Chapter 3: Carbon and the Molecular Diversity of Life – Study Notes

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Objectives

Explain the principles of chemical bonding and apply those principles to the formation and properties of both inorganic and organic molecules.
Describe the building blocks, levels of structure, and the synthesis/degradation of polymers.
Describe the structure and function of enzymes and their roles in metabolic pathways.

Carbon

Carbon Skeleton

Carbon is the foundational element of organic molecules due to its ability to form four covalent bonds, allowing for a diversity of molecular structures.

Covalent Bonds: Each carbon atom forms four covalent bonds, enabling complex molecules.
Bonding Partners: Carbon is commonly bonded to hydrogen, oxygen, nitrogen, and other carbon atoms.
Hydrophobic vs. Hydrophilic: Molecules with many C-H bonds are typically hydrophobic (water-repelling).
Carbon Skeleton Variations: Carbon skeletons can vary in length, branching, double bonds, and ring structures, contributing to molecular diversity.

Isomers

Isomers are compounds with the same molecular formula but different structures and properties.

Similarity: Isomers have identical numbers and types of atoms.
Difference: Isomers differ in the arrangement of atoms.
Structural Isomers: Differ in covalent arrangement of atoms.
Enantiomers: Mirror-image isomers, important in biological systems due to their different effects.

Seven Functional Groups

Functional Groups in Organic Molecules

Functional groups are specific groups of atoms within molecules that confer particular chemical properties.

Functional group name	Structure	Properties
Hydroxyl	-OH	Polar, forms hydrogen bonds, increases solubility in water
Carbonyl	C=O	Found in aldehydes and ketones, increases reactivity
Carboxyl	-COOH	Acts as an acid, can donate H+
Amino	-NH2	Acts as a base, can accept H+
Sulfhydryl	-SH	Forms disulfide bonds, stabilizes protein structure
Phosphate	-OPO32-	Contributes negative charge, involved in energy transfer
Methyl	-CH3	Nonpolar, affects gene expression

General Properties of Macromolecules

Monomers and Polymers

Macromolecules are large molecules composed of smaller subunits called monomers. Polymers are chains of monomers linked by covalent bonds.

Monomers: The repeating units that serve as building blocks of polymers.
Polymers: Long molecules consisting of many similar or identical monomers.

Dehydration and Hydrolysis Reactions

Polymers are synthesized and broken down by dehydration and hydrolysis reactions, respectively.

Type of reaction	Polymer: building or breaking down?	Water: add or remove?	Energy: required or released?
Dehydration	Building	Remove	Required
Hydrolysis	Breaking down	Add	Released

Macromolecule 1: Carbohydrates

Polysaccharides

Carbohydrates are sugars and their polymers, serving as energy sources and structural materials.

Polysaccharide	Function (structure or energy)	Cell Type (plants, animals, or fungi)
Starch	Energy storage	Plants
Glycogen	Energy storage	Animals
Cellulose	Structural support	Plants
Chitin	Structural support	Fungi, animals (exoskeletons)

Starch vs. Cellulose: Both are polymers of glucose, but differ in glycosidic linkages, affecting digestibility and structure.

Macromolecule 2: Proteins

Protein Structure and Function

Proteins are polymers of amino acids, performing a wide range of functions in cells.

Monomer: Amino acid
Polymer: Polypeptide

Level of structure	Part of the amino acids	Type(s) of bonds
Primary	Sequence of amino acids	Peptide bonds
Secondary	Backbone	Hydrogen bonds
Tertiary	Side chains (R groups)	Hydrogen, ionic, disulfide, hydrophobic interactions
Quaternary	Multiple polypeptides	Same as tertiary (between subunits)

Denaturation: Loss of protein structure due to environmental changes, resulting in loss of function.

Macromolecule 3: Nucleic Acids

DNA and RNA Structure

Nucleic acids store and transmit genetic information. DNA and RNA differ in structure and function.

Nucleic acid type	Sugar	Bases	Polymer structure
RNA	Ribose	A, U, C, G	Single-stranded
DNA	Deoxyribose	A, T, C, G	Double-stranded helix

Macromolecule 4: Lipids

General Properties of Lipids

Lipids are hydrophobic molecules mainly composed of carbon and hydrogen, serving as energy storage, structural components, and signaling molecules.

Main Elements: Carbon and hydrogen
Hydrophobicity: Lipids are generally hydrophobic due to nonpolar C-H bonds

Types of Lipids

Type 1: Fats

Glycerol Backbone: The 3-carbon backbone of fats is called glycerol.
Fatty Acids: The long chains of carbon and hydrogen are called fatty acids.
Structure: Fats consist of glycerol linked to three fatty acids by ester bonds.
Functions: Energy storage, insulation, and protection.
Also Known As: Triglycerides

Type 2: Phospholipids

Structure: Phospholipids have a glycerol backbone, two fatty acids, and a phosphate group.
Membrane Formation: Phospholipids arrange in bilayers, with hydrophilic heads facing water and hydrophobic tails facing inward, forming cell membranes.

Type 3: Steroids

Chemical Structure: Steroids have a structure of four fused carbon rings.
Functions: Hormones (e.g., cholesterol, testosterone, estrogen), membrane fluidity.

Key Equations and Concepts

Dehydration Reaction:
Hydrolysis Reaction:

Additional info: Academic context and table entries have been expanded and completed for clarity and completeness.