General Biology I: Unit 1 Study Guide – Foundations of Life, Chemistry, Macromolecules, and Cells

Chapter 1: Basic Introduction to the Organization of Life

Hierarchical Organization of Living Systems

Life is organized in a hierarchy from the smallest chemical units to the entire biosphere. Understanding this organization helps explain how complex biological systems arise from simpler components.

• Levels of Organization: Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

• Cells: The basic unit of life; all living things are composed of one or more cells.

• Emergent Properties: New properties that arise at each level of organization, not present at the preceding level.

• Structure vs. Function: Biological structures are closely related to their functions (e.g., the shape of a protein determines its role).

• Energy Flow vs. Chemical Cycling: Energy flows through ecosystems (usually entering as sunlight and exiting as heat), while chemicals cycle within ecosystems.

Evolution Explains the Unity and Diversity of Life

Evolution is the central unifying concept in biology, explaining both the similarities and differences among living organisms.

• Biochemical Similarities: All living things share fundamental biochemical processes (e.g., DNA as genetic material, ATP as energy currency).

• Three Domains of Life: Bacteria, Archaea, and Eukarya. Eukarya includes four kingdoms: Protista, Fungi, Plantae, and Animalia.

• Descent with Modification: Species change over time, and Darwin proposed natural selection as a primary mechanism of evolution.

Science is a Way of Knowing

Science uses systematic methods to investigate the natural world.

• Scientific Method: Observation → Hypothesis → Experimentation → Data Analysis → Conclusion.

• Hypothesis vs. Theory: A hypothesis is a testable explanation; a scientific theory is a well-supported, broad explanation for a wide range of phenomena.

Chapter 2: The Chemical Basis of Life

The Nature of Atoms

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

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Total number of protons and neutrons.

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

• Ions: Atoms that have gained or lost electrons, acquiring a charge.

• Electron Distribution: Electrons occupy energy levels (shells); valence electrons in the outer shell determine chemical reactivity.

Chemical Bonds, Molecular Shape, and Chemical Reactions

Chemical bonds form when atoms share or transfer electrons, resulting in molecules with specific shapes and properties.

• Covalent Bonds: Atoms share electron pairs; can be non-polar (equal sharing) or polar (unequal sharing).

• Ionic Bonds: Transfer of electrons from one atom to another, creating charged ions.

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

• Collision Theory: Chemical reactions involve breaking and forming bonds; reactants must collide with sufficient energy and proper orientation.

• Chemical Equilibrium: The point at which the rate of the forward reaction equals the rate of the reverse reaction.

Characteristics and Properties of Water

Water's unique properties are essential for life and result from its molecular structure and hydrogen bonding.

• Polarity: Water is a polar molecule with partial positive and negative charges.

• Hydrogen Bonding: Leads to cohesion, adhesion, high specific heat, and surface tension.

• Key Terms: Solubility (ability to dissolve substances), hydrophilic (water-loving), hydrophobic (water-fearing), aqueous solution (water as solvent).

Acids and Bases

Acids and bases are substances that affect the concentration of hydrogen ions in solution.

• Acids: Donate H+ ions; Bases: Accept H+ ions.

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

• Buffers: Substances that minimize changes in pH.

• Relationship: As [H+] increases, pH decreases (more acidic); as [H+] decreases, pH increases (more basic).

Chapter 3: Carbon – The Framework of Biological Macromolecules

Carbon's Bonding and Isomerism

Carbon atoms can form up to four covalent bonds, allowing for a diversity of organic molecules.

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

• Functional Groups: Specific groups of atoms that confer particular properties (e.g., hydroxyl, carboxyl, amino, sulfhydryl, phosphate, methyl).

Biological Macromolecules

Macromolecules are large, complex molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

• Polymers: Long chains of monomers joined by dehydration synthesis (removal of water); broken down by hydrolysis (addition of water).

Carbohydrates: Energy Storage, Fuel, and Structural Molecules

Carbohydrates serve as energy sources and structural components in cells.

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

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

• Polysaccharides: Long chains (e.g., starch, glycogen, cellulose, chitin) with storage or structural roles.

Lipids: Diverse Group of Hydrophobic Molecules

Lipids are nonpolar molecules important for energy storage, membrane structure, and signaling.

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

• Saturated vs. Unsaturated Fatty Acids: Saturated have no double bonds (solid at room temp); unsaturated have one or more double bonds (liquid at room temp).

• Phospholipids: Major component of cell membranes; form bilayers due to hydrophilic heads and hydrophobic tails.

• Other Lipids: Steroids (e.g., cholesterol), important for membrane structure and hormones.

Proteins: Molecules with Diverse Structures and Functions

Proteins are polymers of amino acids with a wide range of functions, determined by their structure.

• Amino Acids: 20 types; can be non-polar, polar, or charged; structure affects function.

• Protein Structure:

  • Primary: Amino acid sequence

  • Secondary: Alpha helix, beta pleated sheet (hydrogen bonding)

  • Tertiary: 3D folding (side chain interactions)

  • Quaternary: Multiple polypeptide chains

• Structure-Function Relationship: Example: Sickle-cell hemoglobin (mutation alters function).

• Protein Functions: Enzymes (catalysis), defense, storage, transport, hormones, receptors, contractile/motor, structural.

• Key Terms: Peptide bond, side chain (R group), alpha helix, beta sheet, disulfide bridge, subunit.

Nucleic Acids: Information Molecules (and Energy Conversions)

Nucleic acids store and transmit genetic information; some are involved in energy transfer.

• Nucleotides: Monomers of nucleic acids; consist of a sugar, phosphate group, and nitrogenous base.

• DNA vs. RNA: DNA stores genetic information; RNA involved in protein synthesis and gene regulation.

• Key Structures: Deoxyribose (DNA), ribose (RNA), phosphate backbone, bases (adenine, guanine, cytosine, thymine in DNA; uracil in RNA).

• DNA Structure: Double helix, complementary base pairing (A-T, G-C), antiparallel strands (5' to 3' and 3' to 5').

Chapter 4: Cells – The Fundamental Units of Life

Cell Structure and Function

All living organisms are composed of cells, which share certain structural features but can be classified as prokaryotic or eukaryotic.

• Common Features: Plasma membrane, DNA, ribosomes, cytosol.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have both.

• Cell Size: Limited by surface area-to-volume ratio; smaller cells are more efficient at exchanging materials.

Eukaryotic Cells: Genetic Instructions in the Nucleus

The nucleus is the control center of eukaryotic cells, containing genetic material and directing cellular activities.

• Nucleus: Double-membrane organelle with pores; contains DNA and protein (chromatin).

• RNA Types: mRNA (messenger), rRNA (ribosomal), tRNA (transfer); mRNA leaves nucleus for translation.

• Ribosomes: Sites of protein synthesis; can be free in cytosol or bound to endoplasmic reticulum (ER).

Endomembrane System and Vacuoles

The endomembrane system includes organelles involved in synthesis, modification, and transport of cellular materials.

• Components: Nuclear envelope, ER (rough and smooth), Golgi apparatus, lysosomes, vacuoles, plasma membrane.

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

• Protein Processing Pathway: Nucleus → Ribosomes → Rough ER → Golgi apparatus → Vesicles → Export.

Mitochondria and Chloroplasts: Cellular Generators

Mitochondria and chloroplasts are organelles responsible for energy conversion in eukaryotic cells.

• Mitochondria: Convert food energy into ATP via cellular respiration.

• Chloroplasts: Capture light energy to convert CO2 and water into sugars (photosynthesis).

• Endosymbiotic Theory: Proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Cytoskeleton: Extracellular Structures, Cell Movement, and Cell-to-Cell Interactions

The cytoskeleton provides structural support, enables movement, and facilitates cell communication.

• Cytoskeletal Elements: Microfilaments (actin), intermediate filaments, microtubules; each with specific functions.

• Extracellular Matrix (ECM): Network of proteins and carbohydrates outside animal cells; provides support and regulates cell behavior.

• Cell Junctions: Tight junctions (seal cells), anchoring junctions (desmosomes), gap junctions (communication in animals), plasmodesmata (communication in plants).