cell structure and function

Question 1

endomembrane system

Answer 1

-protein synthesised by rough ER-bound ribosomes enters the lumen of the rough ER.
-transport vesicles containing protein bud off from cisternae of the rough ER and move to the cis face of the Golgi body.
-Membrane of transport vesicles will fuse with the membrane of the cisternae at cis face of Golgi body.
-Protein is emptied into the cisternal space for further modification, sorting and packaging into secretory vesicle

Question 2

structure of rough endoplasmic reticulum

Answer 2

consists of network of sheets ( flattened cisternae)
ribosomes are present on the membrane of the rough ER
ER membrane is continuous with the outer membrane of the nuclear envelope

Question 3

function of the rough ER

Answer 3

-site of protein synthesis: synthesised as polypeptides by ribosomes
- intracellular transport system: transport proteins synthesized by the ribosomes on its surface to golgi body to transport vesicles budding off
- modification of proteins:

Question 4

structure of smooth endoplasmic reticulum

Answer 4

consist of networks of tubules
ribosomes are absent

Question 5

function of smooth endoplasmic reticulum

Answer 5

-synthesis of lipids
-involved in carbohydrate metabolism
-detoxification of drugs and poisons

Question 6

advantages to cells having separate compartments

Answer 6

-membranes surrounding organelles enable separate compartments to be formed inside the cell ; allowing specialised metabolic pathways to take place
-hydrolytic enzymes in lysosomes require lower pH from the rest of the cell to function optimally
-different reactions could take place ; as reactants and enzymes of a metabolic pathway could be kept together

Question 7

processes that occur in Golgi body

Answer 7

-products of smooth and rough endoplasmic reticulum are further modified, sorted and packaged in the Golgi body
- chemical modification of proteins include phosphorylation or glycosylation
- phosphorylation activates the protein while glycosylation targets the protein for association with the membranes

Question 8

roles of hydrolytic enzymes in lysosomes

Answer 8

autophagy- to digest/destroy/breakdown parts of the cell such as damaged worn out organelles
intracellular digestion -to destroy bacteria which the cell took place