Transport Across Cell Membranes Flashcards
what is the model used to describe the cell membrane
fluid mosaic model
what are the 6 components of the cell membrane
phospholipid bilayer
glycoproteins
channel proteins
carrier proteins
glycolipids
cholesterol
what are the glycoproteins and glycolipids on the cell membranes
antigens or receptors
what does cholesterol do for the cell membrane
offers stability
what do the membrane proteins do for the cell membrane
allow larger / polar / water soluble / ions to cross the phospholipid bilayer
what can cross the phospholipid bilayer easily
hydrophobic molecules (O2)
small polar molecules (CO2)
non polar molecules like oxygen
what type of diffusion do the membrane proteins allow to occur
facilitated
does facilitated diffusion use energy
no
how do carrier proteins work
they bind to the molecules, change shape and release it on the other side
define diffusion
the net movement of molecules from an area of high concentration to low concentration down a concentration gradient, across a semi permeable membrane
what is diffusion proportional to
length of diffusion path
define osmosis
the net movement of water from a higher water potential to a lower water potential down a water potential gradient, across a semi permeable membrane
what does adding solute do to the water potential
makes it more negative
what is water potential messured in
units of pressure (KPa)
what is pure waters water potential value
0
what happens if animal cells are placed in pure water
it will absorb the water, causing the cell membrane to strech and the cell to burst, lysis
what happenes if an animal cell is place in a concentrated solution
water will leave the cell and it will shrink, crenation
what happens if plant cells are placed in pure water
water enters the protoplast, causing pressure to build which stops any more water entering, making the cell turgid
no damage
what happenes if a plant cell is place in a concentrated solution
water will leave the cell until the protoplast detaches from the cell wall, this is called plasmolysis
define active transport
the movement of molecules from an area of low concentration to high concentration, against a concentration gradient, through a semi permeable membrane; this requires ATP
how is active transport selective
it requires membrane proteins to be complementary to the moelcule
what type of proteins are used for active transport, what do they act as
membrane proteins, they act as pumps
how does direct active transport work
1 - outside cell, molecule / ion bindsd to the receptor site of the membrane proteins
2 - inside cell, ATP binds to the carrier protein which releases energy, used to change the shape of the carrier protein so it opens to the other side to release the molecule / ion
what cells line the ileum
epithelial
what happens during co transport
glucose binds to Na+ (coupling)
what is the concentration of Na+ ions inside the illeum compared to outside?
Na+
inside - low
outside - high
what is the concentration of glucose inside the illeum compared to the neighbooring capillary?
inside illeum - high
inside capillaries - low
what is the sodium pump
a pump that requires ATP to pump Na+ ions from inside the illeum to the capillaries against an active transport gradient
