Studied by 1 personER lumen side
On which side of ER membrane is the receptor of the transmembrane protein located on?
Cytosol side
On which side of the ER membrane are the binding domains of the transmembrane protein located on?
plasma membrane
GPI anchor attaches proteins to the __________.
Glycosylphosphatidylinositol
What does GPI stand for?
ER enzymes
What catalyzes the GPI anchor?
the C-terminus of a protein
What is the GPI anchor covalently attached to?
In the ER lumen
Where does the linkage of the GPI to the C-terminus of the protein occur?
GPI
Protein cut free from the ER membrane and then attaches to the ________, which is membrane bound and eventually travels to the plasma membrane.
the plasma membrane
What does the GPI anchor attach proteins to?
dynamic
The plasma membrane is very _________, it's always forming and being recycled.
packaging proteins to leave the cell
What is exocytosis?
What is endocytosis?
Golgi apparatus
What is known as the mail office of the cell?
the lumen
What is the interior part of the vesicle called?
transport vesicle
What allows the travel of a substance without passing through the phospholipid bilayer/ membrane?
cargo
What are the components of the lumen called?
they must take up appropriate cargo (budding stage)
must fuse with appropriate target membrane (fusion stage)
What are the two rules of transport vesicles selectivity?
The budding stage
starting to take up the necessary cargo to bud off the vesicle
Fusion stage
The transport vesicle then buds off and after uncoating, tethering and docking, it will fuse to the target membrane.
secretory pathway
What pathway refers to the ER, Golgi apparatus and the vesicles that travel in between them as well as the cell membrane and lysosomes. It's the pathway by which the cell secretes proteins into the extracellular environment.
Exocytosis
a secretory pathway that delivers newly synthesized proteins, carbohydrates, and lipids to the plasma membrane
Endocytosis
the cellular process in which substances are brought into the cell.
Endocytic pathway
Takes things in through the plasma membrane. The cells remove a region of the plasma membrane and delivers these to the lysosomes where they are degraded in internal compartments. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. Includes pinocytosis and phagocytosis.
endosomes
What are these internal compartments called?
formed by the invagination of the plasma membrane and are triggered by the activation of cell surface receptor.
How are endosomes formed?
Invagination
the process of a surface folding in on itself to form a cavity, pouch or tube.
they control the sorting of activated cell surface receptors either to the plasma membrane for further use or to the lysosome for degradation.
Why are endosomes important?
endosomes
membrane bound organelles, internal compartments where things get degraded and can also be used to capture nutrients.
lysosome (digestive organelles)
start with the plasma membrane, which is then removed to bring in the vesicle. Often these vesicles will then fuse with a __________ where the content will then be degraded in the endosome.
coated vesicles
vesicles that bud from membranes and have a coat on their cytosolic surface (surface facing extracellular environment).
shed its coat
After budding, the vesicle will __________, which allows the membrane to interact directly with the target membrane to fuse with it.
where a vesicle is going to fuse
What is a target membrane?
clathrin coated vesicles
these are the most popular type of coated vesicles, their outer coat is made of clathrin
exocytosis of clathrin coated vesicle
they bud from the Golgi apparatus on the outward secretory pathway. What is this process called?
endocytosis of clathrin coated vesicles
bud also from the plasma membrane on the inward path, which creates a clathrin coated pit. What is this process called?
COP coated vesicles (COPI or COPII)
Transport vesicles that transport molecules from the ER to the Golgi and the Golgi to the Golgi (exocytosis)
Clathrin (dark green structure)
assemble into basket-like network on the cytosolic surface on the membrane and this starts to shape the membrane into a vesicle
Dynamin (yellow structure)
GTP binding protein that assembles into a ring around the neck of the invaginated pit and pinches off/ constricts the vesicle from the parent membrane. Uses the power from the phosphate to constrict off of the plasma membrane.
adaptins (light green structure)
second class of coat proteins that helps to select the cargo for transport
adaptin
binds to your cargo and these cargo receptors bind to ________ and helps deliver it to your transport vesicle.
adaptin
What binds to clathrin?
in the cytosol
When does the clathrin coat disassemble?
vesicle docking
once the naked vesicle is within the cell, you have to dock the vesicles at a different location. use motor proteins to move vesicles along the cytoskeleton.
Rab proteins
What are the markers on vesicles called?
tethering proteins
What are receptors on the organelle called that dock vesicles?
tethering protein
Rab proteins bind to _________ on the target membrane.
ensures that transport vesicles fuse with the correct membrane
Unique combination of rab proteins/ tethering proteins ensures what?
vesicle-SNARE
What does v-SNARE stand for?
tethering-SNARE
What does t-SNARE stand for?
SNARE
provides additional recognition as transmembrane proteins. The tethering protein captures a vesicles by grabbing hold of the Rab protein.
vesicle, target membrane
SNAREs are on the ___________ and the _______.
vSNARE, tSNARE
_______ and ______ work together to firmly dock the vesicle in place on the target membrane. They also make sure that the vesicle is binding to the correct membrane.
exocytosis
proteins delivered from the ER to the Golgi to the cell surface via transport vesicles
transport vesicles, ER
These ____________ then fuse with the plasma membrane, and are then covalently modified in the ______ before leaving the cell.
disulfide bonds, glycosylation, and protein folding
What are examples of some covalent modifications that take place in the ER?
Golgi apparatus
has a collection of flattened membrane enclosed sacs and each stack consists of two distinct faces
cisternae
What are these flattened membrane enclosed sacs called?
cis face
Which face of the Golgi apparatus is next to the ER and allows entry into the Golgi?
trans face
Which face of the Golgi apparatus points towards the plasma membrane and allows things to exit from the Golgi?
cis, ER
Proteins enter through the _______ face of the Golgi network via transport vesicles from the _______?
cisternae
Proteins then travel through the ________ through transport vesicles from one cisterna to the next.
trans, plasma membrane
Proteins exit through the _________ face of the Golgi network destined for the _________ or another organelle.
The secretory vesicle
What tells you to release the secretory protein?
constitutive exocytosis pathway
a steady stream of vesicles bud from the trans Golgi network to the plasma membrane, where the plasma membrane supplies the vesicles with newly made lipids and proteins.
secretion
The vesicle carries soluble proteins to the cell surface to be released in the extra cellular fluid, what is this process called? *Keep in mind that the vesicle stays attached to the cell surface and that it contributes to the extracellular matrix.
ER, Golgi
For the constitutive exocytosis pathway to occur, there has to be vesicles coming from the _________ to the ________.
regulated exocytosis pathway
This pathway is not always on and is important for secretory cells. This pathway awaits signal instructions before the vesicle leaves the trans Golgi network with the cargo.
Golgi
The ___________ packages cargo at much higher concentrations.
regulated exocytosis pathway
This pathway is important for the secretion or release of hormones, mucus, and digestive enzymes (extracellular signals like hormones or neurotransmitters).
closest to the ER
Where is the cis face of the Golgi located?
after medial region
Where is the trans face of the Golgi located?
endocytosis
Cells that take up fluid and molecules, small portion of the plasma membrane buds inward and pinched off to form the endocytic vesicle, and many of these become endosomes. This process is called?
the endosome
Where is the ingested material delivered to?
plasma membrane, lysosomes
The ingested material delivered to the endosome is then recycled back to the ___________ or is sent to the ___________(digestive organelle) to be degraded.
Pinocytosis Pino=drinking
cellular drinking for fluid molecules. The ingestion of liquid into a cell by the budding of small vesicles from the cell membrane. One type of endocytosis.
Phagocytosis Phago=eating
Cellular eating. A process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome. One type of endocytosis.
Phagosomes Phago = eating
large vesicles brought in, therefore creating this internal compartment
Phagocytotic cells Phagocytes (neutrophils and monocytes)
Immune cells that play a critical role in both the early and late stages of immune responses.
Macrophages
defense mechanisms engulf or take up smaller cells. They digest and break them down. *Once they are in the cell, they are then delivered to the endosome. One type of endocytosis. a large phagocytic cell found in stationary form in the tissues or as a mobile white blood cell, especially at sites of infection.
Autophagy
the cell recycles components. The mitochondria breaks it down and the plasma membrane recycles it. It's also a lysosome dependent process (digestive organelle).
to promote cell survival
An autophagy performs self-eating ____________. Also known as canabolism of a cell.
development of autophagy
helps reconstruct cells that are differentiating and not dividing, but still need to be maintained
autophagosome
fusion of small vesicles into a double membrane around the organelle and can fuse with the lysosome.
receptor mediated endocytosis
a means to import macromolecules from the extracellular fluid that involves Clathrin coats on the vesicles. Selectively concentrating material mechanism as the vesicles are brought into the cell. Uptake of cholesterol needed to make new membranes.
Cholesterol
___________ depends on receptor mediated endocytosis.
low-density lipoproteins (LDL)
Cholesterol is extremely insoluble, transported to the bloodstream bound to ________________.
liver
Cholesterol-LDL is secreted by the _______ and binds to receptors on the cell surface.
Cholesterol
_____________ is essential to cell membrane health.
Receptor mediated endocytosis
Ingest receptor-LDL complexes and deliver them to the endosomes. LDL then dissociates from the receptor and the receptor is recycled back to the plasma membrane. What is this process known as?
lysosomes
LDL goes back to the _____________.
hydrolytic enzymes
LDL is broken down into ___________ in the lysosomes.
cytosol
Cholesterol is then released from the LDL and will translocate to the ________. Now the LDL is available for membrane synthesis.
cholesterol
The lysosomes release _______ to be used in the plasma membrane.
acidic
Lysosomes are very _________ with their hydrolytic enzymes that use water to break down bonds.
LDL gene
Genetic pre-disposition to high cholesterol means that individuals have inherited defective versions of the _______, which causes the receptor o be missing or non-functional.
atherosclerosis
Cells deficient in taking up LDL-bound cholesterol, causes cholesterol to stay in the blood or the buildup of cholesterol (leading to higher levels of cholesterol), which leads to a disease called _____________.
a lysosome-dependent process that recycles components of itself to survive
What is autophagy?
cellular eating The process by which a cell uses its plasma membrane to engulf a large particle like bacterial cells or viruses, thus giving rise to an internal compartment called the phagosome.
What is phagocytosis?
lysosomes
Where can free cholesterol and hydrolytic enzymes be found?
lysosome
This organelle is very acidic, uses a pump to maintain its H+ environment (against the gradient, so it needs ATP).
Note
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