Membrane Structure And Function 2 Flashcards
Selectively permeable
Some substances cross more easily than others
Small molecules and ions move across the plasma membrane in —- directions
Both
The muscle cell takes in oxygen and expels carbon dioxide
Muscle cell regulates
the concentration of inorganic ions, shuttling them one way or the other across the membrane
Hydrophobic molecules dissolved on the lipid bilayer and pass through the membrane rapidly
Hydrophobic interior of the membrane impedes passage od hydrophilic molecules
Sugars, water, ions pass slowly if at all
Proteins assist and regulate transportation of ions and polar molecules
Hydrophilic big molecules need help
Hydrophobic and small molecules can usually pass through
Channel proteins
Hydrophilic channel that molecules and ions can use as a tunnel
Aquaporins
Special protein that is a channel protein for water molecules
Aquaporins
Carrier proteins
Change their shape to allow molecules to cross
Transport proteins
Move only specific substances
Passive transport is
the diffusion of a substance across a membrane with no energy investment
Concentration gradient
Spontaneous process
The concentration gradient represents — and drives—
Potential energy
Diffusion
Osmosis
The movement of water from a low solute concentration region to a high solute concentration region
Active transport
Transportation with protein and energy
Mostly carrier proteins, not channel proteins
Requires the cell to expend metabolic energy
Always against the concentration gradient
Transport from
Na+ binds to sodium potassium pump
Binding of three sodium ions stimulates phosphoylation by a kinase, using atp
Phosphorylation leads to a change in protein shape, reducing its affinity for na is released on the other side
New shape has an affinity for k+, 2 binding extracellulwr side, triggering released od phosphate group
Loss of phosphate restores original shape and it loses its affinity for k+
2K+ are released and affinity for na is high again, cycle repeats
