Introduction to Scientific Inquiry

Steps of the Scientific Method

The scientific method is a systematic approach used by scientists to explore observations, answer questions, and test hypotheses.

• Observation: Gathering information about a phenomenon.

• Question: Formulating a question based on observations.

• Hypothesis: Proposing a testable explanation or prediction.

• Experiment: Designing and conducting tests to evaluate the hypothesis.

• Data Collection: Gathering and recording results.

• Analysis: Interpreting data to draw conclusions.

• Conclusion: Accepting, rejecting, or modifying the hypothesis based on results.

Experiment vs Control

• Experimental Group: The group exposed to the variable being tested.

• Control Group: The group not exposed to the variable; used as a baseline for comparison.

Hypothesis vs Theory

• Hypothesis: A specific, testable prediction about the outcome of an experiment.

• Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.

Evolution vs Natural Selection

• Evolution: The change in the genetic composition of a population over generations.

• Natural Selection: The process by which individuals with advantageous traits survive and reproduce more successfully.

Properties of Life

• Order

• Regulation

• Growth and development

• Energy processing

• Response to environment

• Reproduction

• Evolutionary adaptation

Atoms, Molecules, and Chemical Bonds

Atoms & Subatomic Particles

An atom is the smallest unit of matter that retains the properties of an element. Atoms are composed of:

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Atomic Number vs Atomic Mass

• Atomic Number (Z): Number of protons in the nucleus.

• Atomic Mass (A): Total number of protons and neutrons.

Valence Shell and Octet Rule

• Valence Shell: The outermost electron shell of an atom.

• Octet Rule: Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell.

Isotopes

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

• Example: Carbon-12, Carbon-13, and Carbon-14.

Noble Gases

• Elements in Group 18 of the periodic table.

• Have full valence shells and are chemically inert.

Ionic vs Covalent Bonds

• Ionic Bonds: Formed by the transfer of electrons from one atom to another.

• Covalent Bonds: Formed by the sharing of electrons between atoms.

Polar vs Nonpolar Bonds

• Polar Covalent Bonds: Electrons are shared unequally, resulting in partial charges.

• Nonpolar Covalent Bonds: Electrons are shared equally.

Electronegativity

• The tendency of an atom to attract electrons in a chemical bond.

Hydrogen Bonds

• Weak attractions between a hydrogen atom (attached to O, N, or F) and another electronegative atom.

Water and Its Properties

Emergent Properties of Water

Water exhibits unique properties essential for life due to its structure and hydrogen bonding.

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes.

• High Heat of Vaporization: Large amount of energy required to convert water from liquid to gas.

• Expansion upon freezing: Ice is less dense than liquid water.

• Versatile solvent: Dissolves many substances.

Specific Heat vs Heat of Vaporization

• Specific Heat: Amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

• Heat of Vaporization: Amount of heat required to convert 1 gram of a liquid to gas.

Cohesion vs Adhesion

• Cohesion: Attraction between molecules of the same substance (e.g., water to water).

• Adhesion: Attraction between molecules of different substances (e.g., water to glass).

Hydrophobic vs Hydrophilic

• Hydrophobic: Substances that repel water (nonpolar molecules).

• Hydrophilic: Substances that attract water (polar molecules).

Molarity

• Molarity (M): Number of moles of solute per liter of solution.

Acids vs Bases, pH, and Buffers

• Acids: Substances that increase the concentration of H+ ions in solution.

• Bases: Substances that decrease the concentration of H+ ions.

• pH: Measure of hydrogen ion concentration; scale from 0 (acidic) to 14 (basic).

• Buffer: Substance that minimizes changes in pH by accepting or donating H+ ions.

Carbon Chemistry and Biological Molecules

Organic vs Inorganic Compounds

• Organic Compounds: Contain carbon and hydrogen, often found in living organisms.

• Inorganic Compounds: Do not contain both carbon and hydrogen together.

Miller-Urey Experiment Conclusion

• Demonstrated that organic molecules could be synthesized abiotically under early Earth conditions.

Carbon Bonds and the Octet Rule

• Carbon forms four covalent bonds to satisfy the octet rule.

• Types of bonds: single, double, and triple bonds.

Dehydration vs Hydrolysis

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Polymer vs Monomer

• Monomer: Small building block molecule.

• Polymer: Large molecule made of repeating monomers.

Types of Biological Molecules

• Carbohydrates: Sugars and starches; energy storage and structure.

• Proteins: Polymers of amino acids; diverse functions.

• Lipids: Fats, oils, phospholipids, steroids; energy storage, membranes.

• Nucleic Acids: DNA and RNA; genetic information.

Carbohydrates: Structure and Function

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

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

• Polysaccharides: Long chains (e.g., starch, cellulose, glycogen, chitin).

Lipids: Types and Properties

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

• Phospholipids: Glycerol + 2 fatty acids + phosphate; cell membranes.

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

• Waxes: Long-chain fatty acids bonded to alcohols.

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

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

Proteins: Structure and Function

• Amino Acids: Building blocks of proteins; 20 standard types.

• Peptide Bonds: Covalent bonds linking amino acids.

• Levels of Protein Structure:

  • Primary: Sequence of amino acids.

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

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

  • Quaternary: Multiple polypeptide chains.

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

Nucleic Acids: DNA and RNA

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

• DNA: Double helix; stores genetic information.

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

• Central Dogma: DNA → RNA → Protein

Transcription vs Translation

• Transcription: Synthesis of RNA from DNA template.

• Translation: Synthesis of protein from RNA template.

Cell Structure and Function

Cell Theory

• All living things are composed of cells.

• Cells are the basic unit of life.

• All cells arise from pre-existing cells.

Prokaryotes vs Eukaryotes

• Prokaryotes: No nucleus, no membrane-bound organelles (e.g., bacteria, archaea).

• Eukaryotes: Nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

Endosymbiotic Theory

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

Animal vs Plant Cells

• Animal Cells: Lack cell wall, have centrioles, small or no vacuoles.

• Plant Cells: Have cell wall, chloroplasts, large central vacuole.

Basic Cell Features and Organelles

• Cytoskeleton: Structural support, cell movement.

• Cilia/Flagella: Movement.

• Nucleus: Contains DNA.

• Nucleolus: Ribosome synthesis.

• Endoplasmic Reticulum (ER): Protein and lipid synthesis.

• Golgi Apparatus: Modifies, sorts, and packages proteins/lipids.

• Mitochondria: ATP production.

• Vesicles: Transport materials.

• Lysosomes: Digestion of macromolecules.

• Peroxisomes: Breakdown of fatty acids, detoxification.

Cell Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between animal cells.

• Plasmodesmata: Channels between plant cells for communication.

Additional Plant Cell Structures

• Cell Wall: Rigid structure for support.

• Vacuoles: Storage and maintenance of cell shape.

• Chloroplasts: Site of photosynthesis.