BackGeneral Biology: Core Concepts and Processes Study Guide
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Nature of Science
Characteristics of Scientific Knowledge
Scientific knowledge is based on empirical evidence, observation, and experimentation.
It is tentative (subject to change with new evidence) and self-correcting.
Role of Models, Theories, and Laws
Models are simplified representations of complex biological processes (e.g., the cell membrane model).
Theories are well-substantiated explanations (e.g., cell theory, theory of evolution).
Laws describe consistent natural phenomena (e.g., Mendel’s laws of inheritance).
Experimental Design Considerations
Variables: Independent (manipulated), dependent (measured), and controlled (kept constant).
Controls: Standard for comparison to validate results.
Sources of Error: Random and systematic errors can affect data reliability.
Interpretation of Data and Trends
Analyzing patterns, correlations, and anomalies in experimental results.
Correlation vs. Causation
Correlation indicates a relationship between variables, but does not imply one causes the other.
Causation means one variable directly affects another.
How Evidence Supports or Refines Scientific Understanding
New evidence can confirm, refute, or modify existing scientific ideas.
Chemistry of Life
Water Properties and Biological Consequences
Cohesion and adhesion enable water transport in plants.
High specific heat stabilizes temperature in organisms and environments.
Solvent properties allow biochemical reactions in aqueous solutions.
Role of Hydrogen Bonds in Biological Systems
Hydrogen bonds stabilize DNA structure and protein folding.
They contribute to water’s unique properties.
Carbon’s Bonding Capacity and Molecular Diversity
Carbon forms four covalent bonds, allowing for diverse organic molecules (chains, rings, branches).
Functional Groups and Their Effects on Molecules
Common functional groups: hydroxyl, carboxyl, amino, phosphate, methyl.
They determine molecular reactivity and interactions.
Macromolecule Structure-Function Relationships
Proteins, nucleic acids, carbohydrates, and lipids have specific structures that determine their biological roles.
Enzyme Action
Active site: Region where substrate binds and reaction occurs.
Induced fit: Enzyme changes shape to accommodate substrate.
Factors affecting enzyme activity: Temperature, pH, substrate concentration, inhibitors.
Levels of Biological Organization
Hierarchical Organization
Levels: Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biosphere.
Emergent Properties
New properties arise at each level due to interactions among components (e.g., consciousness in the brain).
Feedback Mechanisms
Negative feedback: Maintains homeostasis (e.g., body temperature regulation).
Positive feedback: Amplifies responses (e.g., blood clotting).
Systems Thinking in Biology
Understanding how components interact within and across levels (e.g., gene regulation affecting organism traits).
Examples Connecting Multiple Levels
Photosynthesis: Molecular (chlorophyll) to ecosystem (carbon cycling).
Microscopy and Cell Observation
Resolution Limits of Light Microscopy
Light microscopes resolve structures down to ~200 nm; electron microscopes provide higher resolution.
Components of Microscopy
Light microscopy: Uses visible light to observe cells and tissues.
Electron microscopy: Uses electron beams for higher magnification and resolution (TEM vs. SEM).
Importance of Scale and Magnification
Understanding cell and organelle sizes is crucial for interpreting biological function.
Why Microscopy Shaped Cell Theory
Microscopy enabled discovery of cells, leading to the development of cell theory.
Interpretation of Micrographs
Analyzing images to identify structures and understand cellular organization.
Cellular Respiration & Energy Transfer
Redox Reactions and Electron Carriers
Cellular respiration involves oxidation-reduction (redox) reactions transferring electrons via carriers like NADH and FADH2.
ATP Synthesis via Substrate-Level and Oxidative Phosphorylation
Substrate-level phosphorylation: Direct transfer of phosphate to ADP during glycolysis and Krebs cycle.
Oxidative phosphorylation: ATP produced using energy from electron transport chain and chemiosmosis.
Chemiosmosis and Proton Gradients
Proton gradients across membranes drive ATP synthesis via ATP synthase.
Mitochondrial Structure-Function Relationships
Inner membrane folds (cristae) increase surface area for electron transport and ATP production.
Comparison of Aerobic vs. Anaerobic Pathways
Aerobic respiration: Uses oxygen, yields more ATP.
Anaerobic respiration/fermentation: Occurs without oxygen, yields less ATP.
Energy Efficiency and Heat Loss
Not all energy from glucose is converted to ATP; some is lost as heat.
Key Equations
Overall cellular respiration:
ATP synthesis (oxidative phosphorylation):
IB-Level Expectations
Use labeled process diagrams to illustrate concepts.
Show connections between topics (e.g., how chemistry underpins cellular processes).
Include cause-and-effect relationships in explanations.
Emphasize understanding of why processes occur, not just what happens.
