CELL BIO: CH. 15.: INTRACELLULAR COMPARTMENTS AND PROTEIN TRANSPORT

How does receptor-mediated endocytosis work?

part that we want binds to receptors on cell surface and sucked into the cell which then goes to an endosome and then the receptor is transferred back to the cell membrane while the piece we want goes to lysosome

what is the significance of having membrane-enclosed organelles

can compartmentalize chemical processes

do eukaryotes or prokaryotes have membrane bound organelles

eukaryotes

are membranes only on the outside of the cell or they on the inside; or both?

both (membrane and organelles)

how did intracellular membranes evolve

via invagination of the plasma membrane

how did the nucleus acquire a membrane

invagination of the plasma membrane where some of it moved into the cell and enclosed the nuclear material and over time pinches off from the cell membrane

where are ALL proteins made

ribosomes

where are the ribosomes located

rough ER

signal sequence

AA sequence on the protein that signals where it needs to go

if signal sequences are removed from the protein, does the protein move to its required destination

no

what kind of membrane is the nucleus and why

double membrane; created during invagination which allows for extra protection of precious DNA

nuclear lamina

A netlike array of protein filaments lining the inner surface of the nuclear envelope; it helps maintain the shape of the nucleus.

nuclear pores

holes in the nuclear envelope that allow materials to pass in and out of the nucleus

nuclear pores have to go through how many layers of the nucleus

3 (outer layer, inner layer, nuclear lamina)

are nuclear pores very complex

yes

how are nuclear pores complex

they have nuclear baskets on the inside and nuclear fiblra on the outside

nuclear localization sequence

A sequence of amino acids (usually basic) that directs a protein to the nuclear envelope, where it is imported by a specific transport mechanism.

in order to go into the nucleus, what must be on the protein

nuclear localization sequence

what is the process of getting proteins into the nucleus

nuclear localized protein must attache to a nuclear protein and make it past the fibrils, into the pore, and make it past the nuclear basket where it can detach

since import into the nucleus is too energetically demanding, what energy source does it use

GTP

how are proteins fed into the mitochondria

proteins with the mitochondria SS is recognized by receptor protein which then moves to the translocator in the out membrane and then it pushes the proteins into a inner membrane translator

when are mitochondrial proteins folded

on the inside of the mitochondria (when its outside and being fed, the protein is not folded)

in the nucleus, are proteins folded prior to going to the nucleus or no

yes, folded as it heads into the nucleus

if there is a ER SS, as soon as the protein is being made by the ribosome, what happens

fed into ER

do proteins go into ER folded or unfolded

unfolded

single pass transmembrane proteins

Membrane protein in which the polypeptide chain crosses the lipid bilayer only once and is partly on the inside or outside

how do transmembrane proteins work

start AA sequence recognized, the protein goes through until it hits the stop portion and then the protein is spit out with one part of the protein being inside, one outside an the stop sequence in the membrane

is the stop and start part of the protein hydrophobic or hydrophilic

hydrophobic

double pass transmembrane protein

has two parts (ends of proteins) on outside and a loop on the inside

what is the difference between double pass transmembrane proteins and single pass

in double pass, the start sequence is not at the beginning of the protein

for proteins that need to go to ER, are they fed directly as made or after they're done

as they are being made

for ER, when do their proteins get folded

when inside

for proteins that are in the ER, what happens to them as soon as all of the protein is in the ER

they are folded and modifications are added to them

for multi-pass membrane proteins, what do they need more of in order to have various parts of themselves inside/outside of the membrane

additional pairs of stop and start sequences

what energy do multiple pass membrane proteins need in order to work

GTP

what are the two types of chemical modifications that occur in the ER once the ER signaled protein is inside

disulfide bonds, glycosylation

disulfide bonds

strong covalent bonds between cysteine side chains of different proteins

are disulfide bonds very strong or weak

strong

why are STRONG disulfide bonds needed

a lot of our proteins will go outside of the cell which is very dangerous and hostile, so disulfide bonds serve as an extra layer to protect the shape of the proteins (shape=function)

glycosylation

addition of carbohydrate chains (sugar units) to proteins

why would proteins want carbohydrate chains

proteins extracellular proteins, form carb layer, and help with cell to cell recognition

where does glycosylation occur

inside the ER

while some proteins will fold by themselves, what protein helps other proteins fold

chaperones

chaperones

a type of protein that assists in the folding of other proteins

unfolded protein response

misfolded proteins will bind to a receptor and will start a signaling cascade which activates a transcription factor which will go into the nucleus and affect the expression of our genes

in an unfolded protein response, what genes will the transcription factor affect

genes that affect the misfiled protein (make more chaperones, make more ER proteins)

why would we want more ER as a response to misfolded proteins

make ER larger, we can fold proteins faster

transcription factors

A regulatory protein that binds to DNA and affects transcription of specific genes.

if there are too many misfolded proteins in the cell, what will the signalling cascade do instead of trying to salvage it

apoptosis (programmed cell suicide)

after the ER, where do the proteins go

Golgi body

Golgi body

post office; proteins are sent here to be packaged and transported throughout the cell

proteins always travel in what

vesicles

how do proteins in the ER get transported to the Golgi body

proteins are encolsed in a vesicle which was membrane that has been pinched off of the Er membrane and then it goes to the Golgi and forms the Cis face of it

vesicles are formed using what coat

protein coat

what are the two functions of the protein coat

shapes membrane into a bud, helps capture molecules for onward transport

clathrin

a protein that plays a major role in the formation of coated vesicles

how does clathrin work

clathrin has three branches that come out and when they click together to the receptor on the protein coat, they form a ball where it pulls membrane out and forms it into a vesicle, then clathrin falls off

does the formation of vesicles need energy

no

how are vesicles transported

actively transported by motor proteins that move along the cytoskeleton

once vesicles get to where they need to go, what must happen

vesicles must pop into target membrane

what are the two proteins that help with the recognition and docking of vesicles into organelle

RAB proteins, SNARES

what are the three phases of recognition and docking with the organelle

tethering, docking, fusion

how do vesicles dock

vesicle snare will recognize organelle snare and then they will get tangled and launch the vesicle into the organelle; RAB proteins will be recognized by tethering proteins which allows for the right allinghtment of snares

How does botox work?

injects antibotcholism drug which limits their range of motion

snares are bound by what toxin

botcholism

if we inhibit snares, what will happen

shut off signaling in the body (no cell to cell communication or carrying out of function)

does botox work on snares

yes (botox binds to snares which inhibits it from forming)

why is it normal for the Golgi body to send proteins/vesicles to outside of the cell

cell are always talking to one another

secretion

cells are releasing proteins into outside world

what are the two types of secretion

constitutive, regulated

constitutive secretion

proteins that are released one at a time all the time

regulated secretion

proteins that are released not all the time, but need a signal to be released (cell signal will bind to receptor at surface of cell which creates a signalling cascade which will enable the vesicle to be released)

what is the best example of regulated secretion

insulin (when blood sugar is high, there is a signalling cascade that prompts insulin to be released into the cell)

endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

what are the two types of endocytosis

phagocytosis, pinocytosis

phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

is phagocytosis or pinocytosis used to fight off bacteria

phagocytosis

what are the two main function of phagocytosis

fight off bacteria, engulf old cells

while pinocytosis is indiscriminate, what type of pinocytosis is selective

receptor-mediated endocytosis

receptor mediated endocytosis/controlled pinocytosis

pick out something specific to take into the cell

Endosomes

sorting station in our cells (where things are brought in, taken apart, and sorted out; for ex: taking a piece off its receptor)

receptor mediated endocytosis

part that we want binds to a specific receptor and that is taken to the endosome by a vesicle where it is sorted and the receptor and protein are separated and the receptor goes to the cell membrane while the protein goes to the lysosome

Are lysosomes acidic or basic?

acidic (allows for intracellular digestion)

there are a lot of what type of enzymes in the lysosome

digestive enzymes

autophagy

where organelles are broken down