Microbiology: Lab Review Chapter 3

Chapter 3 Laboratory Review Questions

A few ideas to get down before answering this lab review.

Ocular lens/Eyepiece - Lens of the eyepiece, usually 10X in our case.

Objective lens - Three lenses on the nose piece, 4X, 10X,40X, 100X. Light goes up through the objective lens into the ocular lens. 

Condenser - Gathers light from the microscope light source and concentrates it into a cone of light that illuminates the specimen with uniform intensity over the entire view field.

Rheostat - Controls the intensity of the light produced.

1) [CH-03-01] Why is the light microscope described as compound microscope?

The light microscope uses multiple lenses together to magnify a image. In the case of our microscope in the lab: one for the optical lens and one for the objective lens. These multiple lenses are where the compound: composed of one or more parts, comes from. 

2) [CH-03-02] How is the orientation of the letter "e" changed by the lenses of the microscope?

The orientation of the letter "e" is reflected over the x and y axis.

3) [CH-03-03] Explain the differences between magnification and resolving power of microscope?

Magnification is how much an image is dilated (enlarged) from its original.

Resolving power is the ability of an optical instrument or type of film to separate or distinguish small or closely adjacent images.

4) [CH-03-04] What is meant by the limit of microscope's resolution? Which objective has higher resolving power, 40X or 100X?

Limit of a microscope's resolution is the smallest distance between two objects that a microscope is still able to identify two objects as separate objects. Thus the lens with the greater magnification has a high resolving power, in this case the 100X.

5) [CH-03-05] Why do microscopists always start with the low magnification lens?

The low magnification serves as a "scanning lens" that allows people to find the object that they are looking for. Once the image is centered, higher magnification lenses can be used. 

6) [CH-03-06] Compare the function of the brightness control with the iris diaphragm?

Brightness or intensity of the light is controlled by the rheostat, while the amount of light that is allowed to strike the stage is controlled by the iris diaphragm.

7) [CH-03-07] Explain the term parfocal. Which objective produces a larger field of view, 10X or 40X? 

Parfocal focusing on the image in the center plane so that the same image can be reacquired quickly after switching lenses. Sample kept in focus since object is on same focal plane.

The 10X objective produces a larger field of view because of its low magnification.

8) [CH-03-08] Calculate the limit of resolution for yellow light (wavelength 550nm) and blue light (wavelength 450nm). Which light produces superior resolution?

The formula for resolution is D = λ/(NAcondenser + NAobjective) or ≈ D = λ/2. Where λ is wavelength.
For Yellow light resolution: D = λ/2, D = (550*10^-9)m/2 = (2.75*10^-7)m
For Blue light resolution: D = λ/2, D = (450*10^-9)m/2 = (2.25*10^-7)m

Blue light has a smaller resolution limit, making it the super resolution.

9) [CH-03-09] If all other variables remain constant, explain why light of shorter wavelengths will produce a clearer image than light of longer wavelength?

As demonstrated by the formula above, light of shorter wavelengths are able to have smaller resolution limits, and therefore better resolution. Smaller wavelengths are able to produce higher resolution images (e.g. comparison between light microscope and electron microscope).

10) [CH-03-10] Why should closing the iris diaphragm in light microscope improve your ability to see more details in the resulting image?

Closing the iris diaphragm decreases the amount of light hitting the specimen on the stage and increases the contrast between the specimen and its surroundings. Thereby, making the specimen easier to make out. 

Microbiology: Lab Review Chapter 2

Chapter 2 Laboratory Review Questions

A few ideas to get down before answering this lab review.

Sanitizing agents - Reduce microbial contamination by physical removal of microbes.

Antiseptics - Remove and kill at least some of the microbes.

Disinfectants - Kills microbes and even spores, but are too harsh to be used on skin.

1) [CH-02-01] What are mechanisms of action for Triclosan and Povidone?

Triclosan - Targets the fatty acid synthesis mechanism.

Povidone iodine - Iodine permeates through the cell membrane and attacks the bacteria's proteins and DNA.

2)[CH-02-02] What concentration of ethanol or propanol is required for hand antiseptics?

At least 60% alcohol (But less than 100% for reasons stated below in Q3), 60% - 95% is optimal.

3)[CH-02-03] Why isn't 100% ethanol effective against bacteria?

100% alcohol rapidly dehydrates the area forming a crust on bacterials cells that prevents the alcohol from permeating into the cell.

4) [CH-02-04] Rate the following in terms of their resistance to disinfectants (1-Least resistant, 7-Most 

resistant)

6 Bacterial endospores

1 Enveloped viruses

4 Fungal spores

2 Gram-positive bacteria

5 Gram-negative bacteria

3 Non-enveloped viruses

7 Prions

5) [CH-02-05] How is human immunodeficiency virus (HIV) resistant to disinfectants and antiseptics? Explain why.

HIV is an enveloped virus, which makes them the least resistant to disinfectants. For that reason the virus dies quickly outside the cell and is limited to spreading through bodily fluids.

6) [CH-02-06] Is alcohol an antiseptic or a disinfectant?

Alcohol is an antiseptic as it is often used on skin prior to needle injections or blood draws.

7) [CH-02-07] What is difference between antiseptics and disinfectants? 

*Antiseptic - Removes and kills microbes on living organisms.

*Disinfectant - Kills microbes on inanimate objects.

*How they theoretically should be used.

8) [CH-02-08] Name disinfectants effective in killing bacterial spores?

- Bleach (Sodium hypochlorite)

- Aldehydes

- Ethylene oxide

- Peracetic acid

9) [CH-02-09] How is soap effective as an antiseptic?

Weak antiseptic at best (Not that great for killing microbes), soap functions more as a sanitizing agent that achieves its effect by washing microbes off the skin instead of killing them.

10) [CH-02-10] Name 3 bacterial genera whose species make up the normal flora of human skin.

- Staphylococcus

- Corynebacterium

- Propionibacterium

Wiki links provided for those interested in the bacterial genera.

The Great Depression Historiography and The Opening Chapter of The Body Economic

The Body Economic opens the chapter with the dramatic statement that "health had nothing to do with economic cycles, but depended on how politicians chose to respond to the crisis" (Stuckler & Basu, 2013). Both Stuckler and Basu are essentially saying that health declines during economic downturns are preventable with government social programs, which is why austerity measures to decrease government spending "kills" people.

It is quite clear from these opening remarks that the authors are supporters of a more Keynesian belief in economics, one that proposes that government demand is central to a strong economy. In other words, government spending on public works, social programs, and other services will help provide for a robust recovery. All the more fitting then for the authors to support FDR's New Deal Program, which they bathe with positive health statistics.

However, recent history discussions are now debating whether the New Deal was actually effective in helping the US recover from the Great Depression. In fact, a recent push by conservatives and libertarians say that FDR prolonged the Great Depression through his expansionary fiscal policies of increasing government spending. Their line of reasoning is more akin the Adams Smith's invisible hand, let the markets correct themselves. By messing with the prices, wages, and employment you stop the market from its corrective actions leading to all kinds of problems. In essence, the conservatives and libertarians want the government stop exerting power over the business models so that the natural law of money will work things out.

However, the conservative support for a more hands off government runs counter to the left's push for more government programs. Who would be right in this case?
The left has stated that government spending would definitely improve the healthcare of the population, while the right argues that government spending would actual prolong the population's misery by not allowing the businesses to run effectively. Would the health benefits of the government spending be greater than the negative effects caused by a prolonged economic decline? Or would the benefits of economic recovery be greater than that of health benefits?

Would either policy actually play out as proposed by the left or the right? There are numerous factors and previous historical examples of how both can be completely wrong about their predictions and policies. What would be interesting for our current case of studying government austerity would be compare and contrast between the Keynesian policies under Lyndon B. Johnson's Great Society and the economics of Reaganomics under Ronald Reagan.