In power supply part is only protecting diode 1N4002 - normal for cca 1A or so. In switch circuits are typical 1N.... signal diodes for protecting polarity to J-FET switching transistors. Without problems use 1N4148. There is only one zener diode for 4,7V in branch with LED diode. Current will be here low, max. cca 20mA - according used LED.