BIOL 100: Exam 1 Study Guide – Foundations of Biology, Chemistry, and Biologically Important Molecules

Introduction to Biology

Characteristics of Living Things

Living organisms share a set of fundamental characteristics that distinguish them from non-living matter.

• Order: Living things exhibit complex but ordered organization (e.g., cells form tissues, tissues form organs).

• Regulation (Homeostasis): Organisms maintain stable internal conditions (e.g., human body temperature).

• Growth and Development: Organisms increase in size and complexity, following specific instructions coded in their DNA.

• Energy Processing: Living things obtain and use energy (e.g., plants perform photosynthesis, animals consume food).

• Response to Environment: Organisms detect and respond to stimuli (e.g., plants grow toward light).

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

• Evolutionary Adaptation: Populations evolve over generations through adaptations that enhance survival.

Example: A bacterium reproduces, responds to its environment, and uses energy, thus it is considered alive.

Levels of Life

Biological organization is structured in a hierarchy from smallest to largest:

• Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Each level builds upon the previous, with new properties emerging at higher levels (emergent properties).

Classification of Living Things

Living organisms are classified into hierarchical ranks:

• Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Example: Humans are classified as Domain Eukarya, Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo, Species Homo sapiens.

Three Domains of Life

Domain	Key Characteristics	Examples
Bacteria	Prokaryotic, unicellular, diverse environments	Escherichia coli
Archaea	Prokaryotic, unicellular, often in extreme environments	Halophiles, thermophiles
Eukarya	Eukaryotic, unicellular or multicellular, membrane-bound organelles	Plants, animals, fungi, protists

Kingdoms within Domain Eukarya

• Protista: Mostly unicellular, diverse group (e.g., Amoeba).

• Fungi: Mostly multicellular, absorb nutrients (e.g., mushrooms).

• Plantae: Multicellular, photosynthetic (e.g., trees, ferns).

• Animalia: Multicellular, ingest food (e.g., humans, insects).

Introduction to Chemistry

Matter, Elements, and Atoms

Matter is anything that occupies space and has mass. Elements are pure substances that cannot be broken down chemically. Atoms are the smallest units of elements that retain their properties.

Trace Elements and Human Health

• Trace elements are required in small amounts but are essential for health (e.g., iron, iodine).

• Example: Iodine is necessary for thyroid hormone production; its deficiency causes goiter.

Primary Elements in the Human Body

• Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N) make up about 96% of the human body.

Molecules and Compounds

• Molecule: Two or more atoms held together by covalent bonds (e.g., O2).

• Compound: Substance with two or more different elements combined in a fixed ratio (e.g., H2O).

Structure of an Atom

• Atoms consist of a nucleus (protons and neutrons) and electron shells.

• Protons: Positive charge, in nucleus.

• Neutrons: No charge, in nucleus.

• Electrons: Negative charge, orbit nucleus in shells.

Atomic Number and Atomic Mass

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

$\text{Atomic Mass} = \text{Number of Protons} + \text{Number of Neutrons}$

Electron Shells and Chemical Interactions

• Electrons occupy shells; the outermost shell determines chemical reactivity.

• Atoms with incomplete outer shells tend to form bonds.

Chemical Bonds

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating ions (e.g., NaCl).

• Covalent Bonds: Formed when atoms share electrons (e.g., H2O).

• Hydrogen Bonds: Weak attractions between polar molecules, especially involving hydrogen (e.g., between water molecules).

Water: Structure and Properties

• Polarity: Water is a polar molecule due to unequal sharing of electrons; oxygen is more electronegative than hydrogen.

• Cohesion: Water molecules stick together via hydrogen bonds, important for transport in plants.

• Temperature Resistance: Water has a high specific heat, resisting temperature changes, which stabilizes environments.

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

Acids, Bases, and the pH Scale

• Acid: Substance that increases H+ concentration in solution (pH < 7).

• Base: Substance that decreases H+ concentration (pH > 7).

• pH Scale: Measures acidity/alkalinity from 0 (most acidic) to 14 (most basic); 7 is neutral.

$\text{pH} = -\log_{10} [\text{H}^+]$

Biologically Important Molecules

Organic Compounds and Hydrocarbons

• Organic Compounds: Molecules containing carbon and hydrogen, often with other elements.

• Hydrocarbons: Compounds composed only of carbon and hydrogen (e.g., methane).

Functional Groups

• Groups of atoms attached to carbon skeletons that determine chemical properties (e.g., hydroxyl, carboxyl, amino, phosphate).

Hydrophobic vs. Hydrophilic Molecules

• Hydrophobic: "Water-fearing"; do not dissolve in water (e.g., oils).

• Hydrophilic: "Water-loving"; dissolve in water (e.g., sugars).

Macromolecules, Polymers, and Monomers

• Macromolecules: Large molecules essential for life (carbohydrates, proteins, nucleic acids, lipids).

• Polymers: Long chains of monomers (e.g., starch, proteins, DNA).

• Monomers: Building blocks of polymers (e.g., glucose, amino acids, nucleotides).

Types of Macromolecules

Macromolecule	Monomer	Polymer	Hydrophobic/Hydrophilic	Function
Carbohydrates	Monosaccharides	Disaccharides, Polysaccharides	Hydrophilic	Energy storage, structure
Proteins	Amino acids	Polypeptides	Hydrophilic (some hydrophobic regions)	Enzymes, structure, transport
Nucleic Acids	Nucleotides	DNA, RNA	Hydrophilic	Genetic information
Lipids	Fatty acids, glycerol	Fats, oils, phospholipids, steroids	Hydrophobic	Energy storage, membranes, hormones

Examples of Polymers

• Carbohydrates: Sucrose (disaccharide), starch, glycogen, cellulose (polysaccharides).

• Proteins: Enzymes, structural proteins (e.g., collagen).

• Nucleic Acids: DNA, RNA.

• Lipids: Triglycerides, phospholipids, cholesterol.

Protein Structure and Function

• Proteins must fold into specific three-dimensional shapes to function.

• Denaturation: Loss of protein structure (due to heat, pH, etc.) leads to loss of function.

DNA vs. RNA

• DNA: Double-stranded, deoxyribose sugar, bases A-T-G-C.

• RNA: Single-stranded, ribose sugar, bases A-U-G-C.

DNA Base Pairing

• Adenine (A) pairs with Thymine (T); Guanine (G) pairs with Cytosine (C).

$\text{A} - \text{T}, \quad \text{G} - \text{C}$

Saturated vs. Unsaturated Fats

• Saturated Fats: No double bonds between carbon atoms; solid at room temperature (e.g., butter).

• Unsaturated Fats: One or more double bonds; liquid at room temperature (e.g., olive oil).