The Chemistry of Life: Foundations for General Biology

Unit 1: The Chemistry of Life

Introduction

This unit establishes the chemical basis of life, providing foundational knowledge for understanding biological molecules, their interactions, and their roles in living systems. Key topics include the properties of water, the structure and function of biomolecules, and the chemical context of life.

Chapter 2: The Chemical Context of Life

Properties of Water

• Polarity and Hydrogen Bonds: Water is a polar molecule, meaning it has partial positive and negative charges, leading to hydrogen bonding between molecules.

• Hydrogen Bond: A weak bond between a hydrogen atom and an electronegative atom (often oxygen or nitrogen).

Key Properties of Water

• Cohesion: Water molecules stick together due to hydrogen bonding, contributing to surface tension.

• Adhesion: Water molecules stick to other substances, aiding processes like capillary action.

• High Specific Heat: Water can absorb or release large amounts of heat with little temperature change, stabilizing environments.

• Heat of Vaporization: Water requires significant energy to change from liquid to gas, important for cooling mechanisms like sweating.

• Density of Ice: Ice is less dense than liquid water due to hydrogen bond arrangement, allowing it to float and insulate aquatic life.

Water as a Solvent

• Solubility: Water dissolves many substances, especially ionic and polar compounds, due to its polarity.

• Hydrophilic vs. Hydrophobic: Hydrophilic substances interact well with water; hydrophobic substances do not.

Acids, Bases, and Buffers

• Acids: Substances that increase the hydrogen ion concentration in a solution.

• Bases: Substances that decrease the hydrogen ion concentration.

• Buffers: Compounds that minimize changes in pH by accepting or donating H+ ions.

• Water Dissociation Equation:

$H_2O \rightleftharpoons H^+ + OH^-$

• pH Scale: Measures the concentration of hydrogen ions; lower pH is more acidic, higher pH is more basic.

Environmental Connections

• Water’s high specific heat and heat of vaporization moderate Earth’s climate.

• Ice’s lower density insulates aquatic environments.

• Acid precipitation affects soil and aquatic systems.

Chapter 2: Carbon & The Molecular Diversity of Life

Carbon Chemistry

• Carbon’s Bonding: Carbon forms four covalent bonds, allowing for a diversity of stable organic molecules.

• Functional Groups: Specific groups of atoms attached to carbon skeletons that determine molecular properties and reactivity (e.g., hydroxyl, carboxyl, amino, phosphate).

Polymer Principles

• Monomers and Polymers: Large biological molecules (polymers) are made from smaller subunits (monomers) via dehydration synthesis (removal of water) and broken down by hydrolysis (addition of water).

Biomolecules: Structure and Function

• Carbohydrates: Sugars and starches; provide energy and structural support.

• Lipids: Fats, oils, and steroids; important for energy storage, insulation, and cell membranes.

• Proteins: Polymers of amino acids; perform a wide range of functions including catalysis (enzymes), structure, transport, and signaling.

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

Table: Major Biomolecules and Their Functions

Biomolecule	Monomer	Polymer	Main Functions
Carbohydrates	Monosaccharide	Polysaccharide	Energy storage, structure (cellulose, chitin)
Lipids	Glycerol & Fatty Acids	Triglyceride, Phospholipid	Energy storage, membranes, hormones
Proteins	Amino Acid	Polypeptide	Enzymes, structure, transport, signaling
Nucleic Acids	Nucleotide	DNA, RNA	Genetic information storage and transfer

Protein Structure

• Primary Structure: Sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha-helices and beta-sheets, stabilized by hydrogen bonds.

• Tertiary Structure: Overall 3D shape of a polypeptide, determined by interactions among R groups.

• Quaternary Structure: Association of multiple polypeptide chains.

Nucleic Acids

• DNA: Double helix structure, stores genetic information.

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

• Base Pairing: Adenine pairs with thymine (DNA) or uracil (RNA); cytosine pairs with guanine.

Key Vocabulary

• cohesion

• adhesion

• surface tension

• hydrogen bond

• hydrophilic

• hydrophobic

• buffer

• monomer

• polymer

• dehydration synthesis

• hydrolysis

• amino acid

• nucleotide

• monosaccharide

• triglyceride

• phospholipid

Learning Objectives

• Explain how the polarity of water leads to hydrogen bonding and its unique properties.

• Describe the structure and function of the four major classes of biomolecules.

• Illustrate how monomers combine to form polymers and how polymers are broken down.

• Relate the structure of proteins and nucleic acids to their functions.

• Summarize the environmental significance of water’s properties.

Study Strategies

• Practice identifying functional groups and their properties.

• Use diagrams to visualize molecular structures and interactions.

• Apply concepts to real-world biological examples, such as enzyme function or membrane structure.

Additional info: This summary integrates and expands upon the provided syllabus content, ensuring coverage of all foundational chemistry and biomolecule topics relevant to General Biology.