Golgi, Vesicles Transport + Lysosomes Flashcards
Which chaperone monitors protein folding prior to export from ER to Golgi?
What is the signature this chaperone recognises?
What happens to this MIS-folded protein - what and where?
Calnexin
Single glucose!
Degradation! In Cytosol / cytoplasm
What coat protein causes vesicles destined for Golgi to BUD from ER?
COPII
What are the flattened compartments of Golgi called?
Name the 3 compartments in order
Cisternae!
Cis, medial, trans (cisternae)
What fate awaits a protein containing KDEL sequence when it reaches Golgi?
Retrieval to the endoplasmic reticulum!
Vesicles which RETURN proteins to ER FROM the Golgi are coated in… The return of proteins to ER is known as…
COPI
RETROGRADE Transport
The KDEL receptor binds to cargo in the… conditions of the…. to transport it to the…
Once there, conditions are … and the cargo released!
The empty KDEL receptor is then recycled to the … where it collects another cargo protein!
Acidic / Golgi Apparatus
Endoplasmic Reticulum / neutral!
Golgi Apparatus
Name 2 modifications that can occur to proteins within the Golgi.
- Phosphorylation of oligosaccharides
2. Sulphation of Tyrosines
Match the type of glycosylation to the amino acid.
Alanine, Threonine, Hydroxylysine, Serine, Asparagine, Glycine.
Alanine - NOT glycosylated
Threonine - O linked
Hydroxylysine - O linked
Serine - O linked
Asparagine - N linked
Glycine - NOT glycosylated
Proteins which pass through ER and Golgi are glycosylated.
What are the roles of glycosylation?
Marker for folding
Transport marker
Cell surface marker
Protection!
What is 3 legged structure of Clathrin known as?
Clathrin subunits form basket weave structure. Where would membrane be found?
Triskelion
Inside!
Name of protein that links Clathrin to cargo receptor?
Name of protein that pinches off FULLY formed vesicles?
What occurs immediately after vesicles has been RELEASED?
Transmembranous
Dynamin
Uncoating!
In vesicular transport what are the surface markers on the RECIPIENT compartment called?
T- snares
In vesicular transport what are the surface markers on transport vesicles called?
V- snares!
In vesicular transport, what is the stage BEFORE 2 membranes fuse?
Docking
What is the name of the complex formed between a t and v-SNARE?
Trans-SNARE- complex
In vesicular transport what provides energy to bring vesicles and recipient membranes close together?
(Excluding water and promoting membrane fusion)
Winding of the v and t snare
True or false:
An INCREASE in pH as the secretory vesicles mature contributes to the concentrating of proteins with it?
FALSE
Give an example of type of protein which is modified by Proteolytic Cleavage within the secretory vesicles.
Peptide hormone / hydrolytic enzyme
What is the process where membrane components can be RETRIEVED from plasma membrane following Exocytosis?
Endocytosis
** RECEPTOR MEDIATED ENDOCYTOSIS*
Cholesterol is taken up by mammalian cells particularly hepatocytes of the liver. It is transported in the blood complexed as…
… on the cell surface bind to LDLs and guide them into pits where an … links the receptor to…
A vesicles is formed and transported to the… where the … is released from receptor - can be recycled back to plasma membrane!
Low density lipoprotein (LDL) LDL- Receptor Adaptin Clathrin Early endosome LDL
What is the main function of lysosomes?
Intracellular Digestion
What is the generic name for type of enzyme found in Lysosomes?
Acid Hydrolases
A bacterium has been phagocytosed and needs to be digested in lysosome. Name the 2 classes of enzyme that contribute to its degradation.
Proteases
Nucleases
pH inside of lysosome?
What maintains it?
What provides energy for this process?
5
H+ pump
ATP
How does the cell protect itself from its OWN lysosomal hydrolases?
They only function at LOW pH (as in lysosome)
By keeping them WITHIN a membrane
What are the 3 routes that substrates for intracellular digestion take to the lysosome?
Autophagy
Phagocytosis
Endocytosis
What organelles would a lysosomal hydrolase pass through?
The rough ER
Late endosomes
The Golgi
The smooth ER
What marker is recognised by the receptors which target acid hydrolases into vesicles which will transport them to the lysosome?
Mannose-6-phosphate
On reaching the Late Endosome, what causes M6P on Lysosomal protein to dissociate from its receptor?
The environment is more…
Acidic!!!
What is glycosylation?
What does N-linked glycosylation mean?
Addition of a 14-sugar oligosaccharide
It is attached to the NH2 group of the amino acid
A protein shows N-linked glycosylation.
Where in the cell does this protein come from?
What is the relevance of this modification?
The ER (or possibly the Golgi where it is further processed)
It is used to identify whether a protein is folded properly!
If a protein had O-linked glycosylation where would it be found?
What is the relevance of the O-
In the Golgi!
It is added to the carboxylic acid end of the amino acid through the oxygen
The pH of the lumen of the Golgi apparatus changes as the compartments mature. How does it change?
What is the function of this?
It becomes more ACIDIC (reduces)
Changes in pH change the charges of the amino acids in the protein - this causes a shape change!
This then enables the CARGO to dissociate from its receptor in the membrane.
When the vesicles leave their donor compartment they are covered in a ‘coat protein.’ What are the different coat proteins and when are they used?
What is their function?
COPI - Golgi to ER
Clathrin - Golgi to plasma membrane or lysosome
COPII - ER to Golgi
They bend the membrane to enable ‘budding’ to occur from the donor compartment!
When a vesicle ‘buds’ from a compartment which protein is responsible for completing the release of the vesicle?
Dynamin cuts it off like a string around a piece of playdoh!
Why are coat proteins LOST after their release from the donor compartments?
So that the molecules in the membrane beneath (such as snares) can enable FUSION between membranes.
This also allows recycling of the coat proteins!
What keeps cargo safely in the vesicle?
Transmembrane receptors
Why is there concentration of secretory proteins as the vesicles?
Due to:
Retrieval of the membrane back to the Golgi
Increased acidity in the maturing vesicle lumen, causing tighter aggregation!
Why are there 3 uses of the Regulated Secretory Pathway?
Allows concentration and further processing of secretory proteins.
Also enables release in response to a trigger!
Which of the following modifications do NOT occur in the Golgi?
N- linked glycosylation
What label tells the cell to deliver Acid Hydrolases from the Golgi to the lysosome?
Mannose-6-phosphate
What is an example of constitutive exocytosis?
Release of the glycoproteins of the extracellular matrix
To which amino acid are sugars attached during N-linked glycosylation?
Asparagine!
What is the pH of the lumen of the lysosome?
5
What peroxisomal enzyme causes the breakdown of hydrogen peroxide (H202) into water and oxygen?
Catalase
What coat protein mediates the BUDDING of vesicles during Endocytosis?
Clathrin!
Which of the following organelles would a lysosomal hydrolase NOT pass through?
Early endosomes
Steroid hormone secreting cells have the following characteristics…
Well developed SMOOTH ER and Golgi and an abundance of mitochondria and free lipid
During N-linked glycosylation sugars are added to the amino acid …
A 14 sugar oligosaccharide is preassembled on a special lipid molecule called… and is transferred to the elongating peptide by the enzyme … which is attached to the … side of the ER membrane.
Asparagine
Phosphodolichol / dolichol
Transferase
Luminal / lumen
