Significance of capacitor in this circuit
16, 29, 25, 23 are directly connected to GND. 28 doesn't show any connection.

There are two capacitors and they are connected to pins 19,20,21,22.

Those pins (19-22) could be VCC supply pins and the presence of the capacitor filters out any noise on the voltage supply line. You should not remove those capacitors.

Those capacitors are better known as decoupling capacitors and they:

1) Smooth the supply rail and get rid of any voltage spikes and dips.

2) Prevent high frequency signal/noise from entering or leaving the circuit.

3) Provide the sudden burst of energy required by the micro-controller.