Question

Lab 2-12 Ultraviolet Light 1. What are the wavelengths for ultraviolet light? 2. Which wavelengths can be damaging to cells? 3. Which wavelength is the most germicidal and why? 4. List the factors which determine UV light's killing properties? b 2-8 Temperature Effects 1. What affect does temperature have on proteins? 2. Which temperature category do most human pathogens prefer? 3. Define: a. thermal death point: b. thermal death time: Which temperatures will be used to expose the bacteria?

ANSWER ALL PLEASE

Answer 1

Lab 2-12 Ultraviolet Light

1. Ultraviolet light is a electromagnetic radiation which comes from sun that are transmitted in the form of waves at different wavelengths. The wavelengths of ultraviolet rays varies between 10 nanometer and 400 nanometer.

2. Ultraviolet light damages the cellular DNA causing cell death. Long term exposure may lead to certain types of cancer .Ultra violet rays of wavelength ranging from 290 to 320 nanometers can damage the cells and increases the risk of skin cancer.

3. Ultraviolet light in the wavelength of 260 nanometer is the most germicidal as the DNA absorbs the maximum amount of ultraviolet light in this wavelength and cause destruction of DNA leading to cell death and acting as germicidal.

4. The factors that determine UV light's killing properties are the time duration the microorganism is exposed to ultraviolet rays, the intensity of light and the wavelength of ultraviolet light .

Lab 2- 8 Temperature Effects :

1. The hydrogen bonds in the proteins are distrupted on exposure to heat. Heat increases the kinetic energy causing the molecules in protein to vibrate. This causes denaturation of protein. Temperatures at or above 40 degree celsius causes denaturation of protein .

2. Most of the human pathogens prefer the normal temperature of the human body which is around 37 to 38 degree celsius. Most of the human pathogens are mesophile , a microorganism that lives at the moderate temperatures .

3. a . Thermal death point :

Thermal death point is defined as the temperature at which all the microorganisms in a culture is killed using heat instantaneously or within brief time period.

b. Thermal Death Time :

Thermal death time is defined as the time required to kill a specific microorganism at the specific temperature. This procedure is used for food preservation especially salmonella free non-vegetarian food .

4. Bacteria which are mesophile gets exposed and thrives at moderate temperatures between 20 and 40 degree celsius. At this temperatures,bacteria survives and reproduce with other favourable conditions like food and moisture.