Membrane Permeability/Pumps Flashcards
(51 cards)
What is a semi permeable membrane?
A layer through which only allowed substances can pass
What are examples of hydrophobic molecules? (4) How do they pass through the phospholipid bilayer?
CO2
O2
N2
Benzene
Passive diffusion
What are examples of small polar uncharged molecules? How do they pass through the phospholipid bilayer?
Water
Urea
Glycerol
Passive diffusion
What are examples of large uncharged polar molecules? Can they passively diffuse through the phospholipid bilayer?
Glucose
Sucrose
No
Can ions passively diffuse through the phospholipid bilayer?
No
Can glucose passively diffuse through a phospholipid bilayer?
Yes (but very slowly) so treated as if it cannot
What are permeability coefficients used for in calculations? What scale are they measured in?
To show how long it takes for a molecule to move a certain distance across a bilayer
Logarithmic
What two factors is passive transport across a membrane dependent on?
Permeability
Concentration gradient
Why are models that show membrane transport proteins as ‘rotating’ or ‘flip-flop’ thought to be wrong?
Would require too much energy (thermodynamically unlikely)
How do gated pores transport molecules across a membrane?
Molecule binds —> conformational change —> molecule released on the other side
(Ping pong transport)
What causes voltage gated ion channels to open during membrane depolarisation?
Movement of positive amino acids —> change in conformation (open channel)
An active process will show a ____ value for deltaG
A passive process will show a ____ value for deltaG
+ve (active)
-ve (passive)
Where does the energy come from for active transport to take place?
Some cells spend nearly ___% of their ____ on active transport
Hydrolysis of ATP
50% of their ATP
By the action of which two types of proteins can molecules be carried across a membrane in facilitated diffusion?
Carrier proteins (gated pore model) Channel proteins
Is facilitated diffusion active or passive? Is the movement of molecules by carrier proteins or channels faster?
Passive
Channel proteins are faster
What type of membrane protein does active transport use to transport molecules across a membrane?
Carrier proteins
What is the intracellular [K+] in mM
155mM
What is the intracellular [Na+] in mM
12mM
What is the intracellular [Cl-] in mM?
4.2mM
What is the extracellular [K+] in mM?
4mM
What is the extracellular [Na+] in mM?
145mM
What is the extracellular [Cl-] in mM?
123mM
What is uni-transport? What is an example of a uni-transport protein?
Where only one molecule is transported by the protein at a time
H+ pump
What is co-transport? What two types of co-transport exist? Give an example of a co-transporter protein?
When more than 1 type of ion/molecule are transported per reaction cycle
Anti port (moves two molecules in opposite directions) Symport (moves two molecules in the same direction)
Na/K ATPase pump
