2.b.ii - Synthesis of Membrane Components

Question 1

where are lipids and proteins synthesised?

Answer 1

in the endoplasmic reticulum

Question 2

state the two types of endoplasmic reticulum

Answer 2

smooth endoplasmic reticulum (SER), and rough endoplasmic reticulum (SER)

Question 3

describe the difference between Rough ER and Smooth ER

Answer 3

RER has ribosomes on its cytosolic face whereas SER lacks ribosomes

Question 4

describe the synthesis of lipids

Answer 4

lipids are synthesised in SER and inserted into its membrane

Question 5

describe the synthesis of proteins from the cytosol to the ER

Answer 5

the synthesis of all proteins begins in cytosolic ribosomes. the synthesis of cytosolic protiens is completed there, and these proteins remain in the cytosol. transmembrane proteins carry a signal sequence, which halts translation and directs the ribosome synthesizing the protein to dock with the endoplasmic reticulum, forming RER. translation continues after docking and the protein is inserted into the membrane of the ER

Question 6

what is a signal sequence

Answer 6

a signal sequence is a short stretch of amino acids at one end of the polypeptide that determines the eventual location of a protein in a cell