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Transport And Motility > Transport > Flashcards

Transport Flashcards

1
Q

Describe the specificity of a channel

A

The water molecules are oriented so that H’s always face the channel opening repelling excess H ions on both sides.
Water molecules pass through one at time, rotated 180 degrees in the middle of the channel.

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2
Q

What are the different channel gating structures?

A

Ligand gated: signal molecule binding induces a conformational change to open the channel.
Voltage gated ion channels

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3
Q

Describe voltage gated ion channels.

A

Transmembrane helices, 4 identical subunits
Gating: some have both internal and external gates, some have only an internal gate.
Internal are voltage sensitive, external gate blocks channel to halt ion flow.

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4
Q

Describe the different voltage gating ion channel gating that is possible

A

Both internal and external
Internal only
External voltage sensitive
External to block ion flow

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5
Q

Describe potassium channel selectivity

A 
Negative charges near both openings 
Non polar aas line the middle of the channel
Selectivity filter is a carbonyl ring
Negative charges attract K
Selectivity filter fits k without h2o
Na does not fit.
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6
Q

Describe the k channel events

A

K enters from cytoplasmic side
Non polar aas increase speed of ion movement
Selectivity filter holds 2 ks, incoming ions repel k within selectivity filter

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7
Q

What is the energy source of ATP dependent active transport? What is another name for it? What kind of pump does it use?

A

ATP hydrolysis
Primary active transport
ATPase

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8
Q

What kind of energy source does cotransport use?

A

Gradient energy from a different ion or molecule

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9
Q

Describe ATP dependent active transport

A

Na and k pump
3 Na out and 2 k in per ATP hydrolyzed
Driving force is ATP hydrolysis
Na and k are moving agains their concentration gradient
Pi causes transport protein to change conformation

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10
Q

Describe co transport or secondary active transport

A

Targeting substance moves against its concentration gradient (active transport)
Energy supplied by second substance moving down its gradient–driving force
Symport and antiport

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11
Q

What is symport?

A

Form of secondary active transport where both species move in the same direction

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12
Q

What is antiport?

A

Form of secondary active transport where the species are moving on opposite directions

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13
Q

Describe an example of secondary active transport

A

Glucose transport and uptake
Driving force is Na gradient
Na moving down its concentration gradient allows glucose to accumulate
Symport

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14
Q

What is the extrinsic pathway of apoptosis?

A

Suicide, death signal(FASA ligand) binds death receptor (FAS) , activated initiator caspase 8 , activate effector caspase 3

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15
Q

Describe the intrinsic pathway of apoptosis

A

Cell damage- mitochondrial leakage- release

Cytochrome c- activation of initiatory caspase 9, activation of effector caspase 3

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16
Q

Describe the pathway that both intrinsic and extrinsic pathways of apoptosis go through?

A

Activation of CAD , cut DNA , cleave cytoskeleton, cell rounding, nuclear fragmentation and chromosome condensation, membrane alternations, eat me signal, phosphotidylserine, cell fragmentation into apoptotoc bodies to undergo phagocytosis

17
Q

What are the three stages a voltage gated ion channel can be in?

A

Open
Closed
Inactivated

18
Q

What controls channel opening and closing in VG ion channel?

A

Due to internal gate

Voltage sensing helices within channel

19
Q

How is a VG channel inactivated?

A

Channel opening exposes binding site for inactivating segment. (Ball or flap)

20
Q

What kind of inactivation thing does a K channel have?

A

External gate is ball and flap

21
Q

What kind of gate does Na channel have?

A

Flat

22
Q

Describe a K channel?

A 
Identical subunits
Selectivity pore or filter
Internal gate voltage sensor 
External gated are four ball and chain structures 
Some K channel lack external gates
23
Q

Describe Na channels

A

1 subunit and four domains
Selectivity filter pore
Internal gate is a voltage sensor
External gate is a flap

24
Q

What is the structure of the internal VG?

A

They have sensory helices

Lots of positive charges from lysine and arginine

25
Q

Describe the resting state of an internal VG channel

A

Internal gate is closed

26
Q

What happens during stimulus in a VG channel?

A

Ana cation potential next door changes electrical movement
Voltage sensing helices move toward exterior side of membrane
Internal gates open

27
Q

What happens when a VG channel is inactivated?

A

Inactivation segments block pore, stop ion flow

28
Q

What happens when a VG ion channel returns to resting state?

A

Electrical environment returns to resting state
Inactivation segment releases
Internal gate is closed
Closing is slow, inactivation fast

29
Q

What are the membrane proteins associated with neurons?

A

Na K pumps

VG Na an k channel

30
Q

Wha is the charge of the inside of a neuron relative to the outside?

A

Negatively charges inside in relation to the outside

31
Q

How is electrical charge generated in a nerve impulse?

A

Ion movement

32
Q

What influences the tendency for an ion to move across the membrane?

A

Concentration gradient

Electrical charge

33
Q

What has a higher concentration inside the cell? Na or K?

A

Na

34
Q

What happens during signaling along the axon?

A

Incoming signal opens ion channel on the dendrites
Passive spread of ions across the cell body
Summation of signal. If above threshold:
Nervier impulse and action potential will be generated along the axon
Depolarization occurs Na channels open and Na enters, cytoplasm becomes positive

35
Q

How does an axon return to normal following a signal?

A

Na channels are inactivated or blocked
K internal leaves, cytoplasm returns to negative charge
K channels close Na channels close
Dip below resting potential influences the ability to generate another action potential( refractory period)

36
Q

What is the structure and the details of a channel?

A

Made up of multiple helices
Channel narrows and H2O passes through single file
Non polar amino acids are interspersed throughout the polar amino acids to speed up the water movement.

Transport And Motility (5 decks)

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