Lecture 3: Ion Flux

Question 1

A small biotech company in Boston recently created a more potent version of digoxin for treating patients with CHF. Which of the following is the direct protein target to which this drug binds to in order to exert its effect on cardiomyocytes?
A) Sodium calcium exchanger 
B) Sodium potassium ATPase 
C) Sodium channel 
D) Calcium ATPase
E) Calcium channel

Answer 1

B) Sodium potassium ATPase

Question 2

A 16 year old boy was brought to the emergency room by his mother due to severe abdominal pain. She told the physician that the pain seemed to come in waves. Ultrasound of the abdomen revealed kidney stones. After further testing a diagnosis of cystinuria was made. Transport of which AA is defective in this condition?
A) Cysteine
B) Cystine
C) Glycine 
D) Histidine
E) Methionine

Answer 2

B) Cystine

Question 3

The plasma membrane is semi-permeable. What is it permeable to?

Answer 3

Lipophilic molecules, move easily

Ex. Steroid hormones

Question 4

What is the PM impermeable to?

Answer 4

Hydrophilic/polar molecules

• Needs a specific transport mechanism

Question 5

What ions are high inside the cell?

Answer 5

Potassium

Question 6

What ions are high outside the cell?

Answer 6

Na+, Cl-, Ca2+

Question 7

____________ transport is energy-independent, where molecules move down their concentration gradients

Answer 7

Passive

Question 8

__________ transport is energy-dependent where molecules move against their concentration gradient

Answer 8

Active

Question 9

Where do P type ATPases phosphorylate a protein?

Answer 9

On conserved aspartate residue

Question 10

The difference between ABC transporters and P-type ATPases is in the phosphorylation. What is the difference?

Answer 10

The phosphate covalently attaches to the protein when a P-type ATPase is used but never covalently attaches in an ABC transporter

Question 11

Sodium calcium exchanger is an example of what type of secondary transporter?

Answer 11

Antiporter

Question 12

Lactose permease is an example of what type of secondary active transporter?

Answer 12

Symporter

Question 13

Mito calcium transporter is an example of what type of secondary active transporter?

Answer 13

Uniporter

Question 14

The ________ _________ transporter is present n the epithelial cells that line the small ntestine and renal tubules and mediates UNIdirectional movement. Across small intestine and renal tubules

Answer 14

Sodium glucose transporter (SGLT1)

• Movement of Na+ occurs down its gradient, this provides energy to move glucose against its gradient

**The Na+ gradient is reset by the Na+/K+ATPase

Question 15

What does the Na+/Ca2+ exchanger function to do?

Answer 15

Maintain low levels of intracellular calcium levels

Question 16

The Na+/Ca2+ exchanger imports ________ down their gradient and exports _____ against the gradient

Answer 16

3 Na+; 1 Ca2+

• Uses the energy stored in the Na+ gradient

Question 17

Where is SGLT1 located on an enterocyte?

Answer 17

Apical side

Question 18

What molecules does SGLT1 facilitate the movement of and what type of transport is this?

Answer 18

Glc, Gal, Na+

Secondary active

Question 19

What part of the enterocyte is GLUT5 located on>

Answer 19

Apical side

Question 20

What molecules does GLUT5 facilitate the movement of and what type of transport is this?

Answer 20

Fru

Facilitated diffusion

Question 21

Where is GLUT2 located on an enterocyte?

Answer 21

Basolateral side

Question 22

What molecules does GLUT2 facilitate the movement of and what type of transport is this?

Answer 22

Glc, Gal, Fru

Facilitated diffusion

Question 23

Where is Na+/K+ ATPase located on an enterocyte?

Answer 23

Basolateral side

Question 24

What is the movement of Na+ and K+ through the Na+/K+ ATPase located on an enterocyte

Answer 24

3 Na+ out of enterocyte to the bloodstream and 2K+ into enterocyte from the bloodstream

Question 25

Where do monosaccharides derived from the digestion of polysaccharides such as starch and disaccharides such as sucrose and lactose in the diet need to be transported from?

Answer 25

From the intestinal lumen, across the enterocyte into the blood stream

Question 26

The process of transporting monosaccharides from the intestinal lumen, across the enterocyte and into the blood stream is facilitated by what types of transport?

Answer 26

Facilitated diffusion and active transport

Question 27

What is the first step in neurotransmission?

Answer 27

Sodium channel on presynaptic neuron opens and begins the AP

Question 28

What happens after the sodium channel opens on a presynaptic neuron and an AP has been initiated?

Answer 28

The potassium channel opens on the presynaptic neuron to allow calcium to leave the cell

Question 29

What happens after the potassium channel opens on the presynaptic neuron during neurotransmission?

Answer 29

Voltage gated Ca2+ channel on presynaptic neuron opens causing the formation of vesicles and the release of them into the synapse

Question 30

What happens after the voltage-gated calcium channels open on the presynaptic neuron during neurotransmission?

Answer 30

Ligand-gated ion channels on postsynaptic neuron opens

Question 31

What happens after ligand gated ion channels open on post synaptic neurons during neurotransmission?

Answer 31

Na+/K+ ATPase on postsynaptic neuron is actiated

Question 32

What happens after the Na+/K+ ATPase on the postsynaptic neuron is activated during neurotransmission?

Answer 32

The sodium calcium exchanger is activated on the post synaptic neuron

Question 33

What happens after the sodium calcium exchanger is activated on the postsynaptic neuron durng neurotransmission?

Answer 33

The plasma membrane Ca2+ ATPase on the presynaptic membrane is activated

Question 34

Cystic fibrosis is caused by a mutation in what?

Answer 34

CF transmembrane conductance regulator (CFTR) gene -> Results in defective CFTR protein **CF is an autosomal recessive disorder

Question 35

What is CFTR?

Answer 35

A chloride channel that mediates the active transport of Cl- from inside the cells to the outside in airways and sweat ducts

Question 36

Defective CFTR causes a buildup of what?

Answer 36

Cl- and salt inside the airway epithelial cells creating a thick mucous secretion in lungs that interferes with breathing and leads to secondary microbial infections

Question 37

What is cystinuria caused by?

Answer 37

A defect in the transport responsible for uptake of dimeric AA cystine and other dibasic AAs Arg, Lys, and Ornithine **Cystinuria is an autosomal recessive disorder

Question 38

What is the result (buildup) of Cystinuria?

Answer 38

Results n formation of cystine crystals or stones in the kidney -> patients present with renal cholic (abdominal pain that comes in waves and is linked to kidney stones)

Question 39

What causes Hartnup disease?

Answer 39

A defect in transporter for nonpolar or neutral AAs (Ala, Val, Thr, Leu, Trp, etc.) **Hartnup disease is autosomal recessive!

Question 40

Where is the transporter that is responsible for Hartnup disease located?

Answer 40

Found primarily in kidneys and intestine

Question 41

_____________ deficiency leads to deficiency of serotonin

Answer 41

Tryptophan - This is found in Hartnup disease

Question 42

What are the symptoms of Hartnup disease?

Answer 42

Cerebellar ataxia (lack of muscle coordination), photodermatitis and photosensitivity

Question 43

____________ ___________ such as ouabain and the more lipophilic drug digoxin act as cardiotonic (contraction inducing) drugs

Answer 43

Cardiac glycosides

Question 44

What do cardiac glycosides (such as digoxin) inhibit?

Answer 44

The Na+/K+. ATPase on cardiac myocytes - This leads to increase in intracellular Na+ and a secondary increase in Ca2+ due to slowing of the exchanger -> increased sarcoplasmic Ca2+ results in stronger excitation contraction of heart muscle with each AP