General Biology Study Guide: Themes, Chemistry of Life, and Biological Macromolecules

Chapter 1 – Themes of Biology and Scientific Method

Characteristics and Unity of Life

Biology is the study of living organisms and their interactions with the environment. All living things share certain characteristics that define life and display unity and diversity.

• Characteristics of Life: Organization, metabolism, homeostasis, growth, reproduction, response to stimuli, adaptation through evolution.

• Descent with Modification: Darwin’s concept that species change over generations, giving rise to diversity.

• Unity and Diversity: Unity is shown by shared traits; diversity arises from evolutionary processes.

• Emergent Properties: Properties that arise at each level of biological organization due to the arrangement and interactions of parts. Example: A cell is alive, but its organelles alone are not; tissues form organs with new functions.

Levels of Biological Organization

Life is organized from the molecular to the biosphere level. Each level has unique properties and functions.

• Biosphere: All environments on Earth that support life.

• Ecosystem: All living and nonliving components in a particular area.

• Community: All organisms in an ecosystem.

• Population: Individuals of the same species in an area.

• Organism: An individual living thing.

• Organ and Organ System: Body parts with specific functions; organ systems are groups of organs working together.

• Tissue: Groups of similar cells performing a function.

• Cell: Basic unit of life.

• Organelle: Functional components within cells.

• Molecule: Chemical structure of two or more atoms.

Scientific Method and Hypothesis Testing

The scientific method is a systematic approach to understanding natural phenomena through observation, hypothesis formation, experimentation, and analysis.

• Process of Science: Observation, question, hypothesis, prediction, experiment, analysis, conclusion.

• Hypothesis: A testable explanation for an observation. Must be falsifiable and lead to predictions.

• Difference between Hypothesis and Theory: A hypothesis is a specific, testable statement; a theory is a broad, well-supported explanation.

Experimental Design and Variables

Experiments are designed to test hypotheses by manipulating variables and observing outcomes.

• Experimental Group: Receives the treatment.

• Control Group: Does not receive the treatment; used for comparison.

• Variables:

  • Independent Variable: The factor changed by the experimenter.

  • Dependent Variable: The factor measured in response.

• Controlling Variables: Ensures reliable, reproducible results.

Energy and Matter in Ecosystems

Energy flows and matter cycles through ecosystems, supporting life.

• Energy Movement: Energy flows in one direction, typically from the sun through producers to consumers.

• Matter Movement: Matter cycles between living and nonliving components (e.g., carbon cycle).

Chapter 2 – Chemistry of Life and Properties of Water

Chemical Reactions and Bonds

Chemical reactions rearrange atoms to form new substances. Chemical bonds hold atoms together in molecules.

• Balanced Chemical Equation: Atoms are conserved; number of atoms of each element is the same on both sides. Example: $4NH_3 + 5O_2 \rightarrow 4NO + 6H_2O$

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

Atoms, Ions, and the Periodic Table

Atoms are composed of protons, neutrons, and electrons. Elements are organized by atomic number on the periodic table.

• Isotopes: Atoms of the same element with different numbers of neutrons (e.g., carbon-13 and carbon-14).

• Ions: Atoms with a net charge due to loss or gain of electrons.

  • Anion: Negatively charged (gains electrons).

  • Cation: Positively charged (loses electrons).

• Electron Shells: Electrons occupy shells around the nucleus. The first shell holds 2 electrons, the second up to 8, the third up to 18.

Electronegativity and Types of Bonds

Electronegativity is an atom’s ability to attract electrons. It determines bond type and molecular polarity.

• Electronegativity: Oxygen is highly electronegative; hydrogen is less so.

• Bond Types:

  1. Covalent (strongest in water)

  2. Ionic

  3. Hydrogen (weakest)

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

Properties of Water

Water’s unique properties support life, including cohesion, adhesion, high specific heat, and solvent abilities.

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water resists temperature change.

• Ice Floats: Solid water is less dense than liquid water.

• Universal Solvent: Water dissolves many substances, especially polar molecules.

• Hydrophobic vs. Hydrophilic: Hydrophobic substances repel water (e.g., oils); hydrophilic substances attract water (e.g., salts).

Acids, Bases, and pH

pH measures the concentration of hydrogen ions in a solution, affecting biological processes.

• Water Ionization: Water can dissociate into H+ and OH- ions.

• pH Scale: Ranges from 0 (acidic) to 14 (basic). Neutral pH is 7.

• pH Calculation:

  • Logarithmic form: $pH = -\log[H^+]$

  • Exponential form: $[H^+] = 10^{-pH}$

• Example: If $[H^+] = 1 \times 10^{-9}$ M, then $pH = 9$.

Chapter 3 – Carbon and the Diversity of Biological Macromolecules

Carbon Chemistry and Functional Groups

Carbon’s versatility allows it to form diverse organic molecules essential for life.

• Functional Groups: Chemical groups that affect molecular function (e.g., hydroxyl, carboxyl, amino, phosphate).

• Valence Electrons: Carbon has four valence electrons, allowing it to form four covalent bonds.

Macromolecules: Structure and Function

Biological macromolecules fall into four main classes, each with distinct functions.

• Carbohydrates: Energy storage and structural support (e.g., glucose, starch).

• Lipids: Energy storage, membrane structure (e.g., fats, phospholipids).

• Proteins: Catalysis, structure, transport (e.g., enzymes, hemoglobin).

• Nucleic Acids: Information storage and transfer (e.g., DNA, RNA).

Protein Structure

Proteins have four levels of structure that determine their function.

• 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 side chains.

• Quaternary Structure: Association of multiple polypeptide chains.

Nucleic Acids: DNA and RNA

DNA and RNA are polymers of nucleotides, storing and transmitting genetic information.

• Antiparallel Strands: DNA strands run in opposite directions (5' to 3' and 3' to 5').

• 5' and 3' Ends: Refer to the carbon positions in the sugar molecule of nucleotides.

• RNA vs. DNA: RNA contains ribose and uracil; DNA contains deoxyribose and thymine.

• Sequence Diversity: The number of possible DNA or amino acid sequences increases exponentially with length.

Carbohydrates: Structure and Energy

Carbohydrates are the most abundant organic compounds on Earth and serve as energy sources and structural materials.

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

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

• Energy Storage: Plants store energy as starch; animals as glycogen.

Table: Levels of Biological Organization

Level	Definition	Example
Biosphere	All environments on Earth that support life	Earth
Ecosystem	All living and nonliving components in an area	Forest ecosystem
Community	All organisms in an ecosystem	All plants, animals, and microbes in a forest
Population	Individuals of the same species in an area	All oak trees in a forest
Organism	An individual living thing	A single oak tree
Organ System	Group of organs working together	Digestive system
Organ	Body part with specific function	Leaf
Tissue	Group of similar cells	Muscle tissue
Cell	Basic unit of life	Plant cell
Organelle	Functional component within cell	Chloroplast
Molecule	Chemical structure of atoms	Water (H2O)

Additional info:

• Some explanations and examples have been expanded for clarity and completeness.

• Table entries inferred from standard biology textbook content.