Transport Flashcards
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
integral
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
saturable/maximal/doesn’t
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
- channel-mediated: specificity is low, can be closed by cell (gated)
- 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)
uniporter/antiporter/symporter
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?
- membrane-spanning PRO (active transport carrier)
- ATP-hydrolyzing PRO (provides energy for active transport)
- 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
