BIO 1140 Chapter Notes - Chapter 6: Heterotrimeric G Protein, Signal Transduction, Resting Potential

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ochreduck341

21 Feb 2017

School

University of Ottawa

Department

Biology

Course

BIO 1140

Professor

Caroline Petit- Turcotte

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Document Summary

Uneven distribution of ions creates potential energy; measured in mv: more permeable to k+ than na+, more k+ inside cell and more na+ outside cell, more cl- ions outside than inside the cell. Sodium-potassium pumps redistribute k+ and na+ against their concentration gradients to restore the resting membrane potential before ligand was bound. Connection btwn membrane properties, membrane transport, signal transduction. Ion-channel-coupled receptors regulate flow of ions across the cell membrane. Used by specialized cells i. e muscle cells and neurons. Flow of ions is driven by electrochemical gradient and can change the membrane potential very quickly: can convert chemical signal, the signaling molecule, into an electrical signal, the change in membrane potential. Voltage-gated ion channels act downstream, are sensitive to changes in membrane potential in their vicinity. Tm receptors 1: ligand gated ion channels the ligand does not enter the cell, important for nervous system (used by many nts); focus on acetylcholine.

Related Questions

1. The plasma membrane of rod and cone cells are

a) At resting potential in the dark and deploarized in thelight

b) At resting pootential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperpolarized in the light

d) Hyperpolarized in the dark and at resting potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

2. The equilibrium potential of K+ ions in nerve cells is about-90mV. The membrane potential of a typical nerve cells at rist is-70mV. Therfore

a) Increasing the permeability of a resting neuronal membrane toK+ ions will increase the membrane potential (that is, make it morenegative, inside with respcect to outside)

b) In nerve cells at rest, there is a net diffusion of K+ ionsout of the cell

c) Increasing the membrane potential of a nerve cell would slowthe diffusion of K+ ions out of it.

d) K+ is not the only ion that is permeable at rest

e) All of the above

3. Which of the following is responsible for the replarizingphase of the action potential?

a) Voltage-gated Na+ channels are opened.

b) The Na+-K+ pump restores the ions to theri original restingstate.

c) The permeability to Na+ increases greatly.

d) ATPase destroys the energy supply that was maintaining theaction potential at its peak.

e) The permeability to K+ increases greatly while that to Na+decreases

4. The Relative refractory period of an axonm conincides withthe period of

a) Activation and inactivatioin of voltage-gated Na+channels

b) Increased Na+ flux into the cell

c) Increased K+ flux into the cell

d) Increased K+ flux out of the cell

e) Increased Na+ flux out of the cell

5. The plasma membranes of rod and cone cells are

a) At resting potential in the dark and epolarized in thelight

b) At resting potential in the dark and hyperpolarized in thelight

c) Depolarized in the dark and hyperoplarized in the light

d) Hyperpolarized in the dark and tat resing potential in thelight

e) Hyperpolarized in the dark and depolarized in the light

**Please only answer if you are 100% correct!

1. Why are Na+, K+, and Clâ the only ions considered in the GK equation when calculating resting membrane potential (Vm)?

A. These ions are found in the highest concentrations inside the cell

B. These are the ions to which cell membranes are permeable at rest

C. Only these ions have enough charge to influence Vm

D. These ions bind to receptors that increase the charge on the membrane

2. Voltage-regulated channels are located

A. on the neuron cell body only

B. within the cytosol only

C. in the membranes of axons only

D. in the membranes of dendrites only

E. in the membranes of dendrites, in the membranes of axons, and on the neuron cell body

3. As the charge on the membrane of a typical neuron approaches 0 from -70 mV, the cell is

A. hyperpolarizing and becoming more difficult to stimulate

B. only becoming more difficult to stimulate

C. only hyperpolarizing

D. only depolarizing

E. only repolarizing

1. The plasma membrane of liver cells contains a glucose uniportthat transports glucose by facilitated diffusion. When the[glucose] is higher inside the liver cell than the [glucose]outside the liver cell, the glucose uniport will

A. couple the transport of glucose out of the cell to thehydrolysis of ATP

B. couple the transport of glucose into the cell to thehydrolysis of ATP

C. switch to a closed conformation, allowing no transport ofglucose

D. transport glucose out of the cell by passive transport

E. transport glucose in of the cell by passive transport

2. Unlike the positive charged ion shown in the middle diagramof figure 11-4B, K+ is higher in concentration inside the cell. Howwill the membrane potential of a cell at rest (shown in both themiddle and right-hand diagrams of Figure 11-4B) affect theelectrochemical gradient for K+?

A. The membrane potential will increase the electrochemicalgradient

B. The membrane potential will decrease the electrochemicalgradient

C. The membrane potential will have no effect on theelectrochemical gradient

3. Which of the following proteins carries out activetransport?

A. gluclose symport

B. Bacteriorhodopsin

C. ABC transporter

D. NA K pump

E. All of the above

4. Aquaporin will not transport Na+ ions because

A. Two asparagine residues in the channel prevent the passage ofNa+ ions by binding the oxygen of each water molecule as it passesby

B. Na+ ions are repelled by the positive charges at the entranceto the channel

C. Na+ ions cannot make contact with the carbonyl (C=O) groupson all four sides of the channel

D. The passage of Na+ ions is energetically unfavorable becauseone side of the channel is hydrophobic in nature

5. The acetylcholine receptor is different from other channelproteins we have discussed, such as the K+ leak channel,because

A. The acetylcholine channel is composed of a single polypeptiderather than multiple subunits

B. The acetylcholine channel transports Na+ ions against theconcentration gradient for sodium

C. The acetylcholine channel has a much smaller diameter thanother channel proteins

D. The acetylcholine channel transports ions with theirassociated shell of water molecules

E. The acetylcholine channel is always open, and never switchesto a closed conformation

6. After opening briefly along the axon of a neuron,voltage-gated ion channels switch to an inactivated conformationthat slowly returns to the original closed conformation of theprotein. This slow change in conformation, requiring about amillisecond, is important because

A. all of the ions that were transported across the membranewhen the ion channels were open must be actively transported backto the other side of the membrane, restoring the originalconcentration gradient, before the ion channels can open again

B. ATP hydrolysis is necessary to drive this energeticallyunfavorable change in conformation

C. it prevents the action potential from reversing direction andtraveling back toward the cell body of the neuron

D. the channel protein must be dephosphorylated in order tocomplete the transport process and return to the originalnonphosphorylated conformation

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BIO 1140 Chapter Notes - Chapter 6: Heterotrimeric G Protein, Signal Transduction, Resting Potential

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