L2 Cell Membrane Transport Flashcards
What are all the types of molecules that pass through the membrane?
- Hydrophobic
- Small molecules
- Large molecules
- Ions
What molecules are allowed to pass through the membrane by membrane proteins?
Membrane proteins allow polar and charged molecules to pass through the membrane.
What are the two major membrane transport processes?
Passive transport and Active transport.
Which processes uses passive transport? What is the energy source of passive transport?
- Process - Simple and Faciliated diffusion
- Energy source - Concentration Gradient
Which direction does the solute move in relation to its electrochemical gradient?
Moves down the electrochemical gradient
What is the type of solute and transport protein involved in osmosis?
Solute is water and transport proteins are aquaporins.
What is the type of solute and transport protein involved in facilitated diffusion?
Solutes are large and charged ion such as glucose, amino acids, they require channel proteins to pass through the membrane
What is the type of solute and transport protein involved in simple diffusion?
Solutes are: small uncharged molecules like O2, CO2 and lipids. No transport proteins are involved
Which processes use active transport? What is the energy source, the direction of solute in relation to its electrochemical gradient?
- Process - Primary (Direct) and secondary (Indirect)
- Energy source is ATP
- Solutes move against their electrochemical gradient that means from a lower concentration to higher concentration.
What type of solute and transport proteins are involved in active transport?
- Types of solute are ions (Sodium, potassium and calcium), nutrients (Glucose, amino acids) and larger molecules (Proteins).
- Transport proteins - Carrier proteins and ion pumps eg. NaK Pump.
What is the difference between primary and secondary active transport?
Primary needs ATP
Secondary uses the energy stored in the electrochemical gradient.
What does passive transport depend on?
Concentration Gradient.
Explain simple diffusion
Movement of substances from a high concentration to a low concentration
What is Flux (Jx) and what does it depend on?
Flux- how fast solute X moves across a cell membrane. Flux depends on permeability coefficient of X and difference in concentration of X between ICF and ECF.
What do transmembrane proteins do and what are they made up of?
Transmembrane protein move hydrophilic solutes in and out of the membrane. They are composed of membrane - spanning alpha - helical domains
What does topology mean?
Topology is how protein move in and out of the membrane.
What are the types of transmembrane proteins?
1.Pore ( Non-gated channel)
2. Channel (Gated-pore)
3. Carrier
4. Pump
How do transmembrane proteins transport substances?
Transmembrane proteins create hydrophilic permeation pathways through the membrane
What does the hydrophilic permeation pathways consist of?
They consist of amphipathic helices with alternating hydrophobic and hydrophilic amino acids
Hydrophobic faces the lipid membrane and hydrophilic creates a central pore.
What do pores do and what are the driving forces?
Pores allow faciliated diffusion (Passive Transport)
The driving force is the electrochemical gradient
What do channels do and what are the driving forces?
Channels allow faciliated diffusion (Passive transport) and the driving force is the electrochemical gradient.
What is the major difference between pores and channels?
Pores are always open and channels have gated ion channels.
What are the types of channels?
The types of channels are:
1. Voltage gated
2. Ligand gated intracellular
3. Ligand gated extracellular
4. Mechanical gated
What does each channel have?
Each channel has:
1. A moveable gate
2. A sensor (ligand, voltage or mechanical)
3. A selectivity filter
4. An open channel pore.
What do carriers do and what are the driving forces? Give examples of carriers?
Carriers allow faciliated diffusion and the driving force is the electrochemical gradient. Eg. GLUT
Carriers never have a continous transmembrane path
Carrier’s faciliated diffusion is slow. Why is that?
Binding and confrontational changes
Limited number of binding sites competition for binding sites.
What other components do carriers use to mediate active transport?
They use pumps, co transporters and exchangers.
What do cotransporters do? E.g.?
Co transporters move both solutes in the same direction using the energy provided by the electrochemical gradient. Eg. Na+ glucose cotransporter.
Symporters - same direction
What do exchangers do? Eg?
Exchangers move solute in the opposite direction using the driving solute whose electrochemical gradient provides the energy. eg. Na+/Ca2+ exchangers.
Antiporters - opposite directions
Flux (Jx) can be limited by 2 factors. What are these factors?
Number of carriers in the membrane
Speed by which the carrier can cycle through the steps
How can carriers mediate active transport?
They mediate active transport through the use of pumps, cotransporters and exchangers
What types of protein carriers do primary and secondary active transport use?
Primary active transport - pumps
Secondary active transport - cotransporters and exchangers
