2-5: Transport in Bacterial Cells Flashcards
What molecules move freely across the CM
Small, uncharged, non-polard molecules
e.g. dissolved O2, dissolved CO2
H2O moves but is significantly hindered
Forms of passive and active transport
Passive = simple diffusion, facilitated diffusion
Active = simple transport, ABC transporters, group transport
What is osmosis
Diffusion of water through selectively permeable membrane along its concentration gradient
How does facilitated diffusion work. 2 types?
Molecules move across membrane via membrane protein that acts as channel (e.g. porins of OM)
Types = specific, nonspecific
Channel proteins are _______ whereas carrier proteins are _______
Nonspecific, specific
What is active transport. How is it powered
Molecule transported against its concentration gradient, requires energy
Either from stored chemical energy (ATP hydrolysis) or dissipation of another concentration gradient
What is simple transport. 2 types?
Use of energy stored in chemical gradients (proton motive force) to power transport of mol against its gradient
Symport = same direction
Antiport = one in, other out
What is the sodium proton antiporter
Exchanges protons for Na+ ions to maintain pH/Na+ homeostasis
When would H+ enter the cell in the sodium/proton antiporter
When the cell is under basic/alkaline conditions
What is the lac permease symporter
Proton motive force used to drive uptake of lactose. Acquire nutrients
What is group translocation
Active transport
Transported substance bound by transporter and chemically modified during transport
e.g. phosphotransferase system. Phosphoenolpyruvate is dephosphorylated, P added to sugar mol
What are ABC transporters
ATP used to power transport of substance across membr
A. 2 ATPase proteins provide energy
B. Transmembrane proteins = selective channel
C. Substrate binding protein binds mol, delivers to channel
What is a substrate binding protein, difference between g(-) and g(+)
AKA periplasmic binding proteins. Binds and delivers substrate to channel in ABC transport.
Gram(-) = free floating
Gram(+) = tethered to CM
Example of group translocation
Phosphotransferase system
Glucose phosphorylated during transport
P from phosphoenolpyruvate
