(a) Draw the structure of choline and explain why it needs a transport protein in order to enter cells.          (b) Cells must transport choline from outside the cell (where it is relatively rare) to the inside of the cell (where it is relatively abundant). The diagram below represents a cell with a choline transporter (labeled T). Draw a solid arrow through the transporter to show the direction in which choline travels (into or out of the cell).           (c) Is T an active or passive transport protein for choline?             (d) For every choline molecule that moves through T, a sodium ion moves through the same transport protein at the same time. The sodium ion moves down its gradient. Add a dashed arrow to the diagram in part (b) to show the direction of movement of sodium.          (e) Is T an active or passive transport protein for sodium?

The molecule that condensed with a phosphate group to form the head group of the lipid shown in the first image (picture 6) is choline, an essential component of many cellular molecules.

         (a) Draw the structure of choline and explain why it needs a transport protein in order to enter cells.

         (b) Cells must transport choline from outside the cell (where it is relatively rare) to the inside of the cell (where it is relatively abundant). The diagram below represents a cell with a choline transporter (labeled T). Draw a solid arrow through the transporter to show the direction in which choline travels (into or out of the cell). 

         (c) Is T an active or passive transport protein for choline? 

         (d) For every choline molecule that moves through T, a sodium ion moves through the same transport protein at the same time. The sodium ion moves down its gradient. Add a dashed arrow to the diagram in part (b) to show the direction of movement of sodium.

         (e) Is T an active or passive transport protein for sodium?