Organization: Hierarchy from atoms → molecules → organelles → cells → tissues → organs → organisms → populations → communities → ecosystems → biosphere.
Information Flow: DNA as the genetic material; gene expression process.
Energy & Matter: Energy flow (one-way) vs. matter cycling in ecosystems.
Interactions: Feedback mechanisms regulate biological processes.
Evolution: Natural selection drives adaptation and diversity.
Inductive reasoning: Specific observations → general principles.
Deductive reasoning: General principles → specific predictions.
Hypothesis-based science: Must be testable and falsifiable.
Elements & Compounds: 96% of life’s matter = C, H, O, N.
Atomic Structure: Protons (+), Neutrons (0), Electrons (-).
Chemical Bonds:
Covalent Bonds (strongest; share electrons).
Ionic Bonds (transfer electrons).
Hydrogen Bonds (weak but crucial in biology).
Chemical Reactions: Matter is rearranged, not created/destroyed.
Cohesion & Adhesion – Water molecules stick together and to surfaces (e.g., plant transport).
High Specific Heat – Stabilizes temperature.
Expansion Upon Freezing – Ice is less dense than liquid water.
Versatile Solvent – Dissolves many substances due to polarity.
pH <7 = Acidic, >7 = Basic, 7 = Neutral.
Buffers help maintain homeostasis (e.g., carbonic acid in blood).
Carbon's Versatility: Forms 4 covalent bonds, allowing complex molecules.
Organic Molecules: Backbone of life’s molecules.
Isomers: Molecules with same formula but different structures:
Structural: Different connectivity.
Cis-trans: Differ in spatial arrangement.
Enantiomers: Mirror images.
Functional Groups (e.g., Hydroxyl, Carbonyl, Carboxyl, Amino, Phosphate).
Carbohydrates – Monosaccharides, disaccharides, polysaccharides (e.g., starch, glycogen, cellulose).
Lipids – Hydrophobic, includes fats, phospholipids, steroids.
Proteins – Made of amino acids, function depends on shape (4 levels of structure).
Nucleic Acids – DNA/RNA, store and transmit genetic info.
Fluid Mosaic Model: Membranes = phospholipid bilayer + proteins.
Transport Across Membranes:
Passive Transport (no energy): Diffusion, Osmosis, Facilitated Diffusion.
Active Transport (requires ATP): Moves against concentration gradient.
Bulk Transport: Endocytosis (into cell), Exocytosis (out of cell).