| Term | Definition |
|---|
| oxidative phosphorylation | ATP are generated this way via respiratory chain |
| Where are mitochondria typically located? | Ans. concentrated at sites of high ATP consumption and can move around via microtubules |
| outer mitochondrial membrane | is permeable to molecule <5000 and has porin, an aqueous channel |
| inner mitochondrial membrane | Important for ATP synthesis- contains the proteins that make up the respiratory chain |
| cristae | these are folds in the inner mitochondrial membrane that give it more surface area |
| intermembrane space | this is between the inner and outer membranes- where te H+ are pumped from the inner membrane |
| matrix | This is a space within the mitochondria and contains enzymes, the genome, ribosomes, and is where the citric acid cycle, fatty acid synthesis, and metabolism of pyruvate happens |
| ATP synthase | H+ comes in from innermembrane space into matrix via this enzyme complex and converts ADP to ATP |
| How are cytosolic proteins targeted to specific locations in mitochondria? | Ans. Protein translocators in mitochondrial membranes catalyze protein transport |
| TOM complex | Transfers proteins across OUTER membrane |
| TIM complexes | Transfers proteins across INNER membrane |
| SAM complex | Helps fold proteins in OUTER membrane |
| OXA complex | Mediates insertion of inner membrane proteins that are made in mitochodrial matrix |
| What must happen to a protein destined for the mitochondria before it can go in through TOM? | ans. It must be unfolded and remain that way by Hsp70 chaparones while the mt signal peptides direct it to TOM. |
| mitochondrial signal peptides | these are 20-80 aa at amino terminus that signal protein to mitochondria and also has one side with + charged aa. |
| contact sites | These are sites where protein can enter through both membranes bc they look "fused" |
| mitochondrial signal peptides | these get cleaved off once a protein enters the mitochondria |
| mitochondrial Hsp70 | this binds to proteins entering through TIM to help prevent folding. Can be released via ATP hydrolysis |
| mitochondrial Hsp60 | this promotes folding of imported proteins and requires ATP |
| How are imported proteins inserted into outer mitochondrial membrane? | ans. Once translocated through TOM, beta-barrel proteins bind to chaparoens in intermediate space and then SAM complex inserts UNFOLDed protein into membrane and helps fold them. |
| How are proteins inserted into the inner mitochondrial membrane? | ans. The protein inserts it's N-terminal sequence through the TIM and then the Stop Transfer sequence is identified and the protein is migrated into the membrane. The signal sequence is cleaved inside matrix. |
| stop transfer sequence | Indicates protein should be placed into inner membrane |
| peroxisomes | small membrane bound organelles that contain oxidative enzymes. Can break down a number of things |
| catalase | this is 40% of protein in perioxisomes and uses H2O2 to oxidize phenols, alcohols, formicacid and formaldehyde |
| oxidation of fatty acids | this is a function of perioxisomes and generates acetyl CoA. |
| Import of proteins into perioxisomes | A 3 aa motif (SKL) that is recognized by a receptor on perioxisome membrane |
| Zellweger syndrome | Made because of defect in import of proteins into perioxisomes. Leads to no enzymes in perioxisomes and causes severely abnormal brain, liver, kidneys |
| receptor mediated endocytosis | macromolecules bind to complemenary transmembrane receptors in coated pits and then enters via clathrin-coated vesicles |
| What are some common lignads that are transported in via receptor mediated proteins? | ans. LDL, transferring, antibodies, viruses, toxins... |
| coated pits | specialized region coated with clathrin on cytoplasmic face. Invaginates into coated vesicles and fuse with early endosomes |
| clathrin | the protein on the cytoplasmic side of coated pits, has three light and heavy chains and forms triskelion |
| coated vesicles | these travel to early endosomes after sheding protein coat |
| triskelion | three legged structure that is a form of clathrin. They form the basket that pinches off membrane vesicle |
| adaptins | this binds transmembrane proteins and clatrin. It promotes the uptake of certain ligands and binds to certain 4 aa motifs of transmembrane receptors. |
| receptor recycling | receptors bound to ligands dissociate when entering the low pH of endosomes. They are then transported back to plasma membrane via small vesicle |
| What is the fate of ligands in endosomes? | ans. These get degraded in the late endosome. |
| transcytosis | If receptor is transported to different location within plasma membrane. |
| Xanthomas | a result of high blood triglyceride levels. This can occur when plasma membrane receptors don't effectively bind to LDLs. |
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