Propionic acid is a short-chain fatty acid produced by living beings, such as gut microbiota, as part of the metabolism of the fatty acids.
It has a chemical formula of CH₃CH₂CO₂H, and this would be its 2D representation:
This is a linear molecule, so its 3D representation only shows the bond angles:
Each carbon has 4 bonds, so each corner represents one carbon with hydrogens.
It can be seen clearer in this colored representation, where carbons are black, oxygens are red, and hydrogens are white:
If we compare it with glucose, we can see that propionic acid is a much simpler molecule, given that glucose is cyclic and has more atoms.