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Membrane Transport Flashcards

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1
Q

What does the rate at which a solute can cross a lipid depend on?

A

Size and solubility

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2
Q

What is a rate that a small non-polar molecule can pass through a lipid bilayer?

A

Small non-polar molecules can rapidly diffuse because they readily dissolve in lipid bilayer.

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3
Q

Can an uncharged polar molecule cross the lipid bilayer?

A

Uncharged polar molecule can only cross if they are small enough. Larger uncharged polar molecule hardly cross at all?

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4
Q

Can an a charged molecule cross the lipid bilayer?

A

No they cannot. No matter how small or how big the molecule is, any charged molecule cannot cross the lipid bilayer.

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5
Q

Why is the concentration of ion of the cell’s interior different from the concentration of ion outside the cell?

A

Lipid bilayer are impermeable to inorganic ions.

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6
Q

Why is the difference in ion concentration between the interior and the exterior of the cell so important?

A

The differences in ion concentration are crucial to a cell’s survival and function. The movement of ion across cell membrane plays a role in the production of ATP in the cell.

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7
Q

What must happen for a cell to avoid being torn apart from by electrical force of ions?

A

The quantity of positive charge must be balanced by the quantity of negative charge.

Ex:
The high concentration of Na+ outside the cell is balanced by the extracellular Cl-.
High concentration of K+ inside the cell is balanced by variety of negatively charged ion inside or outside.

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8
Q

What does channel protein let through?

A

Small ions and water molecules

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9
Q

What controls whether molecules move into the cells or out of it?

A

The direction of transport depend only on the relative concentration of the solute on either side.

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10
Q

What is passive transport?

A

Cellular transport in which no energy is invested because the molecule is flowing from a spontaneous high concentration to low concentration.

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11
Q

What is active transport?

A

Transport of molecules in which energy is invested to move the molecule against the concentration gradient

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12
Q

Why is moving from a high concentration to a lower concentration a passive transport?

A

It is more energetically favorable, thus no energy is needed to invest in order to move a molecule from a high concentration to low concentration

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13
Q

Why is energy needed for transport to move the molecule against the concentration gradient?

A

The molecule must travel uphill and is energetically unfavorable.

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14
Q

What type of energetic transport can a channel protein do?

A

Only passive transport

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15
Q

What type of energetic transport can a transport protein do?

A

Both passive and active

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16
Q

What type of molecules require the use of membrane protein?

A

Polar and charged molecules. Non polar do not need membrane protein because they can diffuse into the lipid bilayer.

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17
Q

What are the three types of active transport?

A
  1. Gradient driven pump
  2. ATP-driven pump
  3. Light driven pump
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18
Q

Why is actively transporting solutes against the concentration gradient essential?

A

Cells need to achieve the appropriate intercellular ionic composition.

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19
Q

What is a ATP driven pump?

A

Pumps that use the energy released by the hydrolysis of ATP to drive uphill transport

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20
Q

How does sodium-potassium pump work in animal cells?

A

A phosphate group from an ATP and a Na+ binds to the pump. This induce a confirmation change to the protein that transfer the Na+ across the membrane and release it outside the cell. The K+ ion from the outside of the cell bind to the pump and the pump dephosphorylates itself, allowing the protein to return to its normal configuration, transferring the K+ across the membrane and releasing it into the cytosol.

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21
Q

Why are ATP driven pump so important in animal cells?

A

It help maintain the proper concentration of Na+ and K+ inside and outside of the cell for the animal to maintain membrane potential

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22
Q

What is a Ca2+ pump?

A

An ATP driven pump that actively transport calcium out of the cell from a low concentration to a high concentration

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23
Q

What makes the Ca2+ pump different from the Na-K pump?

A

The Ca2+ is exactly like the sodium-potassium pump but the Ca2+ pump returns to its original confirmation after pumping Ca2+ out of the cell. The Ca2+ does not require a second ion to return to its original confirmation, whereas the Na-K pump require a second ion (K+) to return to its original shape.

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24
Q

What is a coupled transport?

A

The simultaneous transport of two substances across a membrane. The molecules can be symport or antiport.

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25
Q

What is the differences in symport and antiport coupled transport?

A

The solutes in symport travel to the same place while the solutes in antiport travel in opposite direction

26
Q

How does a symporter work?

A

Two molecules are transported to the same place. However one molecule is using the kinetic energy of the other molecule to travel because it is moving against the concentration gradient.

Example
There are two molecules: A and B
There is a greater concentration of A and B inside the cell than outside the cell. However molecule A needs to travel to the inside (against the concentration gradient) while molecule B can freely enter the transport (with the concentration gradient). Therefore, while molecule B is flowing, it will generates kinetic energy in which molecule A can use to travel against the concentration gradient.

27
Q

How does a anti
porter work?

A

Two different molecules traveling opposite to each other.

For example:
There are two molecules: A and B
There are more concentration of A inside the cell than outside the cell, and molecule A need to go inside the cell (moving against the concentration gradient). On the other hand, there is a greater concentration of molecule B inside the cell than outside, and molecule B needs to go outside the cell (moving with the concentration gradient). Therefore, when molecule B flows with the concentration gradient, molecule A will use molecule B’s kinetic energy to travel against the concentration gradient.

28
Q

What is an ion channel?

A

Channel proteins that allow the passive movement of small, water-soluble molecules and into or out of the cells

29
Q

What are the properties of ion channels?

A
  1. They show ion selectivity
  2. Ion channels are not continuously open. They only briefly open and close again.
30
Q

Why is the maximum transport rate for channel so much greater than transporter?

A

Channel do not have a sequence of energetic interaction which saves time. Transporter do so it’s slower

31
Q

What are the four ways an ion channel can open?

A
  1. Change in voltage difference across the membrane; voltage gated
  2. Binding of ligand to extracellular face; Ligand-gated extracellular
  3. Binding of ligand to intracellular face; Ligand-gated intracellular
  4. Mechanical stress; stress
32
Q

Why do is there different inside/outside concentration of ions/charged molecule?

A

Ions/charged molecules are impenetrable through the lipid bilayer.

33
Q

What is a membrane potential?

A

Voltage difference across a membrane due to a slight excess of positive ions on one
side and of negative ions on the other;

34
Q

What cause a membrane potential?

A

Different ion concentration on either side of the lipid bilayer

For example: more positive ion on one side of the bilayer than the other

35
Q

What does Nerst Equation depend on, assuming the lipid bilayer is at equilibrium?

A

The concentration of ions outside of the cell and inside the cell.

36
Q

What does Nerst Equation tell us?

A

The theoretical resting membrane potential if the ion concentrations on either side of the membrane are known.

37
Q

What determines the more influential ion for a membrane potential when using nerst equation?

A

The more influential ion is always going to be the one closest to the cell membrane potential

38
Q

What are the three main components that makes up a neuron?

A
  1. Cell Body
  2. Dendrites
  3. Axon
39
Q

What does the axon do?

A

Conduct electrical signal away from the cell body towards its target cell

40
Q

What does the dendrites do?

A

Receive signals from the axons of other neurons

41
Q

How do neurons communicate with each other?

A

They send each other electrical signals called action potential.

42
Q

What is an action potential?

A

an electrical signal that travels along a neuron’s membrane

43
Q

What causes an action potential?

A

The voltage gate Na+ and K+ play a role in action potential. The voltage gate contribute to a rapid rise and subsequent fall in membrane potential across a cellular membrane, causing an action potential.

44
Q

What is the process of creating an action potential

A
  1. When a neuron is stimulated, the membrane potential will depolarize (become less negative). This cause the voltage gated Na+ channel to open, allowing the Na+ to enter the cell.
  2. If conditions are met, the threshold of membrane voltage will be passed and
  3. There will be a rapid increase in Na+ because more Na+ channel will open, further depolarizing the cell.
  4. If the desired voltage of the membrane potential is reached, the voltage-gated channel will be inactivated, thus no more Na+ will enter the cell.
  5. Because the cell is depolarized, voltage-gated K+ channels will be opened, K+ ions will flow out of the cell down to their electrochemical gradient.
  6. The voltage of the membrane potential is lowered, repolarizing the cells as K+ ions flow out of the cell.
  7. Both the Na+ and K+ channel will close because the membrane is back to its resting potential
45
Q

What happens if the membrane is fully depolarized?

A

The voltage gated Na+ channel will adopt an inactive confirmation and the voltage gated K+ channel will activate.

46
Q

What controls the direction of action potential?

A

The inactivation of sodium channel. The sodium channel have a refractory period, during which they cannot open again. Therefore, the action potential cannot move backward because the sodium channel are not facilitating the action potential’s backward direction.

47
Q

How does action potential move fast?

A

The neurons in vertebrate have a myelin sheath which allow faster propagation of an action potential

48
Q

What is a myelin sheath?

A

An insulated layer that forms around the nerve

49
Q

What happens if the myelin sheath around a neuron is damaged?

A

Nerve impulse slow down or may even stop, causing disorder.

Ex: Sclerosis is caused because the immune system is attacking the myelin around the neuron.

50
Q

What happens when an action potential reaches the end of an axon - the nerve terminals?

A

The action potential is converted from an electrical signal into a chemical signal, called a neuro-transmitter because it cannot cross a synapse.

51
Q

What is a synapse?

A

the site of transmission of electric nerve impulses between two nerve cells (neurons)

52
Q

What happens after an action potential is converted into a chemical signal

A

The neurotransmitter (chemical signal) are stored inside a synapse vesicle.

The voltage gate Ca2+ channel will be activated in the presence of an action potential.

Because there is a greater concentration of Ca2+ outside the nerve terminal, Ca2+ will rush in, triggering the fusion of the vesicle to the plasma membrane.

This will release the neurotransmitter in which the neurotransmitter will bind and open to the ion channel of the postsynaptic cell.

The resulting flow will alter the membrane potential of the postsynaptic cell, depolarizing the cell which will convert the chemical signal back to an electrical one.

53
Q

What does it mean for a neurotransmitter to be excitatory

A

If a neurotransmitter is excitatory. channels will allow an influx of Na+, which depolarize the plasma membrane which activate the postsynaptic cell, encouraging it to fire an action potential.

54
Q

What does it mean for a neurotransmitter to be inhibitory

A

If a neurotransmitter is inhibitory, channels will open, allowing Cl- to enter the cell. The influx of Cl– inhibits the postsynaptic cell by making its plasma membrane harder to depolarize.

55
Q

What are the chief receptors for excitatory neurotransmitter?

A

Glutamate and Acetylcholine

56
Q

What are the chief receptors for inhibitatory neurotransmitter?

A

g-aminobutyric acid (GABA) and Glycine

57
Q

What does the acetylcholine receptor do?

A

Mediates signal from nerves to muscle

58
Q

What happens if there is a defect in ion channels?

A

A number of inherited disorders may be caused

Ex:

  • Migraines (Ca+2 channel; voltage activated/gated),
  • Myasthenia gravis (Na+ channel; acetylcholine Receptor),
  • Cystic Fibrosis
59
Q

What is the application of understanding inhibitory neurotransmitter?

A

Psychoactive drugs can be made. They affect synaptic signaling by binding to neurotransmitter receptors

60
Q

What is channelrhodopsin

A

Light gated ions that serves as sensory photoreceptors

Biology (20 decks)

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