Biology Revision Sheet

1. 📌 Essentials

• Biology: Study of life, interactions, and cellular structures.
• Characteristics of Life: Organization, metabolism, growth, reproduction, response.
• Cell Theory: All organisms are made of cells; cells arise from pre-existing cells.
• etic Material: DNA is the hereditary molecule, double helix structure.
• Metabolic Processes: Cellular respiration (energy release) and photosynthesis (energy capture).
• Levels of Organization: Cell → Tissue → Organ → Organ System → Organism.
• Taxonomy Hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Macromolecules: Proteins, carbohydrates, lipids, nucleic acids.
• Cell Membrane: Lipid bilayer with embedded proteins; controls substance entry/exit.
• Cell Division: Mitosis for growth/repair; meiosis for reproduction and genetic diversity.
• Genetic Code: Transcription (DNA to mRNA), translation (mRNA to protein).
• Enzymes: Catalysts lowering activation energy; specific to substrates.
• ATP: Main energy currency, produced in mitochondria.
• Water: Cohesion, surface tension, essential for biological reactions.
• Genetic Inheritance: Mendel’s laws, dominant/recessive, Punnett squares.
• Genetic Technologies: PCR, cloning, gene editing.

2. 🧩 Key Structures & Components

• Cell Membrane: Lipid bilayer with proteins and carbohydrates; barrier and communication.
• Nucleus: Contains genetic material, controls cell activities.
• Mitochondria: Powerhouse; site of ATP production via respiration.
• Chloroplasts: Photosynthesis in plant cells; convert light to chemical energy.
• Endoplasmic Reticulum: Protein and lipid synthesis.
• Golgi Apparatus: Modifies, sorts, and packages proteins.
• Vacuoles: Storage of nutrients, waste, water.
• Organelles in Plant vs. Animal Cells:
  • Plant: Chloroplasts, large central vacuole.
  • Animal: Centrioles, smaller vacuoles.

3. 🔬 Functions, Mechanisms & Relationships

• Cell membrane regulates substance flow; maintains homeostasis.
• Nucleus transcribes DNA into mRNA for protein synthesis.
• Mitochondria produce ATP through respiration (glycolysis, Krebs, ETC).
• Chloroplasts capture light energy, produce glucose (photosynthesis).
• Protein synthesis: Transcription in nucleus, translation at ribosomes.
• Enzymes facilitate metabolic reactions; specific to substrates.
• Energy flow: Photosynthesis → autotrophs; respiration → all organisms.
• Cell cycle regulation prevents uncontrolled division; cancer occurs if regulation fails.
• Genetic inheritance follows Mendel’s principles; alleles segregate independently.
• DNA replication involves unwinding, primer synthesis, and nucleotide addition.

4. Comparative Table: Mitosis vs. Meiosis

5. 🗂️ Hierarchical Diagram

Biological Organization
 ├─ Cell
 │    ├─ Nucleus
 │    ├─ Mitochondria
 │    ├─ Endoplasmic Reticulum
 │    └─ Cell Membrane
 ├─ Tissue
 │    └─ Epithelial, muscle, nerve, connective
 ├─ Organ
 │    └─ Heart, leaf, kidney
 └─ Organ System
      └─ Circulatory, respiratory, digestive

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing mitosis (growth) with meiosis (reproduction).
• Mistaking DNA structure: double helix with complementary base pairing.
• Overlooking water’s role in cohesion and biological reactions.
• Confusing autotrophs (self-feeders) with heterotrophs (consume others).
• Forgetting enzymes are specific and reusable.
• Misunderstanding energy flow: photosynthesis captures energy, respiration releases it.
• Confusing haploid (1 set) with diploid (2 sets) cells.
• Overgeneralizing cell cycle regulation; ignoring cancer causes.
• Mixing DNA replication enzymes: helicase (unzip), primase (primer), polymerase (nucleotides).

7. ✅ Final Exam Checklist

• Define biology and its core characteristics.
• Describe cell theory and levels of biological organization.
• Identify key organelles and their functions.
• Explain water’s role in biological systems.
• Outline macromolecules: structure and functions.
• Summarize cellular respiration and photosynthesis equations.
• Describe the cell cycle, mitosis, and meiosis.
• Understand DNA structure, replication, and protein synthesis.
• Apply Mendel’s laws to inheritance patterns.
• Recognize the purpose and methods of genetic technology.
• Differentiate between plant and animal cell organelles.
• Explain enzyme function and specificity.
• Describe energy flow in biological systems.
• Identify common pitfalls in understanding cell division and genetics.
• Prepare to interpret comparative tables and hierarchical diagrams.

End of Revision Sheet