Here are some Bible references
The Eucharist is our link to participation in the life of Christ John 6:47-58 Amen, amen, I say to you, whoever believes has eternal life. I am the bread of life. Your ancestors ate the manna in the desert, but they died; this is the bread that comes down from heaven so that one may eat it and not die. I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world.” The Jews quarreled among themselves, saying, “How can this man give us [his] flesh to eat?” Jesus said to them, “Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you. Whoever eatsmy flesh and drinks my blood has eternal life, and I will raise him on the last day. For my flesh is true food, and my blood is true drink. Whoever eats my flesh and drinks my blood remains in me and I in him. Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me.
The Sacrament was instituted by Jesus Matthew 26:26-29 While they were eating, Jesus took bread, said the blessing, broke it, and giving it to his disciples said, “Take and eat; this is my body.” Then he took a cup, gave thanks, and gave it to them, saying, “Drink from it, all of you, for this is my blood of the covenant, which will be shed on behalf of many for the forgiveness of sins. I tell you, from now on I shall not drink this fruit of the vine until the day when I drink it with you new in the kingdom of my Father.”
It is a serious thing to receive the Eucharist I Corinthians 11:26-29 As often as you eat this bread and drink the cup, you proclaim the death of the Lord until he comes. Therefore whoever eats the bread or drinks the cup of the Lord unworthily will have to answer for the body and blood of the Lord. A person should examine himself, and so eat the bread and drink the cup. For anyone who eats and drinks without discerning the body, eats and drinks judgment on himself.
Here are some references from the Catechism
Paragraph 1324 The Eucharist is "the source and summit of the Christian life." "The other sacraments, and indeed all ecclesiastical ministries and works of the apostolate, are bound up with the Eucharist and are oriented toward it. For in the blessed Eucharist is contained the whole spiritual good of the Church, namely Christ himself, our Pasch."
Paragraph 1333 The signs of bread and wine become, in a way surpassing understanding, the Body and Blood of Christ; they continue also to signify the goodness of creation. [emphasis added]
Paragraph 1362, 1363 The Eucharist is the memorial of Christ's Passover, the making present and the sacramental offering of his unique sacrifice, in the liturgy of the Church which is his Body. In the sense of Sacred Scripture the memorial is not merely the recollection of past events but the proclamation of the mighty works wrought by God for men. In the liturgical celebration of these events, they become in a certain way present and real. This is how Israel understands its liberation from Egypt: every time Passover is celebrated, the Exodus events are made present to the memory of believers so that they may conform their lives to them. [emphasis added]
Paragraph 1367 The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: "The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different." "And since in this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner. . . this sacrifice is truly propitiatory."