General Biology I: Core Concepts and Study Guide

Chapter 1: Foundations of Biology

Basic Introduction to the Organization of Life

The organization of life is hierarchical, ranging from atoms to the biosphere. Understanding this structure is essential for grasping biological complexity and the defining characteristics of living organisms.

• Hierarchical Organization: Life is organized into levels: atoms → molecules → organelles → cells → tissues → organs → organ systems → organisms → populations → communities → ecosystems → biosphere.

• Characteristics of Life: Living things share features such as cellular organization, metabolism, homeostasis, growth, reproduction, response to stimuli, and adaptation.

• Cells as Basic Units: All living organisms are composed of cells, which are the fundamental units of life.

• Structure vs. Function: Biological structures are adapted to their functions; energy flow refers to the movement of energy through living systems, while chemical cycling involves the transfer of matter.

• Emergent Properties: New properties arise at each level of organization due to the interactions of components.

Evolution Explains the Unity and Diversity of Life

Evolution accounts for both the similarities and differences among living organisms. It is the central unifying concept in biology.

• Biochemical Similarities: All living things share fundamental biochemical processes, such as DNA as genetic material and ATP as an energy currency.

• Domains and Kingdoms: Life is classified into three domains (Bacteria, Archaea, Eukarya) and four kingdoms within Eukarya (Protista, Fungi, Plantae, Animalia).

• Descent with Modification: Darwin's theory of evolution by natural selection explains how species change over time.

Science is a Way of Knowing

Science uses systematic methods to investigate natural phenomena and build knowledge.

• Scientific Method: Involves observation, hypothesis formation, experimentation, and analysis.

• Hypothesis vs. Theory: A hypothesis is a testable statement; a scientific theory is a well-substantiated explanation based on evidence.

Chapter 2: Chemistry of Life

The Nature of Atoms

Atoms are the basic units of matter, composed of protons, neutrons, and electrons. Their arrangement determines chemical properties.

• Element Composition: Defined by the number of protons (atomic number), neutrons, and electrons.

• Key Terms: Atomic number, mass number, atomic mass, ions, isotopes, molecular mass.

• Electron Distribution: Electrons occupy energy levels; valence electrons influence chemical reactivity.

Chemical Bonds, Molecular Shape, and Chemical Reactions

Chemical bonds hold atoms together, determining molecular structure and function. Chemical reactions involve the making and breaking of these bonds.

• Types of Bonds: Non-polar covalent, polar covalent, single/double covalent, ionic, hydrogen bonds.

• Collision Theory: Chemical reactions occur when reactants collide with sufficient energy.

• Key Definitions: Reactants, products, chemical equilibrium.

Chapter 2: Water, Acids, and Bases

Characteristics and Properties of Water

Water's unique properties arise from its polarity and ability to form hydrogen bonds, making it essential for life.

• Polarity and Electronegativity: Water is a polar molecule; oxygen is more electronegative than hydrogen.

• Hydrogen Bonds: Weak attractions between water molecules lead to cohesion, adhesion, surface tension, and high specific heat.

• Key Terms: Solubility, aqueous solution, hydrophilic, hydrophobic.

Acids and Bases

Acids and bases affect the pH of solutions, which is crucial for biological processes.

• Definitions: Acids donate H+ ions; bases accept H+ ions. Buffers stabilize pH.

• pH Scale: Measures hydrogen ion concentration; lower pH = higher [H+].

• Key Ions: Hydrogen ions (H+), hydroxide ions (OH-).

Chapter 3: Biological Macromolecules

Carbon: The Framework of Biological Macromolecules

Carbon's versatility allows it to form diverse macromolecules essential for life.

• Covalent Bonds: Carbon can form up to four covalent bonds.

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

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

• Macromolecules: Carbohydrates, proteins, lipids, nucleic acids; formed by polymerization (dehydration synthesis) and broken down by hydrolysis.

Carbohydrates: Energy Storage, Fuel, and Structural Molecules

Carbohydrates serve as energy sources and structural components in cells.

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

• Disaccharides and Polysaccharides: Sucrose, starch, glycogen, cellulose, chitin.

Lipids: Diverse Group of Hydrophobic Molecules

Lipids are hydrophobic molecules involved in energy storage, membrane structure, and signaling.

• Triglycerides: Composed of glycerol and three fatty acids; main energy storage molecules.

• Saturated vs. Unsaturated Fatty Acids: Saturated have no double bonds; unsaturated have one or more double bonds.

• Phospholipids: Form bilayers in membranes; other lipids include steroids and cholesterol.

Proteins: Molecules with Diverse Structures and Functions

Proteins are polymers of amino acids with varied structures and functions.

• Amino Acids: 20 types; classified as polar, non-polar, or charged.

• Protein Structure: Four levels: primary (sequence), secondary (α-helix, β-sheet), tertiary (3D folding), quaternary (multiple polypeptides).

• Structure-Function Relationship: Amino acid sequence determines protein shape and function (e.g., sickle-cell hemoglobin).

• Protein Functions: Enzymes, defense, transport, hormones, receptors, contractile, structural.

• Key Terms: Peptide bond, side chain, α-helix, β-pleated sheet, disulfide bridges, subunits.

Nucleic Acids: Information Molecules

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

• Nucleotides: Composed of a sugar, phosphate group, and nitrogenous base; form polynucleotides.

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

• Key Terms: Deoxyribose, ribose, phosphate, bases (adenine, guanine, cytosine, thymine, uracil), sugar-phosphate backbone, double helix, complementary base pairing, 5' and 3' ends, antiparallel structure.

Chapter 4: Cells - The Fundamental Units of Life

Cells: The Fundamental Units of Life

Cells are the basic units of life, sharing structural similarities but differing in complexity.

• Cell Structure: All cells have a plasma membrane, DNA, ribosomes, and 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 stores genetic material and coordinates cellular activities.

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

• RNA Types: mRNA, tRNA, rRNA; mRNA leaves the nucleus for translation.

• Ribosomes: Sites of protein synthesis; found in cytosol or attached to endoplasmic reticulum.

Vacuoles

Vacuoles are membrane-bound organelles involved in storage and transport.

• Endomembrane System: Includes organelles such as the ER, Golgi apparatus, and vesicles.

• Animal vs. Plant Cells: Some organelles are unique to plant cells (e.g., large central vacuole).

• Protein Processing: Pathways involve the nucleus, ribosomes, rough ER, and Golgi apparatus.

Mitochondria and Chloroplasts: Cellular Generators

Mitochondria and chloroplasts are organelles responsible for energy conversion.

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

• Chloroplasts: Capture light energy to synthesize carbohydrates (photosynthesis).

• Endosymbiotic Theory: These organelles likely originated from free-living prokaryotes.

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

The cytoskeleton provides structural support, enables movement, and mediates cell interactions.

• Cytoskeletal Elements: Microfilaments, intermediate filaments, microtubules.

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

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