Cell Biology Revision Sheet

1. 📌 Essentials

• All living organisms are composed of cells, the fundamental units of life.
• Cells are classified into prokaryotic (no nucleus) and eukaryotic (nucleus present).
• The nucleus contains genetic material and controls cellular activities.
• Organelles like mitochondria produce energy;osomes synthesize proteins.
• The cell membrane is a phospholipid bilayer regulating substance exchange- Cell walls provide structural support; composition varies (cellulose, chitin, peptidoglycan).
• Cytoskeleton maintains cell shape and facilitates intracellular transport.
• Prokaryotic DNA is in the cytoplasm; eukaryotic DNA is in the nucleus.
• Lysosomes degrade waste; vacuoles store nutrients and maintain turgor in plants.
• Chloroplasts perform photosynthesis in plant cells.

2. 🧩 Key Structures & Components

• Nucleus — contains DNA, nuclear pores regulate transport, nucleolus synthesizes rRNA.
• Ribosomes — synthesize proteins, either free in cytoplasm or attached to ER.
• Rough Endoplasmic Reticulum (Rough ER) — synthesizes and folds proteins destined for secretion or membrane.
• Smooth Endoplasmic Reticulum (Smooth ER) — lipid synthesis, calcium storage, detoxification.
• Golgi Apparatus — modifies, sorts, and ships proteins and lipids.
• Mitochondria — produce ATP via cellular respiration, double membrane with cristae.
• Chloroplasts — perform photosynthesis, contain thylakoids (grana) and stroma.
• Cytoskeleton — microtubules, actin filaments, intermediate filaments; shape and transport.
• Cell Wall — provides support; cellulose (plants), chitin (fungi), peptidoglycan (bacteria).
• Vacuoles — storage and turgor in plants; small in animals.
• Cilia & Flagella — microtubule-based structures for movement.

3. 🔬 Functions, Mechanisms & Relationships

• Genetic Material Flow: DNA in nucleus → transcribed to mRNA → translated by ribosomes.
• Protein Processing: Ribosomes → Rough ER → Golgi → vesicles → destination.
• Energy Production: Mitochondria convert glucose into ATP; chloroplasts convert light into chemical energy.
• Structural Support: Cytoskeleton maintains shape, enables movement, and organelle positioning.
• Membrane Function: Phospholipid bilayer with embedded proteins controls permeability.
• Waste Management: Lysosomes hydrolyze waste; vacuoles store excess materials.
• Transport Pathways: ER and Golgi form a system for protein/lipid trafficking.
• Movement: Cilia/flagella use microtubules for motility.

4. 🧪 Comparative Table

5. 🗂️ Hierarchical Diagram

Cell
 ├─ Nucleus
 │    ├─ Nuclear envelope
 │    ├─ Nuclear pores
 │    └─ Nucleolus
 ├─ Cytoplasm
 │    ├─ Cytosol
 │    ├─ Organelles
 │    │    ├─ Mitochondria
 │    │    ├─ Chloroplasts
 │    │    ├─ ER (rough & smooth)
 │    │    ├─ Golgi apparatus
 │    │    ├─ Lysosomes
 │    │    └─ Vacuoles
 │    └─ Cytoskeleton
 ├─ Cell membrane
 └─ Cell wall (plants, fungi, bacteria)

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing prokaryotic and eukaryotic cell features.
• Overlooking the role of the smooth ER in lipid metabolism.
• Mistaking the nucleus for the entire cell's control center.
• Forgetting that mitochondria have their own DNA.
• Confusing lysosomes with peroxisomes.
• Assuming all cells have a cell wall.
• Misidentifying cilia and flagella structures.
• Overgeneralizing organelle functions across cell types.

7. ✅ Final Exam Checklist

• Understand the core principles of cell theory.
• Differentiate between prokaryotic and eukaryotic cells.
• Identify key organelles and their functions.
• Know the structure and function of the nucleus, ribosomes, ER, Golgi, mitochondria, chloroplasts.
• Describe the composition and role of the cell membrane.
• Recognize the components of the cytoskeleton.
• Explain the purpose of cell wall types.
• Understand the pathways of protein synthesis and transport.
• Know the differences between plant and animal cell organelles.
• Be aware of common pitfalls and misconceptions.
• Memorize the hierarchy and relationships of cell components.
• Be able to draw and interpret ASCII diagrams of cell organization.
• Review the key features of cell energy production and photosynthesis.
• Recognize the structural basis of cell motility (cilia/flagella).

End of Revision Sheet