General Biology Exam 1 Study Guide: Foundations, Chemistry, Water, and Biomolecules

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Life's Hierarchy

Levels of Biological Organization

Biology studies life at multiple levels of organization, from the smallest molecules to the entire biosphere. Understanding these levels helps explain how comple x biological systems function.

Atom: The basic unit of matter.
Molecule: Two or more atoms bonded together.
Organelle: Specialized structures within cells.
Cell: The fundamental unit of life.
Tissue: Groups of similar cells performing a function.
Organ: Structures composed of tissues with specific functions.
Organ System: Groups of organs working together.
Organism: An individual living being.
Population: Group of organisms of the same species.
Community: Different populations living together.
Ecosystem: Community plus its physical environment.
Biosphere: All ecosystems on Earth.

Scientific Inquiry and Data

Variables in Scientific Inquiry

Scientific experiments involve identifying and manipulating variables to test hypotheses.

Independent Variable: The factor that is changed or controlled.
Dependent Variable: The factor that is measured or observed.
Controlled Variables: Factors kept constant to ensure a fair test.

Quantitative vs. Qualitative Data

Data collected in scientific studies can be classified as quantitative or qualitative.

Quantitative Data: Numerical measurements (e.g., mass, length, temperature).
Qualitative Data: Descriptive observations (e.g., color, texture, behavior).

Basic Chemistry for Biology

Definitions and Examples

Matter: Anything that has mass and occupies space. Example: Water, air, rocks.
Element: A substance that cannot be broken down into simpler substances by chemical means. Example: Oxygen (O), Carbon (C).
Compound: A substance formed when two or more elements are chemically bonded. Example: Water (H2O), Carbon dioxide (CO2).

Atomic Structure

Neutron: A neutral particle in the nucleus of an atom.
Proton: A positively charged particle in the nucleus.
Electron: A negatively charged particle orbiting the nucleus.
Atomic Number: Number of protons in an atom's nucleus.
Atomic Mass: Sum of protons and neutrons in the nucleus.
Isotope: Atoms of the same element with different numbers of neutrons.
Electron Shells: Energy levels where electrons are found around the nucleus.

Examples: Helium and Carbon

Helium (He): Atomic number = 2; Atomic mass = 4.
Carbon (C): Atomic number = 6; Atomic mass = 12.
Electrons in Carbon: 6 electrons.
Neutrons in Carbon: 6 neutrons (12 - 6).

Isotopes and Radioactive Isotopes

Isotopes are important in biology for tracing processes and medical applications.

Isotopes of Carbon: C12, C13, C14
Radioactive Isotopes: Unstable isotopes that decay, emitting radiation. Medical Application: C14 is used in radiocarbon dating and as a tracer in metabolic studies.

Valence Electrons and Electron Distribution

Valence electrons determine an atom's chemical properties and bonding behavior.

Valence Electrons: Electrons in the outermost shell.
Example: Sodium (Na): 1 valence electron; atomic number = 11.

Molecules, Compounds, and Chemical Bonds

Classification Table

The following table classifies substances as molecules or compounds and provides their formulas.

Substance	Molecule? (y/n)	Compound? (y/n)	Molecular Formula	Structural Formula
Water	Yes	Yes	H2O	H-O-H
Carbon dioxide	Yes	Yes	CO2	O=C=O
Methane	Yes	Yes	CH4	Additional info: Tetrahedral structure
Oxygen	Yes	No	O2	O=O

Covalent and Ionic Bonds

Covalent Bond: Atoms share electrons. Example: O2 molecule (O=O).
Ionic Bond: Atoms transfer electrons, forming charged ions. Example: NaCl (sodium chloride) forms when Na donates an electron to Cl.

Strong and Weak Chemical Bonds

Strong Bonds: Covalent and ionic bonds.
Weak Bonds: Hydrogen bonds, van der Walls interactions.

Water and Its Biological Importance

Properties of Water

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

Cohesion: Water molecules stick together via hydrogen bonds.
Adhesion: Water molecules stick to other surfaces.
High Specific Heat: Water resists tekjjjjjjjjjjjure changes.
Solvent Properties: Water dissolves many substances.
Ice Floats: Solid water is less dense than liquid water.

Water Movement in Plants[p

Water moves upward in plants due to cohesion and adhesion (capillary action).

pH Scale and Biological Substances

pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic).
Biological Importance: Enzyme activity and cellular processes depend on pH.

Carbon Chemistry

Valence Electrons and Bonding

Carbon: 4 valence electrons.
Bonds Formed: Carbon can form 4 covalent bonds.
Types of Bonds: Single, double, or triple covalent bonds.

Hydrocarbons

Hydrocarbon: Molecules consisting only of carbon and hydrogen.
Examples: Methane (CH4), Ethane (C2H6).
Hydrophobicity: Hydrocarbons are hydrophobic (do not mix with water).

Biomolecules

Formation of Polymers

Biomolecules are often polymers, formed by joining monomers through dehydration synthesis.

Polymer: Large molecule made of repeating units (monomers).
Dehydration Synthesis: Reaction that joins monomers by removing water.

Types of Biomolecules and Their Monomers

Carbohydrates: Monomer = monosaccharide (e.g., glucose).
Proteins: Monomer = amino acid.
Nucleic Acids: Monomer = nucleotide.
Lipids: Not true polymers; made from fatty acids and glycerol.

Protein Structure Levels

Primary Structure: Sequence of amino acids.
Secondary Structure: Folding into alpha-helices and beta-sheets.
Tertiary Structure: 3D shape formed by interactions among side chains.
Quaternary Structure: Association of multiple polypeptide chains.

DNA Structure and Differences from RNA

DNA: Double helix, deoxyribose sugar, bases A-T-G-C.
RNA: Single-stranded, ribose sugar, bases A-U-G-C.
Structural Organization: DNA is organized from nucleotides to double helix.

Additional info: Some explanations and examples have been expanded for clarity and completeness.