Question

3. The Structure of the acetylcholine receptor is shown below: (A) (B) B Extracellular domain Membrane-spanning segments Segments Inside the cell 3.A. Knowing the amino acid sequence of this protein, what tool would you use to identify the membrane-spanning region and explain how it works? 3.B. What do you expect the length of the membrane-spanning region to be and why? 3.C. What type of channel is the acetylcholine receptor and what activates it? 3D. Briefly indicate what the role of the acetylcholine receptor is in an action potential.

Answer 1

3A) hydropathy index technique used for finding out the sequence which intetects with cell membrane.

Hydropathy index is graph between ∆G and no. Of amino acids. There is fixed value of ∆G fir each amino acids as this energy can be possible or negative depending upon amino acids interection with water. If hydrophilic amino acids will be more soluble in water and hence ∆G will be negative as it is favourable interection, while ∆G is positive if amino acid is hydrophobic as this interection is unfavourable.

So contnious patch of amino acids with ∆G positive value will indicates that those amino acids will interect with lipid present in cell membrane. So no. Of patch indicates no. Of spanning protein sequence in cell membrane.

3b) thickness of membrane is 7OA and in one alpha helical structure is having 3.6amino acids with distance of 5.4A so tota no.of amino acids that required to cross width of cell membrane will be

(70A/5.4A)x 3.6 amino acids= 46.67 or almost 47 amino acids are required.

3c) acetyl choline is ligand gated cation channel and opened by binding with two molecule of acetylcholine ligand

3d) it generates action potential. When 2 molecule of acetyl choline bonds with receptor them it's conformatiomal changed and it cause free flow of Na+, Ca2+ and K+ through this channel to inside of cell and change membrane potential from -70 to +35 mV and start action potential.

Thanks..!