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Molecular Cell Biology LSCI > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

Que signifie ‘’ the lipid-bilayer is SEMI-PERMEABLE’’ ?

A

Que la membrane est perméable (permissive) à certaines substances, mais pas toutes.

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2
Q

V\F

The more charged the molecule, the more easily it crosses the lipid bilayer.

A

F

The more charged the molecule, the less easily it crosses the lipid bilayer.

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3
Q

Place ces substances en ordre de facilité à traverser la membrane cellulaire:
H2O, sucrose, Ca2+, O2.

A
  1. O2 (Hydrophobic)
  2. H2O (Small Uncharged Polar)
  3. Sucrose (Large Uncharged Polar)
  4. Ca2+ (Ions)
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4
Q

What is the name of a transporter that can bind to a specific solute molecule and allows it to cross the cellular membrane?

A

A membrane protein

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5
Q

What kind of links form membrane proteins?

A
  1. Temporary Hydrogen bond

2. Electrostatic interactions

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6
Q

Is there binding to the solute molecules in channel proteins

?

A

No. Channel proteins simply keeps a hole open. NO BINDING.

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7
Q

Without energy input, in what direction does the solute move?

A

Which direction it goes depend on the CONCENTRATION GRADIENT (from high to low concentration).

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8
Q

What are the 3 part of passive transport and what characterized them?

A
  1. Simple diffusion
  2. Channel mediated
  3. Transport mediates
    NO ENERGY INPUT (from high to low concentration)
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9
Q

What allows active transport?

A

To move from low to high concentration

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10
Q

If the inside of the cell is positive, which of the cation or the anion would move inside more easily?

A

The negative anion , because it would be attracted by the positive charge.

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11
Q

Is there a maximum to transport rate?

A

There is a maximum to transport rate for transporters, because they can only transport a maximum number of molecules at a time. However, diffusion rate is linear, it only depends on gradient concentration.

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12
Q

What are the 3 most types of active transport?

A

I. Coupled transport: uses the concentration gradient of a solute to move another solute
II. ATP diven
III Light

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13
Q

What is the name type of a simple transporter that moves a single solute molecule?

A

Uniport

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14
Q

What is the name type of a transporter that moves 2 molecules at a time in the same direction?

A

Coupled-SYMPORT

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15
Q

What is the name type of a transporter that moves 2 molecules in opposite direction?

A

Coupled-ANTIPORT

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16
Q

What is the occluded form?

A

Meaning that the transporter is closed

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17
Q

How does the glucose moves trough the membrane?

A

The glucose move through COUPLED-SYMPORT movement with a coupled-transporter that uses (Na+)SODIUM

18
Q

How is the sodium transported in the extracellular fluid?

A

The sodium is actively transported out of the cell in a Sodium-Potassium ANTIPORTER that uses ATP

19
Q 
Name the molecules used in those type of ATP transporters.
I. P-type pump
II. ABC transporters
III. V-type proton pump
IV. F-type ATP synthase
A

I. P-type pump: IONS out of the cells
II. ABC transporters: wide variety of small molecules
III. V-type proton pump: protons, ATP (hydrolysis)
IV. F-type ATP synthase: protons (synthesize ATP)

20
Q

What type of ATP transporters is able to move anti-cancer drugs?

A

ABC transporters

21
Q

What is the role of the P-type calcium transporter in the ER muscle cells?

A

To bring the calcium ions OUT of the sacroplasmic reticulum of the cell while using ATP (symporter of calcium and protons)

22
Q

Name 2 exemple of P-types transporters

A

I. Calcium SYMPORTER of the ER of muscle cells

II. Sodium-Potassium ANTIPORTER

23
Q

How many molecules of ATP usually use ATP transporters?

A

2 ATPs

24
Q

What is the name of the part of a channel proteins that only allows some molecules in the channel?

A

The selectivity filter

25
Q

Is the channel protein always open?

A

No. It can be closed or open

26
Q

What are the different signals that channel proteins can respond to?

A

I. Voltage: voltage-gated channel
II. Ligands (small molecules) IN or OUT - ligand-gated channels (extra\intra cellular)
III. Physical\mechanical movement -mechanically gated channel

27
Q

What is the particularity of the alpha helix in the voltage gated potassium channel?

A

The alpha helix is slightly positive at one end, and slightly negative at the other (POLAR)

28
Q

What are the 4 important parts of the voltage-gated potassium channel?

A
  1. Alpha helices
  2. Central pore
  3. Vestibule
  4. Selectivity filter
29
Q

Is the voltage gated potassium channel permeable to water?

A

No. The selectivity filter is too small for water to pass through.

30
Q

Is the vestibule and the pore of the voltage gated potassium channel selective?

A

No. They allow for different types of ions and water to get in until they reach the selectivity filter.

31
Q

How come the potassium can passe the selectivity filter of the voltage fated potassium channel but not the sodium?

A

Because potassium is able to make transcient 4 H bounds in the selectivity filter, wich removes water, but not sodium (too small). Therefore the energy required to remove water is too low.

32
Q

How works the mechanosensor in bacteria that responds to osmotic presur?

A

Water entering the cell make the volume increase, which make the membrane stretched and opens the channel.

33
Q

What are the 4 importants part in the voltage gated sodium channel in the neurones?

A
  1. Ion channel
  2. Selectivity filter
  3. Voltage sensors
  4. Inactivation domain
34
Q

T\F

The alpha helices in neurones move in response to a change in voltage

A

T

35
Q

What is the normal voltage difference across the neurone membrane?

A

-60 mV to -70 mV

36
Q

What is the level of mV where the voltage triggers the channel to open and autorise ion flow across the membrane in neurones?

A

-55 mV

37
Q

When is voltage gated sodium channel open?

A

When the extracellular space is negative and the cytosol positive.

38
Q

What are the name of the channels in the post-synaptic membrane that respond tu neurotransmitters?

A

Ligand-gated ion channels.

39
Q

How many subunits is there in the ligand-gated ion channel of the post synaptic membrane?

A

5

40
Q

What does the selectivity filter passes in the post synaptic membrane?

A

Positive ions

Molecular Cell Biology LSCI (2 decks)

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