QUESTIONS 1. Label the parts of the typical Gram-negative bacterial cell shown b
ID: 202440 • Letter: Q
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QUESTIONS 1. Label the parts of the typical Gram-negative bacterial cell shown below. Capsule Cell wall pLasma menbrane nucleoia Cciruwlor DNA) Peptidoglycan ribosomes Flagellum Cy toplasm Pili ClHayden-McNeil, LLC 2. Describe the structure of a bacterial chromosome. How does it differ from a eukaryotic chromosome? 3. Cyanobacteria can carry out photosynthesis, yet they do not contain chloroplasts. Where is chlorophyll found in these organisms? 4. Your doctor tells you that you have a bacterial infection in your salivary glands. You are given the opportunity to view the slide made from a sample of your saliva. It is labeled "Gram-negative, coccus." Describe what you will see on the slide. 5. Explain how the structure of the bacterial cell wall affects the results of the Gram-staining procedure. WORK SHFETExplanation / Answer
1. I don't see any needs of changes in nomenclature.
2. The Bacterial chromosome is a circular DNA. Bound in some pattern by DNA binding protein. It is found directly into the cytoplasm of the bacterium(i.e. it isn't enveloped in to any nuclear membrane). Mostly bacteria contains more then 1 circular DNA sequences. The larger, Genomic DNA and other smaller ones floating in cytoplasm are Plasmid DNA.
Where as a Eukaryotic DNA are linear ones. And are compactly bound in a structure with the help of protein Chromatin, and making a DNA-Protein complex. And generally this Eukaryotic chromosomes are found inside the nuclear membrane.
3. Cyanobacteria are so called because of their blue green colour. Now these all pigments including Chlorophyll A and Chlorophyll B(in few cases, when phycobilisomes are absent) are found in the sacs of membrane through out the cytoplasm of bacteria. These sacs are called 'thylakoids' just like in the Eukaryotic chloroplast. All the photosynthetic pigments available in the blue-green algae are found on this thylakoid membrane.
4. The slide with Gram negative will show the bacteria stains in pink colour. And as they are coccus, clusters or chains of small round shaped or small kidney or coffeebean shaped bacteria can be observed.
5. In Gram positive bacteria the cell wall is made up of thick layer of peptidoglycan. So when this layer is exposed to Crystal Violet and the mordent, Iodine solution, thicker layer of peptidoglycan takes up the dye. In the second step, decolorization, alcohol is applied which promotes dehydration in the peptidoglycan layer causing closure of the pores in it. Thus the violet colours stays on the membrane.
In Gram negative bacteria, the outer thick layer contains lipid molecules. And under this layer is a thin layer of peptidoglycan. When the fist stain Crystal Violet with the mordent is applied, outer lipid layer takes up the dye. But in the second step of decolorization the lipid molecules get dissolved in alcohol and get washed off. Now the inner peptidoglycan layer gets exposed to second stain- saffranin. And thus, gram negative bacteria stains red/pink in colour.
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