Question

4. Create some drawings/models of membrane transport proteins. Blob models are fine but they should be annotated as instructed below. In your drawing include a model for a lipid bilayer clearly showing the polar and non-polar nature of the lipid components. The models of the proteins should include annotation/shading or other indication that indicates the types of amino acid functional groups you might expect to see in (a) the exterior of the protein in contact with the lipid bilayer, (b) the regions of the exterior part of the protein that interacts with the lipid polar groups, (c) and some attempt to illustrate the types of residues one might expect to find in the core of the protein (depending on substrate being transported. Also indicate whether the protein should act as a channel (passive no need for external energy) or pump (active and requiring the coupling of an energy source) Do this for: (1) a hypothetical protein that transports Cl- ions down/with their chemical gradient and (2) a transporter of glucose up/against the chemical gradient.

Answer 1

A membrane model is shown in the diagram below.

In case of ion chanel non polar amino acids like valine (-CH CH₃ CH3 ), alanine (- CH₃) , leucine(- CH₂ CH CH₃CH₃), isoleucine (-CH CH₃ CH₂ CH₃) are present towards non polar tails of the lipid bilayer, i.e at external side of ion channel and Polar amino acids like serine (-CH₂OH), Threonine (- CHOHCH₃), Aspargine (-CH₂CONH₂), Cysteine (- CH₂SH) are present towards interior of protein, Which makes hydrophilic channel from which ions can pass.

Low donc, aiu cos Polars Head [phosphate Pbe Lieid Bil oye LEN F Non Polas Chplestero ATP ADP ate tajl ok cules C Lipi Loa Non Polas Ami noacid cono High conc- Sli Actve tanspot of Glucose cI jon Chon using ATP