Exam 2 Flashcards
What are mechanisms for restricting the movement of proteins in the membrane?
Tethering proteins to the cell cortex, using barriers such as tight junctions, tethering proteins to the surface of another cell, and tethering proteins to the extracellular matrix
What type of molecules can readily (without the help of a protein) pass the lipid bilayer?
Small polar molecules that have no charge, such as ethanol and small hydrophobic molecules like gases
How does Ca2+ get removed from the cytoplasm of a muscle cell after a contraction?
Active transport using Ca2+ pump (ATPase)
Movement of glucose out of intestinal epithelial cells in order to enter into the bloodstream is via what mechanism (or transporter type)?
Passive transport/facilitated diffusion
In animals, the concentration gradient of what ion is often used to drive the movement of other molecules against their concentration gradients?
Na+
What are properties of a passive transporter?
The transporter binds to the molecule prior to transferring it across the membrane and the molecule transported can go either direction across the membrane, depending on the concentration gradient.
What is osmosis?
The movement of water from an area of low solute (high water) concentration to an area of high solute (low water) concentration.
What is the difference between transporters and channels?
Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate.
Where are sugars located in the intestinal epithelial cell?
In the lumen in the gut; they enter in to the cell and diffuse out the other side
Why are transporters kept in their place in epithelial cells?
Because they have diffusion barriers called tight junctions that prevent the movement of transporters because it’s important that transporters maintain in either the apical membrane or the basal/lateral membrane
Why do amino acids have a harder time getting across a membrane?
Their side chains are charged
What is a difference between flow in channels and passive transporters?
Transporters can open either direction via a confirmation change and move the molecule in either direction but channels can open or close but when they’re open the molecules just flow through the poer
What are ways to achieve active transport?
Coupled pump, ATP-driven pump, and light-driven pump
What are the natural concentration of Na and K in the cytosol?
Low Na concentrations and high K concentrations
What is the process of the Na/K pump?
Na ions enter binding sites on cytosolic sides to pump Na against concentration gradient and pump is phosphorylated to expose the Na ions to the cell. Binding of K allows the pump to return to normal
What is a uniport?
Carries one type of molecule
What is a symport?
Coupled transporter that carries two types of molecules in the same direction
What is an anti port?
Coupled transporter carries two types of molecules in different directions
What is the difference between a pump and a coupled transporter?
A pump requires ATP to drive the reaction
What is the Na/glucose co-tranporter?
Na movement down its electrochemical gradient drives glucose transport against its concentration gradient
What transporters are required for moving glucose from the intestine to the bloodstream?
Na/glucose symport and glucose uniport
Why do we have different ion concentrations inside the cell?
Transport molecules across the membrane, regulate cell volume/turgor, regulate absorption or release of water, and electrical signaling
What are the three types of gated ion channels?
Voltage-gated, ligand-gated, and mechanically-gated
Why are excitable membranes necessary?
Diffusion is inefficient over distance and very rapid signaling can occur through voltage changes
When do voltage gated K+ channels and K+ leak channels open during induction?
When the action potential is reached
What would happen if voltage gated Na+ channels were blocked?
The cell would be depolarized to the threshold potential of ~-40mV and then return to the resting potential of ~-60mV
What would happen if K+ channels are blocked?
Once action potential is reached, repolarization would be very slow
What would happen if the Na+/K+ pump was blocked?
Nothing because the pump sets up the concentration gradient but the action potential doesn’t really change concentration (would need many action potentials to have an effect if Na+/K+ pump was blocked)
What is the process of an action potential?
Local depolarization to threshold, depolarization opens nearby voltage-gated Na+ channels, initiating action potential, and resting potential is restored by rapid inactivation of Na+ channels and slower opening of voltage-gated K+ channels
What is the signaling pathway for a muscle contraction from the brain to the contraction?
Neurotransmitter released onto post-synaptic motoneuron in spinal cord, neurotransmitter opens receptor (ligand-gated) channels and depolarizes membrane, depolarization triggers action potential which is propagated to the synapse using voltage-gated Na+ and K+ channels, depolarization at the presynaptic terminal opens voltage-gated Ca2+ channels, Ca2+ influx triggers ACh release, and ACh binds ACh receptors and triggers a contraction
What is a neurotransmitter at the neuromuscular junction?
Acetylcholine
What is the most common excitatory neurotransmitter in the brain?
Glutamate
What is the most common inhibitory neurotransmitter?
GABA