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Questions and Answers
What is the primary role of microfibrils in the cell wall?
What is the primary role of microfibrils in the cell wall?
- They facilitate the transmission of macromolecules into the cell.
- They contribute to the tensile strength of the wall. (correct)
- They provide the primary energy source for cell metabolism.
- They are responsible for nutrient storage within the cell.
Which statement accurately describes the function of plasmodesmata?
Which statement accurately describes the function of plasmodesmata?
- They restrict movement of water and nutrients between cells.
- They connect protoplasts of adjacent cells and transmit solutes. (correct)
- They provide mechanical support to the cell wall.
- They are primarily involved in storing macromolecules.
What is the estimated diameter of the smaller pores in the cell wall?
What is the estimated diameter of the smaller pores in the cell wall?
- 0.4 to 0.6 nm
- 4.0 to 6.5 nm (correct)
- 2.0 to 4.0 nm
- 8.0 to 10.0 nm
What do secondary wall layers mainly contribute to in plant structures?
What do secondary wall layers mainly contribute to in plant structures?
Which molecules are typically blocked from passing through the smaller wall pores?
Which molecules are typically blocked from passing through the smaller wall pores?
Flashcards
Microfibrils
Microfibrils
Tiny, thread-like structures composed of cellulose that provide strong, flexible support to the plant cell wall.
Matrix
Matrix
The substance between the microfibrils in the plant cell wall, predominantly consisting of pectin and other complex sugars.
Secondary Wall
Secondary Wall
A type of cell wall that forms after the primary wall, providing additional rigidity and often containing compounds like lignin, suberin, and other special substances.
Plasmodesmata
Plasmodesmata
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Small Wall Pores
Small Wall Pores
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Study Notes
Plant Cell Wall Structure and Function
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Microfibrils: Clusters of crystalline cellulose, approximately 10 nm in diameter, contributing significantly to cell wall tensile strength.
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Matrix: Binds and organizes microfibrils. May influence cell growth rate.
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Cell Wall Aging: As a cell ages, growth stops, and additional layers (secondary walls) are deposited inside the primary wall. These secondary layers often contain lignins, suberins, and other compounds that provide rigidity and water resistance to the wall.
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Secondary Walls: Contribute to properties of wood, bark, nutshells, and other plant parts.
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Pores: Two types of pores exist in the cell wall.
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Plasmodesmata: Large pores filled with protoplasm, lined with plasmalemma. Connect adjacent cell protoplasts, facilitating water and solute transfer.
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Smaller Pores: Numerous, small pores not filled with protoplasm. Filled with cell exterior solution. Has diverse diameters (4.0–6.5 nm). Freely transmits small molecules (water, sugars, amino acids, small proteins) with diameters up to 8.5nm. Molecules larger than 60,000 D are blocked. Plasmalemma passes through the pore ends, but its thickness (4.5-25 nm) allows it to support itself.
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Small Solute Movement: Small solutes easily move through the wall pores, reaching the cell surface's plasmalemma for selective transport. This often requires energy.
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Macromolecules & Solutes: Macromolecules (proteins, nucleic acids) are present in low concentrations compared to small solutes and inorganic ions (0.5-1 molal). But they are important because they regulate metabolites, membrane properties, and cell wall nature via their enzymatic/nucleic acid functions. Consequently, although water relations are affected by macromolecules, small solutes and membranes immediately influence water.
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Description
Explore the intricate details of plant cell wall structure and its vital functions. This quiz covers topics such as microfibrils, secondary walls, and the role of pores in cellular connectivity and substance transport. Test your knowledge on how these components contribute to plant resilience and growth.
