Ion Channels And Transporters Flashcards
What do channel proteins transport?
Water or specific types of ions and hydrophilic small molecules
Channel proteins transport these substances down their concentration or electric potential gradients.
What are nongated channels?
Ion channels that are open much of the time
What are gated channels?
Ion channels that open only in response to specific chemical or electrical signals
What is a ligand-gated channel?
A channel that opens in response to a ligand (chemical molecule)
What is a voltage-gated channel?
A channel that opens in response to changes in electrical potential (polarization and depolarization)
What triggers muscle contraction at the neuromuscular junction?
Opening of Acetylcholine-Gated Cation Channels
What are transporters also called?
Carriers
What are the three types of transporters?
- Uniporters
*Antiporters
*Symporters
What do uniporters transport?
A single type of molecule down its concentration gradient via facilitated diffusion
Glucose and amino acids cross the plasma membrane into most mammalian cells with the aid of uniporters
Give an example of a uniporter.
GLUT1 Uniporter
What do cotransporters use to power the uphill movement of another substance?
Energy stored in the electrochemical gradient of Na+ or H+ ions
What is a symporter?
A cotransporter that imports molecules together, such as glucose with Na+ ions
What is an antiporter?
A transporter that moves one substance in one direction and another in the opposite direction
What is the function of the Na+-linked antiporter in cardiac muscle cells?
Exports Ca2+ from cardiac muscle cells
This plays a principal role in maintaining a low concentration of Ca2+in the cytosol
What is the typical concentration of free Ca2+ in the cytosol of cardiac muscle cells?
Less than 0.2 micromolar (2×10-7M)
What happens to cytosolic pH during anaerobic metabolism of glucose?
Lactic acid is produced, leading to an increase in H+ ions
What are two types of cotransport proteins that help regulate cytosolic pH?
- Na+-linked symporters
- Na+-linked antiporters
How do membrane transport proteins regulate cytosolic pH?
By removing excess protons generated during metabolism
Describe the biological mechanism of GLUT1 uniporter.
It undergoes conformational changes to transport glucose into cells
Describe the biological mechanism of the two-Na+/one-glucose symporter.
It couples the import of glucose with the import of two Na+ ions
How does glucose transport from the intestinal lumen into the blood?
Through transcellular transport involving multiple transport proteins
Fill in the blank: Channel proteins transport water or specific types of _______ and _______ molecules down their concentration or electric potential gradients.
ions, hydrophilic small
Fill in the blank: Gated channels include _______-gated channels and _______-gated channels.
ligand, voltage
Fill in the blank: Three types of transporters have been identified. They are _______, _______, and _______.
uniporters, cotransporters, antiporters
