KA2: Proteins: The synthesis and transport of proteins

Question 1

What do eukaryotic cells have?

what do they do?

Answer 1

*system of internal membranes
*increases the total area of membrane

Question 2

why do eukaryotes have a relatively small surface area to volume ratio?

so why can plasma membrane of eukaryotic cells not carry out all the vital functions carried out by membranes?

Answer 2

due to their size

the plasma membrane is too small an area

Question 3

Describe the structure of the endoplasmic reticulum

Answer 3

forms a network of membrane tubules continuous with the nuclear membrane

Question 4

Describe the structure of The Golgi Apparatus

Answer 4

a series of flattened membrane discs

Question 5

Describe the structure of lysosomes

Answer 5

membrane bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates

Question 6

Describe the role of vesicles

Answer 6

transport materials between membrane compartments

Question 7

Where are lipids and proteins synthesised?

Answer 7

ER

Question 8

where does the synthesis of all proteins begin?

Answer 8

in cytosolic ribosomes

Question 9

Describe the difference between the rough er (RER) and smooth er (SER)

Answer 9

Rough ER=> has ribosomes on its cytosolic face

Smooth ER=> lacks ribosomes

Question 10

Give the location where lipids are produced

Answer 10

the SER and inserted into its membrane

Question 11

Give the location where cytosolic proteins are produced

Answer 11

completed in the SER, and remain in the cytosol

Question 12

Describe the location of transmembrane protein production

Answer 12

• Transmembrane proteins carry a signal sequence
• halts translation and directs the ribosome synthesising the protein to dock with the ER
• forming RER

Question 13

what is a signal sequence?

what does it determine?

Answer 13

a short stretch of amino acids at one end of the polypeptide chain

the eventual location of a protein in a cell

Question 14

translation continues after __________, and the protein is _________ into the __________ of the ___ .

Answer 14

*docking
*inserted
*membrane
*ER

Question 15

What happens to the proteins when they are in the ER?

Answer 15

-transported by vesicles that bud off from the ER

-fuse with the Golgi apparatus

Question 16

What happens to proteins as they move through the golgi apparatus?

Answer 16

they undergo post translational modification

Question 17

explain how molecules move through the golgi discs

Answer 17

*in vesicles that bud off from one disc and fuse with the next one in the stack

Question 18

describe the actions of enzymes in the Golgi

what is the major modification?

Answer 18

*catalyse the addition of various sugars in multiple steps to form carbohydrates

the addition of carbohydrate groups is the major modification

Question 19

What do the vesicles that leave the golgi apparatus do?

Answer 19

take proteins to the plasma membrane and lysosomes

Question 20

What do vesicles move along and what do they do?

Answer 20

They move along microtubules to other membranes and fuse with them within the cell

Question 21

Give the location of translation of proteins which are secreted from the cell

Answer 21

The RER and enter its lumen

Question 22

Give examples of a secreted protein that require proteolytic cleavage to become active

Answer 22

Digestive enzymes and peptide hormones

Question 23

Describe the secretory pathway

Answer 23

-proteins move through the gorgi apparatus and are packaged into secretory vesicles

-vesicles move to andf use with the plasma membrane releasing proteins out of the cell

Question 24

what are many secreted proteins synthesised as?

Answer 24

inactive precursors and require proteolytic cleavage to produce active proteins

Question 25

what is proteolytic clevage?

give an example of secreted proteins that require proteolytic cleavage to become active

Answer 25

another type of post-translational modification

digestive enzymes

Question 26

What does binding cause?

Answer 26

conformational change in the protein, which may result in a ltered function and may be reversible