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).

• Energy Processing: Organisms acquire and use energy to power activities.

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

• Response to Environment: Organisms respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

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 (e.g., Bacteria, Archaea).

• Eukaryotic cells: Have a nucleus and membrane-bound organelles (e.g., Plants, Animals, Fungi, Protists).

Classification: Domains and Kingdoms

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

• Kingdoms in Eukarya: Plantae, Animalia, Fungi, 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: $\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$

Energy and Matter in Living Systems

• Energy: Flows through ecosystems (e.g., sunlight → chemical energy → heat).

• Matter: Cycles within ecosystems (e.g., carbon, nitrogen cycles).

• Difference: Energy is lost as heat; matter is recycled.

Feedback Regulation

• Negative Feedback: Output reduces the original effect (e.g., body temperature regulation).

• Positive Feedback: Output enhances the original effect (e.g., blood clotting).

Natural Selection

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

• Mechanism: Variation, inheritance, differential survival and reproduction.

• Result: Populations become better adapted to their environment over generations.

The Scientific Process

• Steps: Observation, Question, Hypothesis, Experiment, Data Collection, Conclusion.

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

Inductive vs. Deductive Reasoning

• Inductive Reasoning: Specific observations → general conclusions.

• Deductive Reasoning: General premises → specific predictions.

• Example: Inductive: "All observed swans are white; therefore, all swans are white." Deductive: "All mammals have hair; this animal is a mammal; therefore, it has hair."

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 made of two or more elements in a fixed ratio.

• Emergent Properties: Compounds have properties different from their constituent elements.

Essential and Trace Elements

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

• Bonding: C (4 bonds), H (1 bond), O (2 bonds), N (3 bonds).

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

• Isotopes: Atoms of the same element with different numbers of neutrons; used in dating fossils, medical imaging.

Electron Energy Levels and Orbitals

• Electrons: Occupy energy levels (shells); outermost shell = valence shell.

• Valence Electrons: Determine chemical properties and bonding behavior.

• Orbitals: 3D spaces where electrons are found; shape affects molecular geometry.

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 ions.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N); important in water and DNA structure.

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: δ-, H: δ+).

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

Cohesion and Adhesion

• Cohesion: Water molecules stick to each other (surface tension).

• Adhesion: Water molecules stick to other substances (capillary action in plants).

High Specific Heat

• Definition: Water absorbs a lot of heat before changing temperature.

• Biological Impact: Stabilizes climate and organismal temperatures.

Ice Floats

• Reason: Hydrogen bonds in ice are more ordered, making ice less dense than liquid water.

• Impact: Insulates aquatic life in winter.

Water as a Universal Solvent

• Solution: Homogeneous mixture of solute dissolved in solvent.

• Hydrophilic: Substances that dissolve in water (polar/charged).

• Hydrophobic: Substances that do not dissolve in water (nonpolar).

Acids, Bases, and Buffers

• pH Scale: Measures hydrogen ion concentration; 0-6.9 = acid, 7 = neutral, 7.1-14 = base.

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

Macromolecules

Carbon: The Backbone of Life

• Versatility: Carbon has 4 valence electrons, allowing it to form 4 covalent bonds and diverse structures (chains, rings, branches).

• Isomers: Molecules with the same formula but different structures; can have different properties.

Functional Groups

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

• Importance: Affect molecular function and reactivity.

Macromolecules, Polymers, and Monomers

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

• Polymers: Long chains of monomers (except lipids).

• Monomers: Building blocks (e.g., monosaccharides, amino acids, nucleotides).

Dehydration Synthesis and Hydrolysis

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

• Hydrolysis: Breaks polymers by adding water; releases monomers.

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	Organism
Starch	Energy storage	Plants
Glycogen	Energy storage	Animals
Cellulose	Structural	Plants
Chitin	Structural	Fungi, Arthropods

Lipids

• Fats: Glycerol + 3 fatty acids; energy storage.

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

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

• Phospholipids: Glycerol + 2 fatty acids + phosphate group; form cell membranes (hydrophilic head, hydrophobic tails).

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

Proteins

• Monomer: Amino acids (20 types).

• Polypeptide: Chain of amino acids.

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

• Levels of Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helices and beta sheets (hydrogen bonding).

  • Tertiary: 3D folding (interactions among R groups).

  • Quaternary: Multiple polypeptides joined.

Nucleic Acids

• DNA: Double helix; stores genetic information.

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

• Monomer: Nucleotide (sugar, phosphate, nitrogenous base).

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

• Differences: DNA has deoxyribose, thymine; RNA has ribose, uracil.

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard biology textbooks.