General Biology Exam 1: Study Guide and Key Concepts

General Biology: Core Concepts and Exam Preparation

Introduction

This study guide covers foundational topics in General Biology, focusing on the chemical context of life, water and its properties, biological molecules, cell structure, and the basics of genetics and evolution. The content is structured to help students prepare for introductory college-level biology exams.

Chemical Context of Life

Atomic Structure and Chemical Bonds

• Atoms are the basic units of matter, composed of protons, neutrons, and electrons.

• Ions are atoms that have gained or lost electrons, resulting in a net charge.

• Covalent bonds involve the sharing of electron pairs between atoms.

• Ionic bonds result from the transfer of electrons from one atom to another.

• Hydrogen bonds are weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

• Hydrophobic interactions occur when nonpolar molecules aggregate to avoid water.

Example: Sodium chloride (NaCl) forms via ionic bonding between sodium (Na+) and chloride (Cl-).

Elements Essential to Life

• Major elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

• Trace elements: Required in small amounts (e.g., iron, iodine)

Additional info: These elements make up the majority of living matter and are involved in forming biological macromolecules.

Water and Life

Properties of Water

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• High specific heat: Water resists temperature changes due to hydrogen bonding.

• Solvent properties: Water dissolves many substances, making it the "universal solvent."

• Density anomaly: Ice is less dense than liquid water due to hydrogen bond arrangement.

Example: Water's high heat of vaporization helps organisms maintain temperature homeostasis.

Acids, Bases, and pH

• Acids increase the concentration of H+ ions in solution.

• Bases decrease the concentration of H+ ions (often by releasing OH-).

• pH scale: Measures hydrogen ion concentration; $pH = -\log[H^+]$

• Buffers help maintain stable pH in biological systems.

Example: The bicarbonate buffer system in blood: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$

Carbon and the Molecular Diversity of Life

Organic Molecules and Functional Groups

• Carbon forms four covalent bonds, allowing for diverse molecular structures.

• Functional groups are specific groups of atoms that confer chemical properties (e.g., hydroxyl, carboxyl, amino, phosphate).

Example: Amino acids contain both amino (-NH2) and carboxyl (-COOH) groups.

Isomers

• Structural isomers: Differ in covalent arrangement of atoms.

• Cis-trans isomers: Differ in spatial arrangement around double bonds.

• Enantiomers: Mirror images of each other, important in pharmaceuticals.

The Structure and Function of Large Biological Molecules

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides joined by glycosidic linkage (e.g., maltose, sucrose).

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

Type	Example	Function
Monosaccharide	Glucose	Energy source
Disaccharide	Maltose	Energy transport
Polysaccharide	Starch	Energy storage (plants)
Polysaccharide	Cellulose	Structural (plants)

Lipids

• Fats: Glycerol + fatty acids; energy storage.

• Phospholipids: Major component of cell membranes; amphipathic nature.

• Steroids: Four fused rings; e.g., cholesterol, hormones.

Additional info: Lipids are hydrophobic due to nonpolar hydrocarbon chains.

Proteins

• Amino acids: Building blocks of proteins; contain amino and carboxyl groups.

• Peptide bonds: Link amino acids via dehydration synthesis.

• Levels of structure:

  • Primary: Sequence of amino acids

  • Secondary: Alpha helices and beta sheets (hydrogen bonding)

  • Tertiary: 3D folding (side chain interactions)

  • Quaternary: Multiple polypeptide chains

Example: Hemoglobin is a quaternary protein with four subunits.

Nucleic Acids

• DNA: Double-stranded, stores genetic information.

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

• Nucleotides: Monomers of nucleic acids; consist of a sugar, phosphate, and nitrogenous base.

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Strands	Double	Single
Bases	A, T, C, G	A, U, C, G
Function	Genetic storage	Protein synthesis

Cell Structure and Function

Domains of Life

• Bacteria and Archaea: Prokaryotic cells (no nucleus)

• Eukarya: Eukaryotic cells (nucleus present); includes protists, fungi, plants, animals

Additional info: Prokaryotes are classified into two domains: Bacteria and Archaea.

Cellular Organization

• Prokaryotic cells: Lack membrane-bound organelles.

• Eukaryotic cells: Have nucleus and organelles (e.g., mitochondria, chloroplasts).

Evolution and the Diversity of Life

Evolutionary Principles

• Evolution: Change in genetic composition of populations over time.

• Natural selection: Mechanism by which advantageous traits become more common.

Example: Antibiotic resistance in bacteria is a result of natural selection.

Practice and Application

Sample Questions and Applications

• Identify the type of bond formed between sodium and chlorine in NaCl.

• Explain why water is a good solvent for ionic compounds.

• Draw the structure of a peptide bond between two amino acids.

• List three differences between DNA and RNA.

Summary Table: Key Biological Molecules

Molecule	Monomer	Bond Type	Example
Carbohydrate	Monosaccharide	Glycosidic linkage	Starch
Lipid	Fatty acid, glycerol	Ester bond	Triglyceride
Protein	Amino acid	Peptide bond	Hemoglobin
Nucleic acid	Nucleotide	Phosphodiester bond	DNA

Conclusion

Understanding the chemical and molecular foundations of life is essential for further study in biology. Mastery of these concepts provides the groundwork for exploring cell structure, genetics, evolution, and the diversity of living organisms.