A bipolar plate for a fuel cell is provided. The bipolar plate having flow channels for oxidant gas; said flow channels for oxidant gas comprising one or more grooves each representing a serpentine path; wherein each said serpentine path independently comprises N consecutive legs L1, L2, . . . LN; connected to each other by N−1 consecutive turn sections, T1, T2, . . . TN-1; wherein each leg L1, L2, . . . LN-1 being lengthwise separated from its consecutive leg L2, L3, . . . LN by a wall section, W1, W2, . . . WN-1; wherein each turn section representing a 180° change of flow direction of oxidant gas; wherein N is an odd integer of 3 or more; and wherein one or more of the wall sections W1, W2, . . . WN-1 independently comprise one or more by-pass channels for allowing oxidant gas to flow via a short cut from one leg Lx to its consecutive leg Lx+1; 1≦x≦N−1; thereby by passing a part of the leg Lx and a part of the leg Lx+1. Furthermore, a cooling plate having a similar design is provided. The bipolar plate as well as the cooling plate provide for more efficient supply of fluids over the surface of the plate.