KA2: Proteins: The synthesis and transport of proteins Flashcards
(26 cards)
What do eukaryotic cells have?
what do they do?
*system of internal membranes
*increases the total area of membrane
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?
due to their size
the plasma membrane is too small an area
Describe the structure of the endoplasmic reticulum
forms a network of membrane tubules continuous with the nuclear membrane
Describe the structure of The Golgi Apparatus
a series of flattened membrane discs
Describe the structure of lysosomes
membrane bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates
Describe the role of vesicles
transport materials between membrane compartments
Where are lipids and proteins synthesised?
ER
where does the synthesis of all proteins begin?
in cytosolic ribosomes
Describe the difference between the rough er (RER) and smooth er (SER)
Rough ER=> has ribosomes on its cytosolic face
Smooth ER=> lacks ribosomes
Give the location where lipids are produced
the SER and inserted into its membrane
Give the location where cytosolic proteins are produced
completed in the SER, and remain in the cytosol
Describe the location of transmembrane protein production
- Transmembrane proteins carry a signal sequence
- halts translation and directs the ribosome synthesising the protein to dock with the ER
- forming RER
what is a signal sequence?
what does it determine?
a short stretch of amino acids at one end of the polypeptide chain
the eventual location of a protein in a cell
translation continues after __________, and the protein is _________ into the __________ of the ___ .
*docking
*inserted
*membrane
*ER
What happens to the proteins when they are in the ER?
-transported by vesicles that bud off from the ER
-fuse with the Golgi apparatus
What happens to proteins as they move through the golgi apparatus?
they undergo post translational modification
explain how molecules move through the golgi discs
*in vesicles that bud off from one disc and fuse with the next one in the stack
describe the actions of enzymes in the Golgi
what is the major modification?
*catalyse the addition of various sugars in multiple steps to form carbohydrates
the addition of carbohydrate groups is the major modification
What do the vesicles that leave the golgi apparatus do?
take proteins to the plasma membrane and lysosomes
What do vesicles move along and what do they do?
They move along microtubules to other membranes and fuse with them within the cell
Give the location of translation of proteins which are secreted from the cell
The RER and enter its lumen
Give examples of a secreted protein that require proteolytic cleavage to become active
Digestive enzymes and peptide hormones
Describe the secretory pathway
-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
what are many secreted proteins synthesised as?
inactive precursors and require proteolytic cleavage to produce active proteins
