Membrane bound organelles
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what did the nuclear genome of a eukaryotic cell evolve from
ancient archeaon
evolution of mitochondria
anaerobic archea formed symbiotic relationship with bacteria and the bacteria evolved into mitochondria
function of peroxisomes
fatty acid beta oxidation
what is the endomembrane system
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
which organelles are in the endomembrane system
ER plasma membrane lysosome nuclear envelope golgi body endosomes vesicles they are separate from the cytoplasm equivalent to external environment
role of translocons in ER membrane
protein conducting channels as a protein is being synthesised, it gets pushed into the lumen of the ER via these channels
which side of the ER membrane does protein synthesis occur
cytoplasmic
what is N-glycosylation
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
where is the oligosaccharide anchored
covalently linked to dolichol lipid anchor in ER membrane
how is the oligosaccharide transferred to the protein
catalysed by oligosaccaryl transferase transfers it as a single unit
which proteins does N-glycosylation occur to
ones that go into ER lumen (not cytosilic proteins)
glucose trimming
glucose residues in oligosaccharide added trimmed by glucosidases, preparing the protein for folding
what happens to incompletely folded proteins
undergoes cycle of glucose addition and removal glucosyl transferase adds glucose back to the oligosaccharide to mark it for another round of folding attempts
calnexin binding
chaperone protein helps protein fold correctly by stabilising the intermediate states of the folding process
glucosidase action
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
why do few disulfide bridges form in the cytoplasm but many form in the ER lumen
cytoplasm is a reducing environment lumen of ER is an oxidising environment protein disulfide isomerases
organisation of the golgi apparatus
divided into multiple cisternae that contain different enzymes that carry out sequential modifications of proteins as they move through
constitutive secretion
no signal needed continuous process
regulated secretion
storage of secretory vesicles within the cell until an external signal triggers their release
O linked glycosylation
addition of sugars onto the oxygen of hydroxyl groups of serine and threonine residues in proteins. occurs in golgi apparatus
A blood group antigen
enzyme adds N-acetylgalactosamine
B blood group antigen
enzyme adds galactose