Cell Bio Ch 11

Question 0

2 main classes of membrane transport proteins

Answer 0

Transporters and channels

Question 1

Without proteins in lipid bi-layer:

Answer 1

Membrane is highly impermeable to ions

Question 2

Active vs passive transport

Answer 2

Passive transport- facilitated diffusion, uses concentration gradient to drive transport.
Active transport- requires energy to move solution against concentration gradient.

Question 3

Factors determining electrochemical gradient

Answer 3

Chemical and electrical gradient

Question 4

Common ways transport is couple to energy

Answer 4

Coupled transport
ATP-driven pump
Light-driven pump

Question 5

Couple transport can be

Answer 5

Symport or antiport

Question 6

Transporter moving one type of molecule

Answer 6

Uniport

Question 7

3 classes of ATP-driven pumps

Answer 7

P-type pump - ion transport couple to ATP hydrolysis (ATPases)
F-type (and V-type) proton pump - transport of H+ ions coupled with ATP synthesis (ATP synthases)
ABC transporter - small molecule transport coupled to ATP hydrolysis (ATPases)

Question 8

Ca2+ pump is this kind of pump

Answer 8

P-type ATPase

Question 9

Na+/K+ pump

Answer 9

P-type ATPase

Important in almost cellular function and regulating cytotolic pH

Question 10

Na+/K+ pump works in a cyclic manner

Answer 10

1. Sodium from cytosol enters pump
2. Pump phosphorylates with ATP
3. Phosphorylation triggers conformational change, sodium is ejected out of cell
4. Potassium from outside cell binds to pump
5. Pump dephosphorylates
6. Pump returns to original confirmation, potassium is ejected

Question 11

ABC transporters are different in bacteria from eukaryotes

Answer 11

Bacteria- used for import and export

Eukaryotes- specialized in export

Question 12

ABC transporters

Answer 12

Ancient protein
Transport many different types of small molecules
“Multi-drug resistant transporters” export drugs from the cell

Question 13

ABC transporters and disease

Answer 13

Cancer cells- over-expression of ABC transporter multi-drug resistant (MDR) makes cancer cell immune to a variety of drugs
Malarial strain- amplified a gene coded for an ABC transporter that pumps chloroquine out of the cell
Cystic fibrosis- cystic fibrosis transmembrane conductance regulator protein (CFTR) is an ABC transporter that’s been mutated, regulates Cl-

Question 14

Channels

Answer 14

100 million ions can pass through 1 channel in 1 sec, 10^5 times faster than any transporter.
No ATP

Question 15

Types of channels

Answer 15

Voltage gated
Ligand gated (Extracellular)- neurotransmitters
Ligand gated (Intracellular)- ion or nucleotide gated
Mechanically gated- linked to cytoskeleton

Question 16

Membrane potential

Answer 16

Another name for the electrochemical gradient

More Na+ outside of cell, and more K+ inside the cell.

Question 17

Parts of a neuron

Answer 17

Cell body (containing nucleus)
One long axon
Dendrites from body, to receive signals
Terminal branches on axon to send signals

Question 18

Voltage gated ______ channels convert ________ signals to __________ signals.

Answer 18

Ca++, electrical signals to chemical signals

Neurotransmitters released to act on ligand gates of dendrites on next neuron (post synaptic)

Question 19

Voltage gated _______ channels carry signal down the axon

Answer 19

Na+

Question 20

Neuron activation

Answer 20

Resting potential -70 mV
ligand gated Na+ channels open
Depolarization occurs -50 mV
At depolarization voltage gated Na+ channels open
K+ gates open slowly
\+50 mV reached
K+ rushes out reestablishing -70 mV
Na+/K+ pumps reestablish gradient

Question 21

Neuromuscular junction activation

Answer 21

1. Depolarization if nerve terminus opens voltage-gated Ca++ channels
2. Higher Ca++ concentration triggers release of acetylcholine
3. Acetylcholine released into synaptic cleft or synapse
4. Acetylcholine acts on ligand-gated Na+ channels, Na+ flows in causing depolarization
5. Voltage gated Na+ channels open, more Na+ pours in and spreads depolarization
6. Depolarization is transmitted to the sarcoplasmic reticulum, releases Ca++ causing muscle contraction