write function and structure cell wall
Answers
Answer:
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Explanation:
A cell wall is a rigid, semi-permeable protective layer in some cell types. This outer covering is positioned next to the cell membrane (plasma membrane) in most plant cells, fungi, bacteria, algae, and some archaea. Animal cells however, do not have a cell wall. The cell wall has many important functions in a cell including protection, structure, and support
Plant Cell Wall Structure
A section of the cell wall in a plant cell
By LadyofHats (Own work) [Public domain], via Wikimedia Commons
The plant cell wall is multi-layered and consists of up to three sections. From the outermost layer of the cell wall, these layers are identified as the middle lamella, primary cell wall, and secondary cell wall. While all plant cells have a middle lamella and primary cell wall, not all have a secondary cell wall.
Middle lamella: This outer cell wall layer contains polysaccharides called pectins. Pectins aid in cell adhesion by helping the cell walls of adjacent cells to bind to one another.
Primary cell wall: This layer is formed between the middle lamella and plasma membrane in growing plant cells. It is primarily composed of cellulose microfibrils contained within a gel-like matrix of hemicellulose fibers and pectin polysaccharides. The primary cell wall provides the strength and flexibility needed to allow for cell growth.
Secondary cell wall: This layer is formed between the primary cell wall and plasma membrane in some plant cells. Once the primary cell wall has stopped dividing and growing, it may thicken to form a secondary cell wall. This rigid layer strengthens and supports the cell. In addition to cellulose and hemicellulose, some secondary cell walls contain lignin. Lignin strengthens the cell wall and aids in water conductivity in plant vascular tissue cells.
Support: The cell wall provides mechanical strength and support. It also controls the direction of cell growth.
Withstand turgor pressure: Turgor pressure is the force exerted against the cell wall as the contents of the cell push the plasma membrane against the cell wall. This pressure helps a plant to remain rigid and erect, but can also cause a cell to rupture.
Regulate growth: The cell wall sends signals for the cell to enter the cell cycle in order to divide and grow.
Regulate diffusion: The cell wall is porous allowing some substances, including proteins, to pass into the cell while keeping other substances out.
Communication: Cells communicate with one another via plasmodesmata (pores or channels between plant cell walls that allow molecules and communication signals to pass between individual plant cells).
Protection: The cell wall provides a barrier to protect against plant viruses and other pathogens. It also helps to prevent water loss.
Storage: The cell wall stores carbohydrates for use in plant growth, especially in seeds.
Plant Cell Structures and Organelles
Cell (Plasma) Membrane: This membrane surrounds the cytoplasm of a cell, enclosing its contents.
Cell Wall: The outer covering of the cell that protects the plant cell and gives it shape is the cell wall.
Centrioles: These cell structures organize the assembly of microtubules during cell division.
Chloroplasts: The sites of photosynthesis in a plant cell are chloroplasts.
Cytoplasm: This gel-like substance within the cell membrane supports and suspends organelles.
Cytoskeleton: The cytoskeleton is a network of fibers throughout the cytoplasm.
Endoplasmic Reticulum: This organelle is an extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER).
Golgi Complex: This organelle is responsible for manufacturing, storing and shipping certain cellular products.
Cell Wall Key Points
The cell wall is an outer protective membrane in many cells including plants, fungi, algae, and bacteria. Animal cells do not have a cell wall.
The main functions of the cell wall are to provide structure, support, and protection for the cell.
The cell wall in plants is composed mainly of cellulose and contains three layers in many plants. The three layers are the middle lamella, primary cell wall, and secondary cell wall.
Bacterial cell walls are composed of peptidoglycan. Gram-positive bacteria have a thick peptidoglycan layer and gram-negative bacteria have a thin peptidoglycan layer.