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Lab Quiz # 4 Review

Lab Ex. 's 15,16,17,24,25,26

Proteins Are large organic molecules that include cellular enzymes and many structures.
Amino Acids The subunits that make a protein.
Peptide bonds A bond joining the amino group of one amino acid to the carboxyl group of a second amino acid with the loss of a water molecule.
Peptide A small chain formed by peptide bonds
Polypeptide (1) A chain of amino acids. (2) A group of antibiotics.
Nutrient gelatin Dissolves in warm water (50C), solidifies (gels) when cooled below 25 degrees Celsius, and liquifies (sols) when heated to about 25 degrees Celsius. (when an exoenzyme hydrolyze gelatin, it liquifies and does not solidify even when cooled below 20C.
Urea is a waste product of protein digestion in most vertebrates and is excreted in the urine.
Urease The presence of this enzyme liberates ammonia from urea. (Useful in diagnostic tests for identifying bacteria)
Urea agar Contains peptone, glucose, urea, and phenol red.
What is the pH in the urea agar? How does it change when with bacteria? What color does it change if ammonia is present? The pH of the prepared medium is 6.8 (phenol red turns yellow). During incubation, bacteria possessing urease will produce ammonia, which raises pH of the medium, turning the indicator fuchsia at pH 8.4
What bacteria we used in lab produced urease? P. vulgaris produces urease and gelatinase, but all student responses may differ/vary.
Nutrient gelatin can be incubated at 35 degrees Celsius. What would you have to do to determine hydrolysis after incubation at 35 degrees Celsius? Cool below 25 degrees Celsius.
What is the source of urea in an animal's body? End-products of amino acid catabolism.
Why is agar used as a solidifying agent in culture media instead of gelatin? Gelatin liquifies at the commonly used incubation temperature of 35 degrees Celsius, resulting in a liquid medium.
A person changing a baby's wet diaper smells ammonia. Why? Urea in urine is hydrolyzed by bacteria from the baby's feces or skin.
Helicobacter pylori bacteria grow in the human stomach. These bacteria produce a large amount of urease. Of what value is the urease to Helicobacter? Ammonium ion can neutralize stomach acids.
Deamination The removal of an amino group from an amino acid to form ammonia, which can be excreted from the cell. Results in the formation of an organic acid.
Decarboxylation The removal of carbon dioxide from an amino acid.
Hydrogen sulfide (H2S) Some bacteria liberate this from sulfur-containing amino acids: cystine, cysteine, and methionine. To detect H2S production, a heavy-metal salt containing ferrous ion is added to a nutrient culture medium. Produce visible black precipitation when present.
Indole test Performed by inoculating a bacterium into a tryptone broth and detecting indole by the addition of dimethylaminobenzaldehyde (Kovacs reagent). Which will turn the medium in the tube blue.
MIO A single culture medium in which motility, indole production, and ornithine decarboxylase activity can be determined.
When canned foods spoil, what causes the blackening of the cans? Reduction of sulfur in various compounds from hydrogen sulfide. The H2S reacts with metal ions (eg. ferrous ions) to form metal sulfides, which are black.
Why look for black precipitate (FeS) in the butt instead of on the surface of an H2S test? Hydrogen sulfide formed at the surface of the tube can escape as a gas. In the butt, hydrogen sulfide will combine with ferrous ions to form ferrous sulfide.
An oxidation reaction Releases electrons, so it must always be paired with a reduction reaction to accept the electrons. (In photosynthesis, chlorophyll loses electrons (oxidation), and the electrons are ultimately used to reduce carbon dioxide.
Aerobic respiration Respiration in which the final electron acceptor in the electron transport chain is molecular oxygen.
Anaerobic Respiration Respiration in which the final electron acceptor in the electron acceptor chain is an inorganic molecule other than molecular oxygen; for example a nitrate ion of CO2.
Reduction The addition of electrons to a molecules.
Why does hydrogen peroxide bubble when it is poured on a skin cut? Human cells are catalase positive (+).
Differentiate fermentation from anaerobic respiration. Fermentation does not use an electron transport chain, and the final electron acceptor is usually an organic molecule. Anaerobic respiration does use and electron transport chain, and the final electron acceptor is and inorganic atom, ion or molecule.
In the nitrate reduction test, what does the presence of gas indicate? Nitrate reduction. The nitrate was reduced to Nitrite, then to nitrous oxide, and finally to nitrogen gas.
Is nitrate reduction beneficial of harmful to farmers? Harmful. Plants use nitrate as a nutrient. When nitrate is reduced the nitrous oxide or nitrous gas, the soil is depleted of nitrates.
Antimicrobial agents Chemicals used for controlling the growth of microbes.
Disinfectants Are chemical agents used on inanimate objects to lower the level of microbes on their surfaces.
Antiseptics Chemicals used o living tissue to decrease the number of microbes present.
Bactericidal agents Kills bacteria (example bleach).
Bacteriostatic agents Cause temporarily inhibition of microbial growth (example antibiotics).
American Official Analytical Chemist's use-dilution test The standard method fro measuring the effectiveness of a chemical agent.
Antibiotic An antimicrobial agent, usually produced naturally by a bacterium or fungus.
Antibiosis (against life) The word used for inhibition, when some microbe inhibited the growth of others.
Antimicrobial drugs Antimicrobial chemicals absorbed or used internally, whether natural (antibiotics) or synthetic.
Pathogen A disease-causing organism.
Disk-diffusion method also known as Kirby-Bauer test A Petri plate containing agar growth medium is inoculated uniformly over it's entire surface. Paper disk impregnated with various antimicrobial agents are placed on surface of agar. it is then incubated. An effective agent will inhibit bacterial growth.
Zone of inhibition The area if no bacterial growth around an antimicrobial agent in the disk diffusion method.
Minimum inhibitory concentration (MIC) The lowest concentration of a chemotherapeutic agent that will prevent the growth of the test microorganisms.
Why is the disk-diffusion technique not a perfect indication of how the drug will perform in vivo? What other factors are considered before using the antimicrobial agent in vivo? Variables such as the effect of serum, the body's pH, and ionic content, and Oxygen level, how the drug is metabolized and excreted; as well as the side effects of the drug.
Normal microbiota The microorganisms that colonize a host without causing disease; also called normal flora. (The organisms that are more or less permanent)
Transient microbiota The microorganisms that are present in an animal for a short time without causing a disease.
what is a surgeon trying to accomplish with a 10-minute scrub with a brush followed by an antiseptic? Scrubbing is an attempt to dislodge as many microbes as possible, and an antiseptic is used to kill as many remaining microbes after hand scrubbing.
How do normal microbiota and transient microbiota differ? Normal microbiota colonize on/in the body and are more or less permanent. Transient microbiota are present for a brief period of time, depending on local conditions and competing microorganisms. Neither group causes disease.
If most of the normal microbiota and transient microbiota aren't harmful, then why must hands be scrubbed before surgery? Any microbe that enters a normally sterile location or a compromised host can be a harmful.
Oxidase test A test useful in identifying bacteria because some bacteria do not have cytochrome c.
Catalase An enzyme that breaks sown hydrogen peroxide to water and oxygen.
Created by: KJones040607