11013484
Descripción
Fichas por Candice Young, actualizado hace más de 1 año
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Creado por Candice Young
hace alrededor de 7 años
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| Pregunta | Respuesta |
| What determines phospholipid "identity"? | The hydrophilic head group and the length of the tail determines this |
| Intercalaters of cell membranes: | eukaryotes: cholesterol prokaryotes: hopanoids |
| How can bacteria attack eukaryotic cell membranes? | Bacteria can secrete pore forming toxins to bind to CHOLESTEROL, not hopanoids |
| What percent of proteins of bacteria reside in the cell membrane? | 10-20% of prokaryotic proteins reside here |
| major functions of cytoplasmic membrane | permeability barrier protein anchor energy conservation |
| comparative permeabilities of membrane to various molecules | water >>>> Na+ or K+ |
| What is the proton gradient used to power? (IN GENERAL) | Powers ATP synthesis, transport reactions, flagellar rotation |
| hallmarks of all protein mediated transport: | 1) transport rate is saturable (finite) 2) inactivation of an individual protein can block transport |
| What do ACTIVE transport systems specially allow for? | Allow for the accumulation of solutes in the cell to be >>> than surrounding fluid |
| How does glycerol enter the cell? | Enters through the GlpF protein by facilitated diffusion --> transporter will work to keep levels on inside and out of cell always even |
| What are the three families of energy dependent transport? | 1) Simple transport 2) Group translocation 3) ABC system |
| simple transport | Driven by energy used in proton motive force |
| group translocation/transport | substrate enters by facilitated diffusion, is modified by an energy using reaction to prevent reverse transfusion |
| ABC system | periplasmic binding proteins involved, energy comes directly from ATP *also known as ATP binding cassette transporters* |
| simple transport example | use energy from proton motive force/existing ion gradient (Na+) |
| symport | two solutes go the same way (in simple transport) EX: H+ and lactose |
| antiport | two solutes go the same way (in simple transport) EX: Na+ and H+ |
| group transport example | El and HPr gain a phosphate when PEP forms pyruvate, these then phosphorylate sugars and block them from entering IIC |
| ABC transport examples | reverse: no use of periplasmic binding protein, pump OUT substrates (antibiotics) G+: PBP = lipoprotein anchored in cytoplasmic membrane |
| TonB dependent transporters | *Also known as TBDT* used when a substrate is too large for a nonspecific OM protein TBDT interacts with TonB box which interacts with TonB, ExbB, ExbD, proton motive force powers uptake of substrate which is then carried by PBP in periplasm to ABC transporter and into the cytoplasm |
| Two pathways that lead to SecY, SecE, and Sec G transmembrane transport channel | 1) SecB chaperone binds fully synthesized protein and keeps it unfolded, export powered by SecA ATPase 2) SRP binds to signal sequences from ribosome & halts translation, this complex is transferred to SecYEG and continued translation pushes protein across membrane |
| What types of proteins is SecB used for? | Used to transport OM, lipo, and periplasmic proteins (hydrophilic) |
| What types of proteins is SRP used for? | Used for integral IM proteins (hydrophobic) |
| Twin Arginine Transport (Tat) pathway | proteins that cant fold outside of cytoplasm are folded within it, and then transported using proton motive force |
| Why might proteins not fold properly in the periplasm? | Protein needs 1: a complex cofactor built by cytoplasmic assembly factors 2: Cytoplasmic chaperones 3: another protein to bind to in the cytoplasm for stability |
| Difference between Sec signal peptides and Tat signal peptides | Tat signal peptides have an RR motif 3 to 5 amino acids away from the N terminus of the hydrophobic region AND can transport larger substrates |
| Similarities between Sec and Tat pathways | both pathways use the proton motive force for energy and dispel similar amounts of protons |
| TatABC mechanism | 1) TatB and C make a dimer 2) TatC binds Tat signal peptide, this + PMF allows TatA to polymerize and bind to BC 3) Substrate crosses through TatA complex 4) Signal peptide cleaved, TatA disassembles (can no longer maintain a permeability barrier) |
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