MODULE 1: Cells Flashcards
Cytosol
metabolic pathways, protein synthesis, cytoskeleton
Cytosol is the intra-cellular fluid that is present inside the cells (cytoplasm is a cell component, not fluid)
Nucleus
DNA and RNA synthesis
Endoplasmic Reticulum
synthesis for lipids, proteins (for distribution to many organelles and plasma membrane)
Lysosomes
intracellular degradation
Highly acidic organelles that contain hydrolytic enzymes that degrade proteins, nucleic acids, oligosaccharides and lipids
- Lysosome acidity is maintained by a proton pump
- Membrane proteins are highly glycosylated to protect the membrane from digestion by the hydrolases
- Membrane contains metabolite transporters to transfer final products of digestion (amino acids, sugars, nucleotides) to the cytosol where they can be excreted/used by cell.
Endosome
sorting endocytosed (vesicled) material
Mitochondria
powerhosue of cell; ATP synthesis by oxidative phosphorylation
phosphorylation
how ADP + P –> ATP
Golgi apparatus
modification, sorting, packaging of proteins and lipids for either secretion or delivery to another organelle
Chloroplast
(in plants) ATP synthesis and carbon fixation by photosynthesis
Peroxisomes
Organelles that help with Oxidation of toxic molecules
Where are cellular proteins synthesized?
On the cytoplasmic ribosomes (except the few mitochondrial proteins)
How do proteins know to go to the right organelle?
They have amino acid sequences and signal. sequences, which are recognized by receptors that target them
How is orientation of protein determined across the membrane of an ER?
Internal hydrophobic stop/start sequences.
How do proteins go through the nuclear membrane?
Mediated by nuclear pores, the nuclear localization signal is recognized by the nuclear import receptor that interacts w/ cytosolic fibers from the pore.
How do proteins import into the mitochondria?
Same as nucleus mostly. Signal recognized by OUTER membrane receptor that brings protein to OUTER membrane translocator that interacts w INNER translocator to import protein.
What is ER quality control?
Chaperones (like calnexin) fix misfolded proteins
What is the Unfolded Protein Response? (UPR)
Sensors detect a misfolded protein in the ER and induce:
1) ER expansion
2) Gene activation of chaperones and other proteins associated with ER quality control
3)Inhibition of protein synthesis to prevent accumulation of more unfolded proteins.
4) IF ER can’t cope, UPR directs the cell to (cell-f) self-destruct vis apoptosis
Apoptosis
Cell dies in these steps:
Cell shrinks.
Cell fragments.
Cytoskeleton collapses.
Nuclear envelope disassembles.
Cells release apoptotic bodies.
Secretory Pathways
newly made lipids and proteins delivered from the ER via the Golgi to the cell surface and exocytosis
(ER -> Golgi -> PM)
Endocytic Pathway
internalization of extracellular material at the cell surface that is targeted first to endosomes and then to lysosomes for degradation
(PM -> Endosomes -> lysosomes)
Golgi main functions after proteins are delivered to the CIS face:
- Protein modification
- Protein targeting
Protein modification
As proteins traverse the Golgi stack, their oligosaccharides (large saccharides) are modified generating complex oligosaccharides
*Most multiple and varied glycan (sugar) modifications in the cell are made in the Golgi apparatus
Protein Targeting
after traversing Golgi, proteins exit the TRANS face of the Golgi stack in transport vesicles for delivery to different cellular destinations
What causes Diabetes?
Defective Insulin Secretion. Endocrine insulin secreting B cells store insulin in granules that are released following a large meal in response to increased glucose levels.
What are Exocrine acinar cells?
Cells in the pancreas that secrete digestive enzymes into the gut to aid in proper digestion
Constitutive Exocytosis
Vesicles buf grom the TGN (trans-Golgi network) and fuse directly with the plasma membrane.