Role Of The Endoplasmic Reticulum And Golgi Apparatus

Question 1

How can a protein be modified

Answer 1

By adding carbohydrates to it to form a glycoprotein, these modifications can be critically important for protein function

Question 2

Four destinations of proteins and examples

Answer 2

Cytoplasm
Organelles (eg digestive enzymes transported to lysosomes)
Cell membrane (receptor proteins)
Secreted from cell (eg hormones or antibodies)

Question 3

Describe shape of ribosome and function

Answer 3

Made up of one large and one small subunit with each subunit containing a number of different proteins and ribosomal RNA
-where translation occurs in protein synthesis

Question 4

Role of rough endoplasmic reticulum

Answer 4

Where protein synthesis takes place for proteins that are then transported to organelles, cell membrane or secreted from cell

Question 5

Structure of rough endoplasmic reticulum

Answer 5

-consists of sheets of membranes forming flattened sacs called cisternae
-cisternae contain a range of different enzymes and the membranes of cisternae are covered with ribosomes which are where translation takes place for proteins

Question 6

Explain process of how a protein is synthesised in rough endoplasmic reticulum

Answer 6

-mRNA binds to ribosome on the surface of rough endoplasmic reticulum and growing polypeptide chain passes through membrane and into the lumen of rough endoplasmic reticulum
-polypeptide chain then folds into its tertiary structure in the lumen and makes it way through the lumen where modifications can be made to it eg carbohydrates can be added to form a glycoprotein
-then packaged into vesicles to go to the Golgi apparatus

Question 7

Describe structure of Golgi apparatus

Answer 7

-made up of cisternae (sheets of flattened discs) and surrounded by vesicles

Question 8

Describe role of Golgi apparatus

Answer 8

-vesicles from rough endoplasmic reticulum bind to Golgi apparatus cisternae and as polypeptide chain makes it way through Golgi apparatus it can be modified further eg additional carbohydrates can be added
-at some point the polypeptide will have reached its final structure and now called a functional protein to be packaged into vesicles which can fuse with cell membrane for protein to be secreted from cell/form part of the structure of cell membrane/ enter vesicles which go on to form lysosomes

Question 9

What does the final destination of a protein depend on

Answer 9

Depends on the amino acid sequence and how the protein is modified in the rough ER and Golgi apparatus

Question 10

Which cells will have a lot of rough ER

Answer 10

Cells that secrete large amounts of protein

Question 11

Role of smooth ER and how they differ from rough

Answer 11

Not covered with ribosomes
Job is to make and store lipids and carbohydrates which can then pass through Golgi apparatus where they can be modified and transported to final destination