The bread is a symbol of the Passover because when the Israelites were leaving Egypt they didn't have time for the bread to rest. the bread was then flat and looks like the Host in todays Mass. Moses also instructed the Israelites to not eat any yeast.
The Wine is a symbol of the Passover because when Moses instructed the Israelites to kill a lamb they put the blood of the lamb on their doorways. In the Mass the priest says "lamb of God take away the sins of the world." Jesus is the lamb. God is our shepherd.
Fire is a symbol of the Passover because when God spoke to Moses he spoke to him through a burning Bush.