Chapter 8

Biology 329 with Hoyle at University of Louisville

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By: Laura Valladao
Created: 2012-03-13
Size: 72 flashcards
Views: 14

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endomembrane system

extensive network of membrane bound organelles in the cytoplams

What is included in the Endomembrane System?

two major shuttling pathways

1. secretory/biosynthetic

2. endocytic

endocytic pathway

pathways bring materials in from:

-extracellular space

-plasma membrane ( bound to receptor)

secretory/ biosynthetic pathway

pathways move proteins synthesized at rough ER through Golgi to final destination of :

- extracellular space

-plasma membrane ( integral membrane proteins)

-lysosomes

endosome

organelle formed by endocytosis

how are proteins directed to their proper destination?

targeting signals/sorting proteins

sequences of amino acids in the proteins themselves or oligosaccharides attached to proteins.

where are the targeting/sorting signals recognized?

by the internal receptors in the membrane of the transport vesicle

where are sorting signals encoded

in the amino acids

Name three techniques for visualizing proteins

Radioactive labeling
GFP fusion proteins
Antibodies to Proteins

when cells are homogenized (to break up) , membrane fragments of the endomembrane system form smaller vesicles called

microsomes (not an organelle)

How do PURIFIED microsomes differ from "regular" microsomes?

They maintain some biological activity & thus provide a cell free system for experiments.
Can further purify proteins of ER or Golgi for identification, antibody production

Rough ER

ribosomes attached on cytosolic surface

cisternae

flattened, membrane-bound compartments that make up the Golgi apparatus

Smooth ER

lacks ribosomes, channels are tubular

functions of the SER

synthesis of steroid hormones in endocrine cells of adrenal cortex and gonads
detoxification in the liver of various organic compounds, convert them to more hydrophillic derivatives
sequestration of calcium ion into cytoplasm of muscle cells

liver cells are loaded with?

Smooth ER

Ca2+ is higher inside when in ?

Smooth ER

regulated release of Ca2+ ions from Smooth ER triggers

1. skeletal and cardiac muscle cell contraction

2. fusion of secretory granules with the plasma membrane

Rough ER functions

1. site of synthesis for proteins that are secreted, integral membrane proteins, proteins localized to endomembrane organelles

2. site of synthesis form membrane phospholipids

nascent proteins

ones that are being synthesized

cotranslationally

while being translated

Rough ER secretory cells are

endomembrane structures that are highly polarized, reflecting the flow of secretory products from synthesis at RER to discharge at the duct

where does translation of all mRNA's into proteins start

on free ribosomes in the cytoplasm

signal sequence =

6-15 hydrophobic amino acids at N-terminus

In signal sequence Function what does the Signal Recognition Particle (SRP) bind to?

signal sequence and ribosome

what does the SRP in the signal sequence Function serve as

a tag that enables the entire complex to bind specifically to cytosolic surface of the ER membrane

In signal sequence Function what does the SRP bind to on the RER

SRP receptor and docks the ribosome at RER

SRP

signal recognition particle

SRP and SRP receptor are

G proteins

In signal sequence Function what does the docked ribosome bind to, and then what happens (step 3)

translocon, and the SRP is released. Signal sequence is passed into translocon displacing the plug.

translocon

protein lined channel in the RER membrane

In signal sequence Function what happens in step 4 after signal sequence is passed into translocon

the growing polypeptide is cotranslationally inserted into RER lumen

Process of newly synthesized protein in the RER after the signal sequence function. (step 1) how is the signal peptide removed on the N-terminus?

signal peptidase

Process of newly synthesized protein in the RER after the signal sequence function.(step 2) how are carbohydrates added

oligosaccharyltransferase

both signal peptidase and oligosaccaryltransferase are what

integral membrane proteins located close to the translocon. Both act on Nascent proteins as they enter the ER lumen

Process of newly synthesized protein in the RER after the signal sequence function.(step 3) proper folding of protein is assisted by?

molecular chaperones ex. BIP

Process of newly synthesized protein in the RER after the signal sequence function.(step 4) Formation of disulfide bonds are by

protein disulfide isomerase: cysteine sylfhydrls(-SH) are oxidized to disulfide bonds (-S-S)

what do disulfide bonds do?

help maintain stability

when is the passage of integral membrane proteins halted

if a hydrophobic transmembrane segment is made

which terminus is always onthe extracellular side

the positive side (cytosolic side)

when carbohydrates are added to an -NH2 of asparagine this equals what and where does it start

N-linked oligosaccharide. Starts in RER

when carbohydrates are added to an -OH of ser or Threoinine this equals what and where does it start

O-linked oligosaccharide. it is done in the golgi.

VTC

vesicular tubular clusters

Vesicular tubular clusters (VTCs) are

transport vesicles from RER (w/o ribosome) and fuse to form larger vesicles and interconnected tubules

region between ER and golgi complex is called

ERGIC

Endoplasmic reticulum golgi intermediate compartment

vesticular transport model

different cisternae remain a place as stable compartments. cargo proteins are shuttled through in vesicles that bud from one compartment and fuse w/ next one, going from cis to trans

cisternal maturation model

cisternae are transient structures: form at cis face then physically move to trans face then disperse into TGN and vesicles. each cisternae matures, changing its composition as it progresses

2 rules of cisternal maturation moel

1. cargo stays in cisternae ( moves w/in not as vesicle)

2. golgi glycoslylation enzymes are in cisternae and transport vesivles, which can move backward (trans->cis)

transport vesicles

made by cicular membrane/lipid bilayer surrounded by protein coat (except secretory vesicles/granules)

COP II- coated vesicles

moves materials forward = anterograde from RER to (VTC) vesticular tubular clusters or golgi complex

COP I coated vesicles

moves materials backwards from VTC to golgi stacks to RER

-backwards from (trans-cis)

clatherin coated vesicles

moves materials from TGN (trans golgi network) to endosomes then ultimately lysosomes= endocytic pathway

secreted proteins

aggregate into rims

plasma membrane proteins

have sorting signals in cytoplasmic domains that cause them to be packaged into secretory vesicles

lysosomal proteins

are packaged into clatherin coated vesicles which transfer them to late endosomes. from there the proteins are transported to lysosomes

movements of vesicles toward their specific target compartment s though to be directed by

microtubules

where are secretory granules stored at until proper stimulation of cell (hormone, nerve impulse)

cytoplasm

regulated exocytosis

triggered by a local increase in Ca2+ in the cytoplasm

lysosomal proteins are packaged into ______ which transport them to _____. from there proteins are transported to ______

clatherin coated vesicles

late endosomes

lysosomes

lysosome

full of hydrolytic enzymes that degrade of break down all types of molecules

what 3 things to lysosomes break down

1. materials brought into cell for use (nutrients, cell components)

2. destruction of infectious bacteria or lysosomes

3. destruction of organelles = autophagy

endocytosis

uptake of small molecules ( dissolved or suspended) and surrounding fluid- into cell

phagocytosis

the uptake of large particles matter like bacteria-- cell eating

bulk phase endocytosis

nonspecific uptake of extracellular fluid and molecules

housekeeping receptors

are for uptake of materials that cell needs routinely.

ex. LDL receptors bind LDL= package of cholesterol surrounded by protein coat

signaling receptors

bind extracellular ligands that are messanger/signals to change cell activities ex. hormones, growth factors

what is the protein that signaling receptors are tagged with when in early endosome

ubiquitin, which marks receptor for destruction

do signaling receptors recycle back into membrane

no they are sent to late endosomes and then to lysosomes where they are destroyed

About this deck

By: Laura Valladao
Created: 2012-03-13
Size: 72 flashcards
Views: 14

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis