Unit 1 General Biology Study Guide: Foundations, Chemistry, Water, and Macromolecules

Introduction to Biology & Characteristics of Life

Properties of Life

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

• Order: Living things exhibit complex but ordered organization.

• Regulation: Organisms maintain stable internal conditions (homeostasis).

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

• Energy Processing: Living things acquire and use energy for metabolism and work.

• Response to Environment: Organisms respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations through natural selection.

Levels of Biological Organization

Biological systems are organized in a hierarchy, from smallest to largest:

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

Emergent properties arise at each level due to the arrangement and interactions of parts as complexity increases.

• Example: A cell is alive, but its organelles alone are not.

Eukaryotic vs. Prokaryotic Cells

• Prokaryotic cells: Lack a nucleus and membrane-bound organelles (Domains: Bacteria and Archaea).

• Eukaryotic cells: Have a nucleus and membrane-bound organelles (Domain: Eukarya; Kingdoms: Plantae, Fungi, Animalia, Protista).

Classification of Life

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

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

Role of DNA and Gene Expression

• DNA: The molecule of heredity; stores genetic information.

• Gene Expression: The process by which information from DNA is used to synthesize RNA and proteins.

Central Dogma:

• DNA → RNA → Protein

Energy and Matter in Living Systems

• Energy: Flows through ecosystems (usually enters as sunlight, exits as heat).

• Matter: Cycles within ecosystems (recycled and reused).

Feedback Regulation

• Negative Feedback: A process in which the end product slows or stops its own production (e.g., body temperature regulation).

• Positive Feedback: A process in which the end product speeds up its own production (e.g., blood clotting).

Natural Selection

• Definition: The process by which organisms with advantageous traits survive and reproduce more successfully.

• Result: Over generations, populations become better adapted to their environments.

The Scientific Process

• Controlled Experiment: Includes independent variable (manipulated), dependent variable (measured), and control group (baseline for comparison).

• Inductive Reasoning: Deriving general principles from specific observations.

• Deductive Reasoning: Predicting specific results from general principles.

Chemistry of Life

Matter, Elements, and Compounds

• Matter: Anything that takes up space and has mass.

• Element: A substance that cannot be broken down by chemical means.

• Compound: A substance consisting of two or more elements in a fixed ratio.

Emergent properties arise when elements combine to form compounds (e.g., sodium and chlorine form table salt).

Essential and Trace Elements

• Essential Elements: Four elements make up ~96% of living matter: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

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

Atomic Structure

• Subatomic Particles: Protons (positive, in nucleus), Neutrons (neutral, in nucleus), Electrons (negative, orbit nucleus).

• Atomic Number: Number of protons; defines the element.

• Mass Number: Number of protons + neutrons.

Equation:

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

Isotopes

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

• Applications: Used in biological research and medicine (e.g., radioactive tracers).

Electron Energy Levels and Orbitals

• Electrons occupy energy levels (shells) and orbitals; the arrangement affects chemical behavior.

• Valence Electrons: Electrons in the outermost shell; determine chemical properties.

Chemical Bonds

• Covalent Bonds: Atoms share electrons; can be polar (unequal sharing) or nonpolar (equal sharing).

• Ionic Bonds: Electrons are transferred from one atom to another, creating charged ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Chemical Reactions

• Reactants: Starting materials.

• Products: Substances formed.

• Example Equation: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$

Water and Life

Structure and Properties of Water

• Polar Covalent Bonds: Oxygen is more electronegative than hydrogen, creating partial charges (O: negative, H: positive).

• Hydrogen Bonds: Form between water molecules due to polarity; responsible for many unique properties.

Cohesion and Adhesion

• Cohesion: Water molecules stick to each other (important for transport in plants).

• Adhesion: Water molecules stick to other substances (helps water move up plant vessels).

High Specific Heat

• Water absorbs or releases a large amount of heat with little temperature change, stabilizing temperatures in organisms and environments.

Ice Floats

• Hydrogen bonds in ice are more ordered, making ice less dense than liquid water; this insulates aquatic life in winter.

Water as a Universal Solvent

• Solution: Homogeneous mixture of substances.

• Solvent: Dissolving agent (water).

• Solute: Substance dissolved.

• Water dissolves polar and ionic substances (hydrophilic), but not nonpolar substances (hydrophobic).

Acids, Bases, and pH

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Buffers: Substances that minimize changes in pH; crucial for maintaining homeostasis.

Macromolecules

Carbon: The Backbone of Life

• Carbon has 4 valence electrons, allowing it to form up to 4 covalent bonds and a variety of structures (chains, rings, branches).

• Structural variation leads to different properties and functions in molecules with the same formula (isomers).

Functional Groups

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

Macromolecules, Polymers, and Monomers

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

• Polymers: Long chains of monomers (repeating units).

• Monomers: Building blocks of polymers.

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: Joins monomers by removing water; forms polymers.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

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

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

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

• Comparison Table:

Polysaccharide	Function	Found In
Starch	Energy storage	Plants
Glycogen	Energy storage	Animals
Cellulose	Structural	Plant cell walls
Chitin	Structural	Fungi, arthropod exoskeletons

Lipids

• Fats: Glycerol + fatty acids; energy storage.

• Saturated Fats: No double bonds; solid at room temperature.

• Unsaturated Fats: One or more double bonds; liquid at room temperature.

• Phospholipids: Glycerol, two fatty acids, phosphate group; form cell membranes (hydrophilic head, hydrophobic tails).

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

Proteins

• Polypeptides: Chains of amino acids (20 types).

• Functions: Enzymes, structure, transport, signaling, defense, etc.

• Levels of Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Coils and folds (alpha helix, beta sheet).

  • Tertiary: 3D shape due to side chain interactions.

  • Quaternary: Association of multiple polypeptides.

Nucleic Acids

• DNA: Double-stranded; stores genetic information.

• RNA: Single-stranded; involved in protein synthesis.

• Gene Expression: DNA → RNA → Protein.

• Structure: Nucleotides (sugar, phosphate, nitrogenous base).