Transport

Question 1

Describe the specificity of a channel

Answer 1

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.

Question 2

What are the different channel gating structures?

Answer 2

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

Question 3

Describe voltage gated ion channels.

Answer 3

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.

Question 4

Describe the different voltage gating ion channel gating that is possible

Answer 4

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

Question 5

Describe potassium channel selectivity

Answer 5

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.

Question 6

Describe the k channel events

Answer 6

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

Question 7

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

Answer 7

ATP hydrolysis
Primary active transport
ATPase

Question 8

What kind of energy source does cotransport use?

Answer 8

Gradient energy from a different ion or molecule

Question 9

Describe ATP dependent active transport

Answer 9

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

Question 10

Describe co transport or secondary active transport

Answer 10

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

Question 11

What is symport?

Answer 11

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

Question 12

What is antiport?

Answer 12

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

Question 13

Describe an example of secondary active transport

Answer 13

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

Question 14

What is the extrinsic pathway of apoptosis?

Answer 14

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

Question 15

Describe the intrinsic pathway of apoptosis

Answer 15

Cell damage- mitochondrial leakage- release

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Open
Closed
Inactivated

Question 18

What controls channel opening and closing in VG ion channel?

Answer 18

Due to internal gate

Voltage sensing helices within channel

Question 19

How is a VG channel inactivated?

Answer 19

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

Question 20

What kind of inactivation thing does a K channel have?

Answer 20

External gate is ball and flap

Question 21

What kind of gate does Na channel have?

Answer 21

Flat

Question 22

Describe a K channel?

Answer 22

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

Question 23

Describe Na channels

Answer 23

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

Question 24

What is the structure of the internal VG?

Answer 24

They have sensory helices

Lots of positive charges from lysine and arginine

Question 25

Describe the resting state of an internal VG channel

Answer 25

Internal gate is closed

Question 26

What happens during stimulus in a VG channel?

Answer 26

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

Question 27

What happens when a VG channel is inactivated?

Answer 27

Inactivation segments block pore, stop ion flow

Question 28

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

Answer 28

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

Question 29

What are the membrane proteins associated with neurons?

Answer 29

Na K pumps | VG Na an k channel

Question 30

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

Answer 30

Negatively charges inside in relation to the outside

Question 31

How is electrical charge generated in a nerve impulse?

Answer 31

Ion movement

Question 32

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

Answer 32

Concentration gradient | Electrical charge

Question 33

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

Answer 33

Na

Question 34

What happens during signaling along the axon?

Answer 34

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

Question 35

How does an axon return to normal following a signal?

Answer 35

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)

Question 36

What is the structure and the details of a channel?

Answer 36

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.