Unit 1 General Biology Study Guide: Introduction, Chemistry, Water, and Biomolecules

Introduction to Biology

Characteristics of Life

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

• Order: Living things exhibit complex organization, from cells to tissues to organs.

• Regulation: Homeostasis maintains internal conditions (e.g., temperature, pH).

• Growth and Development: Organisms grow and develop according to inherited instructions.

• Energy Processing: Organisms obtain and use energy for metabolic processes.

• Response to Environment: Living things respond to stimuli.

• Reproduction: Organisms reproduce, passing genetic material to offspring.

• Evolutionary Adaptation: Populations evolve over generations.

Example: Plants grow toward light (response to environment), use sunlight for photosynthesis (energy processing), and reproduce via seeds.

Levels of Biological Organization

Biological systems are organized hierarchically, with each level displaying emergent properties.

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

• Emergent Properties: New properties arise at each level due to interactions among components.

Example: A cell can perform functions that its individual molecules cannot.

Eukaryotic vs. Prokaryotic Cells

Cells are classified as either prokaryotic or eukaryotic based on structural features.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; found in Bacteria and Archaea domains.

• Eukaryotic Cells: Have a nucleus and organelles; found in Eukarya domain (kingdoms: Plantae, Animalia, Fungi, Protista).

Example: Human cells are eukaryotic; bacterial cells are prokaryotic.

Classification of Organisms

Organisms are classified into domains and kingdoms based on cell structure.

• Domains: Bacteria (prokaryotic), Archaea (prokaryotic), Eukarya (eukaryotic)

• Kingdoms in Eukarya: Plantae, Animalia, Fungi, Protista

Role of DNA and Gene Expression

DNA stores genetic information; gene expression is the process by which information flows from DNA to RNA to proteins.

• Central Dogma: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$

• Proteins: Carry out cellular functions.

Energy and Matter in Ecosystems

Energy flows through ecosystems, while matter cycles.

• Energy: Originates from the sun, flows through food webs, and is lost as heat.

• Matter: Cycles via biogeochemical processes (e.g., carbon, nitrogen cycles).

Example: Plants convert solar energy to chemical energy; decomposers recycle nutrients.

Feedback Regulation

Biological systems use feedback mechanisms to regulate processes.

• Negative Feedback: Reduces change; maintains homeostasis (e.g., blood glucose regulation).

• Positive Feedback: Amplifies change (e.g., blood clotting).

Natural Selection

Natural selection drives evolution by favoring traits that enhance survival and reproduction.

• Mechanism: Variation → Differential survival → Reproduction → Change in population genetics

• Environment: Selects for advantageous traits.

Example: Peppered moth coloration changes in response to pollution.

Scientific Process and Experimentation

Scientific inquiry involves controlled experiments to test hypotheses.

• Independent Variable: Manipulated factor

• Dependent Variable: Measured outcome

• Control Group: Baseline for comparison

Inductive vs. Deductive Reasoning

Scientists use both inductive and deductive reasoning.

• Inductive Reasoning: Generalizations from specific observations

• Deductive Reasoning: Predictions from general principles

Chemistry of Life

Matter, Elements, and Compounds

Matter is composed of elements, which combine to form compounds with emergent properties.

• Matter: Anything that occupies space and has mass

• Element: Pure substance consisting of one type of atom

• Compound: Substance formed by two or more elements in fixed ratio

Essential and Trace Elements

Living organisms require certain elements in large (essential) or small (trace) amounts.

• Essential Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

• Bonds Formed: C (4), H (1), O (2), N (3)

• Trace Elements: Required in minute quantities (e.g., iron, iodine)

Example: Iron is needed for hemoglobin function.

Atomic Structure

Atoms consist of subatomic particles that determine their properties.

• Protons: Positive charge, determine atomic number

• Neutrons: No charge, contribute to mass

• Electrons: Negative charge, involved in chemical bonding

Atomic Number and Mass Number

Atomic number and mass number are key identifiers for elements and isotopes.

• Atomic Number: Number of protons

• Mass Number: Number of protons + neutrons

Equation:

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

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons.

• Use in Biology: Radioactive isotopes for dating, tracing, medical imaging

Electron Energy Levels and Orbitals

Electrons occupy energy levels and orbitals, influencing molecular shape and reactivity.

• Valence Electrons: Electrons in the outer shell; determine chemical properties

• Orbitals: Regions where electrons are likely found; shape affects bonding

Chemical Bonds

Atoms form bonds to achieve stable electron configurations.

• Covalent Bonds: Sharing of electrons; can be polar (unequal sharing) or nonpolar (equal sharing)

• Ionic Bonds: Transfer of electrons; forms charged ions

• Hydrogen Bonds: Weak attractions between partial charges (e.g., in water)

Chemical Reactions

Chemical reactions rearrange atoms to form new substances.

• Reactants: Starting materials

• Products: Resulting substances

Example: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$ (cellular respiration)

Water and Life

Structure and Properties of Water

Water's unique properties arise from its molecular structure and hydrogen bonding.

• Polar Covalent Bonds: Oxygen has a greater pull on electrons, creating partial charges

• Hydrogen Bonds: Form between water molecules due to polarity

Cohesion and Adhesion

Water molecules stick to each other (cohesion) and to other surfaces (adhesion).

• Cohesion: Responsible for surface tension

• Adhesion: Helps water move up plant vessels (capillary action)

High Specific Heat

Water resists temperature changes due to strong hydrogen bonds.

• Impact: Stabilizes climate and organism temperature

Ice Floats

Ice is less dense than liquid water because hydrogen bonds form a lattice, increasing volume.

• Impact: Insulates aquatic life in winter

Water as Universal Solvent

Water dissolves many substances due to its polarity.

• Solution: Homogeneous mixture

• Solute: Substance dissolved

• Solvent: Substance doing the dissolving (water)

• Hydrophilic: Polar substances dissolve

• Hydrophobic: Nonpolar substances do not dissolve

Acids, Bases, and Buffers

The pH scale measures hydrogen ion concentration; buffers maintain pH stability.

• Acids: pH < 7; donate H+

• Bases: pH > 7; accept H+

• Neutral: pH = 7

• Buffers: Resist changes in pH; crucial for homeostasis

Biomolecules

Carbon and Molecular Diversity

Carbon's versatility as a building block arises from its four valence electrons.

• Valence Electrons: 4; allows formation of diverse structures (chains, rings)

• Structural Variation: Isomers have same formula, different structures

Functional Groups

Functional groups are specific clusters of atoms that confer unique properties to molecules.

• Examples: Hydroxyl (-OH), Carboxyl (-COOH), Amino (-NH2), Phosphate (-PO4)

Macromolecules, Polymers, and Monomers

Macromolecules are large biological molecules made of repeating units (monomers).

• Polymer: Chain of monomers

• Monomer: Single unit (e.g., amino acid, nucleotide)

Dehydration Synthesis and Hydrolysis

Macromolecules are assembled and broken down by specific reactions.

• Dehydration Synthesis: Joins monomers by removing water

• Hydrolysis: Breaks polymers by adding water

Carbohydrates

Carbohydrates are energy sources and structural molecules.

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

• Disaccharides: Two monosaccharides (e.g., sucrose)

• Polysaccharides: Many monosaccharides (e.g., starch, glycogen, cellulose, chitin)

Comparison Table:

Type	Structure	Function
Starch	Polysaccharide	Energy storage in plants
Glycogen	Polysaccharide	Energy storage in animals
Cellulose	Polysaccharide	Structural in plant cell walls
Chitin	Polysaccharide	Structural in fungi and arthropods

Lipids

Lipids are hydrophobic molecules important for energy storage and cell structure.

• Fats: Saturated (no double bonds; solid) vs. unsaturated (double bonds; liquid)

• Phospholipids: Hydrophilic head, hydrophobic tail; form cell membranes

• Steroids: Four fused rings; hormones (e.g., cholesterol)

Proteins

Proteins are polymers of amino acids with diverse functions.

• Polypeptides: Chains of amino acids

• 20 Amino Acids: Differ by side chains (R groups)

• Functions: Enzymes, structure, transport, signaling

• Structure Levels:

  • Primary: Sequence of amino acids

  • Secondary: Alpha helix, beta sheet (hydrogen bonding)

  • Tertiary: 3D folding (R group interactions)

  • Quaternary: Multiple polypeptides

Nucleic Acids

Nucleic acids store and transmit genetic information.

• DNA: Double-stranded; stores genetic code

• RNA: Single-stranded; involved in protein synthesis

• Gene Expression: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$

Comparison Table:

Feature	DNA	RNA
Strands	Double	Single
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Function	Genetic storage	Protein synthesis