Which of the following is part of a seed?
A. stamen
B. pistil
C. seed coat
D. anther

The plant cell wall is strengthened by the molecular structure of cellulose. Cellulose is made up of ß-glucose arranged upside down, this arrangement aided hydrogen bonds between the hydrogen ions of the  hydroxyl group and oxygen of the of the ring   of same  betta -glucose.

The aggregation of the hydrogen  bonds give bundles of  strong tensile  strength of cellulose called the  microfibrils (of 60-70 celluose molecules).They are  held together in bundled called fibers.These is the source of  plant cell walls  strength.

Collagen is the main extracellur matrix (EM) in animal cells.It is a glycoprotein made up of 25%of body protein of animals.Each collagen molecule is made of helix shaped ,three polypeptide chains, wound around each other to form triple helix.The bonds  holding helix together are hydrogen and covalent bonds.

Each triple helix is attached to adjacent collagen molecule, parallel  to it. The covalent bonds formed a cross link which held  the collagen molecules together forming FIBRILS.  This gives flexibility to collagen, while maitaing strong tensile strength. This is what is responsible for the structural strength of cell membrane .

.The  EM,is  futher reinforced with  carbohydrate molecules(proteoglycans) which aided in water movements by  osmosis following  sodium movements into the matrix.