Question

Q5.  Aquaporins are water channels that allow rapid transport across cell membrane. You are interested in the role that these channels play in cerebral edema (brain swelling) after traumatic brain injury (TBI). This channel is expressed on a type of cell in the brain called an astrocyte which is responsive to osmotic pressure and helps regulate fluid balance in the nervous system.

A) Describe what happens to astrocytes when they are placed in i) hypertonic solution and ii) hypotonic solution. How might each of these conditions impact the activity of the aquaporins?

B) you are interested in designing a drug to block aquaporins after chronic TBI. Based on the structure of the channel what structural and chemical properties would be important to block channel activity (BE SPECIFIC).

Answer 1

Answer:

A):

• The astrocytes contain the water channel called Aquaporin- 4. it is often to   expresses throughout the brain, especially at the blood-brain barrier where AQP4 is highly polarized to astrocytic foot processes in contact with blood vessels.
• After the traumatic brain injury, the fluid is trapped into the neural cell , astrocytes, which cause the cerebral edema.
• Cerebral edema can restrict the supply of blood to the brain. Blood carries oxygen to the brain, which the brain requires to function.
• A lack of oxygen in the brain can damage brain cells or cause them to die.
• If the astrocytes placed in the hypertonic solution :- There will be osmotic imbalance. The osmotic pressure in the side the cell decreases and on the solution it increases.
• Opposite to that , the osmotic potential of the cell is higher than the surrounding medium.
• And at this condition water moves from higher osmotic potential to lower osmotic potential.
• During this osmotic imbalance, the water moves from its higher concentration [lower osmotic pressure ] to its lower concentration[higher osmotic pressure], means from astrocytes to the solution.
• As a result the water contain in side the astrocytes decreases [due to exosmosis]and the cell is shrinked.
• If the astrocytes placed in the hypotonic solution : - The osmotic pressure in side the cell is higher than the surrounding medium.
• Now , in this case the endosmosis if going on,the water moves in the cell and cell become swollen.

B):

• The structure of aquaporin see the photo graph

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