The Roman Catholic Church teaches that when Christ broke the bread at the Last Supper, saying "this is my body" (Matthew 26:26, Mark 14:22, Luke 22:19), that He was giving the apostles his actual body to eat (Catechism of the Catholic Church 1376, 1413, etc.).
Christ's literal body was sitting at that table. It was not torn apart and given to the Apostles (including Judas) to eat. He's using bread as a symbol of Himself, and breaks it to symbolize what was about to happen to to His body:
Matthew 26:26
26 And as they were eating, Jesus took bread, and blessed it, and brake it, and gave it to the disciples, and said, Take, eat; this is my body.
"The bread that I just broke - this is my body." In so many words, "My body is about to be broken". The fact that He's being figurative is obvious - otherwise that bread would've transformed into meat.
The fact that the bread remained only bread caused the creation of a doctrine known as Transubstantiation, where Jesus's body is present "under the species" of bread and wine (Catechism of the Catholic Church 1376, etc.). This is an attempt to somehow reconcile a hyper-literal interpretation of the passage, when the passage itself refutes the idea that Jesus's actual body was offered and eaten at the Last Supper.
If the Last Supper was an offering of Jesus's body and blood to God, that would mean that His crucifixion the next day was the second offering that He made. But Hebrews 10:10-14, which will be covered a bit later in this article, makes it clear that Christ made one offering of one sacrifice to God, and it was the sacrifice made on the cross - not the Last Supper.
So too, when Christ says of the wine "this is my blood which is shed for you" (Matthew 26:27-28, Mark 14:23-24, Luke 22:20), the Catholic Church teaches that the wine is actually Christ's blood (Catechism of the Catholic Church 1376, 1413, etc.).
Firstly, this would have violated the Old Testament Law, where a clear commandment is given to abstain from eating blood:
Leviticus 17:11-12, 14
11 For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul.
12 Therefore I said unto the children of Israel, No soul of you shall eat blood, neither shall any stranger that sojourneth among you eat blood.
14 For it is the life of all flesh; the blood of it is for the life thereof: therefore I said unto the children of Israel, Ye shall eat the blood of no manner of flesh: for the life of all flesh is the blood thereof: whosoever eateth it shall be cut off.
Adding to this, once again I will point out the obvious - His real blood hadn't even been shed yet. He's talking about tomorrow when He will be crucified:
Matthew 26:27-28
27 And he took the cup, and gave thanks, and gave it to them, saying, Drink ye all of it;
28 For this is my blood of the new testament, which is shed for many for the remission of sins.
Had Christ's literal blood been shed at this point? No. Christ is using another metaphor - "Just like this wine pours from this bottle, my blood will be shed". The wine remained wine, according to the passage, as none of the Apostles remarked that they were now drinking metallic-tasting blood.
Catholics often accuse those who don't believe this false doctrine of not taking Christ literally. We do. We take Him literally, by saying that if that wine was His blood, it would've been His blood. The fact that Catholics assert that it was blood "under the species of wine" simply arises from the fact that they are cramming a literal interpretation into an obviously figurative passage.
Alongside the passages from the Last Supper, Roman Catholics also cite a passage in John chapter 6, where Christ uses similar metaphors to those He used during the Last Supper:
John 6:51-56
51 I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world.
52 The Jews therefore strove among themselves, saying, How can this man give us his flesh to eat?
53 Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you.
54 Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
55 For my flesh is meat indeed, and my blood is drink indeed.
56 He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him.
If one were to keep the above piecemeal from the context, as is often done by Roman Catholics, you could see their point. However, you will note that almost no Catholic that quotes this passage will include verse 57.
This is because verse 57 is the interpretation of the passage, by the same One who spoke the passage:
John 6:57
57 As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me.
Christ says that just like how He lives by the Father, so they that "eat Him" live by Him. Does Jesus eat God the Father? Does He drink God the Father's blood?
No, and Christ explains within the passage that the way we "eat and drink" of Him is to believe in Him. How do we know that Christ uses the imagery of "eating and drinking" as a metaphor for belief? Same chapter:
John 6:47, 54
47 Verily, verily, I say unto you, He that believeth on me hath everlasting life.
...
54 Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
The spiritual application is belief, and the physical metaphor is eating and drinking. This metaphor is intended to show how we subsist and get life from Christ - by faith.
This is part of a running theme in the Gospel of John where people take Christ's spiritual lessons too literally. First, we have Nicodemus thinking that being "born again" would requiring entering his mother's womb a second time (John 3:4). Then in chapter 4, we have the woman at the well thinking that the "Living Water" will ensure that she doesn't have to come to the well to draw again (John 4:15).
Then here in John 6, we have the people mistakenly thinking that eating Jesus's flesh is literal (John 6:52). You have to read the Bible in context. All three instances were spiritual metaphors, which in the case of John 6 particularly, becomes very clear by the time we finish the chapter:
John 6:63
63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life.
Christ says that "the flesh profiteth nothing", so naturally Catholicism teaches that unless you eat quasi-literal flesh, you will go to Hell. If that's true, the flesh profiteth everything.
Furthermore, Catholics do not actually take this passage literally. After they eat their wafer, they still hunger again later, and none of them believe that they have absolute assurance of their eternal destiny. Yet Jesus said that anyone who eats the "bread of life" will "never hunger" (John 6:35), and will "live forever" (John 6:51, 6:58).
They all apply the "bread of life" to Christ's physical body, yet they all take the "never hunger" and "live forever" passages to be spiritual metaphors, and then they don't even believe those, because they teach that a Christian can eat the "bread of life" and still go to Hell if they don't behave. Therefore, they don't take Jesus Christ "literally" at all, except in the only way they weren't intended to.
Also, to point out the obvious - the Lord's Supper wasn't instituted until many months after this event in John chapter 6. Christ spoke in the present tense in the passage when mentioning "eating" His flesh and "drinking" His blood, meaning it was something that was possible to do while He was talking. That's because it was a reference to belief, which could have been done long before the Lord's Supper was ever instituted.
The final passage used by Catholics to argue for Transubstantiation is found in 1 Corinthians 11, specifically verses 27 and 29:
1 Corinthians 11:23-29
23 For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread:
24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25 After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.
27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.
28 But let a man examine himself, and so let him eat of that bread, and drink of that cup.
29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body.
We have no issue with this passage, since we never deny that the bread and wine used in the Lord's Supper represent His body and blood. Therefore, someone disrespecting the symbol sins in the same grievous way that someone disrespecting baptism disrespects Jesus's death and resurrection. That is all that is asserted in the passage.
There isn't anything in this passage that makes impossible the interpretation of breaking bread and pouring wine merely being used as symbols and metaphors of Christ's body and blood. The Catholic Church simply reads their false doctrine into the passage, so they hallucinate that something has been said that hasn't been.
Furthermore, in the previous chapter, a statement is made that strongly supports our assertion that the Lord's Supper is to be understood symbolically:
1 Corinthians 10:16-17
16 The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ?
17 For we being many are one bread, and one body: for we are all partakers of that one bread.
Above, the Apostle Paul says that we Christians are one bread. Does that mean we are supposed to teach that the actual bodies of all Christians are present "under the species" of bread as well?
No, because we have the spiritual discernment to take spiritual metaphors as they are to properly be taken, rather than assert a bizarre, hyper-literal interpretation, with Biblically impossible implications.
The Catholic Church also teaches that Jesus Christ's actual body and blood being present in the bread and wine means that in some aspect, the sacrifice of Jesus Christ is renewed, and Christ is re-offered to God as a sacrifice, approximately 5,000,000 times every Sunday all around the world (Catechism of the Catholic Church 1323, 1365-1367, 1414).
The fact that they consider every Mass a "re-offering" of Christ is manifest by what they do - place bread and wine (Jesus, allegedly) on an altar, label this section of the Mass "The Offertory" (Catechism of the Catholic Church 1350), and say:
The Order of the Mass - Eucharistic Prayer I
84. The Priest, with hands extended, says:
"To you, therefore, most merciful Father, we make humble prayer and petition through Jesus Christ, your Son, our Lord:"
He joins his hands and says:
"that you accept"
He makes the Sign of the Cross once over the bread and chalice together, saying:
"and bless these gifts, these offerings, these holy and unblemished sacrifices,"
With hands extended, he continues:
"which we offer you firstly for your holy catholic Church."
In response, I would reply that the idea that communion/The Lord's Supper somehow repeats, re-offers, or renews the sacrifice of Jesus on the cross, is refuted powerfully in the book of Hebrews:
Hebrews 9:25-28
25 Nor yet that he should offer himself often, as the high priest entereth into the holy place every year with blood of others;
26 For then must he often have suffered since the foundation of the world: but now once in the end of the world hath he appeared to put away sin by the sacrifice of himself.
27 And as it is appointed unto men once to die, but after this the judgment:
28 So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
Hebrews 10:10-14, 18
10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all.
11 And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins:
12 But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God;
13 From henceforth expecting till his enemies be made his footstool.
14 For by one offering he hath perfected for ever them that are sanctified.
18 Now where remission of these is, there is no more offering for sin.
Notice - "once", "one sacrifice", "one offering" perfects us forever. Not a sacrifice every Sunday morning at 10:15 AM. Not a repeated or distinct offering of the "same sacrifice" - one offering. Christ "hath once suffered for sins" (1 Peter 3:18), and that was when the one sacrifice that was ever to be made was made.
That means that at the Last Supper, no blood was shed and no body was offered. It was figurative, because there was only one offering, and it happened at Calvary. If Christ offered His literal body and blood at the Last Supper (even if it was "under the appearance of bread and wine", as Catholicism teaches), that would make two sacrifices.
This also proves that when Christ said, in speaking of the Lord's Supper, "do this in remembrance of me" (Luke 22:19: 1 Corinthians 11:24-25), He couldn't be talking about a re-sacrifice, or re-offering of His actual body and blood (to be eaten afterwards). The sacrifice was made once, and we partake in the Lord's Supper to remember that sacrifice. The remission of sins has been accomplished, and there is no more offering for sins made by anybody (Hebrews 10:18).
So, to add to the other errors regarding this doctrine, the Catholic Church also blasphemes Jesus Christ by attempting to re-offer and re-sacrifice Him when He was clear that it was done once, finally, for all, forever.
The doctrine of Transubstantiation relies on taking passages that are metaphors, and reading a literal interpretation into them, even though such an interpretation, given its ramifications, is totally impossible and refuted elsewhere in the New Testament, and often within the passages themselves.
This doctrine is a focal point of Roman Catholicism, and the entire Mass is centered around Communion, and therefore, Transubstantiation. Catholicism, then, is centered around this bizarre hyper-literal interpretation, which besides being bad reading comprehension, is blasphemously a re-offering and re-sacrifice of what the Bible repeatedly says was offered and sacrificed "once".