Revision sheet: Cell Biology Essentials

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

Item	Key Features	Notes / Differences
Prokaryotic Cell	No nucleus, circular DNA, plasmids, small size (~2 µm)	Bacteria; simpler structure
Eukaryotic Cell	Nucleus, membrane-bound organelles, larger (~10-30 µm)	Animal and plant cells
Plant Cell	Cell wall, chloroplasts, large vacuole	Photosynthesis, support
Animal Cell	No cell wall, no chloroplasts, small vacuole	Motility, diverse functions
Mitochondria	Energy production via respiration	Present in all eukaryotic cells
Ribosomes	Protein synthesis	Free in cytoplasm or attached to ER

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