General Biology Study Guide: Chemical Context, Water, Biological Molecules, and Cell Structure

Ch. 2: The Chemical Context of Life

2.1 Formation and Function of Molecules via Chemical Bonding

This section covers the basic principles of chemical bonding and how these bonds contribute to the structure and function of biological molecules.

• Covalent Bonds: Atoms share electrons to form molecules. Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.

• Ionic Bonds: Atoms transfer electrons, resulting in oppositely charged ions that attract each other.

• Hydrogen Bonds: Weak attractions between a hydrogen atom covalently bonded to an electronegative atom (like oxygen or nitrogen) and another electronegative atom.

• Types of Noncovalent Interactions: Includes hydrogen bonds, ionic interactions, van der Waals forces, and hydrophobic interactions.

• Functional Groups: Specific groups of atoms within molecules that have characteristic properties and chemical reactivity (e.g., hydroxyl, carboxyl, amino, phosphate).

Example: Water molecules are held together by hydrogen bonds, which are crucial for many of water's unique properties.

Ch. 3: Water and Life

3.1 Water & Hydrogen Bonding

Water's structure and hydrogen bonding are fundamental to its role in biology.

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

• Hydrogen Bonding: Each water molecule can form up to four hydrogen bonds, leading to high cohesion, adhesion, and surface tension.

• Unique Properties: High specific heat, high heat of vaporization, expansion upon freezing, and excellent solvent abilities.

Example: Hydrogen bonding allows water to moderate Earth's climate and support life.

3.3 Acidic and Basic Conditions Affect Living Organisms

• Acids and Bases: Acids donate protons (H+), bases accept protons.

• pH Scale: Measures hydrogen ion concentration; pH = -log[H+].

• Buffers: Substances that minimize changes in pH by accepting or donating H+ ions.

Ch. 4: Carbon and the Molecular Diversity of Life

4.2 Carbon Atoms Can Form Diverse Molecules by Bonding to Four Other Atoms

• Tetravalence: Carbon can form four covalent bonds, allowing for a variety of stable structures (chains, rings, branches).

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

4.3 Chemical (Functional) Groups Are Key to Molecular Function

• Functional Groups: Hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, methyl.

• Role: Determine the properties and reactivity of organic molecules.

Ch. 5: The Structure and Function of Large Biological Molecules

5.1 Macromolecules Are Polymers, Built from Monomers

• Polymers: Long molecules made of repeating units (monomers) joined by covalent bonds.

• Dehydration Synthesis: Monomers are joined by removing water.

• Hydrolysis: Polymers are broken down by adding water.

5.2 Carbohydrates: Energy Storage and Structural Molecules

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

• Disaccharides: Two monosaccharides joined by a glycosidic bond (e.g., sucrose).

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

• Structure and Function: Starch and glycogen are energy storage; cellulose and chitin provide structural support.

5.3 Lipids: Hydrophobic Molecules

• Fats: Glycerol + fatty acids; energy storage.

• Phospholipids: Major component of cell membranes; amphipathic (hydrophilic head, hydrophobic tails).

• Steroids: Four fused rings; includes cholesterol and hormones.

5.4 Proteins: Molecules with Diverse Structure and Function

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

• Peptide Bonds: Link amino acids into polypeptides.

• Protein Structure: Four levels—primary (sequence), secondary (alpha helix, beta sheet), tertiary (3D folding), quaternary (multiple polypeptides).

• Function: Enzymes, structural support, transport, signaling, defense.

5.5 Nucleic Acids: Store, Transmit, and Help Express Hereditary Information

• DNA and RNA: Polymers of nucleotides (sugar, phosphate, nitrogenous base).

• Function: DNA stores genetic information; RNA involved in protein synthesis.

Ch. 6: A Tour of the Cell

6.1 and 7.1: Prokaryotes vs. Eukaryotes

• Prokaryotes: No nucleus, simple structure (e.g., bacteria, archaea).

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

6.2 Eukaryotic Cells Have Internal Membranes

• Compartmentalization: Organelles allow for specialized functions.

• Nucleus: Contains DNA; nucleolus synthesizes ribosomes.

• Ribosomes: Protein synthesis.

6.4 Endomembrane System

• Components: Nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, plasma membrane.

• Functions: Protein and lipid synthesis, transport, detoxification.

6.5 Mitochondria and Chloroplasts

• Mitochondria: Site of cellular respiration (ATP production).

• Chloroplasts: Site of photosynthesis in plants and algae.

6.6 Cytoskeleton

• Components: Microtubules, microfilaments, intermediate filaments.

• Functions: Structural support, cell movement, intracellular transport.

Ch. 7: Membrane Structure and Function

7.1 Cellular Membranes Are Fluid Mosaics

• Phospholipid Bilayer: Hydrophilic heads face outward, hydrophobic tails inward.

• Fluid Mosaic Model: Membrane proteins float in or on the fluid lipid bilayer.

7.2 Membrane Structure Results in Selective Permeability

• Selective Permeability: Only certain molecules can cross the membrane freely (e.g., small nonpolar molecules).

7.3 Passive Transport Across Membranes

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Facilitated Diffusion: Transport proteins help move substances across membranes.

7.4 Active Transport Uses Energy

• Active Transport: Moves substances against their concentration gradient using ATP (e.g., Na+/K+ pump).

7.5 Bulk Transport Across Cell Membranes

• Endocytosis: Cell takes in materials by engulfing them in vesicles.

• Exocytosis: Vesicles fuse with the membrane to release contents outside the cell.

Ch. 8: An Introduction to Metabolism

8.2 The Free-Energy Change of a Reaction Tells Us Whether or Not the Reaction Occurs Spontaneously

• Free Energy ($\Delta G$): Determines whether a reaction is spontaneous ($\Delta G < 0$) or requires energy input ($\Delta G > 0$).

• Equation: $\Delta G = \Delta H - T\Delta S$

8.3 ATP Powers Cellular Work by Coupling Exergonic Reactions to Endergonic Reactions

• ATP: Main energy currency of the cell; hydrolysis of ATP releases energy.

• Coupling: Exergonic reactions (release energy) drive endergonic reactions (require energy).

Additional info: This study guide is based on a learning guide for the first weeks of a General Biology course, covering foundational topics in chemistry, water, macromolecules, cell structure, membranes, and metabolism. The content is organized to align with standard introductory biology textbooks and includes expanded academic context for clarity and completeness.