vshape[id:{x_,y_}]:=id->Graphics[{EdgeForm[{GrayLevel[.1],Thickness[0.01`]}],White,Disk[{0,0},1.2],Disk[{4,0},1.2],Black,Inset[Style[x,12],{0,0}],Inset[Style[y,12],{4,0}],GrayLevel[.2],Inset[Style["+",13],{2,0}]}];
vshape[id:{x_}]:=id->Graphics[{EdgeForm[{GrayLevel[.1],Thickness[0.02]}],White,Disk[{0,0},1.2],Black,Inset[Style[x,12],{0,0}]}];
vsize[id : {x_, y_}] := id -> {.2, .08};
vsize[id_] := id -> .2;
label[id : {x_, y_}, idnames_] := id -> Placed[{Style[x, FontFamily -> "Arial"], Style[y, FontFamily -> "Arial"]} /. idnames, {{Above, Before}, {Below, After}}];
label[id : {x_}, idnames_] := id -> Placed[Style[x, FontFamily -> "Arial"] /. idnames, {Below, After}]
edges = {{7, 3} -> {4, 5}, {7, 3} -> {10}, {9, 6} -> {7, 3}, {8, 7} -> {9, 6}, {11} -> {8, 7}, {5, 3} -> {1, 6}, {1, 6} -> {2}};
vlist = {{1, 6}, {2}, {7, 3}, {4, 5}, {9, 6}, {8, 7}, {10}, {11}, {5, 3}};
vcoords = {{1.426138554717633, 
       -3.514483641864844}, {0.42613855471763307, -3.514483641775051}, 
      {1.0716357789981577, -1.544172543509389}, {0.42613855471763307, 
       -0.42613855471763307}, {1.7171330034125383, -1.171494547322752}, 
      {2.362630227860383, -0.7988165511940764}, {1.7171330032117547, 
       -2.6622065323397854}, {3.008127452308227, -0.42613855506540066}, 
      {2.426138554717633, -3.5144836420444308}};
idnames = {1 -> "D-(+)-glucose", 2 -> "glucose-6-P", 3 -> "maltotriose", 4 -> "alpha-glucose", 5 -> "maltose", 6 -> "maltotetraose", 7 -> "cori ester", 8 -> "a limit dextrin", 9 -> "a debranched limit dextrin", 10 -> "glucose-6-phosphate", 11 -> "a glycogen"};
style = {EdgeStyle -> Gray, VertexShape -> (vshape /@ vlist), VertexSize -> (vsize /@ vlist),
   VertexLabels -> (label[#, idnames] & /@ vlist), VertexCoordinates -> vcoords , ImageSize -> 490, ImagePadding -> {{90, 60}, {30, 30}}};

Graph[vlist, edges, style]