Protein Trafficking Flashcards
Pathways cells use to moves proteins across plasma membrane
Carrier proteins, channels, endocytosis (caveolae-mediated, receptors, receptor-mediated), exocytosis, phagocytosis, transcytosis
Carrier proteins
Bring proteins across the membrane that cannot simply diffuse
Channel proteins
Allows the protein to enter when given the signal to
Caveolae-mediated endocytosis
Pit lined with caveolin brings molecules in a membrane bound vesicle
Receptor-mediated endocytosis
Bound receptors in coated pits get encircled by coated vesicle
Exocytosis
Early endosome is at a low pH, late endosome fuses with a lysosome to break down material and then fuses with a phagosome to dispose of the material
Phagocytosis
Microbe is encapsulated and combines with lysosome to create phagolysosome, and digested material is released
Transcytosis
Molecules are brought into the cell via vesicle, then released
Bilayer sheet
Make up membranes, composed to two sheets, the lipid bilayer
Liposome
Spherical lipid bilayers, inside is hollow or filled with liquid
Micelle
Spherical, single lipid layer, outside is polar while inside is nonpolar
Channels
Use passive diffusion and go with the concentration gradient
Pumps
Use active energy-dependent transport and goes agains the concentration gradient
ABC transporters
Ligand binds open dimer, ATP binding causes a conformational change that releases the ligand, ATP hydrolyzed and ADP released to open up the dimer again
Nucleus
Made up of two lipid bilayers (inner and outer membranes) separated by perinuclear space (lumen). Membranes have nuclear pores
How do proteins enter the nucleus?
Small proteins can just diffuse in, but larger proteins need a nuclear localization signal bound to get through the nuclear pore
ER/Golgi membrane protein trafficking pathway
Proteins co-translationally inserted into RER through translocons, packaged into vesicles in RER, vesicles take proteins to Golgi, where the proteins are sorted and sent to either the lysosome, plasma membrane, or secretory vesicle
Misfolded/unfolded proteins
Chaperone takes protein to an ER protein translocator and takes into cytoplasm where ubiquitin tags it and sends to the proteosome, which degrades it into small peptides and amino acids to be recycled
Lysosome function
To degrade macromolecules and cells using internal low pH and acid hydrolases
Lysosome storage diseases
Tay-Sachs, Guacher’s, metachromatic leukodystrophy
Caused by mutations in lysosome that prevent breakdown of damaged proteins, so these proteins are stored when they shouldn’t be
Cystic fibrosis
Caused by mutation in CFTR gene where there is no Ca2+ channels on the epithelial cells, leading to dehydration of tissues and mucous
Botulism
Blocks SNARE interactions so neurotransmitters are released by the presynaptic cell, but cannot be taken up by the post-synaptic cell. Causes autonomic system to fall apart.
