Untested but something like this should work. This is considering you have the same field names for all the structures, and that you have less than 26 fields per structure.
fn = fieldnames(gc{1,1});
for i = 1:length(gc)
writecell(fn','excel_file.xls','Sheet',i)
for j = 1:length(fn)
[~,sizey] = size(gc{1,i}.(fn{j}));
if sizey > 1
gc{1,i}.(fn{j}) = gc{1,i}.(fn{j})';
end
writecell(gc{1,i}.(fn{j}),'excel_file.xls','Range',[char(j-1+'A') '2'],'Sheet',i)
end
end
