Cell Biology Ch. 12

all proteins are from

nuclear genes

movement of proteins and lipids between organelles

trafficking

parts of endomembrane system

ER, golgi, lysosomes/edosomes, nuclear envelope, cell membrane, peroxisomes

which of the following constitutes the ER?

a. continuous flattened sacs, tubules, and vesicles

b. separate sacs, tubules, and vesicles

c. single lipid bilayer and crystalloid core

d. porous membrane

a

functions as entry point for proteins going to endomembrane system

ER

the flattened sacs of the ER are called (__) and teh space inside is called (__)

cisternae / lumen

smooth vs. rough ER

rough has ribosomes on cytoplasmic surface

rough ER is associated with (__), which are involved in formation of (__) that shuttle lipids and proteins between ER and golgi

transitional elements / transition vesicles

specialized, ribosome-free regions of the rough endoplasmic reticulum where newly synthesized proteins and lipids are packaged into transport vesicles for delivery to the Golgi apparatus

transitional elements

t or f: rough and sooth ER are continuous with each other

t

ratio of rough to smooth ER depends on?

cells tat produce more (__) have more rough ER

job of cell / secretory proteins (hormone, digestive, liver cells)

production, processing, and trafficking site for proteins going to EMS organelles and membranes

rough ER

the biological process by which a polypeptide chain is completely synthesized on free ribosomes in the cytosol and then transported across a cellular membrane (such as the endoplasmic reticulum [ER]) after translation is finished

post-translational translocation

a cellular process where proteins are moved across or integrated into the membrane of the endoplasmic reticulum (ER) while they are still being synthesized by ribosomes

co-translational translocation

how are rough ER proteins translated? insert into (__) in RER membrane

cotranslationally / pore complex

a cellular stress-signaling pathway activated within the rough endoplasmic reticulum (RER) when unfolded or misfolded proteins accumulate faster than the organelle's folding machinery can process them

unfolded protein response

what mediates folding of proteins in rough ER

chaperons, unfolded protein response, multimeric protein assembly

rough ER mediates protein modifications, such as

initial steps of glycosylation and disulfide bond formation

smooth ER has (__) structure. cells that produce (__) will have more smooth ER

tubular / steroid hormones, lipids, cholesterol

processes and stores nonprotein molecules

smooth ER

how does smooth ER detoxify drugs?

hydroxylation (add OH group)

how does hydroxylation affect solubility? promotes? catalyzed by?

increases solubility / excretion / cytochrome P-450 (monooxygenases)

example of drug tolerance: (___). as you take more, you increase? so then (__) doses required to achieve effect. (__) involved can decrease effectiveness of other (__) referred to as (__) effect

phenobarbital / barbiturate-detoxifiying enzymes and SER / higher / enzymes / drugs / bystander

smooth ER uses (__) to release glucose because it does what?

glucose-6-phosphatase (G6P) / cleaves phosphate from G6P

G6P is formed from (__) by (__) enzyme

G1P / phosphoglucomutase

G6P is only found in (__) and prominent in (__) cells. promotes (__) from these cells because glucose is more (__) across membrane than G6P

ER / liver / release / soluble

what is stored in smooth ER?

calcium

specialized ER in muscle cells is (__). it releases (__) to initiate (__)

sarcoplasmic reticulum / calcium / muscle contraction

calcium released from ER due to (__) by a (__). pumped into ER/SR by (__)

signaling / second messenger / ATP-driven calcium pumps

steroids share? but differ in number and arrangement of

4 ring / carbon side chains and hydroxyl groups

what is synthesized in smooth ER

cholesterol and steroid hormones

rate limiting enzyme of cholesterol biosynthesis

hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase)

HMG-CoA reductase is found in (__) of (__) cells and targeted by cholesterol-lowering drugs called (__)

smooth ER / liver / statins

phosphatidylethanolamine made by

ER and mitochondria

cholesterol made by

smooth ER and peroxisomes

phospholipids are made and inserted into the (__) leaflet of ER membrane.

(__) mediate the transfer of a phospholipid from cytosolic to luminal leaflet

cytosolic / phospholipid translocators (flippases)

which glycerophospholipid is found in both cytosolic and luminal leaflets of ER?

phosphatidylcholine

phosphatidylethanolasmine, phosphatidylinositol, and phosphatidylserine found in which leaflet of ER? are there flippases for them?

cytosolic / no

transfer phospholipids from ER to other organelles like mitochondria and chloroplasts

phospholipid exchange proteins

is golgi continuous with ER? what does golgi do?

no / processes and packages glycoproteins and lipids from Er

golgi composed of sacs called (__) and a golgi stack is made of (__) of these. inside of sac called (__)

cisternae / 3-8 / lumen

bring glycoproteins and lipids from ER to golgi

transition vesicles

carry proteins and lipids from Golgi to endosomes/lysosomes and cell membrane

transport vesicles

polarized face of golgi oriented toward ER

cis face

polarized face of golgi oriented toward cell membrane

trans face

what are the 3 compartments of golgi apparatus

cis-golgi network (CGN), trans-golgi network (TGN), and medial cisternae

t or f: each compartment of golgi has its own set of enzymes for processing lipids and proteins

t

model that says cisternae are stable structures

stationary cisternae model

stationary cisternae model uses (__) for transport. it buds and fuse from (__) → (__) → (__)

shuttle vesicles / cis / medial / trans

model that says cisternae are dynamic structures and enzyme contents change as cisternae mature

cisternal maturation model

in cisternal maturation model, (__) shuttle enzymes to appropriate cisternae. early enzymes in (__) or (__) are shuttled back to (__) cisternae

vesicles / medial / TGN / earlier

t or f: cisternae changes, changing biochemical environment, then protein changes according to stationary cisternae model

f (cisternal maturation model)

golgi transport that moves ER → CGN → medial cisternae → TGN → lysosoome/endosome/cell membrane

anterograde transport

antibodies, hormones, and cell membrane lipids use what type of golgi transport

anterograde transport

golgi transport that moves TGN → medial cisternae → CGN

retrograde transport

3 parts of protein processing

protein folding, quality control, glycosylation

oligosaccharide attached to terminal amine of asparagine amino acids

N-linked glycosylation

oligossacharide attached to terminal OH on serine, threonine, or tyrosine amino acids

O-linked glycosylation

protein folding in the ER is an (__) and dynamic process where polypeptides undergo repeated cycles of (__) binding, release, and modification rather than folding in a single continuous step. Folding often starts while the polypeptide is still being (__) during (__)and meaning parts of the protein can fold or collapse locally before the full chain is even present

intermittent / chaperone / synthesized / cotranslational translocation

if hydrophobic regions are exposed, this could be due to incorrect (__) and leads to (__). why?

folded / aggregation / avoid contact with fluid

(__) transiently binds exposed hydrophobic regions and (__) aggregation to allow for correct folding

BiP / prevents

Unfolded polypeptide chains have a high degree of flexibility and (__) entropy. When a disulfide bond locks specific (__) pairs together, it restricts the movement, (__) its entropy and making the folded (native) state thermodynamically more (__)

high / cysteine / lowering / favorable

As secretory or transmembrane proteins are synthesized, (__) bonds often form (__) (before the full chain is even finished) to lock in domain-by-domain stability

disulfide / co-translationally

In the endoplasmic reticulum (ER), specialized enzymes called (__) catalyze oxidative folding.

protein disulfide isomerase

protein quality control that occurs when proteins aren’t folding correctly and shifts protein production to proteins that promote protein folding or degradation

unfolded protein response (UFR)

vital quality-control mechanism that targets misfolded proteins inside the endoplasmic reticulum

ER-associated degradation (ERAD)

ERAD transports proteins back to (__) of ER where they can be degraded by (__)

cytosol / proteasome

ERAD is utilized for (__) proteins, incomplete (__) structure, and proteins unable to acquire (__) conformation

mislocalized / quaternary / stable

ER-N-linked glycosylation:

ER: (__) is synthesized and transferred to recipient (__). (__) are removed

core oligosaccharide / protein / misfolded proteins

ER-N-linked glycosylation:

CGN: (__) attached and phosphorylation of (__) proteins

N-acetylgalactosamine (GalNac) / lysosomal

ER-N-linked glycosylation:

medial cisternae: (__) removed, (__) attached, also add (__) and (__)

mannose / N-acetylglucosamine (GlcNac) / galactose / sialic acid

ER-N-linked glycosylation:

TGN: attachment of (__) to (__)

sulfate / tyrosine

proteins receive same or different core oligosaccharides? containing?

same / 2 GlcNac, 9 mannose, 3 glucose

(N-linked glycosylation) core oligosaccharide is built on (__) which provides energy for transfer. This synthesis begins on (__) face of ER where is is (__) built. Then (__) transfers it to ER (___) where it is finished

dolichol phosphate / cytosolic / partially / flippase / lumen

(N-linked glycosylation) core oligosaccharide after being finished is transferred to (__) of (__) en masse and promotes proper folding. process called (__)

NH3 / asparagine / cotranslational glycosylation

(__) in the ER membrane acts as the carrier of oligosaccharide units for protein glycosylation

dolichol phosphate

transfer of completed core oligosaccharide to asparagine residue of recipient protein catalyzed by

oligosaccharyl transferase

adds/removes sugars to provide variability among glycosylation patterns and acts as further processing in the Golgi

terminal glycosylation

terminal glycosylation is mediated by what two enzymes?

glucan synthetases and glycosyl transferases

glucan synthetases synthesize (__) from (__) by adding (__) while glycosyl transferases attach (__) to (__)

oligosaccharides / monosaccharides / glucose / carbohydrates / proteins