Do animals (specifically arthropods) synthesise proteins?

Factual Questions
1

The other day I opened a container of semolina (intending to make biscuits), to find that the contents were heaving with little creatures - not weevils, they were much smaller, maybe some kind of mite or something.

Anyway, the same day, I read somebody’s comment in some thread or other (good memory eh?) that invertebrates in dried foods could contribute significantly to a person’s protein intake (if he or she were to eat it, of course).

Now this got me thinking; my tub of semolina contained about 10% protein and it was sealed in such a way as to be, to all intents and purposes, a closed system.
I’f I’d allowed the bugs to reach the maximum possible population would the contents have been higher or lower in protein overall?

Unless the critters can actually synthesise proteins themselves from simpler chemicals, the protein content must decrease, mustn’t it (assuming that they do also metabolise proteins in some way).

2

I am sure these critters, (probably flour beetles of some kind) can synthesise new amino acids from the limited assortment af amino acids in the protein of the semolina;
if they don’t do it themselves they will probably have symbiotic bacteria to do it for them.
They will use up energy from the starch and produce wate and CO2, causing the semolina to go mouldy; but weevily bread and biscuit and other infesting arthropods were minor sources of protein for the crews of long haul wooden ships and for concentrationcamp inmates, IIRC.

3

slight edit
I am sure these critters, (probably flour beetles of some kind) can synthesise new amino acids from the limited assortment of amino acids in the protein of the semolina;
if they don’t do it themselves they will probably have symbiotic bacteria to do it for them.

They will use up energy from the starch and produce water and CO2, causing the semolina to go mouldy; but weevily bread and biscuit and other infesting arthropods were minor sources of protein for the crews of long haul wooden ships and for concentration camp inmates, IIRC.

4

Mangetout, forgive me, but I’d like to expand the scope of your question a bit. Not really a hijack I don’t think.

I’ve always wondered how herbivores get protein in their diet. How does a cow for example, produce all that protein laden meat from simply eating grass?

To echo the OP, do herbivores synthesize proteins from simpler chemicals?
(and if it turns out that grass contains proteins, then I’ll slink away in embarrassment.)

5

All living creatures, including arthropods, convert carbohydrates into amino acids. They then string those amino acids together into the proteins necessary for metabolism and catabolism.
As the number of flour mites increases, they’ll use up the sugars (starches, carbohydrates) in the flour, by converting some of it to CO[sub]2[/sub] and water, and some to proteins. By the time the little guys start starving for lack of food, your flour will have been converted into a reduced mass of stuff with lower carbohydrate levels, and more protein.

6

No,
cows and other ruminants definitely rely on amino acid synthesising bacteria to produce their raw materials from grass.

7

Sorry, Squink; I was talking to Algernon;
but what I’d like to know is
to what extent are amino acids synthesised in non-ruminant herbivores, omnivores and carnivores respectively?

8

Be my guest; I was actually thinking about extending it in that general direction myself.

Another question though (as my chemistry is not particularly brilliant); what elements are required to build proteins? (for some reason, I thought it was more than C H and O)

9

There are 20 kinds of amino acids commonly used in life forms (some exceptional cases use modified ones, but basically, there are only 20 ever used). I’d name them, but that’s boring to do.

All nitrogen found in amino acids comes from the reduction of N2 to NH3 by nitrogen-fixing organisms. When in water, the NH4+ made can then be incorporated into amino acids.

Of the 20 amino acids, 11 are synthesized from the intermediates in the citric acid cycle, a major energy-producing cycle present in all cells. The pathways for these are actually quite simple. The missing 9 (in humans) are called essential amino acids, since they cannot be synthesized in human cells, They must be obtained through diet. Eating pretty much anything with protein (plants or animals) yields enough of the necessary amino acids in the form of proteins, which are broken up back into amino acids and reused in the body.

Bacteria, such as E. Coli, can synthesize all the necessary 20 amino acids. Some of the amino acids we use are made in our gut by our very own slave population of E. Coli.

When we say an amino assid is essential, its sort of a situational thing. FOr example the urea cycle might produce enough arginine for an adult, but not for a growing child (which needs more).

As for the breakdown ofherbivores, carnivores and omnivores, I think what is essential and what isnt is somewhat species dependedent. I would venture a somewhat educated guess that ALL multicellular organisms must depend somewhat on diet or symbiotic relationships (such as gut bacteria) to provide some of the necessary amino acids. Bateria, as stated before, can make all of them, as long as they can consume a carbon source (glucose, for example), and plants (IIRC) can make them all from the CO2 that they respire. I imagine the bug-eating plants evolved from some sort of amino acid deficiency, but then I’m really getting into a WAG.

Now, as for whether we synthesise proteins: of course. We only eat protein in order to get the building blocks of protein -the amino acids. We break down every bit of protein we eat into its components, then carry those back to our cells and use them again to make the proteins WE need, according to OUR DNA templates. While we have pretty much every protein in common with other mammals, our own DNA will code for a better-suited one for us, and so thats what we use. Besides, we label our proteins in such a way that foreign ones get destroyed, assuming they are able to enter the cell in the first place (which doesnt happen).

The proteins we make are used for a bunch of things, I’ll leave it to you to read a biochem textbook if you want details. Basically, though, our cells can only function with proteins, since they do everything from copy DNA to make more, or to make RNA, to breaking down glucose for energy, to giving your skin that lovely colour.

Sorry if thats a bit random, I was skipping through a Biochem textbook (Stryer, 1998) and trying to get relevent info.

10

C, H, O, N and S are used in the 20 common amino acids. Other elements may be added as modifications once the protein is made or the get an enzyme (a type of protein) to work, such as phosphorylation (adding a PO4(2-) group).

http://www.people.virginia.edu/~rjh9u/aminacid.html

that page has a picture of the structures of all 20 amino acids. It also explains the name a bit, and some of their characteristice. I didn’t go read it, but the “peptide bond” link should explain how they are strung together. A long string of attached amino acids is a polypeptide, or eventually, a protein.

I recommend simply googling this stuff - it isn’t that complicated to get the basics of how DNA, amino acids and proteins are connected, and what it is that proteins do in the body.

11

So does that mean that man can live on bread alone? :smiley:

Seriously though, if the human gut has the necessary bacteria and we have the appropriate enzymes, why not?

Or do we not have the “right stuff” to generate enough of what we need? I hear that to be healthy, vegetarians need to consume legumes so that they get enough protein in their diet. That leads me to the conclusion that we don’t have what it takes to synthesize proteins, either via enzymes or via bacteria. True?

It would seem to me that there would be great evolutionary benefit to be able to synthesize proteins. Is it generally held that once carnivores and omnivores began eating meat, that we lost the ability to create protein from grasses and leaves, etc.? Don’t monkeys have a diet primarily of leaves? How are we so different from them?

And why don’t cows get scurvy?
(Upon re-reading what I’ve written, I sound like a five year old with an endless stream of “why” questions. But, I’m honestly curious.)

12

Lightning contributes about 5% of total nitrogen fixation.

13

And if I may correct my last post, when I wrote “synthesize proteins” I really meant “synthesize amino acids”.

14

There’s more to the diet that just amino acids. Humans cannot make most vitamins, and so they need to get them from a source that can. Plants are a good source of most vitamins needed, though we can get some from animal products too. Breads and other carbohydrates cannot provide them. Vitamins are needed as cofactors to help make other proteins, or to make a protein function as it should.

Cows don’t get scurvy because they have an adequate source of vitamin C.

The bacteria in our guts might help us get SOME of the amino acids needed, but I imagine they cannot make enough, so we need to seek out more sources. We do have what it takes to make all our proteins and enzymes in the sense that our DNA can code for it all. The thing is, proteins are used to make other proteins (try not to think on that too much, it becomes a chicken-and-the-egg problem) and so we need to go get those building blocks. Also, making amino acids requires an input of energy, and so it might be more advantageous to not make it yourself and to take it from another source.

Just remember, it isn’t an inability to create PROTEINS that leads us to the diets we have, but rather an inability to make some of the building blocks. We don’t eat proteins because we need the proteins, we eat them because we need the PIECES of them. There is a difference there.

The other thing to consider is that the enzymes we do have are very specific things. Although its easy to say that we have carbon sources, and nitrogen sources, and oxygen and sulfur, our enzymes cannot necessarily grab any of these sources and bang them together to get a lacking amino acid. They need a specific starting point, and can only make a specific product. I imagine that our genome DOES contain the genes needed for synthesizing the 9 essential amino acids, but these genes are inactive for whatever evolutionary purposes. Symbiotic relationships with bacteria, or the availability of a food source that could provide them (thereby making your own cells NOT spend energy to make them) were beneficial, and so individuals who didn’t waste energy making them survived. Eventually, this led to a dependance, but other advantages likely came along with it, in the grand scheme of things.

I guess monkeys either get what they need from their diets, or can make some of the amino acids we can’t. It might be as simple as a single base change (creating a Stop codon in the promotor region, for example) in the DNA that makes a whole synthetic protein active or inactive. I admit I don’t know any specifics, but that these are possibilities based on my knowledge of biochemistry.

Am I making sense here?

15

All quotes by mnemosyne

Yes. Very much so. I appreciate the time you’re taking.

Grass and/or hay has vitamin C? I guess I didn’t realize that. IIRC humans have difficulty digesting grasses, so I suppose that ruled out Drake, Columbus, et al. from taking hay along on their sailing ships to prevent scurvy.

In college long ago, I had a friend argue that evolution was impossible because it requires enzymes to build proteins, yet enzymes were proteins themselves! Catch-22.

This makes sense.

I guess this is the crux of my questioning. A simple diet like what a horse or cow eats would seem to be evolutionarily more advantageous than the complex diet humans require. Yet because we’ve evolved to require a complex diet, the conclusion I have to draw is that my intuition is false.

I think my college attending son could use your help right now in his Biochem class. :slight_smile:

16

Phew - I’m glad that did make sense to you. I am not very good at explaining things like this in writing! I like to use pictures and lots of words!

Grasses do contain vitamin C, but they are difficult to get to because of the difficult-to-digest cell wall. Humans can’t digest it, and even cows need to ruminate it and have specialised bacteria helpers to break down the cell walls to get to what’s inside. It wouldn’t have done any good to have hay for sailors, but other plant products, such as fruits and vegetables, are digestible, and so we can get to the Vit C.

The simple diet of the horse and cow is advatageous to it, because it can basically find grass anywhere. BUT, digesting that grass requires more energy, which in return requires more food fuel, and so they must eat pretty much constantly. Thats why they graze. That is also why they live in herds, and why they are prey. Because they need to spend so much time eating, they are vulnerable.

Predators, like carnivores and omnivores (humans), dispensed with the time-consuming grass eating, and figured it was easier to get what they needed from the lazy-looking horses and cows. The prey became faster, and started living in groups, but the predators were still able to pick off enough of them that they eventually lost the ability to digest grasses. The Circle of Life. Omnivores just kept some plant-eating habits (like fruits) and dispensed with the harder to digest stuff in favour of meat.

I am not a nutritionist or biologist, though, so I don’t really think I can elaborate on this too much more.

17

So, does this mean we could design (through breeding or genetic engineering) a strain of E. coli that produces all of the necessary amino acids and vitamins humans need? Then, once this strain was established in people, they could get by with less nutritious food. What would the drawbacks be?

18

Now I know why you call yourself Mangetout!

19

Overproducers of many amino acids exist (one of the biggest commercial ones being mono-sodium gulatamate, or MSG) but I doubt this could be done in a single strain, since overproduction of one thing usually requires a defect somewhere else in the organism, and so overproduction of everything might not make a viable organism.

I’m afraid I don’t really know the answer to your question, though. Theoretially, anything is possible, I suppose, but I think we are a long way from it. As easy as it is to manipulate E. coli, we don’t know everything yet. I imagine some things just aren’t possible from a bacteria-only source, though. I’m not sure, but I think mitochondria have functions which require certain vitamins, but since bacteria don’t have mitochondria, they likely don’t have those vitamins. There are also issues of getting the products out of the bacteria and into the human blood stream. I don’t believe there are vitamin export proteins, and manipulating inport protiens might be WAY beyond us.

I wish I did know how to answer this, because it’s an interesting thought. Hopefully someone with more knowledge than me will come along!

20

Ooooh No! I dumped the contents of the pot into the (rat proof) compost bin - I prefer to get my protein from sources other than insects - probably an irrational criterion, but one that has served me well thus far.

BTW I bought some fresh semolina and the biscuits were an anormous success.