Chapter 6: 6.4 Membrane Transport Flashcards
What are the types of membrane transport?
- Passive transport
- Active transport
What are characteristics of passive transport?
- Molecules moves with a concentration gradient
- No energy is required
What are the two types of passive transport?
- Simple diffusion
- Facilitated diffusion
What is the difference between simple diffusion vs. facilitated diffusion?
Simple diffusion:
* No transport protein
Faciliatated diffusion:
* Requires transport protein
Where does facilitated diffusion occur through?
Occurs through:
* Protein channels that form a pore in the membrane
* Carrier proteins that physically bind to molecules and guide them through the membrane
What are the characteristics of active transport?
- Molecules move against the concentration gradient
- Requires an input of energy
What are the two types of active transport?
- Primary active transport
- Secondary active transport
Describe:
Osmosis
A form of passive/simple diffusion
* Water moves down its concentration gradient across a selectively permeable membrane
Describe the movement of water:
In an isotonic solution
Movement of water is even across the membrane in either direction
Describe the movement of water:
In a hypertonic solution
A gradient created by a molecule (e.g. too much salt outside the cells) results in a net movement of water out of the cell
* Results in shrivelling
Describe the movement of water:
In a hypotonic solution
A gradient created by a molecule (e.g. too much salt inside the cells) results in a net movement of water into the cell
* Results in swelling
In selective permeability:
What affects the permeability of molecules through the phospholipid bilayer?
Size and polarity
* The smaller the molecule, the easier it can cross the membrane
* Non-polar molecules are more permeable than polar molecules
In selective permeability:
What are non-polar molecules are more permeable than polar molecules?
The lipid bilayer has a largely non-polar interior, thus non-polar molecules are favoured
In selective permeability:
What is the exception to the polarity rule in permeability? Explain why
Water
* There are numerous aquaporin (water channels) in the membrane, allowing polar water to cross the membrane very quickly
Osmosis and Selective Permeability are forms of…
Passive/Simple Diffusion
True or False:
Facilitated diffusion requires energy
False, it only requires the help of a membrane protein, no energy required
Does facilitated diffusion go towards or away from the concentration gradient?
Towards (i.e. from high to low concentration)
What membrane proteins are used in facilitated diffusion?
- Channel proteins
- Carrier proteins
Compare:
Channel proteins vs. Carrier proteins
Channel proteins:
* Less selective
Carrier proteins:
* Selective towards on particular molecule
Describe:
Primary Active Transport
Uses energy for transport of a molecules against its concentration gradient
* Energy comes from ATP
What purpose does primary active transport have?
(Besides transporting against concentration gradient)
Can be used to generate an electrochemical gradient
* This may then be used as an energy source for secondary active transport
Give an example of:
Primary Active Transport
Na+/K+ pump
Describe:
Secondary Active Transport
Uses energy for transport of a molecules against its concentration gradient
* Energy comes from an electrochemical gradient generated by primary active transport
Explain:
The movement of molecules in secondary active transport
Movement of two molecules across membrane is coupled
* Molecule moving with its concentration gradient provides the energy for the one moving against its concentration gradient
