As a guess because they can be a right answer and some times they are not
I believe the anwser you are looking for is the
Cell Membrane.
It is a substance that lets things in and out of the cell
Food webs normally start at the bottom and work their way up. Like the plants will be at the bottom, and then each level shows the animals getting bigger while losing energy. You continually lose energy as you work your way up an ecosystem, so normally there are only three or four levels. I hope this helps!
Answer:
The answer to your question is: Nucleic acids.
Explanation:
All biomolecules are composed by Carbon (C), Hydrogen (H) and Oxygen (O)
and others elements composed just a certain biomolecules as we can see below.
Biomolecule Elements Biomolecule
A) C H O Carbohydrates
B) C H O and sometimes P Lipids
C) C H O N S Proteins
D) C H O N P Nucleic acids.