Cell Biology Revision Sheet

1. 📌 Essentials

• Cells are the basic units of life prokaryotic (bacteria) and eukaryotic (animal, plant).
• Eukaryotic cells contain a nucleus, mitochond, ribosomes; plant cells have additional cell wall and vacuole.
• Bacterial cells lack a nucleus, have circular DNA, and plasmids.
• Microscopes: light microscopes for general observation, electron microscopes for detailed internal structures.
• Diffusion moves particles from high to low concentration; osmosis is water diffusion across a membrane.
• Active transport moves substances against concentration gradient, requiring energy.
• Cell cycle involves growth, DNA replication, mitosis, producing identical daughter cells.
• Stem cells can differentiate into various cell types; embryonic stem cells are pluripotent.
• Exchange surfaces (alveoli, villi, gills) are adapted for efficient gas and nutrient exchange.
• Surface area to volume ratio influences cell efficiency; smaller cells have higher ratios.

2. 🧩 Key Structures & Components

• Nucleus — controls cell activities, contains genetic material (DNA).
• Cytoplasm — site of chemical reactions, contains enzymes.
• Mitochondria — site of aerobic respiration, energy production.
• Ribosomes — synthesize proteins.
• Cell membrane — controls entry/exit of substances, semi-permeable.
• Cell wall — provides support; cellulose in plants.
• Vacuole — stores cell sap, maintains turgor.
• Chloroplasts — carry out photosynthesis in plant cells.
• Bacterial cell components — circular DNA, plasmids, flagella.

3. 🔬 Functions, Mechanisms & Relationships

• Cell structures work together to maintain cell function and integrity.
• Nucleus directs cell activities; cytoplasm hosts metabolic reactions.
• Mitochondria supply energy for active processes like transport and division.
• Ribosomes produce proteins needed for growth and repair.
• Cell membrane regulates substance exchange, working with exchange surfaces.
• Diffusion and osmosis occur across cell membranes, driven by concentration gradients.
• Active transport enables uptake of nutrients against gradients, especially in roots and intestines.
• Cell cycle ensures growth and replication; mitosis produces genetically identical cells.
• Stem cells can differentiate, enabling tissue growth and repair.

4. 📊 Comparative Table

5. 🗂️ Hierarchical Diagram (ASCII)

Cell
 ├─ Nucleus
 │    ├─ Contains DNA
 │    └─ Controls cell activities
 ├─ Cytoplasm
 │    ├─ Site of chemical reactions
 │    └─ Contains enzymes
 ├─ Mitochondria
 │    └─ Energy production
 ├─ Ribosomes
 │    └─ Protein synthesis
 ├─ Cell membrane
 │    └─ Regulates substance entry/exit
 ├─ Cell wall (plants/bungi)
 │    └─ Structural support
 └─ Vacuole (plants)
      └─ Stores cell sap

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing prokaryotic and eukaryotic cell structures.
• Assuming all cells have chloroplasts or a cell wall.
• Overlooking the role of the cell membrane in active transport.
• Misunderstanding the difference between diffusion and osmosis.
• Forgetting that mitochondria are present in all eukaryotic cells.
• Confusing the stages of mitosis or the purpose of the cell cycle.
• Assuming stem cells can differentiate into any cell type in adults.
• Overestimating the size of bacteria; they are typically around 2 µm.

7. ✅ Final Exam Checklist

• Know the differences between prokaryotic and eukaryotic cells.
• Be familiar with key cell structures and their functions.
• Understand how microscopes work and the magnification formula.
• Explain diffusion, osmosis, and active transport mechanisms.
• Describe the cell cycle and mitosis stages.
• Recognize the role and types of stem cells.
• Understand adaptations of exchange surfaces (alveoli, villi, gills).
• Know the importance of surface area to volume ratio.
• Be able to interpret simple ASCII diagrams of cell hierarchy.
• Recognize common misconceptions and pitfalls.
• Recall the key features of plant and animal cells.
• Understand the significance of mitochondria and ribosomes.
• Be aware of the structural differences in bacterial cells.
• Know the applications of stem cells in medicine and agriculture.

End of Revision Sheet