The Synthesis and Transport of Proteins 1.2 Flashcards
what do intracellular membranes eukaryotic cells have?
a system of internal membranes which increases the total area of membrane
what is the Golgi apparatus?
a series of flattened discs
proteins from the ER are packaged and processed here
what do vesicles do?
transport materials between membrane compartments
what is the endoplasmic reticulum (ER)?
a network of membrane tubules continuous with the nuclear membrane
where are lipids and proteins synthesised?
in the ER
lipids are synthesised in the smooth endoplasmic reticulum (SER) and inserted into its membrane
where do the synthesis of all proteins begin?
in the cystolic ribosomes
where is the synthesis of cystolic proteins completed?
in the cystolic ribosomes and then these proteins remain in the cytosol
what do transmembrane proteins carry and what does it do
they carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the ER - forms RER
what is a signal sequence?
a short stretch of amino acids that tells the ribosome where its going
what happens after the protein docks with the ER?
translation continues and the protein is inserted into the membrane of the ER
what happens once the proteins are in the ER?
they are transported by vesicle that bud off from the ER and fuse with the Golgi apparatus
describe the vesicles moving through the Golgi apparatus
molecules move through the Golgi discs in vesicles that bud off from one disc and fuse to the next one in the stack
what happens as the proteins move through the Golgi apparatus?
proteins undergo post-translational modifications
-examples: addition of a carbohydrate
what do vesicles move along and why?
they move along microtubules to other membranes and fuse with them within lysosomes
give two examples of secreted proteins
peptide hormones and digestive enzymes
what do secreted proteins do once they enter the lumen of the RER?
they move through the Golgi apparatus and are packaged into secretory vescicles
what do secretory vesicles do once the proteins have been packaged into them?
they move to and fuse with the plasma membrane, releasing the proteins out of the cell
what is proteolytic cleavage?
a form of post-translational modification
why do many secreted proteins require proteolytic cleavage?
because they are synthesised as inactive precursors, so they need it to produce active proteins
what are lysosomes?
membrane-bound organelles containing a variety of hydrolyses that digest:
-proteins
-lipids
-nucleic acids
-carbohydrates
what happens as the proteins leave the Golgi apparatus?
the vesicles takes the proteins to the plasma membrane and lysosomes
where are secreted proteins translated?
in ribosomes on the RER and enter its lumen - goes in ER basically
