Term
| What are the three main jobs of a neuron with respect to a "signal"? |
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Definition
The three main jobs of a neuron are:
1. To receive signals
2. To conduct signals
3. To transmit signals |
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Term
| What are the three names of the parts of a neuron? |
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Definition
1. Cell Body - location of the nucleus
2. Axon - single long protrusion that sends/conducts signals away from the cell body
3. Dendrites - cell protrusions that receive signals from axons |
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Term
| What is the charge inside of a nerve cell before and after action potential firing? |
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Definition
The voltage-gated Na+ channel opens briefly but then becomes inactive. It will remain inactive (and closed) until it is “reset” by the return to the original resting potential. Only after resetting, can the channel respond again to another threshold potential.
The charge inside a nerve cell before action potential firing is negative.
The charge inside a nerve cell after action potential firing is positive. |
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Term
| Is transport of K+ through the K+ leak channel in the plasma membrane active or passive? |
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Definition
| The transport of K+ through the K+ leak channel in the plasma membrane is passive. (All transport through protein channels is passive). |
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Term
| What role do they play in establishing the resting membrane potential? |
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Definition
Resting potential = the potential occurring when there is no net flow of ions
The return back to resting potential (repolarization) partly relies on the opening of the voltage-gated K+ channels; these channels open more slowly than the voltage-gated Na+ channels so there is time for the influx of Na+ to depolarize the membrane before the efflux of K+ begins to repolarize the membrane. |
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Term
| What is a membrane potential and how does the Na+/K+ pump play a role in setting it up? |
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Definition
Membrane potential can be thought of as the threshold that must be reached to get the channel to open.
The return to the resting potential [repolarization] relies, in part, in inactivation of the voltage-gated Na+ channel. It also relies on the opening of the voltage-gated K+ channels. These open more slowly than the voltage-gated Na+ channels so there is time for the influx of Na+ to depolarize the membrane before the efflux of K+ begins to polarize the membrane. |
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Term
| What is a threshold potential? What happens if it is exceeded? |
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Definition
| Threshold potential = If the polarization reaches the threshold, all voltage-gated Na+ channels will open simultaneously. Na+ rushes in the cell, causing rapid and large depolarization of the membrane. |
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Term
| What are the states of the voltage-gated Na+ channels before, during and after an action potential is generated? What must happen to restore the membrane back to the resting potential? |
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Definition
First, as the charge is building up, the channel is closed at resting potential.
Then the action potential initiates membrane opening and the channel opens briefly.
The channel quickly becomes inactive, not letting anything else pass through.
It remains inactive until the original resting potential is reached.
Only after this “reset” can the channel respond to another threshold potential. |
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Term
| What property of Na+ channels that occurs during membrane depolarization ensures that the electrical signal is only propagated in one direction? |
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Definition
Since they open briefly then become inactive, for it to proceed forward, it needs to be reset by the resting potential
Membrane potential can recover after action potential fires |
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Term
| Which opens first to initiate an action potential: ligand gated Na+ channel, voltage gated Na+ channel, or voltage gated K+ channel? |
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Definition
| Voltage-gated Na+ channel |
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Term
| How are signals passed from one neuron to another? |
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Definition
| A nerve impulse results from electrical disturbances in the plasma membrane that spread from one part of the cell to another – this electrical disturbance is called action potential and it consists of a wave of membrane depolarization that moves down the axon. This signal travels unidirectional from dendrites to axon branches. Once the signal has been transmitted along the length of the nerve cell, it needs to be sent to the next nerve cell (dendrites to axon branches to dendrites of the next nerve cell). |
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Term
| List 6 organelles found in a eukaryotic cell? Know the functions of these organelles |
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Definition
• Nucleus = contains main genome, DNA and RNA synthesis
• Cytoplasm = everything from nucleus-to-plasma membrane
• Cytosol = most protein synthesis, glycolysis and metabolic pathways synthesizing amino acids, nucleotides
• Endoplasmic Reticulum (ER) = synthesis of membrane proteins and secreted proteins, lipid synthesis
• Golgi Apparatus = covalent modification of proteins for transport to other parts of the cell
• Mitochondria and Chloroplasts = ATP synthesis |
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Term
| Would proteins in the lumen of the ER have disulfide bridges? What other differences would you expect compared to cytosolic proteins? |
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Definition
Yes, proteins in the lumen of the ER have disulfide bridges because the inside of the secretory pathway (ER, Golgi) is equivalent to the outside of the cell.
I would also expect that the lumen would have oligosaccharide sugars and no reduced SH groups. |
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Term
| How is a signal sequence attached to a protein and what is the function of a signal sequence? |
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Definition
| Proteins are targeted/sorted to specific compartments using specific Signal Sequences. Most newly synthesized proteins begin synthesis in the cytosol and their destinations depend on the sorting signals encoded in their amino acid sequence. These signals are recognized by sorting receptors. |
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Term
| Proteins destined for which compartment in the cell are likely to lack a signal sequence? |
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Definition
| A protein with no signal remains in the cytosol. |
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Term
| The nuclear localization signal is usually composed of which type of amino acids? |
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Definition
The nuclear localization signal (NLS) is located anywhere in the primary sequence of the protein. Usually, arginine and lysine-rich and quite short.
NLS = the amino acid sequence of the cargo protein. |
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Term
| What effect does Ran-GTP have on the interaction between the nuclear import receptor and its cargo? |
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Definition
| Ran-GTP causes the NLS (amino acid sequence of the cargo protein) to dissociate from the nuclear import receptor. |
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Term
| Which is active for nuclear import: Ran-GTP or Ran GDP? Which predominates in the cytosol? |
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Definition
Ran-GTP is active and predominant in the nucleus
Ran-GDP predominates in the cytosol |
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Term
| What is a nuclear import receptor bound to when it moves into the nucleus? |
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Definition
| The nuclear import receptor recognizes and binds to the cargo. The import receptors deliver the cargo to the NPC and escort it through the pore. |
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Term
| When it the nuclear import receptor transported back into the cytoplasm? |
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Definition
The receptor must be recycled back to the cytoplasm for transport to continue; this occurs in step 4 of the transport cycle.
The Ran-GTP/receptor complex associates with the nuclear pore and travels out of the nucleus via the pore. |
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