CB1 Cells & Cell Compartments

Question 1

Compare the structure & organisation of Pro-& eukaryotic cells

Answer 1

Prokaryotic cells: smaller than eukaryotic cells, cell wall, ribosomes, circular DNA (plasmids), no internal membranes or organelles

Eukaryotic cells: larger than prokaryotic cells, cytoskeleton, ribosomes, vesicles, linear DNA (chromosomes), endoplasmic reticulum, Golgi apparatus lysosome, mitochondria

Question 2

Explain the principle of selective toxicity of antibiotics

Answer 2

Antibiotics are poisons that act on prokaryote cells selectively over eukaryotes
- penicillin inhibits peptidoglycan synthesis
- streptomycin, chloramphenicol, and tetracyclines inhibit bacterial ribosomes and block protein synthesis

Question 3

Describe the compartmentalisation of the eukaryotic cell as a segregation of function

Answer 3

Different proteins act in distinct cellular compartments, to help organelles & alls to function within their own boundary

Question 4

Outline the structure & function of the nucleus

Answer 4

• Diameter 5-10 microns, largest organelle
• bounded by a double membrane
• carries most genomic info. (~20,000 genes)
• site of RNA synthesis (transcription) and splicing
• chromaton structure
• the nucleolus is the site of ribosome synthesis
- heterochromatin (densely stained, DNA packed together, low transcriptional activity)
- euchromatin (light staining, DNA spread out, high transcriptional activity)

Question 5

Outline the structure & function of the mitochondrion

Answer 5

• 0.5-2 microns in length
• abundant in metabolically active cells (muscle, brown adipose tissue)
• double membrane - inner (folded) & outer (smooth)

Question 6

Outline the structure & function of the rough endoplasmic reticulum

Answer 6

• Studded with ribosomes
• mRNA encoded with signal sequence → ribosome will bud with ER
• continuous with nuclear outer membrane
• protein synthesis

Question 7

Outline the structure & function of the Golgi apparatus

Answer 7

• Peripheral (not continuous with nucleus)
• new proteins/ lipids from Er are packaged & carried in transport vesicles
• ‘cis’ Golgi = arrival of vesicles, protein phosphorylation
• ‘Medial’ Golgi = addition of sugar residues
• ‘trans’ Golgi = proteolysis, sorting of lipid & protein, vesicle release

Question 8

Outline the structure & function of transport vesicles & secretory vesicles

Answer 8

Transport vesicles = Er → Golgi apparatus
Secretary vesicles = Golgi apparatus → plasma membrane

Regulated = will not fuse with plasma membrane until it receives a signal
Constitutive = will go straight to plasma membrane

Question 9

Outline the structure & function of the smooth ER

Answer 9

• Tubular structure
• synthesis & processing of lipids (hydrophobic molecules)

Question 10

Outline the structure & function of lysosomes

Answer 10

• Protein are broken down by lysosome
• not prominent in cell
• contains hydrolase enzymes
• pH is 5
• receptor-mediated endocytosis, macroautophagy, phagocytosis, pinocytosis

Question 11

Evaluate the selective advantages of eukaryotic organisation

Answer 11

• Special environments (e.g. Hydrophobic, acidic)
• concentrated environments
• high membrane surface area