CHAPTER 4 - LIPIDS AND MEMBRANE TRANSPORT Flashcards
What is Phospholipid Bilayers?
-Phospholipids are amphipathic (with hydrophilic phosphate heads and hydrophobic fatty acid tails Iff in water, they will form tiny single-layered micelles and larger bi-layered liposomes to hide their tails while letting only their heads touch.
- The bilayer acts as a thin barrier that separates the water inside and outside.
Are the Bilayer selective?
Yes they are. Only small and hydrophobic molecules that can get through the oily fatty acid tails can pass.
-small, nonpolar molecules can cross fast
-small polar molecules with no charge can cross but slowly
-Large polar molecules and charged ions cant cross easily.
Passive transport of solutes happen by…
Simple diffusion
What is simple diffusion?
The dissolved solute will passively (no energy) moe from areas of higher [ ] to areas of lower [ ] by diffusion as long as there isn’t a barrier stopping its movement.
Passive transport of solutes happens by….
Facilitated Diffusion.
What is facilitated diffusion?
When big molecules such as sugars and ions want to cross the plasma membrane, we can use proteins to cross-polar and charged things. We can add Channels and Transport proteins that act like canals to let these big molecules through, just like CO2 and O2.
Once [ ] are equal across the membrane, there is —– more net movement.
NO
What is Active Transport?
AT (active transport) always uses energy to transport solutes across membranes against the [ ] gradient. Their primary source of energy is ATP.
Example of Active Transport?
the Na+ and K+ pump.
Difference between active and passive transport.
PASSIVE- transports down its [ ] gradient, and does not require energy.
SIMPLE DIFFUSION- if the molecule is the water we call this “osmosis”
FACILITATED DIFFUSION- via transporter or a channel (proteins)
ACTIVE- transports against its [ ] gradient, Requires input of energy.
PRIMARY AT and SECONDARY AT
WHICH FEATURES APPLY TO THE PROCESS OF FACILITATED DIFFUSION (PEQ)
How many statements apply?
1) This process can occur in a pure phospholipid bilayer with no membrane proteins.
2) ATP is required for movement.
3) A transporter can only ever move its molecule in one direction.
4) Molecules move down (along) their concentration gradient.
ONLY #4
WHICH FEATURE APPLIES TO A MOLECULE THAT IS ACTIVELY TRANSPORTED?
How many statements apply?
1)This process can occur in a pure phospholipid bilayer with no membrane proteins.
2) ATP is directly required for movement.
3) An energy source is always required for movement.
4) The molecule moves down (along) its concentration gradient.
5) A given transporter can only ever move this particular molecule in one direction.
2 OF THEM ( #3 and #5)
If ATP is not directly required what type of active transport is it?
Secondary active transport
What might the energy source be for Secondary active transport?
A [ ] gradient of a second molecule ion being transported.
What is Endocyotsis and does it use energy?
Endocytosis means that particles are entering the cell, and it does use energy.
