b2.2 organelles and compartmentalisation

Question 1

What is an organelle?

Answer 1

A discrete structure within a cell adapted for a specific function.

Question 2

List solid organelles vs. membrane-bound organelles.

Answer 2

• Solid organelles: Ribosomes, centrosomes
• Single membrane organelles: Lysosomes, Golgi apparatus, endoplasmic reticulum
• Double membrane organelles: Nucleus, mitochondria, chloroplasts

Question 2

Why are the cell wall, cytoskeleton, and cytoplasm not organelles?

Answer 2

They lack membranes and do not function as discrete units within the cell.

Question 3

What are the benefits of DNA compartmentalisation in the nucleus?

Answer 3

• Protects genetic material from cytoplasmic interactions
• Regulates gene expression through controlled access
• Allows post-transcriptional modification before mRNA leaves

Question 4

Compare transcription & translation timing in prokaryotic vs. eukaryotic cells.

Answer 4

Transcription: (Prokaryotes - Cytoplasm, Eukaryotes - Nucleus).
Translation: (Prokaryotes - Immediately after transcription, Eukaryotes - After mRNA exits nucleus)

Question 4

Why can’t prokaryotic cells modify RNA post-transcription?

Answer 4

Transcription & translation occur simultaneously, preventing modifications like splicing.

Question 5

What is compartmentalization in cells?

Answer 5

The separation of cellular processes into different membrane-bound regions.

Question 6

What are the advantages of compartmentalization?

Answer 6

• Isolates reactions (prevents interference)
• Increases efficiency of cellular processes
• Maintains specialised environments (e.g., pH differences)
• Allows storage & processing of molecules

Question 7

How does compartmentalisation benefit lysosomes & phagocytic vacuoles?

Answer 7

• Lysosomes: Isolate digestive enzymes, preventing damage to the cell.
• Phagocytic vacuoles: Contain engulfed pathogens for safe breakdown.