General Biology Study Notes: Key Concepts from Chapters 1–6

Chapter 1: Themes of Biology and Evolution

Major Themes in Biology

Biology is the study of living organisms and their interactions with each other and their environments. Several unifying themes help organize biological knowledge.

• Organization: Biological systems are structured hierarchically, from molecules to biospheres.

• Information: Genetic information is stored in DNA and transmitted between generations.

• Energy and Matter: Life requires energy transfer and transformation, such as photosynthesis and cellular respiration.

• Interactions: Organisms interact with each other and their environment, affecting survival and evolution.

• Evolution: Populations change over time through natural selection and adaptation.

Domains of Life: The three domains are Bacteria, Archaea, and Eukarya.

• Scientific Method: Involves observation, hypothesis formation, experimentation, and inductive/deductive reasoning.

Theory vs. Hypothesis: A theory is a broad, well-supported explanation; a hypothesis is a testable prediction.

Chapter 2: The Chemical Context of Life

Elements and Compounds

All matter is composed of elements, which combine to form compounds essential for life.

• Essential Elements: Four elements (C, H, O, N) make up most living matter.

• Structure of an Atom: Atoms consist of protons, neutrons, and electrons.

• Atomic Number and Mass: Atomic number is the number of protons; mass includes protons and neutrons.

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

Chemical Bonds

• Covalent Bonds: Atoms share electrons; can be polar or nonpolar.

• Ionic Bonds: Atoms transfer electrons, forming charged ions.

• Hydrogen Bonds: Weak attractions between polar molecules.

• Van der Waals Interactions: Weak, transient interactions between molecules.

Chapter 3: Water and Life

Properties of Water

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

• Polarity: Water molecules have a partial positive and negative charge, allowing hydrogen bonding.

• Cohesion: Water molecules stick together, aiding transport in plants.

• Adhesion: Water molecules stick to other surfaces.

• Surface Tension: Water's surface resists external force due to hydrogen bonding.

• High Specific Heat: Water absorbs and releases heat slowly, stabilizing temperatures.

• Evaporative Cooling: As water evaporates, it cools surfaces.

• Solvent Properties: Water dissolves many substances, making it a universal solvent.

• Acids and Bases: Water can dissociate into H+ and OH-; pH measures acidity.

pH Equation:

$pH = -\log[H^+]$

Chapter 4: Carbon and Life

Organic Chemistry and Carbon Compounds

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds.

• Stanley Miller's Experiment: Demonstrated that organic molecules can form under prebiotic conditions.

• Hydrocarbons: Compounds of only carbon and hydrogen; nonpolar and hydrophobic.

• Isomers: Molecules with the same formula but different structures.

• Structural Isomers: Differ in covalent arrangement of atoms.

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

• Enantiomers: Mirror-image isomers; important in pharmaceuticals.

ATP (Adenosine Triphosphate): The primary energy carrier in cells.

Chapter 5: Large Biological Macromolecules

Types and Functions of Macromolecules

Cells contain four major classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Sugars and polymers; include monosaccharides, disaccharides, and polysaccharides. Examples: glucose, starch, glycogen, cellulose, chitin.

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

• Proteins: Polymers of amino acids; functions include catalysis, structure, transport. Four levels of structure: primary, secondary, tertiary, quaternary.

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

Protein Structure

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding.

• Tertiary Structure: Overall 3D shape due to interactions among R groups.

• Quaternary Structure: Association of multiple polypeptides.

Nucleic Acids

• DNA Structure: Double helix, antiparallel strands, complementary base pairing (A-T, G-C).

• RNA Structure: Single-stranded, various functions in gene expression.

• Nucleotides: Composed of a sugar, phosphate, and nitrogenous base.

• Pyrimidines: Cytosine, thymine, uracil.

• Purines: Adenine, guanine.

Chapter 6: A Tour of the Cell

Cell Structure and Function

Cells are the basic units of life. They can be prokaryotic or eukaryotic, differing in complexity and organization.

• Microscopy: Light and electron microscopes are used to study cells.

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

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles.

• Organelles: Specialized structures within cells, including nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes.

• Cytoskeleton: Network of fibers (microtubules, microfilaments, intermediate filaments) that provide structure and movement.

• Cell Wall: Found in plants, fungi, and some protists; provides support.

• Extracellular Matrix: Complex network outside animal cells for support and signaling.

• Cell Junctions: Connections between cells; four types include tight junctions, desmosomes, gap junctions, and plasmodesmata (in plants).

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Organelles	Absent	Present (membrane-bound)
Size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Example: Mitochondria are the site of cellular respiration, converting glucose to ATP.

Additional info: Some details, such as the full list of organelles and cell junction types, were expanded for completeness and clarity.