Introduction to Organic Chemistry and Macromolecules

Introduction to Organic Chemistry

Organic chemistry is defined as the scientific study of the structure, properties, composition, chemical reactions, and preparation of compounds that contain carbon.
While carbon and hydrogen are the primary constituents of most organic compounds, these molecules may also incorporate a variety of other elements, including:
- Nitrogen ( $N$ )
- Oxygen ( $O$ )
- Halogens (e.g., Chlorine, Bromine, Iodine)
- Phosphorus ( $P$ )
- Silicon ( $Si$ )
- Sulphur ( $S$ )

IUPAC Nomenclature and Naming Rules

The naming of organic molecules is governed by rules established by the International Union of Pure and Applied Chemistry (IUPAC).
Base Name Derivation: The nomenclature is centered on identifying the molecule’s longest continuous chain of carbon atoms connected by single bonds. This chain can be linear (continuous) or arranged in a ring.
Substituents and Deviations: Any deviation from the parent carbon-hydrogen structure is indicated through specific prefixes or suffixes. These deviations include:
- Multiple bonds (double or triple bonds).
- Atoms other than carbon or hydrogen.
A specific set of priorities is used to determine which functional groups or structural features dictate the suffix versus the prefix in the final name.

Functional Groups in Organic Chemistry

A functional group is a specific arrangement of atoms or bonds within a chemical compound that is responsible for the characteristic chemical reactions of that compound.
Common functional groups include:
- Carbonyls ( $C=O$ )
- Alcohols ( $-OH$ )
- Carboxylic acids ( $CO_{2}H$ )
- Esters ( $CO_{2}R$ )
- Amines ( $NH_{2}$

Detailed Functional Group Classification

Hydroxyl Group
- Structure: $-OH$
- Example: Ethanol
- Biological Occurrence: Found in carbohydrates, proteins, nucleic acids, and lipids.
Carbonyl Group
- Structure: $C=O$
- Example: Acetaldehyde
- Biological Occurrence: Found in carbohydrates and nucleic acids.
Carboxyl Group
- Structure: $-COOH$
- Example: Acetic acid
- Biological Occurrence: Found in proteins and lipids.
Amino Group
- Structure: $-NH_{2}$
- Example: Alanine
- Biological Occurrence: Found in proteins and nucleic acids.
Sulfhydryl Group
- Structure: $-S-H$
- Example: Cysteine
- Biological Occurrence: Found in proteins.
Phosphate Group
- Structure: $-PO_{4}$
- Example: Glycerol phosphate
- Biological Occurrence: Found in nucleic acids.
Methyl Group
- Structure: $-CH_{3}$
- Example: Alanine
- Biological Occurrence: Found in proteins.

The Four Macromolecules of Life

Biological systems are composed of four primary types of macromolecules, each consisting of specific monomers that build into larger polymers or cellular structures.

Carbohydrates
- Monomer: Monosaccharide (e.g., Glucose, D-fructose).
- Polymer/Structure: Starch (found in starch grains in chloroplasts).
Nucleic Acids
- Monomer: Nucleotide (composed of a phosphate group, a 5-carbon sugar, and a nitrogenous base).
- Polymer: DNA strand, which organizes into chromosomes.
Proteins
- Monomer: Amino acid.
- Polymer: Polypeptide, which forms structures like intermediate filaments.
Lipids
- Subunit: Fatty acids and Triglycerides.
- Structure: Fat droplets within adipose cells.

Carbohydrates: Energy and Physiology

Definition and Sources
- Carbohydrates are essential nutrients that provide primary energy for the body.
- Dietary sources include fruits, vegetables, breads, grain products, sugar, and sugary foods.
Digestion and Absorption
- Carbohydrates are primarily digested in the small intestine.
- They are enzymatically broken down into simple (single) sugars, specifically glucose and fructose.
- Once broken down, these sugars are absorbed directly into the bloodstream for energy use.
Storage and Metabolism
- Glycogen: Excess glucose is converted into glycogen for storage in the liver and muscles.
- Blood Glucose Regulation: Between meals, liver glycogen is converted back into blood glucose to maintain a constant energy supply.
- Physical Activity: Muscle glycogen is utilized specifically for muscle contractions/activity.
- Fat Conversion: Carbohydrates that are not immediately used for energy or successfully stored as glycogen are converted into fat.

Detailed Classification of Carbohydrates

Monosaccharides
- The word "saccharide" means sugar.
- They serve as the key chemical building blocks for larger saccharides.
- Roles include: intermediates in carbohydrate metabolism, nucleic acid precursors (D-Ribose and D-Deoxyribose), and primary sources of energy.
- Examples: D-Glucose, D-Fructose, D-Galactose, D-Deoxyribose, D-Ribose.
Disaccharides
- Formed when two monosaccharides are linked together via a dehydration reaction (a reaction which produces water, $H_{2}O$ , as a byproduct).
- The connection between the two sugars is called a glycosidic bond (or linkage).
- Examples:
  - Sucrose: Glucose + Fructose. It is the stable transport form of sugar in plants, distinct from the circulating glucose found in human blood.
  - Lactose: Glucose + Galactose. This is the primary sugar reserved for offspring (milk sugar).
  - Maltose: Glucose + Glucose.
Polysaccharides
- Defined as long chains of monosaccharide units joined by dehydration reactions.
- The specific type of glycosidic bond determines the resulting structure and function of the polysaccharide.
- Starches:
  - Amylose: A linear chain of $\alpha$ -glucose units connected by $\alpha(1 \rightarrow 4)$ -glycosidic bonds.
  - Amylopectin: A branched chain of glucose. It features $\alpha(1 \rightarrow 4)$ -glycosidic bonds in the main chain and $\alpha(1 \rightarrow 6)$ -glycosidic bonds at the branching points.
- Glycogen: Highly branched storage form of glucose in animals.
- Cellulose: Structural polysaccharide found in plant cell walls.

Saccharide Derivatives and Blood Typing

Glycoproteins
- These consist of protein-carbohydrate chains.
- They are embedded within the cell membrane and are characteristic of an individual organism.
- In vertebrates, they are critical for immune cells to recognize foreign molecules.
Glycolipids and Blood Groups
- Glycolipids determine human blood group types based on the specific saccharides bound to the red blood cell surface.
- Type O: Considered the base structure, containing N-Acetylglucosamine, Galactose, and Fucose.
- Type A: Contains the Type O structure plus N-Acetylgalactosamine.
- Type B: Contains the Type O structure plus an additional Galactose unit.
Immune Compatibility by Blood Group
- Group A: Has A antigens on the cell; produces Anti-B antibodies.
- Group B: Has B antigens on the cell; produces Anti-A antibodies.
- Group AB: Has both A and B antigens; produces no antibodies (universal recipient).
- Group O: Has no antigens; produces both Anti-A and Anti-B antibodies (universal donor).