General Biology: Foundational Concepts and Molecular Basis of Life

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Introduction to Scientific Inquiry

Steps of the Scientific Method

The scientific method is a systematic approach used by scientists to investigate natural phenomena. It involves several key steps:

Observation: Gathering information about a phenomenon.
Question: Formulating a question based on observations.
Hypothesis: Proposing a testable explanation.
Experiment: Designing and conducting tests to evaluate the hypothesis.
Data Collection: Recording and analyzing results.
Conclusion: Drawing inferences and refining the hypothesis if necessary.

Experiment vs Control

Experiments are designed to test hypotheses. A control group is used as a baseline for comparison, while the experimental group receives the variable being tested.

Control: No change; used for comparison.
Experimental: Receives the independent variable.

Hypothesis vs Theory

Hypothesis: A tentative, testable statement about a phenomenon.
Theory: A well-substantiated explanation based on a body of evidence.

Evolution vs Natural Selection

Evolution: Change in the genetic makeup of populations over time.
Natural Selection: Mechanism by which individuals with advantageous traits survive and reproduce more successfully.

Properties of Life

Order
Response to stimuli
Reproduction
Adaptation
Growth and development
Regulation
Homeostasis
Energy processing

Atoms, Molecules, and Chemical Bonds

Atoms & Subatomic Particles

Atoms are the basic units of matter, composed of protons, neutrons, and electrons.

Proton: Positively charged, found in nucleus.
Neutron: Neutral, found in nucleus.
Electron: Negatively charged, orbits nucleus.

Atomic Number vs Atomic Mass

Atomic Number: Number of protons in an atom.
Atomic Mass: Sum of protons and neutrons.

Valence Shell & Octet Rule

Valence Shell: Outermost electron shell; determines chemical reactivity.
Octet Rule: Atoms tend to have eight electrons in their valence shell for stability.

Isotopes

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

Noble Gases

Noble gases (e.g., helium, neon, argon) have full valence shells and are chemically inert.

Ionic vs Covalent Bonds

Ionic Bonds: Transfer of electrons between atoms, forming charged ions.
Covalent Bonds: Sharing of electron pairs between atoms.

Polar vs Nonpolar Bonds

Polar Covalent: Unequal sharing of electrons (e.g., H2O).
Nonpolar Covalent: Equal sharing of electrons (e.g., O2).

Electronegativity

Electronegativity is the tendency of an atom to attract electrons in a bond.

Hydrogen Bonds

Hydrogen bonds are weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen, nitrogen).

Water and Its Properties

Emergent Properties of Water

Water exhibits unique properties due to hydrogen bonding:

Cohesion: Water molecules stick together.
Adhesion: Water molecules stick to other surfaces.
High Specific Heat: Water resists temperature change.
Heat of Vaporization: Water requires much energy to vaporize.
Expansion upon freezing: Ice is less dense than liquid water.

Specific Heat vs Heat of Vaporization

Specific Heat: Amount of heat needed to raise 1g of a substance by 1°C.
Heat of Vaporization: Energy required to convert 1g of liquid to gas.

Cohesion vs Adhesion

Cohesion: Attraction between like molecules.
Adhesion: Attraction between different molecules.

Hydrophobic vs Hydrophilic

Hydrophobic: Repels water (e.g., oils).
Hydrophilic: Attracts water (e.g., salts, sugars).

Molarity

Molarity is the concentration of solute in solution, measured in moles per liter.

Formula:

Acids vs Bases, pH, Buffer

Acids: Donate H+ ions; pH < 7.
Bases: Accept H+ ions; pH > 7.
pH Scale: Measures H+ concentration;
Buffer: Substance that minimizes changes in pH.

Carbon and Organic Molecules

Organic vs Inorganic Compounds

Organic: Contains carbon and hydrogen; found in living organisms.
Inorganic: Does not contain both carbon and hydrogen.

Miller-Urey Experiment Conclusion

The Miller-Urey experiment demonstrated that organic molecules could form under prebiotic Earth conditions.

Carbon Bonds and Octet Rule

Single Bond: Sharing one pair of electrons.
Double Bond: Sharing two pairs of electrons.
Triple Bond: Sharing three pairs of electrons.

Macromolecules: Structure and Function

Dehydration vs Hydrolysis

Dehydration Synthesis: Forms polymers by removing water.
Hydrolysis: Breaks polymers by adding water.

Polymer vs Monomer

Monomer: Small building block molecule.
Polymer: Large molecule made of repeating monomers.

Types of Biomolecules

There are four major classes of biological macromolecules:

Carbohydrates: Energy storage and structure.
Proteins: Enzymes, structure, transport, defense.
Lipids: Energy storage, membranes, signaling.
Nucleic Acids: Genetic information (DNA, RNA).

Carbohydrates: Structure and Types

Glucose: Main energy source.
Starch: Storage in plants.
Cellulose: Plant cell wall structure.
Chitin: Exoskeletons of arthropods.
Glycogen: Storage in animals.

Glycosidic Linkages

Alpha 1,4 vs Beta 1,4: Types of bonds between glucose units; affects digestibility and structure.

Lipids: Types and Properties

Triglycerides: Energy storage.
Phospholipids: Membrane structure.
Steroids: Hormones, signaling.
Waxes: Protection, waterproofing.
Saturated vs Unsaturated: Saturated have no double bonds; unsaturated have one or more double bonds.

Proteins: Structure and Function

Peptide Bonds: Link amino acids in proteins.
Amino Acid Structure: Central carbon, amino group, carboxyl group, R group.
Functions: Enzymes, defense, transport, structure.
Levels of Structure: Primary, secondary, tertiary, quaternary.

Central Dogma of Molecular Biology

DNA → RNA → Protein: Genetic information flows from DNA to RNA to protein.

Transcription vs Translation

Transcription: DNA is copied into RNA.
Translation: RNA is used to build proteins.

Cell Structure and Function

Cell Theory

All living things are composed of cells.
Cells are the basic unit of life.
All cells come from pre-existing cells.

Prokaryotes vs Eukaryotes

Prokaryotes: No nucleus, no membrane-bound organelles (e.g., bacteria).
Eukaryotes: Nucleus and membrane-bound organelles (e.g., plants, animals).

Endosymbiotic Theory

Explains the origin of mitochondria and chloroplasts as formerly free-living bacteria engulfed by ancestral eukaryotic cells.

Animal vs Plant Cells

Animal Cells: No cell wall, have centrioles.
Plant Cells: Cell wall, chloroplasts, large central vacuole.

Basic Cell Structures and Functions

Cytoskeleton: Structural support, movement.
Cilia/Flagella: Movement.
Nucleus: Contains DNA.
Nucleolus: Ribosome synthesis.
Endoplasmic Reticulum (ER): Protein and lipid synthesis.
Golgi Apparatus: Modifies, sorts, ships proteins.
Mitochondria: ATP production.
Vesicles: Transport materials.
Lysosomes: Digestion.
Peroxisome: Breaks down fatty acids, detoxifies.

Cell Junctions

Tight Junctions: Prevent leakage between cells.
Desmosomes: Anchor cells together.
Gap Junctions: Allow communication between cells.

Additional Plant Cell Structures

Cell Wall: Provides structure and protection.
Vacuoles: Storage and support.
Plasmodesmata: Channels for transport between plant cells.
Chloroplast: Site of photosynthesis.

Bond Type	Definition	Example
Ionic	Transfer of electrons	NaCl
Covalent	Sharing of electrons	H2O
Hydrogen	Weak attraction between H and electronegative atom	Between water molecules

Macromolecule	Monomer	Function
Carbohydrate	Monosaccharide	Energy, structure
Protein	Amino acid	Enzymes, structure, transport
Lipid	Fatty acid, glycerol	Energy, membranes
Nucleic Acid	Nucleotide	Genetic information

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