Scientific Principles in Biology: Revision Sheet

1. 📌 Essentials

• The scientific method involves observation, hypothesis, experimentation, analysis, and conclusion.
• SI units: meter (m), kilogram (kg), second (s), mole (mol).
• Atomic structure: protons and neutrons nucleus; electrons orbit.
• Atomic number = number of protons; defines element.
• Isotopes differ in neutron count; used in medical imaging.
• Ionic: transfer electrons; form between metals and nonmetals.
• Covalent bonds: share electrons; can be polar or nonpolar.
• Hydrogen bonds: weak attractions stabilizing DNA and proteins.
• Water's high specific heat (4.18 J/g°C) buffers temperature.
• pH scale: 0-14, acids <7, neutral =7, bases >7.
• Buffers: maintain pH stability (e.g., bicarbonate buffer).
• Organic molecules: carbs, lipids, proteins, nucleic acids.
• Force = mass × acceleration; work = force × distance.
• Energy forms: kinetic, potential, chemical.
• Thermodynamics: energy conservation and entropy increase.

2. 🧩 Key Structures & Components

• Protons / Neutrons — form atomic nucleus; determine atomic number and mass.
• Electrons — orbit nucleus; involved in bonding.
• Ionic Bonds — transfer of electrons creating charged ions.
• Covalent Bonds — sharing of electrons; polar or nonpolar.
• Hydrogen Bonds — attraction between polar molecules, stabilizing structures.
• Water Molecules — cohesive, adhesive, high specific heat.
• pH Buffer Systems — e.g., bicarbonate buffer in blood.
• Carbohydrates — monosaccharides (glucose), polysaccharides (starch).
• Lipids — fats, phospholipids, steroids; hydrophobic.
• Proteins — amino acids linked by peptide bonds.
• Nucleic Acids — DNA, RNA; composed of nucleotides.

3. 🔬 Functions, Mechanisms & Relationships

• Atomic structure determines chemical reactivity and bonding.
• Ionic bonds form between metals and nonmetals, creating stable compounds.
• Covalent bonds allow complex molecules; polarity influences solubility.
• Hydrogen bonds stabilize DNA double helix and protein secondary structures.
• Water’s properties facilitate temperature regulation and biochemical reactions.
• pH and buffers maintain cellular and systemic homeostasis.
• Organic molecules serve as energy sources, structural components, and genetic material.
• Force causes movement; work involves force applied over distance.
• Energy transformations underpin biological processes.
• Thermodynamic laws govern energy flow and entropy increase in systems.

4. Comparative Table: Types of Chemical Bonds

5. 🗂️ Hierarchical Diagram (ASCII)

Atomic and Molecular Structure
 ├─ Atomic Nucleus
 │    ├─ Protons
 │    └─ Neutrons
 ├─ Electron Cloud
 │    ├─ Electron Orbitals
 │    └─ Electron Sharing / Transfer
 ├─ Chemical Bonds
 │    ├─ Ionic
 │    ├─ Covalent
 │    └─ Hydrogen
 └─ Water and Organic Molecules
      ├─ Water Properties
      ├─ Carbohydrates
      ├─ Lipids
      ├─ Proteins
      └─ Nucleic Acids

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing atomic number with atomic mass.
• Mistaking ionic bonds for covalent bonds.
• Overlooking the polarity of covalent bonds.
• Assuming hydrogen bonds are strong covalent bonds.
• Misinterpreting pH scale; pH 7 is neutral, not slightly acidic/basic.
• Confusing monomers (e.g., glucose) with polymers (e.g., glycogen).
• Forgetting water’s high specific heat buffers temperature.
• Assuming all lipids are fats; include steroids and phospholipids.
• Overgeneralizing protein functions; structure determines function.
• Ignoring the role of buffers in pH regulation.

7. ✅ Final Exam Checklist

• Understand the scientific method and experimental design.
• Know SI units and conversion factors.
• Describe atomic structure and isotope applications.
• Differentiate ionic, covalent, and hydrogen bonds.
• Explain water’s properties and their biological significance.
• Define pH, buffers, and their roles in homeostasis.
• Identify major organic molecules and their functions.
• Apply physics principles: force, work, energy in biological contexts.
• Recognize thermodynamic laws and their biological implications.
• Understand molecular stability and interactions in cells.
• Be able to interpret diagrams of molecular structures and bonds.
• Know the hierarchy from atoms to complex biological systems.
• Recognize common pitfalls in understanding chemical bonding and water properties.
• Be prepared to explain how structure relates to function in biological molecules.

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