cells and organelles: 2 Flashcards
(32 cards)
lumen of a membrane bound organelle
= congruent/ in harmony with exterior of cell
constitutive pathway
direct transport
=> exit from trans-golgi network straight to cell membrane
regulatory secretary pathway
particular proteins are synthetised
They are left in a matured secretory granules and when they are needed there is an external signal that is sent to release the molecules
lysosomal pathway
which is responsible for the degradation of materials that are not necessary for that particular process at that time.
vesicles diffuse to late endosomes and this fusion makes them form lysosomes
mobility of transport vesicles
Proteins are packed into transport vesicles.
The transport vesicles are pulled by various motor proteins (e.g., Kinesin or Dynein).
The motor protein pulls the vesicles along the microtubules.
kinesin
a molecular motor protein that transport vesicles away from an organelle along the microtubule
dynein
pull vesicles back to the organelle
microtubles spread out from the cell centre as tracks
Most microtubules emanate from the centrosome.
The Golgi is usually located close to the centrosome in the cell centre.
Other organelles may move or are positioned on microtubules.
centrosome
Centre for organising microtubules.
Centrosomes contain two centrioles (9 array of microtubule triplets).
The role of centrosome is to initiate microtubule growth.
lysosomes
ph = 5 =>
high level activity that allows the activation of the acidic hydrolysis, which are enzymes that are responsible for the degradation of materials
=> materials are dissolved bcs of acidity
fusion of vesicle transported out of golgi and late endosome
high concentration of hydrogen ion to maintain pH
And because of that constant process, it means that it requires energy.
That’s why you have the presence of ATP present here.
cytosol
ph = 7
degradation of mitchondria
fusion between a lysosome and this particular organelle.
This non-functional organelle in this case turns to form autophagosomes.
lysosomal storage disease
lysosomal storage disease means that the lysosome lacks the capability to degrade these materials, which is a disease.
recycling endosome pathway vs lysosome
external molecules surrounded by external vesicle which is fused to early endosomes
either go to late endosomes and then lysosomes (like a bacteria that needs to be degraded) or recycling endosomes
recycle path => once molecules are used by early endosome => receptor is recycled back into the plasma membrane to trap more molecules into the cell.
Membrane/cargo internalised delivered to endosomes and then passed to lysosomes for degradation. Some membrane is recycled back to the cell surface.
how is uptake done? + 3 types
Uptake is by endocytosis
=> large particles by phagocytosis
=> small molecules by pinocytosis
=> receptor-mediated endocytosis.
autophagy
Portions of the cell itself can be walled off and digested in lysosomes
endocytocis
inside cell injection
exocytosis
outside cell ejection
receptor-mediated endocytosis
surface of cell => receptor ligand interaction in a region called clathrin coated pit
receptor binds to ligand
membrane carved + invaginate towards cytiplasmic side
recruitement of clathrin => clathrin coated vesicle
=> vesicle hangs and dynamin chops it off so its internalised
fusion with endosome => low ph => ligands dissasociate
LDL receptor + cholestrol is taken down to late endosome, lysosome and cholesterol is released
Familial Hypercholesterolemia
mutation in low-density lipoprotein (LDL) receptor causes poor uptake of cholesterol bound to LDL in the blood.
Protein Degradation by Proteasome
‘junk proteins’ = tagged with ubiquitin
Proteasome consists of a central barrel complex with a narrow hollow core line with proteolytic enzymes
No membrane involved
Micromolecular complex
In the cytoplasm not in lysosomes
bad protein goes through central pore into central burrow => polypeptide molecule turns into peptide
ubiquitin proteasome pathway = ubiquitination
ubiquitin is tied to the junk protein => forms a poly ubiquitin chain
ubiquitin binding to the carboxy terminal of the ubiquitin activating enzyme = E1=> process is driven by ATP.
E1 = activated
E3 ubiquitin ligase and E2 ubiquitin conjugated enzymes forms a complex.
Once the complex is formed, the E1 moves the ubiquitin molecules and transfer them onto the E2 and E3 complex.
And as a result, those ubiquitin molecules are then fused into the junk proteins.
So now this particular protein is tagged ready for degradation.
The polyubiquitinated protein is recognised and degraded by a proteasome
Once the protein is degraded into small peptides, ubiquitin is released in the process for re-use in another cycle.
mitochondria
produces ATP = chemical energy
2 billion yrs ago archaea engulfs bacteria
has its own DNA
2 membranes => During further evolution cell membrane invaginates to form internal membranes + bcs of power generated
Two membranes – inner membrane folded into interior
108 ATP
Enable cells to grow bigger
Present in all eukaryotic cells
Contain their own DNA – reproduce by dividing in two
All your mitochondria come from your mother’s egg
what does the matrix contain
contains mitochondrial genome and enzymes responsible for reactions of the citric acid cycle and fatty acid oxidation.
