General Biology: Foundations, Chemistry, Water, and Organic Molecules

Chapter 1: Introduction to Biology and the Scientific Method

Key Concepts in Biology

This chapter introduces the foundational principles of biology, focusing on the scientific method, variables, and the characteristics of life. It also covers the basics of evolution and natural selection.

• Scientific Method: A systematic approach to inquiry involving observation, hypothesis formation, experimentation, and conclusion.

• Experiment: A controlled procedure to test a hypothesis.

• Variables:

  • Independent Variable: The factor that is changed or manipulated in an experiment.

  • Dependent Variable: The factor that is measured or observed.

  • Control Variables: Factors kept constant to ensure a fair test.

• Properties of Life: Organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation through evolution.

• Hypothesis: A testable statement or prediction based on observations.

• Prediction: A logical statement about what will happen if the hypothesis is correct.

• Experimental Variables: Variables that are manipulated or measured in an experiment.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Adaptation: A trait that increases an organism's fitness in a particular environment.

• Descent with Modification: The passing on of traits from parent organisms to their offspring, with changes over generations.

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

Example: Charles Darwin's theory of natural selection explains how species adapt and evolve over time based on environmental pressures.

Chapter 2: Chemistry and Biology

Atoms, Elements, and the Periodic Table

This section explores the chemical basis of life, including atomic structure, isotopes, and the periodic table. It also covers chemical bonds and reactions essential for biological processes.

• Atom: The smallest unit of matter that retains the properties of an element.

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

• Subatomic Particles: Protons (positive charge), neutrons (neutral), and electrons (negative charge).

• Atomic Number: Number of protons in an atom's nucleus.

• Mass Number: Total number of protons and neutrons in an atom.

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

• Radioactive Isotopes: Unstable isotopes that decay over time, releasing radiation. Used in medicine and dating fossils.

• Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

• Periodic Table: Organizes elements by increasing atomic number and similar chemical properties.

• Electronegativity: The ability of an atom to attract electrons in a chemical bond.

• Ions: Charged atoms or molecules formed by gaining or losing electrons.

Example: Carbon-14 is a radioactive isotope used in radiometric dating to determine the age of ancient artifacts.

Chemical Bonds and Reactions

• Chemical Bond: The force that holds atoms together in molecules.

  • Covalent Bond: Atoms share electron pairs.

  • Ionic Bond: Transfer of electrons from one atom to another, resulting in oppositely charged ions.

  • Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

• Chemical Reaction: The process by which substances change into different substances through the breaking and forming of bonds.

• Chemical Equilibrium: The state in which the rate of the forward reaction equals the rate of the reverse reaction.

Example: Water (H2O) forms when two hydrogen atoms covalently bond with one oxygen atom.

Chapter 3: Water and Its Properties

States and Properties of Water

Water is essential for life due to its unique physical and chemical properties. This section covers the states of water, its molecular structure, and its importance in biological systems.

• States of Water: Solid (ice), liquid, and gas (vapor).

• Polarity: Water is a polar molecule, with a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms.

• Hydrogen Bonding: Responsible for many of water's unique properties, such as high surface tension and specific heat.

• Cohesion: Attraction between water molecules.

• Adhesion: Attraction between water molecules and other substances.

• Surface Tension: The measure of how difficult it is to stretch or break the surface of a liquid.

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

• Evaporation: The process by which water changes from a liquid to a gas.

• Density: Ice is less dense than liquid water, which is why ice floats.

• Solvent Properties: Water is known as the "universal solvent" because it can dissolve many substances.

• pH: A measure of hydrogen ion concentration; water has a neutral pH of 7.

Example: Water's high specific heat helps regulate temperature in living organisms and environments.

Table: Comparison of Water's Properties

Property	Description	Biological Importance
Cohesion	Water molecules stick together	Enables transport of water in plants
Adhesion	Water molecules stick to other surfaces	Helps water move up plant vessels
High Specific Heat	Resists temperature change	Stabilizes climate and body temperature
Ice Floats	Solid water is less dense than liquid	Insulates aquatic life in winter
Universal Solvent	Dissolves many substances	Facilitates chemical reactions in cells

Chapter 4: Organic Molecules and Biochemistry

Organic Chemistry and Carbon Compounds

This chapter explores the chemistry of carbon, the backbone of all life, and the diversity of organic molecules. It also covers functional groups and isomerism.

• Organic Chemistry: The study of carbon-containing compounds.

• Hydrocarbons: Compounds composed only of carbon and hydrogen.

• Isomers: Molecules with the same molecular formula but different structures.

  • Structural Isomers: Differ in the covalent arrangement of atoms.

  • Cis-Trans Isomers: Differ in spatial arrangement around a double bond.

• Functional Groups: Specific groups of atoms within molecules that determine the chemical properties of those molecules.

  • Hydroxyl (-OH)

  • Carbonyl (C=O)

  • Carboxyl (-COOH)

  • Amino (-NH2)

  • Sulfhydryl (-SH)

  • Phosphate (-PO4)

  • Methyl (-CH3)

Example: The amino group is found in amino acids, which are the building blocks of proteins.

Biological Molecules and Their Functions

• ATP (Adenosine Triphosphate): The primary energy carrier in cells.

• Macromolecules: Large molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.

• Valence Electrons: Determine how atoms bond and form molecules.

• Carbon's Versatility: Carbon can form four covalent bonds, allowing for a variety of complex molecules.

Example: Miller-Urey experiment demonstrated that organic molecules could be synthesized from inorganic precursors under early Earth conditions.

Table: Major Functional Groups in Organic Molecules

Functional Group	Structure	Properties	Example
Hydroxyl	-OH	Polar, forms hydrogen bonds	Alcohols
Carbonyl	C=O	Polar, found in sugars	Aldehydes, Ketones
Carboxyl	-COOH	Acidic, donates H+	Amino acids, fatty acids
Amino	-NH2	Basic, accepts H+	Amino acids
Phosphate	-PO4	Negative charge, energy transfer	ATP, nucleic acids
Methyl	-CH3	Nonpolar, affects gene expression	Methylated DNA

Additional info:

• Scientists use radioactive isotopes in medicine (e.g., PET scans) and to date fossils (e.g., carbon dating).

• ATP stores energy in its phosphate bonds; when these bonds are broken, energy is released for cellular processes.