Cell Bio Homework #5 Flashcards
Why does nitric oxide (NO) act as a paracrine signal that affects only neighboring cells?
It is rapidly converted to nitrates and nitrites in the extracellular fluid.
During the activation of a neuron, the action potential propagates in only one direction. How is this achieved in the neuron?
The Na+ channel becomes inactivated and refractory to reopening for a short time after the action potential passes.
RTKs can activate the enzyme phosphoinositide 3-kinase, which phosphorylates inositol phospholipids. These phospholipids then do what?
serve as docking sites that recruit specific intracellular signaling proteins to the plasma membrane
Cardiac muscle cells contain a Na+/Ca2+ transporter responsible for maintaining a low cytosolic Ca2+ concentration, which helps regulate cardiac muscle contraction. Ca2+ is transported out of the cell as Na+ is brought into the cell. What type of transporter is this protein?
antiport
PI 3-kinase acts by phosphorylating what molecule(s)?
inositol phospholipids
When cells respond to an extracellular signal, they most often convert the information carried by this molecule from one form to another. What is this process called?
signal transduction
Ethylene is a hormone that promotes the ripening of fruit. What happens in the absence of ethylene?
The activated ethylene receptor promotes the degradation of a transcription regulator and the ethylene-responsive genes remain turned off.
For voltage-gated channels, a change in the membrane potential has what effect on the channel?
It alters the probability that the channel will be found in its open conformation.
Which of the following form tiny hydrophilic pores in the membrane through which solutes can pass by diffusion?
channels
What do the phosphorylated tyrosines on activated RTKs do?
They serve as binding sites for a variety of intracellular signaling proteins.
When Na+ channels are opened in an animal cell, what happens to the membrane potential?
It becomes less negative inside the cell.
Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest?
oxygen, glucose, sodium ions
In one experiment, investigators create a liposome—a vesicle made of phospholipids—that contains a solution of 1 mM glucose and 1 mM sodium chloride. If this vesicle were placed in a beaker of distilled water, what would happen the fastest?
H2O would diffuse in.
How do transporters and channels select which solutes they help move across the membrane?
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.
Which statement about cell signaling is correct?
Each receptor is generally activated by only one type of signal molecule.
