cell wall

(noun)

A thick, fairly rigid layer formed around individual cells of bacteria, Archaea, fungi, plants, and algae, the cell wall is external to the cell membrane and helps the cell maintain its shape and avoid damage.

Related Terms

Examples of cell wall in the following topics:

  • Inhibiting Cell Wall Synthesis

    • Two types of antimicrobial drugs work by inhibiting or interfering with cell wall synthesis of the target bacteria.
    • Antibiotics commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cells do not have cell walls.
    • The peptidoglycan layer is important for cell wall structural integrity, being the outermost and primary component of the wall.
    • Diagram depicting the failure of bacterial cell division in the presence of a cell wall synthesis inhibitor (e.g. penicillin, vancomycin).1- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium with a dividing bacterium.2- The cell begins to grow, but is unable to synthesize new cell wall to accommodate the expanding cell.3- As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall.4- Cell wall integrity is further violated.
    • The cell continues to increase in size, but is unable to "pinch off" the extra cytoplasmic material into two daughter cells because the formation of a division furrow depends on the ability to synthesize new cell wall.5- The cell wall is shed entirely, forming a spheroplast, which is extremely vulnerable relative to the original cell.

  • Damage to the Cell Wall

    • The cell wall is responsible for bacterial cell survival and protection against environmental factors and antimicrobial stress.
    • While the peptidoglycan provides the structural framework of the cell wall, teichoic acids, which make up roughly 50% of the cell wall material, are thought to control the overall surface charge of the wall.
    • Damage to the cell wall disturbs the state of cell electrolytes, which can activate death pathways (apoptosis or programmed cell death).
    • A bacterial cell with a damaged cell wall cannot undergo binary fission and is thus certain to die .
    • Discuss the effects that damage to the cell wall has on the bacterial cell

  • Cell Walls of Archaea

    • Archaeal cell walls differ from bacterial cell walls in their chemical composition and lack of peptidoglycans.
    • Around the outside of nearly all archaeal cells is a cell wall, a semi-rigid layer that helps the cell maintain its shape and chemical equilibrium.
    • For instance, the cell walls of all bacteria contain the chemical peptidoglycan.
    • The cell wall of archaeans is chemically distinct.
    • State the similarities between the cell walls of archaea and bacteria

  • The Cell Wall of Bacteria

    • Bacteria are protected by a rigid cell wall composed of peptidoglycans.
    • Bacterial cells lack a membrane bound nucleus.
    • A wall located outside the cell membrane provides the cell support, and protection against mechanical stress or damage from osmotic rupture and lysis .
    • The major component of the bacterial cell wall is peptidoglycan or murein.
    • The cell wall provides important ligands for adherence and receptor sites for viruses or antibiotics.

  • Mycoplasmas and Other Cell-Wall-Deficient Bacteria

    • Some bacteria lack a cell wall but retain their ability to survive by living inside another host cell.
    • For most bacterial cells, the cell wall is critical to cell survival, yet there are some bacteria that do not have cell walls.
    • Cell walls are unnecessary here because the cells only live in the controlled osmotic environment of other cells.
    • It is likely they had the ability to form a cell wall at some point in the past, but as their lifestyle became one of existence inside other cells, they lost the ability to form walls.
    • Other bacterial species occasionally mutate or respond to extreme nutritional conditions by forming cells lacking walls, termed L-forms.

  • Gram-Negative Outer Membrane

    • The Gram-negative cell wall is composed of an outer membrane, a peptidoglygan layer, and a periplasm.
    • In the Gram-negative Bacteria the cell wall is composed of a single layer of peptidoglycan surrounded by a membranous structure called the outer membrane.
    • The Gram-negative's cell wall is thinner (10 nanometers thick) and less compact than that of Gram-positive bacteria, but remains strong, tough, and elastic to give them shape and protect them against extreme environmental conditions .
    • It is in fact an integral compartment of the gram-negative cell wall and contains binding proteins for amino acids, sugars, vitamins, iron, and enzymes essential for bacterial nutrition.
    • Together, the plasma membrane and the cell wall (outer membrane, peptidoglycan layer, and periplasm) constitute the gram-negative envelope.

  • Virus Attachment and Genome Entry

    • Instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell.
    • This is often called "viral entry. " The infection of plant and fungal cells is different from that of animal cells.
    • Plants have a rigid cell wall made of cellulose, and fungi one of chitin, so most viruses can get inside these cells only after trauma to the cell wall.
    • Bacteria, such as plants, have strong cell walls that a virus must breach to infect the cell.
    • However, given that bacterial cell walls are less thick than plant cell walls due to their much smaller size, some viruses have evolved mechanisms that inject their genome into the bacterial cell across the cell wall, while the viral capsid remains outside

  • Peptidoglycan Synthesis and Cell Division

    • Peptidoglycan, also known as murein, is a polymer and consists of sugars and amino acids which form the cell walls of bacteria.
    • That is why the cell wall of Archaea is insensitive to lysozyme.
    • That is why the cell wall of Archaea is insensitive to lysozymes, which are present in human sweat and tears as part of innate immunity.
    • Peptidoglycan serves a structural role in the bacterial cell wall giving it strength, as well as counteracting the osmotic pressure of the cytoplasm.
    • Simplified sc hematic of a cell wall in a Gram-positive bacteria

  • General Features of Virus Replication

    • The infection of plant and fungal cells is different from that of animal cells.
    • Plants have a rigid cell wall made of cellulose, and fungi one of chitin, so most viruses can get inside these cells only after trauma to the cell wall.
    • Bacteria, like plants, have strong cell walls that a virus must breach to infect the cell.
    • However, since bacterial cell walls are much less thick than plant cell walls due to their much smaller size, some viruses have evolved mechanisms that inject their genome into the bacterial cell across the cell wall, while the viral capsid remains outside.
    • Viruses can be released from the host cell by lysis, a process that kills the cell by bursting its membrane and cell wall if present.

  • Injuring the Plasma Membrane

    • The plasma membrane or cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
    • Plasma membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity, and cell signaling.
    • It serves as the attachment surface for several extracellular structures, including the cell wall, glycocalyx, and intracellular cytoskeleton.
    • Fungi, bacteria, and plants also have the cell wall which provides a mechanical support for the cell and precludes the passage of larger molecules.
    • Diagram of a typical gram-negative bacterium, with the thin cell wall sandwiched between the red outer membrane and the thin green plasma membrane.