General Biology: Core Themes, Chemistry, Water, Thermodynamics, Carbon, and Macromolecules

Ch. 1 - Themes of Biology

Major Themes in Biology

Biology is the study of living organisms and their interactions with each other and their environments. Several unifying themes help organize biological knowledge.

• Organization: Biological systems are structured in hierarchical levels, from molecules to the biosphere. Emergent properties arise at each level due to the arrangement and interactions of parts.

• Structure-Function Correlation: The form of a biological structure is closely related to its function.

• Information: Genetic information (DNA) is passed from one generation to the next, guiding development and functioning.

• Energy and Matter: Life requires the transfer and transformation of energy and matter (e.g., photosynthesis, cellular respiration).

• Interactions: Organisms interact with each other and their environment, affecting both.

• Evolution: Populations evolve over time through processes such as natural selection, leading to adaptation and diversity.

• Scientific Method: Science relies on observation, hypothesis formation, experimentation, and reasoning to understand natural phenomena.

Example: The structure of the DNA double helix enables it to store genetic information and replicate accurately.

Ch. 2 - Chemistry

Basic Chemical Principles in Biology

Understanding the chemical basis of life is essential for studying biological processes. Atoms, elements, and compounds form the foundation of biological molecules.

• Element: A pure substance consisting of only one type of atom (e.g., carbon, oxygen).

• Compound: A substance formed from two or more elements in a fixed ratio (e.g., H2O).

• Atomic Composition: Atoms consist of protons, neutrons, and electrons. Electron properties (shells, valence) determine chemical behavior.

• Chemical Bonds: Atoms form bonds to achieve stability. Types include:

  • Covalent Bonds: Atoms share electrons (e.g., H2O).

  • Ionic Bonds: Electrons are transferred from one atom to another (e.g., NaCl).

  • Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (important in water and biological molecules).

  • Van der Waals Interactions: Weak, transient interactions between molecules.

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

• Polarity: Molecules with uneven distribution of charge (e.g., water is polar).

Example: The polarity of water molecules allows them to form hydrogen bonds, giving water its unique properties.

Ch. 3 - Water

Properties and Importance of Water

Water is essential for life due to its unique chemical and physical properties, which arise from its polarity and ability to form hydrogen bonds.

• Cohesion: Water molecules stick together due to hydrogen bonding.

• Adhesion: Water molecules stick to other substances.

• Surface Tension: The surface of water resists external force due to cohesive forces.

• Temperature Moderation: Water has a high specific heat, allowing it to buffer temperature changes.

• Evaporative Cooling: As water evaporates, it removes heat, cooling surfaces.

• Solvent Properties: Water is a versatile solvent, especially for polar and ionic substances.

• Hydrophobic and Amphipathic Substances: Hydrophobic molecules do not mix with water, while amphipathic molecules have both hydrophilic and hydrophobic regions (e.g., phospholipids).

• pH and Buffers: Water can dissociate into H+ and OH- ions. Buffers help maintain stable pH in biological systems.

Example: The high specific heat of water helps organisms maintain stable internal temperatures.

Ch. 8 - Thermodynamics

Energy and Thermodynamic Principles in Biology

Thermodynamics describes the flow and transformation of energy in biological systems. These principles are fundamental to understanding metabolism and cellular processes.

• Energy: The capacity to do work. Forms include kinetic (motion) and potential (stored energy).

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed (conservation of energy).

• Second Law of Thermodynamics: Every energy transfer increases the entropy (disorder) of the universe.

• Free Energy (Gibbs Free Energy): The portion of a system's energy that can perform work. Changes in free energy ($\Delta G$) determine whether a reaction is spontaneous.

• Exergonic Reactions: Release energy; $\Delta G < 0$ (spontaneous).

• Endergonic Reactions: Require energy input; $\Delta G > 0$ (non-spontaneous).

• ATP (Adenosine Triphosphate): The primary energy currency of the cell. Hydrolysis of ATP releases energy for cellular work.

• Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy. Enzyme activity can be affected by temperature, pH, and inhibitors.

Example: Cellular respiration is an exergonic process that releases energy by breaking down glucose.

Ch. 4 - Carbon

Carbon Chemistry and Functional Groups

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds, allowing for diverse molecular structures.

• Covalent Bonding: Carbon forms stable covalent bonds with other atoms, including itself, leading to chains, rings, and complex structures.

• Isomers: Molecules with the same molecular formula but different structures (structural, cis-trans, enantiomers).

• Functional Groups: Specific groups of atoms attached to carbon skeletons that confer unique properties. Examples include:

  • Hydroxyl (-OH)

  • Carbonyl (C=O)

  • Carboxyl (-COOH)

  • Amino (-NH2)

  • Sulfhydryl (-SH)

  • Phosphate (-PO4)

  • Methyl (-CH3)

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

Ch. 5 - Macromolecules

Structure and Function of Biological Macromolecules

Macromolecules are large, complex molecules essential for life. They are formed by the polymerization of smaller subunits (monomers).

• Polymers: Long chains of monomers joined by dehydration reactions (removal of water).

• Hydrolysis: The breakdown of polymers into monomers by adding water.

• Four Major Classes:

  • Carbohydrates: Sugars and their polymers. Functions include energy storage (starch, glycogen) and structural support (cellulose, chitin).

  • Proteins: Polymers of amino acids. Functions include catalysis (enzymes), structure, transport, and signaling. Protein structure has four levels: primary, secondary, tertiary, and quaternary.

  • Nucleic Acids: DNA and RNA, which store and transmit genetic information. Composed of nucleotide monomers.

  • Lipids: Diverse group including fats, phospholipids, and steroids. Functions include energy storage, membrane structure, and signaling.

Example: Phospholipids form the bilayer of cell membranes due to their amphipathic nature (hydrophilic head, hydrophobic tails).

Table: Comparison of Macromolecules

Macromolecule	Monomer	Function	Example
Carbohydrates	Monosaccharides	Energy storage, structure	Starch, cellulose, glycogen
Proteins	Amino acids	Catalysis, structure, transport	Enzymes, hemoglobin
Nucleic Acids	Nucleotides	Genetic information storage	DNA, RNA
Lipids	Glycerol and fatty acids	Energy storage, membranes, signaling	Fats, phospholipids, steroids

Additional info: The table above summarizes the main types of biological macromolecules, their monomers, functions, and examples.