Lernzettel: Fundamentals of Cell Structure and Function

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

Item	Key Features	Notes / Differences
Prokaryotic Cells	No nucleus, no membrane-bound organelles, peptidoglycan wall	Bacteria, archaea
Eukaryotic Cells	Nucleus, membrane-bound organelles, mitosis	Animals, plants, fungi
DNA Location	Cytoplasm (prokaryotes); nucleus (eukaryotes)	Genetic material storage
Cell Wall Composition	Plants: cellulose; fungi: chitin; bacteria: peptidoglycan	Structural support
Ribosomes	Free or ER-bound, site of protein synthesis	Larger in eukaryotes (80S), smaller (70S) in prokaryotes
Mitochondria	ATP production, double membrane, cristae	Powerhouse of the cell
Chloroplasts	Photosynthesis, grana, stroma	Only in photosynthetic organisms

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