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Flashcards in Transport Deck (24)
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The cytoplasmic membrane has a ___ that prevents leakage and functions as a ___ for nutrient transport in and out

permeability barrier/gateway


Why does water transport freely across the membrane?

it is small and weakly polar


___ PRO transport those molecules that the membrane isn't permeable to



Describe facilitated diffusion

transports solutes down a gradient, for uncharged substrates the gradient alone determines the direction but for charged particles the charge and gradient have an effect


Describe active transport

transports solutes against a gradient


Transport systems are ___; the rate of update becomes ___ and increase of substrate ___ increase rate



Transport systems are ___; they transport ___ molecules or molecules ___

specific/single/of a series


True or false: biosynthesis is not very regulated by the cell

false, it is highly regulated


In unicellular organisms nutrients are usually acquired via ___, in multicellular they're usually acquired via ___ or ___

active transport/diffusion/facilitated diffusion


What are the types of facilitated diffusion? Include a brief description

1. channel-mediated: specificity is low, can be closed by cell (gated)
2. carrier-mediated: substrate binds to one side of the membrane and induces a conformational change, the substrate is then released on the other side, much more specific and required no energy


Types of transporters: ___ (one molecule), ___ (one in, another out), ___ (two in the same direction)



Describe pmf-dependant transport

in bacteria and archaea, under conditions where respiration is possible a pmf is generated, if respiration is not possible ATPases can create a pmf, some sym and antiporters can use the pmf to generate energy


What are some pmf transporters that use H+ gradient?

cation uniporter, proton symporter, anion symporter, proton-X symporter


What are some pmf transporters that use Na+ gradient?

Na-anion symporter, Na-X symporter


Where is the Na+ generated pmf common?

marine environments


What are the three components of ABS transporters?

1. membrane-spanning PRO (active transport carrier)
2. ATP-hydrolyzing PRO (provides energy for active transport)
3. substrate-specific binding PRO (has high affinity for specific substrate)


How do ABC transporters function?

binding PRO binds to substrate and transfers it to the transporter where it is actively transported using ATP generated


Where is the binding PRO (for ABC transporter) in G+ and G- organisms?

G+: anchored in the cytoplasmic membrane
G-: free in periplasm


What are the rates of permeability of glucose and glycerol?

glucose: 0.001 (fair/poor)
glycerol: 0.1 (good)


Describe group translocation?

substrate is modified as it passes through transporter across the membrane


What is an example of group translocation?

PEP-dependant sugar phosphotransferase system, used by bacteria to transport common monosaccharides


How is transport done in unicellular eukaryotes?

pmf is generated inside the mitochondria usually but in this case it needs to be generated in the cytoplasmic membrane; proton translocating ATPase in the cytoplasmic membrane used ATP to pump out protons which generates a pmf at cytoplasmic membrane level which is used to power symporters in the cytoplasmic membrane


How many H+ do F-type ATPase and P-type ATPase pump out during generating of the cytoplasmic membrane pmf?

F: 3
P: 1


What are the types of endocytosis with a brief description:

- phagocytosis: large, solid particles enter via food vacuoles
- pinocytosis: small fluid particles enter via vesicle
- receptor-mediated: coated vesicle with coat PRO from a pit coated with receptors