General Biology Study Notes: Carbon Chemistry, Functional Groups, and Biological Macromolecules

Carbon Chemistry and Diversity of Organic Molecules

Properties of Carbon

Carbon is a versatile element that forms the backbone of organic molecules due to its unique chemical properties. Its ability to form four covalent bonds allows for a wide variety of structures and polarities, which is essential for the diversity of life.

• Valence Electrons: Carbon has 4 valence electrons, enabling it to form up to 4 covalent bonds with other atoms.

• Bonding Diversity: Carbon can bond with hydrogen, oxygen, nitrogen, and other carbons, resulting in chains, rings, and complex structures.

• Polarity: Carbon's bonding can create both hydrophilic (water-attracting) and hydrophobic (water-repelling) molecules, which is crucial for biological function.

• Examples: Hydrocarbons (hydrophobic), carbohydrates (hydrophilic).

Example Equation:

$\text{C} + 4\text{H} \rightarrow \text{CH}_4$ (Methane formation)

Functional Groups in Organic Molecules

Major Functional Groups and Their Roles

Functional groups are specific groupings of atoms within molecules that confer distinct chemical properties and reactivity. They are key to the diversity and function of organic molecules in biology.

• Hydroxyl Group (-OH): Polar; found in alcohols; increases solubility in water.

• Carbonyl Group (C=O): Found in ketones and aldehydes; affects reactivity and polarity.

• Carboxyl Group (-COOH): Acidic; can donate a proton; found in amino acids and fatty acids.

• Amino Group (-NH2): Basic; can accept a proton; found in amino acids.

• Sulfhydryl Group (-SH): Can form disulfide bridges; important in protein structure.

• Methyl Group (-CH3): Nonpolar; affects gene expression and molecular interactions.

• Phosphate Group (-PO42-): Negatively charged; key in energy transfer (ATP).

Example Table: Functional Groups and Properties

Functional Group	Structure	Properties	Example Molecule
Hydroxyl	-OH	Polar, forms hydrogen bonds	Ethanol
Carbonyl	C=O	Polar, reactive	Acetone
Carboxyl	-COOH	Acidic, can donate H+	Acetic acid
Amino	-NH2	Basic, can accept H+	Glycine
Sulfhydryl	-SH	Forms disulfide bonds	Cysteine
Methyl	-CH3	Nonpolar	Methionine
Phosphate	-PO42-	Negatively charged, energy transfer	ATP

Biological Macromolecules

Classes and Functions

Biological macromolecules are large molecules essential for life, formed by the polymerization of smaller subunits called monomers. The four major classes are proteins, carbohydrates, nucleic acids, and lipids.

• Proteins: Made of amino acids; function in catalysis (enzymes), structure, transport, and signaling.

• Carbohydrates: Made of monosaccharides; provide energy and structural support.

• Nucleic Acids: Made of nucleotides; store and transmit genetic information (DNA, RNA).

• Lipids: Made of fatty acids and glycerol; function in energy storage, membrane structure, and signaling.

Example Table: Biological Macromolecules

Macromolecule	Monomer	Main Function	Example
Protein	Amino acid	Catalysis, structure	Hemoglobin
Carbohydrate	Monosaccharide	Energy, structure	Glucose
Nucleic Acid	Nucleotide	Genetic information	DNA
Lipid	Fatty acid, glycerol	Energy storage, membranes	Phospholipid

Polymerization: Monomers and Polymers

Formation and Breakdown of Polymers

Polymers are formed by joining monomers through covalent bonds. The process of forming polymers is called dehydration synthesis, while breaking them down is called hydrolysis.

• Dehydration Synthesis: Removes a water molecule to form a covalent bond between monomers.

• Hydrolysis: Adds a water molecule to break a covalent bond, splitting polymers into monomers.

• Example Equation:

$\text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{dehydration}} \text{Polymer} + \text{H}_2\text{O}$

$\text{Polymer} + \text{H}_2\text{O} \xrightarrow{\text{hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2$

ATP and Energy Transfer

Role of ATP in Cells

ATP (adenosine triphosphate) is the primary energy carrier in cells. It releases energy when its terminal phosphate group is removed, converting ATP to ADP (adenosine diphosphate).

• ATP Structure: Contains adenine, ribose, and three phosphate groups.

• Energy Release: Hydrolysis of ATP releases energy for cellular processes.

• Example Equation:

$\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

Covalent Bonds in Biological Molecules

Types and Importance

Covalent bonds are strong chemical bonds formed by the sharing of electron pairs between atoms. They are essential for the stability and function of biological macromolecules.

• Glycosidic Bonds: Link monosaccharides in carbohydrates.

• Peptide Bonds: Link amino acids in proteins.

• Phosphodiester Bonds: Link nucleotides in nucleic acids.

Example Table: Covalent Bonds in Macromolecules

Bond Type	Macromolecule	Function
Glycosidic	Carbohydrate	Joins sugars
Peptide	Protein	Joins amino acids
Phosphodiester	Nucleic Acid	Joins nucleotides

Summary

Understanding the chemistry of carbon, functional groups, and biological macromolecules is fundamental to General Biology. These concepts explain the diversity, structure, and function of molecules essential for life, including how energy is stored and transferred, how molecules interact, and how complex structures are built from simple subunits.