Cell wall

Definition

A cell wall is a rigid outer layer that provides structural support and protection to the cells of plants, fungi, bacteria, and some archaea. It helps maintain the shape of the cell, prevents excessive water uptake, and acts as a barrier against pathogens. The composition of the cell wall varies among organisms, reflecting their specific needs and environmental adaptations.

5 Must Know Facts For Your Next Test

1. Plant cell walls are primarily made of cellulose, which is a carbohydrate that provides tensile strength.
2. Fungal cell walls are composed of chitin, giving them structural integrity similar to that found in the exoskeletons of arthropods.
3. Bacterial cell walls can be classified into two main types: gram-positive and gram-negative, which differ in their structure and response to antibiotics.
4. Cell walls help prevent lysis (bursting) of cells in hypotonic environments by providing an external pressure that counteracts osmotic pressure.
5. The presence of a cell wall is crucial for plant growth as it allows for turgor pressure to develop, which helps maintain rigidity and support for the plant.

Review Questions

• How does the structure of the cell wall contribute to its function in different organisms?
  • The structure of the cell wall varies significantly among different organisms, which directly influences its function. In plants, the cellulose fibers provide strength and flexibility, allowing them to withstand turgor pressure from within. In bacteria, the peptidoglycan structure gives rigidity while allowing for changes in shape. Fungi utilize chitin for structural support. This diversity in composition allows each organism to adapt its cell wall to specific environmental challenges and functional needs.
• Discuss the role of cell walls in maintaining homeostasis within plant cells.
  • Cell walls play a vital role in maintaining homeostasis within plant cells by controlling water uptake and preventing excessive swelling. When plant cells are placed in a hypotonic solution, the cell wall prevents them from bursting by creating turgor pressure, which keeps the plant upright and healthy. Additionally, the rigidity of the cell wall allows plants to grow taller without collapsing under their own weight, enabling them to access more sunlight for photosynthesis.
• Evaluate how differences in cell wall composition affect antibiotic resistance in bacteria.
  • Differences in cell wall composition significantly impact antibiotic resistance in bacteria. Gram-positive bacteria have thick layers of peptidoglycan that can trap certain antibiotics like penicillin, making them susceptible to treatment. In contrast, gram-negative bacteria possess a thinner peptidoglycan layer surrounded by an outer membrane that can act as a barrier to many antibiotics, complicating treatment. This structural difference plays a crucial role in how effectively antibiotics can target bacterial infections, highlighting the importance of understanding cell wall composition for developing new therapeutic strategies.

Related terms

cell membrane: A semi-permeable membrane that surrounds the cytoplasm of a cell, controlling the movement of substances in and out.

peptidoglycan: A polymer that forms a mesh-like structure in the cell walls of bacteria, providing strength and rigidity.

plasmodesmata: Microscopic channels that traverse the cell walls of plants, allowing communication and transport between adjacent cells.