Membrane bound organelles

Question 1

what did the nuclear genome of a eukaryotic cell evolve from

Answer 1

ancient archeaon

Question 2

evolution of mitochondria

Answer 2

anaerobic archea formed symbiotic relationship with bacteria and the bacteria evolved into mitochondria

Question 3

function of peroxisomes

Answer 3

fatty acid beta oxidation

Question 4

what is the endomembrane system

Answer 4

Topologically equivalent compartments in the secretory and endocytic pathways in a eukaryotic cell
molecules can get from one to the other without crossing a membrane via vesicles

Question 5

which organelles are in the endomembrane system

Answer 5

ER
plasma membrane
lysosome
nuclear envelope
golgi body
endosomes
vesicles
they are separate from the cytoplasm
equivalent to external environment

Question 6

role of translocons in ER membrane

Answer 6

protein conducting channels
as a protein is being synthesised, it gets pushed into the lumen of the ER via these channels

Question 7

which side of the ER membrane does protein synthesis occur

Answer 7

cytoplasmic

Question 8

what is N-glycosylation

Answer 8

attachment of an oligosaccharide to specific asparagine amino acids in the polypeptide that are part of: Asn-X-Ser, or Asn-X-Thr where X can be any amino acid except proline

Question 9

where is the oligosaccharide anchored

Answer 9

covalently linked to dolichol lipid anchor in ER membrane

Question 10

how is the oligosaccharide transferred to the protein

Answer 10

catalysed by oligosaccaryl transferase
transfers it as a single unit

Question 11

which proteins does N-glycosylation occur to

Answer 11

ones that go into ER lumen (not cytosilic proteins)

Question 12

glucose trimming

Answer 12

glucose residues in oligosaccharide added trimmed by glucosidases, preparing the protein for folding

Question 13

what happens to incompletely folded proteins

Answer 13

undergoes cycle of glucose addition and removal
glucosyl transferase adds glucose back to the oligosaccharide to mark it for another round of folding attempts

Question 14

calnexin binding

Answer 14

chaperone protein
helps protein fold correctly by stabilising the intermediate states of the folding process

Question 15

glucosidase action

Answer 15

removes glucose after aid by calnexin
signal for protein to be checked again for proper folding
misfolded or missambled proteins do not leave the ER

Question 16

why do few disulfide bridges form in the cytoplasm but many form in the ER lumen

Answer 16

cytoplasm is a reducing environment
lumen of ER is an oxidising environment
protein disulfide isomerases

Question 17

organisation of the golgi apparatus

Answer 17

divided into multiple cisternae that contain different enzymes that carry out sequential modifications of proteins as they move through

Question 18

constitutive secretion

Answer 18

no signal needed
continuous process

Question 19

regulated secretion

Answer 19

storage of secretory vesicles within the cell until an external signal triggers their release

Question 20

O linked glycosylation

Answer 20

addition of sugars onto the oxygen of hydroxyl groups of serine and threonine residues in proteins. occurs in golgi apparatus

Question 21

A blood group antigen

Answer 21

enzyme adds N-acetylgalactosamine

Question 22

B blood group antigen

Answer 22

enzyme adds galactose