What is a semi-permeable membrane?
A layer through which only certain molecules can pass
What types of molecules can permeate a lipid bilayer?
What cells have a lipid bilayer?
Passive transport of molecules through a membrane is dependent on what two things?
Give 3 examples of the important roles of transport processes in the body
Maintaining intracellular pH
Maintaining ionic concentrations
Regulation of cell volume
Expulsion of metabolic waste and toxic substances
Generation of ion gradients in excitable cells
Why would reciprocating “flip-flop” and rotating carriers be very unlikely in a cell transport protein?
Thermodynamically not likely as it would take too much energy to achieve
Is a gated pore that carries out “ping pong” transport an efficient method of movement molecules across a membrane?
No, it is very slow
What can membrane transport proteins do instead of using inefficient “ping pong” transport?
Form channels which can open to allow molecules to pass in and out of the cell via facilitated diffusion
Channels that open in response to agonist binding are known as what?
Give an example
Ligand-gated ion channels
Nicotinic Acetylcholine Receptor
Channels that open in response to changes in ion current are called?
Give an example
Voltage-gated ion channels
Sodium (Na+) channel
On a Michaelis- Menten curve. How would you find the Vmax and the Km
The Vmax is the maximum velocity or rate
The Km is the concentration at half of the Vmax
What can we use to give a more accurate measure of Vmax and Km?
A double reciprocal plot
In relation to change in Gibbs free energy, passive transport is ______ and active transport is _______.
- change is passive transport (-deltaG)
+ change is active transport (+deltaG)
Whether molecules move across the membrane by active or passive transport is dependent on what two things?
The concentration ratio
The membrane potential
Active transport allows the transport of _______ and molecules _________ an unfavourable concentration and or electrical gradient
True or false: Active transport can be direct or indirect
How does direct active transport differ from indirect active transport?
Direct active transport involves the transporters directly binding ATP and using the energy produced. Indirect active transport uses the energy stored in the concentration gradient that has been set up by direct active transport of an ion.
How does simple diffusion differ from facilitated diffusion?
Simple diffusion involves a molecule being transported across the lipid bilayer whereas facilitated diffusion involves a channel or a carrier to transport the molecule across
What are the approximate intracellular and extracellular concentrations of Na+?
What are the approximate intracellular and extracellular concentrations of Cl-?
What are the approximate intracellular and extracellular concentrations of Ca2+?
Intracellular: 10^-7 M
Extracellular: 10^-3 M
What are the approximate intracellular and extracellular concentrations of K+?
Transport of an ion/molecule can be described as what three things depending on the number of ions and the direction of their movement?
Symport is a type of co-transport that does what?
Transports different ions/molecules across the membrane at the same time, in the same direction
Antiport is a type of co-transport that does what?
Transports different ions/molecules across the membrane at the same time, in different directions
Which transporter is responsible for maintaining the concentration gradients of both K+ and Na+?
The sodium pump
The Sodium Pump exchanges how many K+ for Na+ and in which direction do they both travel in relation to the cell?
3Na+ travel OUT of the cell
2K+ travel INTO the cell
The setting up and maintenance of the Na+ K+ concentration gradient is essential for what?
Generating an action potential
Does the Sodium-Potassium Pump use passive or active transport? Primary or secondary?
The Sodium Pump creates a _______ intracellular K+ concentration
_____ diffusion is mainly responsible for resting membrane potential of ______ in neurones
The Sodium Pump is an example of what kind of transport?
The NCX is an example of what kind of transport?
The Sodium-Hydrogen exchanger is an example of what kind of transport?
The Na+- Glucose Co transporter is an example of what kind of transport?
What are the two functions of the Sodium-Potassium Pump?
Form Na+ and K+ gradients
Drive secondary active transport
Pumps are only found where and use what as a primary energy source?
In the plasma membrane