Lecture on Cell Walls: Structure, Biogenesis and Expansion

These flashcards cover key concepts from the lecture on plant cell walls, including their structure, composition, functions, and the processes of biogenesis and expansion.

What are the main components of primary cell walls?

Cellulose microfibrils, hemicelluloses, pectins, and structural proteins.

What is the role of cellulose in plant cell walls?

It provides mechanical strength and stability, excludes water, and is resistant to enzymatic attack.

What is the function of pectins in primary cell walls?

Pectins form a gel that attracts water and supports expansion.

What distinguishes secondary cell walls from primary cell walls?

Secondary walls are synthesized after cell expansion ceases and are highly specialized in composition.

What is the middle lamella?

A thin layer of pectin-rich material at the junction where primary walls of neighboring cells meet.

How do cell walls contribute to plant morphogenesis?

They control cell shape and allow high turgor pressure to develop, influencing the growth and form of plants.

What are expansins and what role do they play in cell wall expansion?

Expansins are proteins that mediate acid-induced extension of cell walls by loosening noncovalent bonds between wall polysaccharides.

What are hemicelluloses and what is their function in primary cell walls?

Hemicelluloses are polysaccharides that bind cellulose microfibrils together in a network, providing structural integrity.

What is the significance of turgor pressure related to cell walls?

Turgor pressure is critical for maintaining cell shape and preventing collapse, particularly in xylem tissue during water transport.

What is the impact of environmental conditions on cell wall elongation rates?

Factors like light and water availability, as well as hormones such as auxin and gibberellin, can alter cell wall yielding and expansion rates.

Describe the process of cellulose microfibril synthesis.

Cellulose microfibrils are synthesized by cellulose synthase complexes located in the plasma membrane.

What happens to cell walls when growth ceases?

Secondary cell walls may be formed, which provide structural support and resistance to mechanical stress.

How do microtubules influence cell wall growth directionality?

Microtubules guide the orientation of cellulose synthase complexes, determining the directionality of cellulose deposition.

What causes acid-induced wall extension in growing cells?

An increase in acidity promotes the relaxation of force in the cell wall, allowing for growth.

What is the role of lignin in secondary cell walls?

Lignin provides hydrophobicity, strength, and resistance against pathogen attack in the cell wall.

What characterized the composition of secondary cell walls in woody tissues?

They consist of cellulose, hemicellulose, and lignin, formed into thick layers for structural support.

Why are oligosaccharides from cell walls important during plant growth or starvation?

They can be mobilized for energy to support growth in times of nutritional deficiency.