compounds with COOH = acids
• fatty acids
• amino acids

AP Biology

*

Amino

• -NH₂
• N attached to 2 H
• compounds with NH₂ = amines
• amino acids
• NH₂ acts as base
• ammonia picks up H⁺ from solution

AP Biology

*

Sulfhydryl

• –SH
• S bonded to H
• compounds with SH = thiols
• SH groups stabilize the structure of proteins

AP Biology

*

Phosphate

• –PO₄
• P bound to 4 O
• connects to C through an O
• lots of O = lots of negative charge
• highly reactive
• transfers energy between organic molecules
• ATP, GTP, etc.

AP Biology

*

Macromolecules

Building Blocks�of Life

2007-2008

AP Biology

Macromolecules

• Smaller organic molecules join together to form larger molecules
• macromolecules
• 4 major classes of �macromolecules:
• carbohydrates
• lipids
• proteins
• nucleic acids

AP Biology

*

Polymers

• Long molecules built by linking repeating building blocks in a chain
• monomers
• building blocks
• repeated small units
• covalent bonds

AP Biology

Dehydration synthesis

*

How to build a polymer

• Synthesis
• joins monomers by “taking” H₂O out
• one monomer donates OH^–
• other monomer donates H⁺
• together these form H₂O
• requires energy & enzymes

AP Biology

Dehydration synthesis

Condensation reaction

*

How to break down a polymer

• Digestion
• use H₂O to breakdown polymers
• reverse of dehydration synthesis
• cleave off one monomer at a time
• H₂O is split into H⁺ and OH^–
• H⁺ & OH^– attach to ends
• requires enzymes
• releases energy

AP Biology

Hydrolysis

Digestion

*

2007-2008

AP Biology