CH5-E.R Flashcards
This network is contineous with E.R membrane
Cisternae
This is the internal compartment of the ER
ER lumen
Contain ribosome
R.ER
What synthesizes protein
Ribosomes (many ribosomes make a polysome)
Two population of ribosomes in cytosol
Membrane bound ( cytosolic side of the RER - synth of prot co-translational Free ribosome- synth prot from nucl.genome
What protein insures folding
chaperones
Post-translational process is done for protein import in the:
mitochondria, chloroplast, peroxisomes
those need chaperones
Co-translational
Not released into cytosol so doesn’t need chaperones
Ribosome sub-units
Large and Small, 18nm
Smooth ER fxn
Lipid synthesis & Detox & Take away Ca2+ from cytosol
Muscle Smooth ER
sarcoplasmic reticulum
How does muscle contract
Uses the Sacro-pl.retic
release and re-uptake of Ca, trigger contraction and relaxation
What are two types of protein imported into the ER + what do they all need
Transmembrane proteins = partly transolcated / partly embedded
Water soluble - fully translocated +released into ER lumen
ALL need an ER Signal sequence
what is the ER signal sequence made of
Hydrophobic a.a resideus , a +’ve residue at Amino end and a polar sequence at carobyxl end.
What is needed to direct the ER signal sequence
a signal recognition particle (SRP) to bind
what are the SRP bound to
SRP-R (integral membr protein complex in the RER)
What ways does protein modification happen in the ER
Glyocosylation
or
GPi anchor
How is glyosylation done
Oligosacc transfer to amino-NH3 grp on ASN-chain
Which give rise to a N-link oligosacch.
What does the O-link oligosacch differ from the N-link
O-link uses a Hydroxy-OH-grp on side chain of ser/threo/OH-Lysine,
Where as N-link uses NH3 on ASN-chain
What is the name of the precursor to oligosaccharide
Dolichol
What enzyme is needed for Dolichol
oligosaccheride-transferase
What are the chaperones of the ER for Glyocosylation
Calnexi and calreticulin
What is the function of proteosomes
they degrade misfolded proteins using retrotranslocation
How is retro-transolocation done to misfolded proteins?
Need a transolcator complex to recognize misfolded proteins , and exported , and then the proteosomes de-glycosylate them
what type of membrane protein is the GPi-anchor
peripheral membran protein
What is ceramide converted to
sphingomyelin
where does the active site face
cytosol
where does lipid synthesis occur
cytosol
What lipid are derived from di-acylglerol
phosphotadyl- ser / choline / ethanolamine
What lipids are derived from sphingosine base
sphingo-myelin and sine
How is di-acylglycerol made
phosphatidic acid –> diacylglycerol using phosphatadase
What enzyme transfer lipid molecules from cytosol side to lumen to keep it equal
scramblase
what enzyme flips phospholipids for asymetry
flipase
Where are new lipid molecules only added to
Cytosol of the ER bilayer
