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CHAPTER 2 : Basic components of living systems
Eukaryotic cell structure
Relative sizes of molecules, organelles and cells

Cells
-The two fundamental types of cell
Prokaryotic
Eukaryotic
-Prokaryotes are single-celled organisms with a simple structure of just a single
undivided internal area - cytoplasm
-Eukaryotic cells make up multicellular organisms, eg
...
There’s two types:
Smooth endoplasmic reticulum - responsible for lipid and carbohydrate
ssssssssssssssssssssssssssssssssssssynthesis, and storage
Rough endoplasmic reticulum - has ribosomes bound to the surface and is
rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr responsible for the synthesis and transport of
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa proteins
-Secretory cells, release hormones or enzymes, have more rough endoplasmic
reticulum than cells that don’t release proteins
Ribosomes
-Can be free-floating in the cytoplasm or attached to endoplasmic reticulum, forming
rough endoplasmic reticulum
-Not surrounded by a membrane
-Constructed of RNA molecules made in cells nucleolus
-Site of protein synthesis
-Mitochondria and chloroplasts contain ribosomes, as do prokaryotic cells

Golgi apparatus
-Similar in structure to smooth endoplasmic reticulum
-Compact structure formed of cisternae, does not contain ribosomes
-Role in modifying proteins and ‘packaging’ them into vesicles
-May be secretory vesicles, if proteins are destined to leave the cell
Or
-May be lysosomes, which stay in the cell
Protein production
-Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum (1)

-Pass into its cisternae and are packaged into transport vesicles (2)
-Vesicles containing newly synthesized proteins move towards the golgi apparatus
via cytoskeletons transport function (3)
-Vesicles fuse with cis face of the golgi apparatus and proteins enter
-Proteins are structurally modified before leaving the golgi apparatus in vesicles from
its trans face (4)
-Secretory vesicles carry proteins that are to be released from the cell
-Vesicles move towards and fuse with the cell-surface membrane, releasing their
contents by exocytosis
-Some vesicles form lysosomes - containing enzymes for use in the cell (5)



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