Transport Functions of Cell Flashcards
(21 cards)
What is the plasma membrane made of ?
Phospholipid bilayer
What does the plasma membrane do as a hydrophobic barrier?
Separates the ICF and ECF
Which molecules can pass through the bilayer? (1)
Lipid soluble molecules (O2/CO2)
Small molecules *also lipid soluble
Which molecules can’t pass through the bilayer? (2)
Ions
Polar molecules (H2O)
Big molecules
What is the protein channel that transports water?
Aquaporin
Factors affecting the direction of transport across a cell membrane (3)
Conc. gradients
Molecular/ionic charge
Membrane potential
Name some proteins that utilize facilitated diffusion
channels / carriers
Features of ion channels
Specific to certain ion(s)
Ions move down electrochemical gradient
= passive diffusion (no energy used)
Can transport high capacities
Named after ion transported
What are 2 types of ion channels?
Leak (open often)
Gated (opens/closes or partially open)
Features of carrier proteins
- Binding site specific to certain molecules
- Shows stereoselectivity (isomer)
- Binding occurs at one side at a time
- Net flux of molecules become saturated as conc. of molecules increase (carriers are used up)
What do carriers generally transport?
Small organic molecules & ions
What happens when carrier proteins are saturated when the cell requires more flux of molecules?
Some hormones enable more transcription of carrier DNA, producing more carriers
Compare and contrast features of channels and carriers (4)
Channels:
Down electrochemical gradient
High transport capacity (faster)
Carriers:
Can be down/against gradient
Transports one/a few molecule(s) at a time (slower)
Similarity:
Specific to transported material
3 types of carrier proteins & what mode of transport they use
Diffusion:
Uniport - moves 1 ion at a time
Active transport:
Symport - moves 2 ions at a time
Antiport - moves 2 ions in opposite directions
Describe generally how a sodium pump works
In - 2 K+
Out - 3 Na+
1 ATP used each rotation
Relationship between phosphorylation of Na pumps and transport of Na+/K+
Na binds to pump
& ATP -> ADP + Pi
= Pump is phosphorylated
K binds to pump
& Pi + ADP -> ATP
pump is de-phosphorylated
How were sodium pumps studied by researchers?
They studied giant squid axons
Because they are unmyelinated & large
What does cyanide do to the sodium pump?
It inhibits ATP production, which causes Na+ to remain in the cell
What’s the difference between primary & secondary active transport?
Both transports molecules against electrochemical gradients
Primary - uses ATP
Secondary - uses ion gradients
What does secondary active transport do?
Transports amino acids & glucose across epithelia
