oad Stop 2: Peptidoglycan eptidoglycan is quite probably the single most importa

Question

oad Stop 2: Peptidoglycan eptidoglycan is quite probably the single most important structural feature found in the Bacteria domain. that, it is worth taking another look about how this remarkable structure is put together in both Gram positive and Gr negative bacteria. We will return later in the course to the medical relevance of understanding how pept Because of synthesized and its important role in the bacterial cell. What is (are) the major role(s) of the peptidoglycan? interesting about three of the amino acids that are found within the tetrapepide of peptidoglycan? What is (are) the major difference() between the cell envelopes found within Gram negative and Gram positive (1) (2) The sugar backbone of peptidoglycan is cross-linked with tetrapeptides. What is a tetrapeptide? What is (3) bacteria? Road Stop 3 Eukaryotic cells vast maiority of this semester will be spent on prokarvotic organisms and viruses. We will, however also look at the

Explanation / Answer

1. Peptidoglycan is a major component of cell wall of gram positive bacteria and occurs at a lower concentration in wall of gram negative bacteria. It provides an essential rigidity in the wall and inhibition of it's synthesis renders gram positive bacteria vulnerable to osmotic shock and can prove to be lethal.

2. Peptidoglycan is a polysaccharide, made up of two glucose derivatives, N-acetyl glucosamine (NAG) and N-acetylene Muramic acid (NAM) alternated in long chains. The chains are cross linked to one another by a tetra peptide that extends off the NAM sugar unit, allowing a lattice like structure to form. The four amino acids that compose the tetra peptide are L- Alanine, D-glutamine, L-lysine or meso-diaminopimelic acid (DPA) and D-alanine . Typically only L -isomeric forms of amino acids utilized by cells, but the use of the mirror image D-amino acids provideprovides protection from proteases that might compromise the integrity of the cell wall by attacking the peptidoglycan.

3. Gram positive bacteria have thick multi layered peptidoglycan where as Gram negative has thin single layered one. Gram + bacteria have techoic acids in their wall and Gram negative don't have techoic acids in their wall. Lipopolysaccharides are in high concentration in gram negative bacteria. The cell wall of gram + bacteria contain 70-80% of murein whereas gram negative bacteria contain 20-30% of murein. Outer membrane is absent in gram + bacteria and present in gram negative bacteria.

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