Less and more alien biopolymers

[snorkack]

We on extant Earth meet a certain choice of biopolymers.
Structural biopolymers include proteins. Most of the rest of the structural biopolymers are polysaccharides. But with one conspicuous exception: lignin which is a polymer of p-propylphenols.
The most common structural polysaccharide on extant Earth is cellulose - which is 1-6 glycoside bonded glucose.
But cellulose is by no means the only polysaccharide on extant Earth.
For example, hemicellulose is also abundant structural polysaccharide, yet it also contains mannose, galactose, xylose and arabinose... and hemicellulose is not even a carbohydrate because it contains some rhamnose (a deoxy sugar) and uronic acids (glucuronic and galacturonic acid) with no guarantee of rhamnose being balanced with uronic acids.
Pectins are largely based on galacturonic acid (so not carbohydrates either) but also contain xylose, apiose, rhamnose, galactose, arabinose... and many methyl esters.

So... if an alien life form has biochemistry largely familiar on Earth but produces a structural polysaccharide unknown on Earth, what can we say about its biomechanical properties, biosynthesis and remodelling based on its structure?

 

[BillTre]

You would have to specify a particular structural polysaccharide in order to say something about its biomechanical properties, biosynthesis and remodeling based on its structure.
Different molecules could have very different properties.

 

[snorkack]

Even given known polymers, you can have various tissues and organs...
Consider wood. Common "trees" of broadleaved and coniferous trees consist of it. It is a tissue that simultaneously carries mechanical loads and transports water. It grows both from the top buds, and from under the bark, forming growth rings if there are any changes in growth conditions. Wood is a composite of 4 different biopolymers - cellulose, lignin, hemicellulose, pectin.
Now look at extant alternatives...
Banana is over 7 m high. It carries its own weight and the weight of the banana stem, without toppling over.
Yet the banana trunk consists of concentric leaf stalks exclusively, and is perceptibly more flexible than a small tree trunk of similar size.
Palms can grow up to 60 m tall (Quindio wax palm). But they have no ability to grow in thickness - palm trunk must grow its full thickness from top bud. So they cannot have tree rings.
Yucca and Dracaena, like some palms, commonly branch but likewise cannot grow in thickness.
Bamboo can grow up to 30 m tall. Like palms, bamboo cannot grow in thickness and shoots must be full thickness... but unlike palms, bamboo trunk has nodes and can grow from nodes, too.
Extant tree ferns can grow over 15 m tall... and yet their trunks contain no "wood". What does a tree fern trunk consist of?
https://en.wikipedia.org/wiki/Dicks...:Dicksonia_antarctica_MHNT.BOT.2012.10.39.jpg
but what is it like, in composition and mechanical properties?
Cycads are another distant group of tall plants. What is the structure of cycad trunk?
Now, among the plants present on Earth but not now...
Lepidodendron grew something like 40 m tall. Unbranched to height of 30+ m
The branching pattern suggests that this was not formed by later loss of lower branches... young Lepidodendron must have been unbranched.

But Lepidodendron trunks are said to have contained little wood.
Well, then, what did Lepidodendron trunks consist of? If you examined a freshly felled (not fossil) log of Lepidodendron, what would it be like in terms of structure and mechanical properties?