3: movement into and out of cells Flashcards
what is the role of membranes in the cell?
- allows chemical reactions on the surface
- enables cells to receive hormone messages
- forms and controls an ionic gradient
what is the phospholipid bilayer?
- hydrophobic and hydrophilic lipid molecule layers that float in a fluid
list the components of the membrane
- phospholipid bilayer
- proteins
- cholesterol
- glycolipids and glycoproteins
what is diffusion?
the net movement of solutes across a partially permeable membrane from a region of high concentration to a region of low concentration due to the random movement of particles
what kind of transport is diffusion?
passive transport- does not require energy
what are the types of diffusion?
- simple diffusion
- facilitated diffusion
what are the factors affecting the rate of diffusion across the membrane? [6]
- steepness of the concentration gradient
- temperature
- surface area
- distance
- nature of mol/ion [size and polarity]
- solubility of lipid/fat
why can’t large, polar molecules pass through the ppm?
the size and charge of these molecules make it too difficult for them to pass through the non-polar region without the use of proteins
where do charged ions pass through the ppm?
carriers made by protein molecules
what is facilitated diffusion
- diffusion but through a protein channel
- not energy dependent
what is the difference between carrier proteins and protein channels?
- protein channels work with the conc. gradient
- carrier proteins work against the conc. gradient
what is osmosis?
the net movement of water molecules from a region of high water potential to a region of low water potential
what is water potential?
tendency of water to move from one place to another
what is the water potential of pure water?
0
what happens when equilibrium is reached in osmosis?
there will be no net movement of water
