The Synthesis and Transport of Proteins 1.2

Question 1

what do intracellular membranes eukaryotic cells have?

Answer 1

a system of internal membranes which increases the total area of membrane

Question 2

what is the Golgi apparatus?

Answer 2

a series of flattened discs

proteins from the ER are packaged and processed here

Question 3

what do vesicles do?

Answer 3

transport materials between membrane compartments

Question 4

what is the endoplasmic reticulum (ER)?

Answer 4

a network of membrane tubules continuous with the nuclear membrane

Question 5

where are lipids and proteins synthesised?

Answer 5

in the ER

lipids are synthesised in the smooth endoplasmic reticulum (SER) and inserted into its membrane

Question 6

where do the synthesis of all proteins begin?

Answer 6

in the cystolic ribosomes

Question 7

where is the synthesis of cystolic proteins completed?

Answer 7

in the cystolic ribosomes and then these proteins remain in the cytosol

Question 8

what do transmembrane proteins carry and what does it do

Answer 8

they carry a signal sequence, which halts translation and directs the ribosome synthesising the protein to dock with the ER - forms RER

Question 9

what is a signal sequence?

Answer 9

a short stretch of amino acids that tells the ribosome where its going

Question 10

what happens after the protein docks with the ER?

Answer 10

translation continues and the protein is inserted into the membrane of the ER

Question 11

what happens once the proteins are in the ER?

Answer 11

they are transported by vesicle that bud off from the ER and fuse with the Golgi apparatus

Question 12

describe the vesicles moving through the Golgi apparatus

Answer 12

molecules move through the Golgi discs in vesicles that bud off from one disc and fuse to the next one in the stack

Question 13

what happens as the proteins move through the Golgi apparatus?

Answer 13

proteins undergo post-translational modifications
-examples: addition of a carbohydrate

Question 14

what do vesicles move along and why?

Answer 14

they move along microtubules to other membranes and fuse with them within lysosomes

Question 15

give two examples of secreted proteins

Answer 15

peptide hormones and digestive enzymes

Question 16

what do secreted proteins do once they enter the lumen of the RER?

Answer 16

they move through the Golgi apparatus and are packaged into secretory vescicles

Question 17

what do secretory vesicles do once the proteins have been packaged into them?

Answer 17

they move to and fuse with the plasma membrane, releasing the proteins out of the cell

Question 18

what is proteolytic cleavage?

Answer 18

a form of post-translational modification

Question 19

why do many secreted proteins require proteolytic cleavage?

Answer 19

because they are synthesised as inactive precursors, so they need it to produce active proteins

Question 20

what are lysosomes?

Answer 20

membrane-bound organelles containing a variety of hydrolyses that digest:
-proteins
-lipids
-nucleic acids
-carbohydrates

Question 21

what happens as the proteins leave the Golgi apparatus?

Answer 21

the vesicles takes the proteins to the plasma membrane and lysosomes

Question 22

where are secreted proteins translated?

Answer 22

in ribosomes on the RER and enter its lumen - goes in ER basically