1. Homogenization performed by passing the cells at high pressure through narrow orifice which can also cause cell rupture is referred to as _______________
a) ultrasonicator
b) freezer
c) mortar and pestle
d) french press
Explanation: French press is one which the cells are forced at high pressure through narrow orifice is referred to as french press. This procedure also causes the cell rupture. Freezer is refrigerator with temperatures as low as -20° C or -80° C. Ultrasonicator uses ultrasonic waves to lyse the cells. Mortar and pestle is a traditional homogenizer.
2. The technique in which the cells are subjected to cold temperature of about -15° C to -25° C is referred to as _____________
a) ultrasonics
b) freezing
c) homogenization
d) osmotic shock
Explanation: In freezing technique, the cells are subjected to cold temperature of about -15° C to -25° C for cell lysis. As compared to Ultrasonics, which uses shock waves formed due to collapses to lyse the cells. Homogenization is a mechanical method to lyse the cells. Osmotic shock uses technology of hypertonic and hypotonic solution to break the cells to extract enzymes from them.
3. ____________ technique is nothing but a cold or psychrophilic shock.
a) Ultrasonication
b) Homogenization
c) Freezing
d) Alkali treatment
Explanation: Freezing technique is one which cells are subjected to cold temperatures as low as minus degree Celsius. Due to which the cells get a cold or psychrophilic shock which leads to cell lysis. Ultrasonication uses shock waves whereas homogenization uses mechanical pressure to lyse the cells. Alkali treatment is a chemical method to lyse the cells because of nucleophilic attack on cell walls by the basic radicals.
4. Freezing technique is not preferred unless otherwise there is a need.
a) true
b) false
Explanation: Freezing involves the cells to be subjected to very cold minus degree Celsius temperatures which may lead to formation intra and extra cellular ice crystals damaging the cells. Also, there is chance of protein denaturation. Hence this technique is not preferred unless otherwise there is a need.
5. Mortar and pestle, french press and homogenizer are widely used to lyse the cells by ultrasonication.
a) true
b) false
Explanation: Mortar and pestle, french press and homogenizer utilizes pressure in different ways may be manually or automated. Hence they are widely used to lyse the cells by homogenization and not ultrasonication. As ultrasonication uses ultrasonic waves to lyse the cells and the machine used is called Ultrasonicator.
6. __________ is a method which is highly used for lab scale procedures than large scale work.
a) Ultrasonication
b) Homogenization
c) Freezing
d) Alkali treatment
Explanation: Ultrasonication is a method which uses ultrasonic waves to lyse the cells. Shock waves are formed due to collapses in area of rarefaction. Hence this method is used for lab scale procedures as compared to large scale work. Homogenization is widely used to disrupt the cell wall or cell membrane. Freezing is nothing but cold or psychrophilic shock. Alkali treatment is a chemical method that uses alkali to lyse the cells.
7. _________________ is the main contaminant present in the resultant free extract from cells.
a) Chemicals
b) Simple sugars
c) Lipids
d) Nucleic acids
Explanation: The resultant cell free extract obtained from extraction procedures possess nucleic acids, lipids, simple sugars and so on. But nucleic acid is the major contaminant and care should be taken to remove it from the system.
8. Enzymes can be isolated from cell free extract by which one of the following methods?
a) Osmotic shock
b) Alkali treatment
c) Factors like pH, temperature and low ionic strength
d) Ultrasonication
Explanation: Osmotic shock, Alkali treatment and ultrasonication are the methods used to extract enzymes from cells. Osmotic shock and alkali treatment is included in extraction by chemical methods as these methods use 1.4% buffered sucrose and NaOH respectively. Ultrasonication utilizes ultrasonic waves fall into physical treatment category. Hence enzymes can be isolated from cell free extracts using factors like pH, temperature and low ionic strength.
9. Which of the following methods cannot be used to isolate enzymes from cell free extract?
a) Use of factors like pH and ionic strength
b) Use of chemicals
c) Homogenization
d) Use of temperature factor
Explanation: Nucleic acid is the major contaminant in the cell free extract along with lipids, simple sugars and so on. Factors like temperature, pH and ionic strength can be used to remove the contaminants and isolate enzymes. Chemicals such as streptomycin sulphate, nucleases etc., can be used to degrade nucleic acids and isolate the required enzymes.
10. Which one if the chemicals is not used to isolate enzymes from cell free extract?
a) 1.4% buffered sucrose
b) Cetyl trimethyl ammonium bromide
c) Nucleases
d) Streptomycin sulphate
Explanation: 1.4% buffered sucrose is the chemical used during osmotic shock which is a chemical method to extract enzymes from cells. Whereas cetyl trimethyl ammonium bromide, nucleases, streptomycin sulphate, etc., are the chemicals used to isolate enzymes from cell free extract which has nucleic acids as the main contaminant along with lipids, simple sugar and so on.