General Biology: Core Concepts and Study Guide

Chapter 1: Introduction to Biology

What is Biology?

Biology is the scientific study of life and living organisms. It encompasses various fields that examine structure, function, growth, origin, evolution, and distribution of living things.

• Structure and Function: Biological structures are closely related to their functions. For example, the structure of a bird's wing enables flight.

• Scientific Method: A systematic approach to inquiry involving observation, hypothesis formation, experimentation, and conclusion.

• Domains of Life: The three domains are Bacteria, Archaea, and Eukarya. Eukarya includes four major kingdoms: Protista, Fungi, Plantae, and Animalia.

• Cell Types: Prokaryotic cells (no nucleus, e.g., bacteria) and eukaryotic cells (with nucleus, e.g., plants and animals).

• Genome: The complete set of genetic material in an organism.

Chapter 2: The Chemical Context of Life

Basic Chemistry for Biology

Understanding the chemical basis of life is essential for studying biological processes.

• Key Terms: Matter (anything that has mass and takes up space), element (a substance that cannot be broken down), compound (a substance made of two or more elements), electron shell, isotope, potential energy, kinetic energy.

• Atomic Structure: Atoms consist of protons, neutrons, and electrons. The atomic number is the number of protons; the mass number is protons plus neutrons.

• Major Elements in Life: C, H, O, N, P, S (carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur).

• Bonds: Covalent bonds (sharing electrons), ionic bonds (transfer of electrons), hydrogen bonds (weak attractions between polar molecules).

• Properties of Water: Cohesion, adhesion, high specific heat, solvent abilities, and its role in temperature regulation.

• pH Scale: Measures hydrogen ion concentration; acids have low pH, bases have high pH.

Example: Water's high specific heat helps maintain stable temperatures in organisms and environments.

Chapter 3: Carbon & The Molecular Diversity of Life

Organic Molecules and Macromolecules

Carbon's ability to form four covalent bonds makes it the backbone of biological molecules.

• Functional Groups: Groups of atoms that confer specific properties (e.g., hydroxyl, carboxyl, amino, phosphate).

• Macromolecules: Large molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

• Monomers and Polymers: Monomers (small units) join to form polymers (large molecules) via dehydration synthesis; hydrolysis breaks them apart.

• Types of Carbohydrates: Monosaccharides (glucose), disaccharides (sucrose), polysaccharides (starch, cellulose).

• Lipids: Hydrophobic molecules including fats, phospholipids, and steroids.

• Proteins: Polymers of amino acids; structure determines function (primary, secondary, tertiary, quaternary).

• Nucleic Acids: DNA and RNA, composed of nucleotides.

Example: Enzymes are proteins that catalyze biochemical reactions.

Chapter 4: A Tour of the Cell

Cell Structure and Function

Cells are the basic units of life. They can be prokaryotic or eukaryotic, each with distinct structures and functions.

• Cell Size: Ranges from micrometers to nanometers.

• Prokaryotic Cells: Lack a nucleus; DNA is in the nucleoid region. Example: bacteria.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles. Example: plant and animal cells.

• Key Organelles:

  • Nucleus: Contains genetic material.

  • Ribosomes: Protein synthesis.

  • Endoplasmic Reticulum (ER): Protein and lipid synthesis.

  • Golgi Apparatus: Modifies and packages proteins.

  • Mitochondria: Site of cellular respiration.

  • Chloroplasts: Site of photosynthesis (plants only).

  • Lysosomes: Digestion of macromolecules.

  • Peroxisomes: Breakdown of fatty acids.

  • Vacuoles: Storage and support (large in plants).

• Plant vs. Animal vs. Prokaryotic Cells: Plant cells have cell walls, chloroplasts, and large vacuoles; animal cells do not. Prokaryotic cells lack membrane-bound organelles.

• Endomembrane System: Includes the nuclear envelope, ER, Golgi apparatus, lysosomes, and vesicles.

• Endosymbiont Theory: Mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Chapter 5: Membrane Transport and Cell Signaling

Membrane Structure and Function

Cell membranes regulate the movement of substances in and out of cells and facilitate communication.

• Amphipathic: Molecules with both hydrophilic (water-loving) and hydrophobic (water-fearing) regions (e.g., phospholipids).

• Fluid Mosaic Model: Describes the membrane as a fluid structure with proteins embedded in or attached to a double layer of phospholipids.

• Selective Permeability: Membranes allow some substances to cross more easily than others.

• Transport Mechanisms:

  • Osmosis: Diffusion of water across a selectively permeable membrane.

  • Diffusion: Movement of molecules from high to low concentration.

  • Facilitated Diffusion: Passive transport via transport proteins.

  • Active Transport: Movement against a concentration gradient, requiring energy (e.g., sodium-potassium pump).

  • Endocytosis/Exocytosis: Bulk transport into/out of the cell.

• Osmotic Terms:

  • Isotonic: Equal solute concentration.

  • Hypertonic: Higher solute concentration outside the cell.

  • Hypotonic: Lower solute concentration outside the cell.

• Aquaporins: Channel proteins that facilitate water movement.

Example: The sodium-potassium pump maintains electrochemical gradients in animal cells.

Chapter 6: An Introduction to Metabolism

Energy and Enzymes in Biological Systems

Metabolism encompasses all chemical reactions in an organism, including those that build up and break down molecules.

• Thermodynamics:

  • First Law: Energy cannot be created or destroyed, only transformed.

  • Second Law: Every energy transfer increases the entropy (disorder) of the universe.

• Types of Metabolic Pathways:

  • Anabolic: Build complex molecules from simpler ones (require energy).

  • Catabolic: Break down complex molecules into simpler ones (release energy).

• Energy Terms:

  • Potential Energy: Stored energy.

  • Kinetic Energy: Energy of motion.

  • Free Energy (G): Energy available to do work.

  • Exergonic: Releases energy ($\Delta G < 0$).

  • Endergonic: Requires energy input ($\Delta G > 0$).

• ATP (Adenosine Triphosphate): The main energy currency of the cell. Structure includes adenine, ribose, and three phosphate groups.

• Enzymes: Biological catalysts that lower activation energy and speed up reactions. They bind substrates at the active site.

Example: The enzyme sucrase catalyzes the hydrolysis of sucrose into glucose and fructose.

Chapter 7: Cellular Respiration and Fermentation

Harvesting Chemical Energy

Cells extract energy from glucose and other molecules through cellular respiration and fermentation.

• Redox Reactions: Involve the transfer of electrons; oxidation is loss, reduction is gain.

• Stages of Cellular Respiration:

  1. Glycolysis (cytoplasm)

  2. Citric Acid Cycle (mitochondrial matrix)

  3. Oxidative Phosphorylation (inner mitochondrial membrane)

• ATP Yield: Up to 32 ATP molecules per glucose molecule.

• Key Molecules: NADH, FADH2, ATP synthase, Acetyl CoA, glucose, pyruvate, cytochromes.

• Fermentation: Anaerobic process that allows glycolysis to continue in the absence of oxygen, producing lactic acid or ethanol.

• Mitochondrial Structure: Intermembrane space, matrix, inner and outer membranes.

Example: During strenuous exercise, muscle cells use lactic acid fermentation when oxygen is scarce.

Process	Location	Oxygen Required?	ATP Yield (per glucose)
Glycolysis	Cytoplasm	No	2
Citric Acid Cycle	Mitochondrial Matrix	Yes	2
Oxidative Phosphorylation	Inner Mitochondrial Membrane	Yes	~28
Fermentation	Cytoplasm	No	2

Additional info: Some details, such as the specific number of ATP produced, may vary depending on cell type and conditions.