Biology 100: Chapters 1–4 Study Notes

Chapter 1: The Nature of Life and Scientific Inquiry

Characteristics of Living Things

Living organisms share several fundamental characteristics that distinguish them from non-living matter.

• Complexity and Organization: Living things are highly organized, composed of cells, and exhibit hierarchical structure (atoms → molecules → organelles → cells → tissues → organs → organ systems → organism).

• Response to Stimuli: Organisms detect and respond to environmental changes.

• Homeostasis: Maintenance of stable internal conditions despite external changes.

• Acquisition and Use of Energy: Organisms obtain energy and use it to power activities and maintain organization.

• Growth: Organisms increase in size and/or number of cells.

• Reproduction: Organisms produce offspring, passing genetic information to the next generation.

• Capacity to Evolve: Populations of organisms change over time, adapting to their environment.

Scientific Inquiry

The scientific method is a systematic approach to understanding the natural world.

• Observation: Gathering information about phenomena.

• Question: Formulating questions based on observations.

• Hypothesis: Proposing a testable explanation for observations.

• Prediction: Making predictions based on the hypothesis.

• Experiment: Testing predictions through controlled experiments.

• Conclusion: Analyzing results to support or refute the hypothesis.

• Inductive Reasoning: Drawing general conclusions from specific observations.

• Deductive Reasoning: Using general principles to predict specific results.

Controlled Experiments: Experiments in which only one variable is changed at a time, while others are kept constant.

Peer Review: Scientific findings are evaluated by other experts before publication.

Theory: A well-supported explanation of natural phenomena, based on extensive evidence.

Chapter 2: The Chemistry of Life

Atoms and Their Structure

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

• Atomic Number: Number of protons in the nucleus; determines the element.

• Mass Number: Sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Electron Shells: Electrons are arranged in shells around the nucleus; chemical reactivity depends on electron configuration.

Chemical Bonding

• Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in charged ions.

• Covalent Bonds: Formed when atoms share electrons.

• Hydrogen Bonds: Weak attractions between partially charged regions of molecules, important in water and biological molecules.

Properties of Water

Water is essential for life due to its unique chemical and physical properties.

• Cohesion: Water molecules stick together due to hydrogen bonding.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water resists temperature changes, helping organisms maintain homeostasis.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

• Density: Ice is less dense than liquid water, allowing it to float and insulate aquatic environments.

pH Scale

• Definition: pH measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• Equation: $pH = -\log_{10}[H^+]$

• Scale: Ranges from 0 (acidic) to 14 (basic); 7 is neutral.

Free Radicals and Buffers

• Free Radicals: Highly reactive molecules with unpaired electrons; can damage cells.

• Buffers: Substances that minimize changes in pH by accepting or donating hydrogen ions.

Chapter 3: The Molecules of Life

Organic Molecules

Organic molecules are carbon-based compounds that form the building blocks of life.

• Functional Groups: Specific groups of atoms that confer particular chemical properties (e.g., hydroxyl, carboxyl, amino, phosphate).

Synthesis and Breakdown of Organic Molecules

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

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

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

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

Lipids

• Fats and Oils: Energy storage molecules; composed of glycerol and fatty acids.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Include cholesterol and hormones.

Proteins

• Amino Acids: Building blocks of proteins; 20 different types.

• Peptide Bonds: Link amino acids together.

• Protein Structure: Primary, secondary, tertiary, and quaternary levels of organization.

Nucleic Acids

• DNA: Stores genetic information; double helix structure.

• RNA: Involved in protein synthesis; single-stranded.

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

Chapter 4: The Cell

Cell Size and Types

Cells are the basic units of life, varying in size and complexity.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; include bacteria and archaea.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles; include plants, animals, fungi, and protists.

Eukaryotic Cell Components

• Nucleus: Contains genetic material (DNA); controls cell activities.

• Endoplasmic Reticulum (ER): Synthesizes proteins and lipids; rough ER has ribosomes, smooth ER does not.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Contain digestive enzymes; break down waste and cellular debris.

• Mitochondria: Site of cellular respiration; generates ATP (energy).

• Chloroplasts: Site of photosynthesis in plant cells.

• Cytoskeleton: Network of protein filaments; provides structure and facilitates movement.

• Cell Membrane: Phospholipid bilayer; regulates entry and exit of substances.

• Cell Wall: Provides support and protection in plant, fungal, and some prokaryotic cells.

Endosymbiotic Theory

This theory proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells, leading to a symbiotic relationship.

• Evidence: Both organelles have their own DNA and ribosomes, similar to prokaryotes.