General Biology I: Study Guide and Key Concepts

Chapter 1 – Biology: Exploring Life

Introduction to Biology

Biology is the scientific study of life and living organisms. This chapter introduces the foundational concepts and characteristics that define life and the scientific methods used to study biological phenomena.

• Definition of Biology: Biology is the study of living organisms, their structure, function, growth, origin, evolution, and distribution.

• Characteristics of Life: Living organisms display organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation through evolution.

• Levels of Biological Organization: Life is organized from molecules to the biosphere: molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

• Structure and Function: The structure of biological components (e.g., proteins, cells) determines their function. Example: The shape of an enzyme's active site allows it to catalyze specific reactions.

• Unity and Diversity: All living things share common features (unity) but also exhibit diversity due to evolution and adaptation.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring. Example: Darwin’s finches with different beak shapes adapted to different food sources.

• Biological Investigation: Involves observation, hypothesis formation, experimentation, data collection, and analysis.

• Hypothesis: A testable statement based on observations. Experiments are designed to test hypotheses.

• Scientific Method: Steps include observation, question, hypothesis, prediction, experiment, and conclusion.

• Variables: Independent variable is manipulated; dependent variable is measured; control group is used for comparison.

Additional info: The scientific method is iterative, and hypotheses can be revised based on experimental results.

Chapter 2 – Chemical Basis of Life

Atoms, Elements, and Molecules

This section covers the chemical foundation of life, including atomic structure, chemical bonds, and the properties of water.

• Atoms: The smallest unit of matter retaining the properties of an element. Composed of protons, neutrons, and electrons.

• Elements: Pure substances consisting of only one type of atom. Example: Oxygen (O), Carbon (C).

• Molecules and Compounds: Molecules are two or more atoms bonded together; compounds are molecules with different elements. Example: H2O, CO2.

• Ions and Isotopes: Ions are charged atoms; isotopes are atoms of the same element with different numbers of neutrons.

• Electron Shell Model: Electrons occupy energy levels (shells) around the nucleus. The arrangement determines chemical reactivity.

• Subatomic Particles: Protons (+), neutrons (0), electrons (–).

• Atomic Number and Mass: Atomic number = number of protons; atomic mass = protons + neutrons.

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

• Polar vs. Nonpolar Covalent Bonds: Polar bonds have unequal sharing of electrons; nonpolar bonds have equal sharing.

• Types of Bonds in Molecules: Example: NaCl (ionic), H2O (polar covalent), O2 (nonpolar covalent).

• Emergent Properties of Compounds: New properties arise when elements combine (e.g., Na and Cl form edible salt).

Properties of Water

• Cohesion: Attraction between molecules of the same substance (e.g., water molecules stick together).

• Adhesion: Attraction between different substances (e.g., water to glass).

• Surface Tension: The measure of how difficult it is to stretch or break the surface of a liquid.

• Hydrogen Bonding: Responsible for water’s unique properties, such as high specific heat and solvent abilities.

• pH and Solutions: pH measures hydrogen ion concentration. Acidic solutions have pH < 7, basic > 7, neutral = 7.

• Solute, Solvent, Solution: Solute is dissolved, solvent does the dissolving, solution is the mixture.

• Chemical Reactions: Reactants are transformed into products. Law of Conservation of Matter: Matter is neither created nor destroyed in chemical reactions.

Chapter 3 – Molecules of Cells

Organic Molecules and Macromolecules

This chapter explores the structure and function of organic molecules essential to life, including carbohydrates, lipids, proteins, and nucleic acids.

• Organic Molecules: Compounds containing carbon, typically found in living organisms.

• Four Major Biomolecules:

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

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

  • Lipids: Fats, oils, phospholipids, steroids; energy storage, membrane structure.

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

• Monomers and Polymers: Monomers are building blocks; polymers are chains of monomers.

• Dehydration Reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates, Lipids, Proteins, and Nucleic Acids

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

• Lipids: Saturated (no double bonds) and unsaturated (one or more double bonds) fats, phospholipids, steroids.

• Proteins: Composed of amino acids; structure determines function. Denaturation alters shape and function.

• Nucleic Acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid); made of nucleotides.

• Key Terms: Monomer, polymer, hydrolysis, dehydration reaction, fatty acid, glycerol, hydrophobic, hydrophilic.

Chapter 4 – Tour of the Cell

Cell Theory and Cell Structure

This chapter introduces the cell as the basic unit of life, explores cell theory, and describes the structure and function of cellular components.

• Cell Theory: All living things are composed of cells; cells are the basic unit of structure and function; all cells arise from pre-existing cells.

• Surface Area to Volume Ratio: As cells increase in size, volume grows faster than surface area, limiting cell size due to transport efficiency.

• Types of Cells: Prokaryotic (no nucleus, e.g., bacteria) and eukaryotic (nucleus, organelles, e.g., plants, animals).

Cellular Components and Their Functions

• Plasma Membrane: Phospholipid bilayer controlling entry/exit of substances.

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

• Nucleolus: Site of ribosome synthesis.

• Ribosome: Protein synthesis.

• Smooth Endoplasmic Reticulum (ER): Lipid synthesis, detoxification.

• Rough Endoplasmic Reticulum (ER): Protein synthesis (has ribosomes attached).

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

• Lysosome: Digests macromolecules and old cell parts.

• Peroxisome: Breaks down fatty acids and detoxifies harmful substances.

• Mitochondrion: Site of cellular respiration; produces ATP.

• Chloroplast: Site of photosynthesis in plant cells.

• Cytoskeleton: Provides structural support, cell movement.

• Centrosome & Centrioles: Organize microtubules during cell division.

• Cilia & Flagella: Movement of cells or substances across cell surface.

• Cell Wall: Provides support and protection (plants, fungi, some protists).

• Extracellular Matrix (ECM): Network outside animal cells for support and signaling.

Additional info: Eukaryotic cells compartmentalize functions within organelles, increasing efficiency and complexity compared to prokaryotic cells.