General Biology Study Guide: Core Concepts, Macromolecules, Cell Structure, and Metabolism

Core Characteristics and Origins of Life

Requirements of Living Organisms

All living organisms share fundamental characteristics that distinguish them from non-living matter.

• Order: Living things exhibit organized structure, often at multiple levels (cells, tissues, organs).

• Energy Processing: Organisms obtain and use energy to power activities and maintain homeostasis.

• Response to Environment: Living things sense and respond to stimuli in their environment.

Evidence for Common Ancestry

Modern biology supports the idea that all life evolved from a common ancestor.

• Universal Genetic Code: All organisms use DNA and RNA to store and transmit genetic information.

• Homologous Structures: Similar anatomical features in different species suggest shared ancestry.

Atoms, Elements, and Chemical Bonds

Atomic Structure and Isotopes

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

• Atomic Number (A): Number of protons in the nucleus (e.g., 8 for Oxygen).

• Element Symbol (B): One- or two-letter abbreviation (e.g., O for Oxygen).

• Element Name (C): Full name of the element (e.g., Oxygen).

• Atomic Mass (D): Average mass of the atom, including isotopes (e.g., 15.999 for Oxygen).

If the atomic mass of an isotope of Nitrogen is 17 and its atomic number is 7, the number of neutrons is:

• Neutrons = Atomic Mass - Atomic Number = 17 - 7 = 10

Valence Electrons and Chemical Bonds

Valence electrons determine an atom's chemical properties and bonding behavior.

• Sulfur (atomic number 16): Has 6 valence electrons.

Types of chemical bonds, ordered from weakest to strongest:

• Van der Waals

• Hydrogen bonds

• Ionic bonds

• Covalent bonds

Covalent bonds result in a near equal sharing of electrons.

Properties of Water

Cohesion and Adhesion

Water molecules interact through hydrogen bonding, leading to unique properties.

• Cohesion: Attraction between water molecules, responsible for surface tension.

• Adhesion: Attraction between water molecules and other substances, aiding capillary action.

Water's Properties

• High Specific Heat: Water resists temperature changes.

• Universal Solvent: Water dissolves many substances due to its polarity.

Acidity and pH

A solution with pH 3 is acidic and has a high concentration of H+ ions.

Organic Molecules: Isomers and Functional Groups

Cis and Trans Isomers

Isomers are molecules with the same formula but different structures.

• Cis Isomer: Functional groups on the same side of a double bond.

• Trans Isomer: Functional groups on opposite sides of a double bond.

Saturated vs. Unsaturated Fats

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

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

Functional Groups Identification

• Carboxyl Group: -COOH (usually depicted as B or C in diagrams).

• Amino Group: -NH2 (usually depicted as D).

Macromolecules: Structure and Function

Macromolecule Table

Major biological macromolecules and their properties:

Macromolecule	Function	Monomer	Polymer	Bond Type
Carbohydrates	Energy storage, structure	Monosaccharide	Polysaccharide	Glycosidic bond
Lipids	Energy storage, membranes	Fatty acid, glycerol	Triglyceride, phospholipid	Ester bond
Protein	Catalysis, structure, transport	Amino acid	Polypeptide	Peptide bond
Nucleic acid	Genetic information	Nucleotide	DNA/RNA	Phosphodiester bond

Lipid Bonds and Saturation

• Saturated lipids: Only single bonds, solid at room temperature.

• Unsaturated lipids: One or more double bonds, liquid at room temperature.

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: Water is lost, monomers join to form polymers.

• Hydrolysis: Water is added, polymers break into monomers.

Cell Membranes and Transport

Types of Solutions

• Hypertonic: Higher solute concentration outside the cell; cell loses water.

• Isotonic: Equal solute concentration; no net water movement.

• Hypotonic: Lower solute concentration outside; cell gains water.

Bulk Transport

• Endocytosis: Cell takes in material by engulfing it.

• Exocytosis: Cell expels material by vesicle fusion with membrane.

Fluid Mosaic Model

The cell membrane is a dynamic structure composed of a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol.

Sodium-Potassium Pump

• Moves 3 sodium ions out and 2 potassium ions in per ATP molecule hydrolyzed.

Cell Organelles

• Nucleus: Stores genetic material.

• Mitochondria: Produces ATP via cellular respiration.

• Endoplasmic Reticulum: Synthesizes proteins and lipids.

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

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic: No nucleus, smaller, no membrane-bound organelles.

• Eukaryotic: Nucleus present, larger, membrane-bound organelles.

Macromolecule Identification

Monomer Identification

• A: Amino acid (protein)

• B: Monosaccharide (carbohydrate)

• C: Nucleotide (nucleic acid)

• D: Nucleotide (nucleic acid)

Cellular Metabolism and Energy

Free Energy Change Formula

The change in free energy ($\Delta G$) determines whether a reaction is spontaneous.

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

• $\Delta H$ = change in enthalpy; $T$ = temperature (Kelvin); $\Delta S$ = change in entropy

Catabolic vs. Anabolic Pathways

• Catabolic: Break down molecules, release energy, spontaneous.

• Anabolic: Build molecules, require energy, nonspontaneous.

Enzymes and Activation Energy

• Enzymes lower activation energy, increasing reaction rate.

Fermentation

• Fermentation is anaerobic (does not require oxygen).

NAD+ in Cellular Respiration

• NAD+ acts as an electron carrier, accepting electrons during glycolysis and the Krebs cycle.

Steps of Cellular Respiration

• Glycolysis: Occurs in cytoplasm; glucose split into pyruvate.

• Krebs Cycle: Occurs in mitochondria; pyruvate broken down, CO2 released.

• Electron Transport Chain: Occurs in mitochondrial membrane; electrons transferred, ATP produced.

Glycolysis

• Occurs in cytoplasm; produces ATP and NADH.

Krebs Cycle Products

• CO2, ATP, NADH, FADH2

Electron Transport Chain

• Protons pumped out of mitochondrial matrix; return via ATP synthase, producing ATP.

Additional info: The study notes expand on brief question prompts to provide full academic context and explanations suitable for exam preparation.