General Biology: Core Concepts and Learning Objectives

Introduction to Science and the Properties of Living Things

The Scientific Method and Hypotheses

The scientific method is a systematic approach used to investigate natural phenomena, acquire new knowledge, or correct and integrate previous knowledge. It involves making observations, forming hypotheses, conducting experiments, and drawing conclusions.

• Scientific Method: A process involving observation, hypothesis formation, experimentation, and analysis.

• Hypothesis: A testable statement or prediction that can be supported or refuted through experimentation.

• Distinguishing between Theories and Hypotheses: A hypothesis is a specific, testable prediction, while a theory is a well-substantiated explanation of some aspect of the natural world.

• Control and Replication: Controls are used to ensure that experimental results are due to the variable being tested. Replication increases reliability.

• Properties of Living Things: Living organisms share characteristics such as organization, metabolism, growth, adaptation, response to stimuli, and reproduction.

• Historical Views: The understanding of life’s properties has evolved, from vitalism to modern cell theory and molecular biology.

Evolution

Biological Evolution and Natural Selection

Evolution is the process by which populations of organisms change over generations. Natural selection is a key mechanism of evolution, where individuals with advantageous traits are more likely to survive and reproduce.

• Biological Evolution: The change in genetic composition of populations over time.

• Darwin’s Mechanism: Natural selection acts on variation within populations, leading to adaptation.

• Evidence for Evolution: Includes fossil records, comparative anatomy, molecular biology, and biogeography.

• Speciation: The formation of new and distinct species in the course of evolution.

• Homologous and Analogous Structures: Homologous structures have a common evolutionary origin; analogous structures serve similar functions but have different origins.

Basic Chemistry

Atoms, Chemical Bonds, and Water

Understanding the chemical basis of life is essential in biology. Atoms combine to form molecules through chemical bonds, and water’s unique properties are vital for life.

• Atoms: The smallest units of matter, composed of protons, neutrons, and electrons.

• Chemical Bonds: Include ionic, covalent, and hydrogen bonds. Covalent bonds involve sharing electrons; ionic bonds involve transfer of electrons.

• Water’s Properties: Water is polar, has high specific heat, and is an excellent solvent, making it essential for biological processes.

• pH and Buffers: pH measures hydrogen ion concentration; buffers help maintain stable pH in organisms.

Biological Macromolecules

Structure and Function of Biomolecules

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

• Carbohydrates: Serve as energy sources and structural components (e.g., glucose, starch, cellulose).

• Lipids: Include fats, oils, and phospholipids; important for energy storage and membrane structure.

• Proteins: Made of amino acids; function as enzymes, structural components, and signaling molecules.

• Nucleic Acids: DNA and RNA store and transmit genetic information.

• Protein Structure: Four levels—primary, secondary, tertiary, and quaternary. Denaturation disrupts protein structure and function.

Cell Structure

Prokaryotic and Eukaryotic Cells

Cells are the basic units of life. Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus and membrane-bound organelles.

• Prokaryotes vs. Eukaryotes: Prokaryotes (e.g., bacteria) are simpler; eukaryotes (e.g., plants, animals) are more complex.

• Cell Organelles: Nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and others perform specialized functions.

• Endomembrane System: A network of membranes involved in transport and processing of cellular materials.

• Cell Walls: Found in plants, fungi, and some protists; provide structure and protection.

Cell Membranes and Transport

The cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell.

• Fluid Mosaic Model: Describes the structure of the cell membrane as a mosaic of proteins floating in a fluid lipid bilayer.

• Membrane Proteins: Integral and peripheral proteins serve as channels, receptors, and enzymes.

• Transport Mechanisms: Include simple diffusion, facilitated diffusion, osmosis, and active transport.

• Osmosis: The movement of water across a semipermeable membrane from low to high solute concentration.

• Isotonic, Hypotonic, Hypertonic Solutions: Affect cell volume and water movement.

Respiration

Cellular Respiration and Energy Production

Cellular respiration is the process by which cells extract energy from organic molecules, primarily glucose, to produce ATP.

• ATP: The main energy currency of the cell; produced through substrate-level and oxidative phosphorylation.

• Enzymes: Biological catalysts that speed up chemical reactions; can be regulated by inhibitors and activators.

• Glycolysis: The breakdown of glucose into pyruvate, producing ATP and NADH.

• Fermentation: An anaerobic process that allows glycolysis to continue in the absence of oxygen.

• Pyruvate Oxidation and Citric Acid Cycle: Further oxidize pyruvate to produce NADH, FADH2, and ATP.

• Electron Transport Chain: Uses electrons from NADH and FADH2 to create a proton gradient for ATP synthesis.

• Aerobic vs. Anaerobic Respiration: Aerobic uses oxygen; anaerobic does not.

Key Equations

• Cellular Respiration Overall Equation:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy (ATP)}$

• ATP Hydrolysis:

$ATP + H_2O \rightarrow ADP + P_i + \text{energy}$

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Cell Size	Generally smaller (0.1–5 μm)	Generally larger (10–100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Additional info: These study notes expand on the learning objectives provided in the syllabus, offering definitions, examples, and context for each major topic in a General Biology course.