Extracellular Matrix and Plant Cell Walls

Flashcards covering the structure and function of plant cell walls and the extracellular matrix (ECM) in animals, including their components and roles.

What is cellulose, the main macromolecule of the plant cell wall, made of?

Repeating glucose units linked end to end.

How do cellulose chains associate with each other to form microfibrils?

Through hydrogen bonding.

When is the secondary cell wall synthesized and deposited?

After a plant cell matures and has stopped increasing in size, between the plasma membrane and the primary cell wall.

What components are found in the thick secondary cell wall of some plants, like the woody parts, that are not in the primary cell wall?

Phenolic compounds called lignins, which impart considerable strength.

When does the primary cell wall develop?

During cell division, between two newly made daughter cells.

What is the primary function of the primary cell wall's flexibility?

It allows new cells to increase in size.

What are the main components of the primary cell wall?

Cellulose, hemicellulose, crosslinking glycans, and pectins.

Which plant cell wall component consists of highly negatively charged polysaccharides that attract water and provide resistance to compression?

Pectins.

What is the key difference in structure between the primary and secondary cell walls regarding cellulose microfibrils?

The primary cell wall has a meshwork pattern, while the secondary cell wall has strong cellulose microfibrils in parallel arrays, with varied direction in each successive layer.

What would happen if the secondary cell wall of a plant cell was made too soon?

The cell would not be able to increase in size or would have severely constrained growth.

What are glycosaminoglycans (GAGs) in the animal extracellular matrix (ECM)?

Long, unbranched polysaccharides containing repeating disaccharide units that are highly negatively charged and attract water.

What is the primary function of GAGs and proteoglycans in the animal ECM?

To resist compression due to their high water content, thereby protecting cells.

What protein is the main component of elastic fibers in the ECM, allowing tissues like lungs and blood vessels to expand and return to their original shape?

Elastin.

What is collagen's primary function in the animal ECM?

To impart tensile strength, which is the measure of how much stretching force a material can bear without tearing apart.

What are the two main types of proteins found in the ECM of animals?

Adhesive proteins (e.g., fibronectin, laminin) and structural proteins (e.g., collagen, elastin).

What is the function of adhesive proteins like fibronectin and laminin in the animal ECM?

They connect cells to the ECM, help organize ECM components, and facilitate the attachment of cells to the ECM.

What are the four important functions of the ECM in animals?

Strength, structural support, organization, and cell signaling.

What gives the animal ECM its gel-like character?

Polysaccharides, which help it resist compression.

What is chitin and where is it found?

Chitin is a nitrogen-containing polysaccharide that forms the hard, protective outer covering (exoskeleton) of many invertebrates like insects and crustaceans.