EVEN Micro HW3 - Prof. Li - Same homework every year PDF

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Prof. Li - Same homework every year, Prof. Li - Same homework every year...

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Environmental Microbiology HW3 Due date: October 28 2016 1. Compare “monomer” and “polymer”. Give three examples of biologically important polymers and list the monomers of which they are composed. Draw the structure formula for each of them. A polymer is a large molecule made up from the polymerization of monomers. Monomers are made up of amino acids that link together to form proteins which produces a polymer when they keep linking together in a chain. One biologically important polymer is poly-B-hydroxyalkanoates which is usually made up of the monomer hydroxybutyrate (C4) but can vary from C3 to C18.

Another important polymer is glycogen which is made up of glucose. It is important for storing carbon and energy.

Another biologically important polymer is teichoic acids, which are imbedded in the cell wall and membrane of gram positive bacteria. They’re important for maintaining the structure of the cell wall and are made up of glycerol phosphate or ribotol phosphate.

2. Draw peptide bond. Describe the structures of protein.

The structure of the protein primarily is a link of covalent peptide bonds. The secondary structure occurs when the polypeptides undergo folding and form the ahelix structure or the B-sheet structure. The tertiary structure is these folded into specific 3D formations. Lastly, the quaternary structure forms when two or more polypeptides in the tertiary structure bind together to form a protein. 3. Why lipid is so important for cell membrane? The cell membrane is made up of a phospholipid bilayer. In the membrane, fatty acids point inward toward eachother while the hydrophilic heads point outward, producing a hydrophobic environment. Structurally, this makes the membrane somewhere between a fluid and rigid body, which gives the proteins more freedom to move around. It also make it relatively permeable meaning that only a few substances can actually diffuse into the cell.

4. Under what condition that protein is denatured. What happen when protein is denatured? One way a protein could be partially denatured is when exposed to urea. This will cause it to lose its ability to function but it will return to its original state as soon as the urea is removed. Another way could be heating a protein to the point where it loses its shape and thus its function. In this case, even if the temperature is lowered to where it was, the protein is unable to be restored. 5. Why we say “the sequence of DNA and RNA determines the structure and function of cells”? The sequence of DNA and RNA refers to the ordering of nitrogen bases which determines the genes that make up the human genome. These genes then form proteins that carry out functions for the cell. Some things that they do are make up the membrane, allow the cell to metabolize, and aid chemical reactions. Nucleic acids are necessary for the existence if cells. 6. Explain the semi-conservative feature of DNA replication. The process in DNA replication is considered semiconservative because the DNA strands are made up of one parental strand and one new strand. In this process, the parental strand acts as the template for the newly synthesized strand. 7. What’s the importance of polymerase in DNA and RNA synthesis? DNA Polymerases are important for synthesis because they catalyze the addition of deoxynucleotides. There’s five different types of enzymes that each carry a different role in replication, such as repairing damaged DNA or participating in chromosomal replication. RNA polymerase has a similar task but helps in the formation of mRNA rather than DNA. 8. Why RNA other than DNA is targeted when environmental samples are tested? Environmental samples usually target RNA because the probes can identify specific species of bacteria by hybridizing to characteristic sequences in the genes in RNA. This allows us to obtain information on the DNA as well without damaging the DNA. Also, RNA is much more abundant in the cell than DNA. 9. What’s the difference between natural mutation and gene recombination? Natural mutation happens almost accidently in the genetic material in a cell. They are totally random and only lead to minor changes in genes. Genetic recombination differs because it brings together genetic components from two separate genomes. 10. Briefly describe the mechanisms of Ames test, and its environmental relevance. The Ames test makes practical use of detecting revertants in large populations of mutant bacteria to test the mutagenicity of potentially hazardous chemicals. Typically this is done by looking for reversion in auxotrophic strains of bacteria. The bacteria forms colonies which increase as the rate of reversion increases.

11. What’s the traditional enrichment culture bias? The bias is in the outcome of enrichments in lab cultures, most profound in liquid cultures where rapidly growing organisms dominate. These successful enrichment cultures are often minor components in the real world microbial community. The bias is thought to be caused by availability of resources and the physical or chemical conditions where reproduction is occurring. This gap is a concern because testing of cultures in the lab may not be a good representation of reality. 12. What’s the mechanism of fluorescent in situ hybridization (FISH)? FISH is a technique where fluorescent probes are used to identify organisms that contain a nucleic acid sequence complementary to the probe. Some of its applications include phylogenetic stains and measuring gene expression. The addition of fluorescent dye to the nucleic acid probes have led to many advancements in tracking certain gene sequences in a sample. 13. State your opinions about traditional enrichment culture approach and genetic material approach. Do you think genetic material approaches can completely replace traditional enrichment culture approach? The genetic material approach is an advancement over the enrichment culture approach because it avoids the large bias mentioned earlier. However, I think there is a reason it has not replaced traditional enrichment cultures thus far. There is some information that genetic material process cannot tell us that only enrichment cultures. There should be an advancement in the traditional method to lessen/negate the bias but until then, both methods have their reasons to be used....