Plant Cell (pt2) Flashcards
What are the main components of the plant cell wall, and how do they function?
The cell wall is made of cellulose microfibrils, hemicellulose, pectin, and (in secondary walls) lignin. Cellulose provides strength, hemicellulose and pectin add flexibility, and lignin (in the secondary wall) provides rigidity for mature cells.
What are the primary and secondary cell walls, and how do they differ?
The primary cell wall is flexible and allows growth, while the secondary cell wall is thicker and lignin-rich, providing added strength in mature cells.
How do auxin, proton pumps, and expansins contribute to cell wall expansion?
Auxin activates proton pumps, lowering the pH in the cell wall, which activates expansins. Expansins loosen cellulose microfibrils, allowing the cell wall to stretch.
How does the vacuole aid in cell growth?
The vacuole absorbs water, increasing turgor pressure against the cell wall, which, combined with expansin action, helps the cell expand.
What is water potential, and why is it important for plant cells?
Water potential (Ψ) measures water movement direction, with water moving from high to low potential. It dictates water flow into cells in hypotonic conditions (causing turgidity) and out in hypertonic conditions (causing plasmolysis).
How does the cell wall affect plant cell behavior in different water potentials?
In a hypotonic solution, the cell wall prevents the cell from bursting by resisting turgor pressure. In a hypertonic solution, it maintains shape but cannot stop plasmolysis.
What are the three types of ground tissue cells, and how do they function?
Parenchyma: Living cells, thin walls, active in photosynthesis and storage. Collenchyma: Living cells with thicker walls for flexible support in growth areas. Sclerenchyma: Dead, lignin-reinforced cells that provide rigidity and strength.
Why is lignin important in sclerenchyma cells?
Lignin strengthens the cell walls, making sclerenchyma cells ideal for structural support in mature plant tissues.
How do dead cells like xylem and sclerenchyma benefit the plant?
Dead xylem cells form tubes for water and mineral transport. Sclerenchyma provides structural support with rigid cell walls, helping the plant maintain its shape.
Why is it useful for xylem cells to be dead?
Dead xylem cells can conduct water efficiently without resistance from living cell components.
What are the roles of xylem and phloem in plants?
Xylem: Transports water and minerals from roots to shoots. Phloem: Transports sugars and nutrients from photosynthetic areas to other parts of the plant.
What is the difference in cell composition between xylem and phloem?
Xylem cells are mostly dead, while phloem cells are living, with sieve tubes and companion cells for nutrient transport.
What product of photosynthesis is exported from the chloroplast, and what is its role?
G3P (Glyceraldehyde-3-Phosphate) is exported. It’s used in glycolysis, converted into glucose or starch for storage, or transformed into sucrose for transport via phloem.
How is G3P involved in both storage and transport?
G3P can be stored as starch in chloroplasts or transformed into sucrose for transport, making it versatile in energy storage and distribution.
Do plant cells become turgid in hypertonic or hypotonic solutions?
Plant cells become turgid in hypotonic solutions, where water enters the cell, increasing turgor pressure.
