That is correct. Proteins we eat are broken down to amino acids; this process is technically called “degradation,” but that shouldn’t imply anything bad. It simply means that the proteins are broken down into the basic building blocks. The digestive system then uses transporters to move them into the blood. The blood carries them around the body, and the body then builds the proteins it needs out of those basic building blocks.
So the shape of eaten proteins is irrelevant to the body; the proteins will be broken down for scrap.
Note: if there is a medical therapy that uses proteins injected into the blood, shape may matter. Also, there are also other substances that we may consume orally where shape may matter - this is known with some chemically synthesized compounds, including synthetic stereoisomers of tocopherols (Vitamin E) - but that list of things doesn’t include proteins, which are all broken down to base amino acids, and the base amino acids do not have a shape.
Tracts. And yes, exactly! The enzymes do require a specific shape: unwound. The technical name for the process of unwinding a protein blob is called “denaturing,” because it takes it from the naturally occurring blob into a more useful state to work on.
Denaturing is the unavoidable first step in protein digestion. If the protein is not denatured (or partially denatured) ahead of time, then the digestive system simply has to do more denaturing work before the enzymes can get busy on the proteins.
Oh, dear. I feel like you’ve invited a windbag to talk.
Proteins can be denatured into a workable strand, or can be renatured into a coiled blob; the body does both: it denatures proteins that it’s going to break down, and it renatures proteins that it creates to use for biological functions. We’ll ignore renaturing here.
Balled chains of amino acids are held in their coiled shapes by hydrogen bonds between unconnected amino acids links; the hydrogen bonds “tie” different parts of the chain together. A close pattern of hydrogen bonds makes a coil; other hydrogen bonds across different sections cause cross-links. All together, they make a blob out of the protein.
Denaturing breaks the hydrogen bonds, allowing it to uncoil, but the aminos in the chain are unchanged.
There are three main methods that denature proteins:
1. Heat. Heat can make the blob relax and uncoil. This is why cooked food is far more digestible… but our bodies also use some heat; whatever we eat gets heated up to 98.6f. Heat is why a cooked egg turns solid-ish, though still gooey; the uncoiled proteins turn into filaments that can tangle together, like this:
Even though the cooked protein is a tangled mess, it’s still much more digestible than those little knots it started out as; more on that later.
2. Chemistry. Acids, bases, alcohols, salts - all of these can denature proteins. Our bodies use a lot of acids in the digestive tract for this purpose; it’s our workhorse mechanism.
3. Violence! Proteins can be physically denatured if you’re aggressive enough. Example? When you whip egg whites, you don’t just inject air. You’re actually busting up the little protein blobs into long protein chains. These long chains (some of which can then cross-link to each other) give the whipped egg whites their stiffness and cause the mixture to retain some air, looking much like the cooked protein above, but fluffier.
Then, proteolysis. No matter how the protein gets denatured, it’s only after the protein is unwound that enzymes can finally go to work on them, breaking them down. Breaking proteins into pieces is called proteolysis, It goes kinda like this:
The proteolytic enzymes are the enzymes that hack long amino acid chains (proteins) into smaller pieces. Some of the pieces are single aminos; others are still chains. An oligopeptide is a chain of amino acids which is quite short (20 links or less; most proteins in nature are hundreds of aminos long.)
An intestinal cell can take in a single amino acid, or can take in an oligopeptide, but longer chains are too big and stay in the digestive tract until digestive enzymes have broken them down further. Single amino acids are easy, but the intestinal cell makes use of an enzyme called aminopeptidase to break oligopeptides down into dipeptides and tripeptides as they’re taken into the cell. A dipeptide (two) or a tripeptide (three) is basically a chain of two or three amino acids.
Once inside the intestinal cell, single amino acids can be transferred directly from the intestinal cell to the blood, but those chains of two or three aminos can only be absorbed with the help of peptidase enzymes, which break down the final links in the chain while they’re handed off to the blood. The blood gets single aminos; that’s what the body uses.
But the key thing is that none of the enzymes can go to work on the proteins until they are uncoiled; a.k.a., denatured. It all starts there.
Fun references (and the sources of these images):
Final note: this is also why proteins from GMOs are as safe as “natural” sources; no matter the composition and shape of the proteins, we break them down to base aminos in our digestion. Now, that’s not to say GMOs are inherently safe - there’s always the question of what the proteins in question do. For example, if a GMO plant has proteins which allow it to produce an insecticide, then the protein that codes the insecticide may be harmless to us, but the insecticide it produces may not be (it’s certainly not harmless to insects!) So, is there any insecticide left in the plant when we get it? And is that insecticide harmful to us?
GMO organisms need to be carefully designed for function, and need to be tested, and we need to be careful about how they interact with native species if they get out in the wild… but they are inherently made of the same building blocks, and so their proteins are as safe as anything else we eat.