Chapter 3

Carbon and the Molecular Diversity of Life

Organic Chemistry is the Study of C

• Carbon is a unique element, able to form large, complex, and varied molecules that make life possible.
• Although carbon is the key component of biomolecules the other important elements make up the term CHNOPS.
• Early chemists followed vitalism or the belief in a life force outside of the laws of science.
• Friedrich Wohler was the 1st to make organic compounds from seemingly inorganic compounds.
• Later Miller and Urey made the 1st organic compounds from truly inorganic sources.
• Early organic chemists shifted chemistry form vitalism to mechanism.

Carbon Atoms form Diverse Molecules

• Carbon atoms complete their valence shell by sharing 4 electrons with other atoms including other carbon atoms.
• Atoms branch off from carbon in up to four directions which makes large molecules possible.
• Carbon atoms bond angles depend on which elements it bonds with and the number of bonds.
• Carbon chains form carbon skeletons that can be straight, branched, or rings.
• Hydrocarbons are organic molecules consisting of carbon and hydrogen atoms.
• Isomers are compounds that have the same number of atoms of same elements but different structures and properties.
• Structural isomers differ in the arrangement of covalent bonds.
• Cis-trans isomers differ in spatial arrangements of double bonds.
• Enantiomers are mirror images of each other.

Functional Groups

ATP: The Energy Source

• Adenosine Triphosphate or ATP contains a molecule called adenosine along with 3 phosphate groups.

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• When bonds break between the phosphate groups energy is released as the molecule becomes adenosine diphosphate (ADP).

�The Structure and Function of Large Macromolecules

Macromolecules are Polymers built from monomers

• A polymer is a long molecule consisting of many similar or identical building blocks or monomers linked by covalent bonds.
• Synthesis reactions or dehydration reactions occur when two or more atoms or molecules combine to form a larger molecule.
• Synthesis reactions absorb energy and underlie all anabolic activities.
• Decomposition reactions or hydrolysis reactions occur when a molecule is broken down into smaller molecules, atoms, or ions.
• Decomposition reactions release energy and underlie all catabolic activities.

Carbohydrates Serve as Fuel and Building Materials

• Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, with a general formula of CH₂O.
• Simple sugars consisting of one single chain or ring structure are monosaccarhides.
• Dissacharides are double sugars constructed of two monosaccharides by a synthesis reaction through a glycosidic linkage.
• Polysaccharides are long branching chains of simple sugars.
• Starch is a storage molecule for plants and glycogen is a storage molecule for animals.
• Cellulose differs from starch in its glycosidic linkages between glucose molecules.
• Chitin is a structural polysaccharide found in insect exoskeletons and in fungi.

glucose

sucrose

starch

Carbohydrate Structure

Lipids are a Diverse Group of Hydrophobic Molecules

• Lipids are organic compounds formed of carbon and hydrogen atoms, ie hydrocarbons.
• Neutral fats or triglycerides are composed of fatty acid chains and glycerol.
• Saturated fats have carbon chains with single bonds, whereas unsaturated fats have carbon chains with at least one double bond.
• Neutral fats yield twice as much energy per gram as carbohydrates or proteins.
• Phospholipids have two fatty acid chains and a glycerol group and are both hydrophobic and hydrophilic, perfect for the cell membrane.
• Steroids are composed chiefly of hydrogen and carbon atoms arranged in a ring structure.
• Cholesterol is the chief steroid of cell membranes.

Computer model of cholesterol

Lipid Structure

Proteins Include a Diversity of Structures & Functions

• A protein is a complex nitrogenous substance composed of a chain of amino acids.
• The building blocks of proteins are amino acids which are composed of: a central carbon atom, a hydrogen atom, amine group, a carboxyl group, and a R-group.
• Amino acid chains less than 50 molecules long are polypeptides formed by dipeptide bonds.
• Protein structure and resulting function is based 4 levels of structure:
• Primary, secondary, tertiary quatenrary
• When protein structure breakds down or denatures the function changes.

Protein Structure

Four Levels of Protein Structure

Nucleic Acids Store, Transmit, and Help Express Hereditary Information

• Nucleic acids are a class of organic compounds that include DNA and RNA.
• The building blocks of nucleic acids are nucleotides which are composed of a sugar, phosphate group, and a nitrogen base.
• DNA provides the instructions for building every protein in the body, whereas RNA carries out the orders for protein synthesis.
• DNA is a twisted double helix or staircase of 2 strands of nucleotides joined by complementary base pairs (A with T and G with C).
• The sugar-phosphate backbone of DNA run in opposite or 5’ to 3’ direction

Nucleic Acid Structure