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2 – Cell structure & organisation
a. Eukaryotes 10-100µm
Nucleus 10-20µm
coordinate cellular activities
DNA replication: codes for protein synthesis – transcription to form mRNA
Nucleolus: rRNA synthesis
assembles ribosomes
Nucleoplasm: contains chromatin – condenses to form chromosomes
Nuclear envelope: double-membrane – outer = continuous with RER
separates DNA from rest of cellular contents/activities – prevents damage
Nuclear pores: allow transport of mRNA / ribosome / nucleotides
Endoplasmic reticulum 30-50nm
Transportation system: network of cisternae (membranous sacs)
Rough: continuous with nuclear envelope
stack of flattened cisternae
ribosomes embedded in membranes
- protein synthesis & transport & packaging into vesicles – transport vesicle to Golgi body
Smooth: randomly dispersed in cytoplasm
more tubular cisternae
- lipid synthesis & transport
Golgi body 2.5µm
Stack of curved cisternae
Store & transport lipids
Modify & package proteins = enzymes / glycoproteins (+carbohydrate)
Synthesise vesicles & lysosomes
- transport vesicles fuse
- secretory vesicles pinch off + transport / fuse with cell membrane – exocytosis
, Mitochondria 1-10µm
Double membrane: inter-membrane space
Cylindrical – large SA:V: efficient respiration
Cristae: increase SA for ATP Synthetase – aerobic respiration to produce ATP
Matrix: 70S ribosomes & circular DNA & lipids & proteins
Ribosomes 30nm
Made of rRNA + protein
- small sub-unit: mRNA attachment site
- large sub-unit: 2 tRNA attachment sites
Free in cytoplasm / RER membrane
Protein synthesis – translation
Lysosome animal 0.5µm
membranous vesicle – contains lysozyme (hydrolytic enzymes)
pinch off Golgi body
fuse with vesicles containing what they’ll digest
- recycle worn-out organelles
- break down debris (from phagocytosis)
Vacuole carries out same function in plant
Centrioles animal 0.15x0.5µm
2 cylinders of microtubules at right angles in centrosome
organise microtubules that make spindle + guide chromosomes in cell division
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