General Biology Study Notes: Life Chemistry & Biomolecules

Life Chemistry: Molecules and Atoms in Biology

Introduction to Biological Chemistry

Understanding the chemical basis of life is essential in biology, as all living organisms are composed of molecules and atoms. This section introduces why biology begins with chemistry and how molecular interactions underpin biological processes.

• Molecules and Atoms: All matter, including living organisms, is made up of atoms, which combine to form molecules.

• Importance in Biology: Biological functions depend on the structure and interactions of molecules such as water, proteins, nucleic acids, and carbohydrates.

• Example: The structure of DNA, a molecule, determines how genetic information is stored and transmitted.

Atoms, Bonds, and Chemical Interactions

Atoms interact through chemical bonds to form molecules. Understanding these interactions is foundational for studying biological molecules.

• Atoms: The smallest units of matter, consisting of protons, neutrons, and electrons.

• Chemical Bonds: Forces that hold atoms together, including covalent, ionic, and hydrogen bonds.

• Example: Water molecules are held together by covalent bonds, and interact via hydrogen bonds.

The Role of Water in Biological Systems

Water is vital for life due to its unique chemical properties. It acts as both a weak acid and a weak base, helping to buffer pH in living organisms.

• Water as a Buffer: Water can donate or accept protons, helping to maintain stable pH levels.

• Acid-Base Reactions: Water participates in acid-base reactions, crucial for cellular processes.

• Example: Blood pH is stabilized by water acting as a buffer.

Functional Groups in Biomolecules

Functional groups are specific groups of atoms within molecules that determine the chemical behavior of biomolecules. While memorization of all groups is not required, understanding their role is important.

• Definition: Functional groups are clusters of atoms that impart specific chemical properties to molecules.

• Examples: Hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and phosphate (-PO4) groups.

• Application: The presence of a carboxyl group makes amino acids acidic.

Additional info: Functional groups influence solubility, reactivity, and interactions of biomolecules.

Biomolecules I: Proteins, Nucleic Acids, and Carbohydrates

Overview of Biomolecules

Biomolecules are large, complex molecules essential for life. The main classes are proteins, nucleic acids, and carbohydrates, each with distinct structures and functions.

• Proteins: Polymers of amino acids that perform structural, enzymatic, and regulatory functions.

• Nucleic Acids: DNA and RNA, which store and transmit genetic information.

• Carbohydrates: Sugars and polysaccharides that provide energy and structural support.

Proteins: Structure and Function

Proteins are composed of amino acids, which are grouped based on their chemical properties. These groups affect how proteins fold and interact with other molecules.

• Amino Acid Groups: Amino acids are classified as nonpolar, polar, acidic, or basic (see Figure 3.2 in textbook).

• Protein Structure: Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.

• Function: Enzymes, antibodies, and structural proteins are all examples of protein functions.

Amino Acid Group	Properties	Example
Nonpolar	Hydrophobic, found in protein interiors	Leucine
Polar	Hydrophilic, can form hydrogen bonds	Serine
Acidic	Negatively charged at physiological pH	Aspartic acid
Basic	Positively charged at physiological pH	Lysine

Additional info: The sequence and chemical properties of amino acids determine protein folding and function.

Nucleic Acids: DNA and RNA

Nucleic acids are polymers of nucleotides and are responsible for storing and transmitting genetic information.

• DNA: Double-stranded helix, stores genetic information.

• RNA: Single-stranded, involved in protein synthesis and gene regulation.

• Nucleotide Structure: Each nucleotide consists of a sugar, phosphate group, and nitrogenous base.

Key Equation:

$\text{DNA Double Helix:} \quad \text{Antiparallel strands held together by hydrogen bonds between bases}$

Carbohydrates: Structure and Function

Carbohydrates are sugars and their polymers, serving as energy sources and structural components in cells.

• Monosaccharides: Simple sugars like glucose and fructose.

• Disaccharides: Two monosaccharides joined together (e.g., sucrose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).

• Function: Energy storage (glycogen, starch) and structural support (cellulose in plants).

Type	Structure	Function
Monosaccharide	Single sugar unit	Immediate energy source
Disaccharide	Two sugar units	Transport and energy
Polysaccharide	Many sugar units	Storage and structure

Summary Table: Major Biomolecules

Biomolecule	Monomer	Function
Protein	Amino acid	Enzymes, structure, regulation
Nucleic Acid	Nucleotide	Genetic information, protein synthesis
Carbohydrate	Monosaccharide	Energy, structure

Additional info: Lipids are another major class of biomolecules, important for membranes and energy storage, but are covered in later chapters.