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Lab 15 and 16
| Question | Answer |
|---|---|
| 15 C1: Do all bacteria produce urease and gelatinase? | P.Vulagaris produces urease and gelatinase. |
| 15 Q1: Nutrient gelatin can be incubated at 35 deg. Celsius. What would you have to do to determine hydrolysis after incubation at 35 deg Celsius? | Cool it below 25 degrees Celsius. |
| 15 Q2: What is the source of urea in an animal's body? | End products of amino acid catabolism. |
| 15 CT1: Why is agar used as a solidifying agent in culture media instead of gelatin? | Gelatin liquifies at commonly used incubation temps, resulting in a liquid medium. Some bacteria can hydrolyze gelatin which also results in a liquid medium. Agar remains solid at temps up to 100deg.C. and is hydrolyzed by few bacteria. |
| 15 CT3: A person changing a baby's wet diaper smells ammonia. Why? | Urea in the urine is hydrolyzed by bacteria from the baby's feces or skin. |
| 15 CT4: Helicobacter pylori bacteria grow in the human stomach. These bacteria produce a large amount of urease. Of what value is this urease to Helicobacter? | Ammonium ion can neutralize stomach acid. |
| Proteins | large organic molecules that include cellular enzymes and many structures. |
| Amino acids | The subunits that make up a protein. They consist of C,H,O,N, and sometimes Sulfur. |
| Peptide Bonds | Amino acids bond together by peptide bonds. |
| Peptide Chain | a small chain of amino acids joined by peptide bonds. |
| Polypeptide | A peptide chain forming a larger molecule. |
| Nutrient Gelatin | Dissolves in warm water, solidifies when cooled, and liquefies when heated |
| Urea | A waste product of protein digestion in most vertebrates; excreted in urine. |
| Urease | Enzyme which liberates(releases) ammonia from urea; useful diagnostic test for identifying bacteria. |
| Urea agar | Contains peptone, glucose, urea, and phenol red; has pH of 6.8. (Bacteria which possess urease will raise pH and turn agar hot pink) |
| Deamination | the removal of an amino group. |
| Decarboxylation | the removal of carbon dioxide from an amino acid. |
| Hydrogen Sulfide(H2S) | "Rotten-egg gas," black precipitate in tube |
| Indole Test | Diagnostic test performed on bacterial species to determine the ability of the organism to split indole from the amino acid tryptophan |
| Kovacs Reagent | Inserted into broth to detect Indole. |
| MIO | "Motility Indole Ornithine;" Differential screening medium used to determine motility, indole production, and ornithine decarboxylase activity. |
| 16 Q1: When canned foods spoil, what causes the blackening of the cans? | Reduction of sulfur in various compounds forms hydrogen sulfide. The H2S reacts with metal ions (e.g. ferrous ions) to form metal sulfides, which are black. |
| 16 CT1: Why look for black precipitate (FeS) in the butt instead of on the surface of an H2S test? | Hydrogen sulfide formed @ the surface of the tube can escape as a gas. In the butt, hydrogen sulfide will combine with ferrous sulfide. |
| Oxidizing | Removing electrons to obtain energy |
| Reduced | In oxidation, the electron acceptor is REDUCED when it accepts an electron |
| Respiration | Oxidative Metabolism |
| Aerobic respiration | Molecular O2 is final electron acceptor |
| Oxidase test (only in aerobic bacteria) | Used to determine the presence of cytochrome c --> which carry electrons to O2 in the plasma membrane. Some bacteria do not have cytochrome c. |
| Catalase | Aerobic organisms produce this enzyme to break down hydrogen peroxide(which is lethal to the cell) into water + O2 |
| anaerobic respiration | Inorganic compounds act as final electron NOT O2. |
| 17 Q1: Define reduction: | When an electron receptor accepts and electron. |
| 17 Q2: Why does hydrogen peroxide bubble when it is poured on a skin cut? | There is a catalase enzyme present on our skin and it cause the hydrogen peroxide to seperate. |
| 17 Q3: Differentiate "aerobic respiration" from "anaerobic respiration": | Aerobic- O2 is final electron receptor. Anaerobic- an inorganic compound is the final electron. |
| 17 Q4: Differentiate "fermentation" from "anaerobic respiration": | Fermentation- glucose is oxidized. Anaerobic- inorganic compounds reduce nitrates |
| 17 CT2: In the nitrate reduction test, what does the presence of gas indicate? | That nitrogen gas was formed |
| 17 CT3: Is nitrate reduction beneficial or harmful to farmers? | HARMFUL- plants use nitrate as a nutrient. When nitrate is reduced to nitrous oxide or nitrous gas, the soil is depleted of nitrates |
Created by:
Lproctor