Transport Flashcards
Describe the specificity of a channel
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.
What are the different channel gating structures?
Ligand gated: signal molecule binding induces a conformational change to open the channel.
Voltage gated ion channels
Describe voltage gated ion channels.
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.
Describe the different voltage gating ion channel gating that is possible
Both internal and external
Internal only
External voltage sensitive
External to block ion flow
Describe potassium channel selectivity
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.
Describe the k channel events
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
What is the energy source of ATP dependent active transport? What is another name for it? What kind of pump does it use?
ATP hydrolysis
Primary active transport
ATPase
What kind of energy source does cotransport use?
Gradient energy from a different ion or molecule
Describe ATP dependent active transport
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
Describe co transport or secondary active transport
Targeting substance moves against its concentration gradient (active transport)
Energy supplied by second substance moving down its gradient–driving force
Symport and antiport
What is symport?
Form of secondary active transport where both species move in the same direction
What is antiport?
Form of secondary active transport where the species are moving on opposite directions
Describe an example of secondary active transport
Glucose transport and uptake
Driving force is Na gradient
Na moving down its concentration gradient allows glucose to accumulate
Symport
What is the extrinsic pathway of apoptosis?
Suicide, death signal(FASA ligand) binds death receptor (FAS) , activated initiator caspase 8 , activate effector caspase 3
Describe the intrinsic pathway of apoptosis
Cell damage- mitochondrial leakage- release
Cytochrome c- activation of initiatory caspase 9, activation of effector caspase 3
Describe the pathway that both intrinsic and extrinsic pathways of apoptosis go through?
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
What are the three stages a voltage gated ion channel can be in?
Open
Closed
Inactivated
What controls channel opening and closing in VG ion channel?
Due to internal gate
Voltage sensing helices within channel
How is a VG channel inactivated?
Channel opening exposes binding site for inactivating segment. (Ball or flap)
What kind of inactivation thing does a K channel have?
External gate is ball and flap
What kind of gate does Na channel have?
Flat
Describe a K channel?
Identical subunits Selectivity pore or filter Internal gate voltage sensor External gated are four ball and chain structures Some K channel lack external gates
Describe Na channels
1 subunit and four domains
Selectivity filter pore
Internal gate is a voltage sensor
External gate is a flap
What is the structure of the internal VG?
They have sensory helices
Lots of positive charges from lysine and arginine
Describe the resting state of an internal VG channel
Internal gate is closed
What happens during stimulus in a VG channel?
Ana cation potential next door changes electrical movement
Voltage sensing helices move toward exterior side of membrane
Internal gates open
What happens when a VG channel is inactivated?
Inactivation segments block pore, stop ion flow
What happens when a VG ion channel returns to resting state?
Electrical environment returns to resting state
Inactivation segment releases
Internal gate is closed
Closing is slow, inactivation fast
What are the membrane proteins associated with neurons?
Na K pumps
VG Na an k channel
Wha is the charge of the inside of a neuron relative to the outside?
Negatively charges inside in relation to the outside
How is electrical charge generated in a nerve impulse?
Ion movement
What influences the tendency for an ion to move across the membrane?
Concentration gradient
Electrical charge
What has a higher concentration inside the cell? Na or K?
Na
What happens during signaling along the axon?
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
How does an axon return to normal following a signal?
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)
What is the structure and the details of a channel?
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.
