1. LON-CAPA Logo
  2. Help
  3. Log In
 
MCB 229 Spring 2000 Study Guide 5 Prof. Terry
Covers Lecture for Feb. 15

This study guide is intended for you to use while you are doing the assigned text reading. Quiz questions will be made with reference to topics in this study guide. Quiz #5, based on questions from this study guide, must be completed by midnight before the class on Tuesday, Feb. 15. You will need to create your "myWebCT" account and visit the MCB 229 WebCT page in order to access this quiz.

Chapter 7
  1. What do the following terms mean? Sterilize, disinfect, sanitize, pasteurize, antiseptic, disinfectant, germicide, bactericide, fungicide? What’s the difference between a bactericidal and bacteriostatic agent?
  2. Does the population size matter when estimating how long to treat a microbial sample to achieve sterility? If so, why?
  3. If 70% ethanol is good, 95% ethanol is better as an antimicrobial, right? Explain.
  4. Fruits and tomatoes can be pasteurized more rapidly than milk. Why?
  5. Does organic matter in water affect the level of disinfectant required to reach acceptable levels? Why?
  6. What procedures are best used to sterilize liquid samples? Dry glassware? Heat-sensitive solutions?
  7. Does the “thermal death time” (TDT) tell you exactly how long you need to heat a sample to achieve sterility? If not, what does it tell you?
  8. What does “decimal reduction time” (D) measure? If you have a sample of 109 bacteria, and D for this organism is 0.5 min, how long will you have to treat in order to get reduce the population theoretically to 1 organism (10o)?
  9. It’s Thanksgiving and you’ve served up the turkey with stuffing at noon. By 6 p.m. the stuffing has become an incubator for S. aureus, and the bacterial population has grown to 104 bacteria/gm. You want to snack later on, and you put the stuffing in a warm oven at 60°C to warm up and, you hope, kill bacteria. How long should you wait to eat the turkey, if you want to reduce the bacterial count to no more than 1 bacterium/gm (10o)? The D60 for Staphylococcus aureus in turkey stuffing is 15.4 minutes.
  10. Skim details of autoclaving, pp. 140-141.
  11. How do depth filters and membrane filters differ? Where would you find a HEPA filter?
  12. Are there any microorganisms that would not be removed from a solution by filtering through a 0.2 micrometer membrane filter?
  13. What are the advantages and disadvantages of using UV and ionizing radiation as sterilizing agents?
  14. Note that the distinction between disinfectants and antiseptics is often fuzzy. Some chemicals such as ethanol can be used for either purpose; in other cases the same chemical may be diluted when used as an antiseptic, relative to its concentration when used as a disinfectant.
  15. Look at Table 7.4. Which compounds have the highest activity? Moderate activity? Low activity? Don’t memorize these, just get a sense of the variation in effects.
  16. What are “phenolics”? Where are they routinely used?
  17. How does each of the following work (i.e., what is their cellular target): alcohols, iodine and chlorine (halogens), heavy metals, detergents, aldehydes.
  18. What is the phenol coefficient test? What is it used for?

Chapter 8
  1. Examine the structure of ATP (Fig. 8.2). There are a few chemicals you should be able to recognize at sight – this is one! ATP hydrolysis is coupled to many cellular reactions, releasing sufficient energy to make these reactions occur spontaneously.
  2. What are the 1st and 2nd laws of thermodynamics? (Easy mnemonics: law 1 = “you can’t get out of the ball game”, law 2 = “you can’t win”).
  3. ΔG is a potentially confusing concept. It is more useful than ΔH, the difference in heat energy, because ΔG measures the available energy (after accounting for entropy, which does not contribute to useful work). We won’t do any calculations, so don’t worry about the mathematical symbolism here. But we need to know the difference between ΔG and ΔGo'. The former is defined in terms of actual concentrations of reactants and products, which change; the latter is calculated based on standard concentrations. ΔGo' values give a first approximation to the magnitude of free energy change involved in a reaction, including a prediction of whether the reaction is endergonic or exergonic.
  4. What characteristics would you expect of a chemical reaction with a ΔGo' of +15 kcal/mole? Of – 0.1 kcal/mole? Of – 54 kcal/mole?
  5. How can you recognize an oxidation reaction? A reduction reaction? Do these two always occur together?
  6. What does NAD stand for? Be able to recognize this molecule from its structural formula (Fig. 8.8). Compare this with the diagram of ATP so you don’t get confused. Note that NAD+ includes and ADP molecule as part of its structure, along with an additional ribose and a nicotinamide group.
  7. What is the difference between NAD+ and NADH? Is the total amount of (NAD+ and NADH) in a cell very small, very large, or somewhere in between?
  8. How does NADP differ from NAD? (See legend to Figure 8.8a, and look closely at the figure). Note that NAD is used primarily in reactions in which molecules are broken down (catabolism), while NADP is used primarily in reactions where molecules are being built up (anabolism). More to come on this as we explore Chapters 9 and 10.
  9. In addition to NAD and NADP, you should be able to recognize two other very common redox carriers: FAD (see Fig. 8.9) and heme (Fig. 8.11). We’ll see more of these in Ch. 9.
  10. What is an enzyme? How is an enzyme different from a catalyst? What is the difference between the following terms: apoenzyme, cofactor, holoenzyme, prosthetic group, coenzyme?
  11. Do enzymes affect the overall energy change of a reaction? The rate of a reaction? The activation energy of a reaction? (give a yes or no for each of these).
  12. What is the active site of an enzyme? What happens there?
  13. What happens to the active site when an enzyme is denatured? Is the protein chain broken into smaller pieces during such a process?
  14. What is the difference between a competitive and noncompetitive inhibitor? In which category would you place a chemical that closely resembles the ordinary substrate? A heavy metal?