The composition of the cell wall varies from that organism that has it. Thus it is different when considering a fungus, a bacterium, or a plant. In bacteria, the cell wall is made of a substance called “peptidoglycan.” The “peptide” part of the substance is from short chains of amino acids called peptides. Amino acids are a major building block of life and are what make up proteins. The “glycan” part is long chains of sugars which along with the peptides make up the mesh of the cell wall.

In plants, the cell wall is mostly made up of various sugars such as cellulose. These sugars are connected in a way such that your body can’t digest them and are also known as “dietary fiber”. Fungi have cell walls made of sugars too, but different ones than you would normally find in a plant. All of these cell walls are made of very different molecules than the cell membrane which is mostly made up of lipids (fats are a type of lipid).

A variety of organisms have cell walls. Plant cell walls are made of mostly of cellulose, hemicellulose, and pectin. There compounds make a rigid cell wall that gives the plant structure to support itself.

Fungi and other organisms like diatoms have cell walls made of different compounds such as chitin and silica.

Animal cells, on the other hand, don't have cell walls and as a result don't have very rigid structures.

Cell walls are usually found in plants, fungi, and various prokaryotes (bacteria, etc.. It is a tough, yet flexible structure that provides structure, protection, and permeability to the cells. Also, it is used to maintain the pressure inside the cells and prevent the cells from over-expansion. The material which makes up cell walls differs in various cell types. Bacterial cell walls are made up of peptidoglycan, a material made from 2 different polysaccharides - N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG).

Cell walls of fungi are composed of chitin, which made up of many N-acetylglucosamines (NAG).

A plant cell wall is composed of cellulose, a complex sugar. Algae and different members of archaea have cell walls composed of different materials. Although the cell walls in all of these organisms are created from different materials, they serve the same function.

That depends on the cell. Plant cell walls are made out of cellulose. Fungal cell walls are made of chitin, the same stuff that insect skeletons are made of. Bacterial cell walls are made out of peptidoglycan, which is a mixed protein-sugar material unique to bacteria. Animal cells don't have cell walls.

Very interesting question. In plants, cell walls are made up of a material called cellulose. It is an extremely tough structural molecule that is very hard to digest. In fact, there are very few animals that can actually eat and digest cellulose. When you read about foods that are high in fiber, they are referring to the tough cellulose in the plant walls. Fiber is good for you but you don't really digest much of it.

The answer to your question depends on which kind of organism we are talking about. The main kinds of organisms that have cell walls are plants, fungi, and certain prokaryotes (bacterial type cells).

In plants, cell walls are mainly comprised of complex polysaccharides (sugar-based polymers) molecules such as cellulose, hemicellulose, and pectin. In between these polysaccharides are lignin, a complex biopolymer made of alcohols that contributes to the structural integrity of the cell wall by crosslinking with the different polysaccharides. Plant cell walls also have various proteins and enzymes embedded in the the wall and as surface accessories which provide various support and functionality in the cell wall.

Fungal cell walls contain different polysaccharides from plants: chitin, glucans, and mannans. They also contain various proteins. However, the composition of fungal cell walls can vary widely between different species.

Bacterial cell walls fall under two main categories: gram positive and gram negative. Gram positive walls are thick, and have many layers of peptidoglycans (protein+sugar) and teichoic acids (polysaccharides). Gram negative walls on the other hand are thin, only have a few peptidoglycans, and are surrounded by a second lipid (fats) membrane consisting of lipopolysaccharides and lipoproteins.