Please help with these questions
question: Oxygen consumption by a growing culture of Escheri...
oxygen consumption by a growing culture of Escherichia coli bacteria.
What could explain the gradual consumption of oxygen, even though no glucose has yet been added to the culture?
If the DO levels drop by 0.5 mg/l in a period of 1 min, and by 1.0 mg/l during
the following 2 min, do those represent different rates of O2 consumption?
You may have observed that after injecting the glucose there was a slight
delay before the rate of O2 consumption changed significantly. What might
be responsible for that delay
If the cells in your culture grow and increase in number during the course of
the lab period, how might your measurements of oxygen consumption rate be
affected?
If you have 10 ml of a culture of cells that has an absorbance of 0.5 A650 units,
what would its absorbance be if you brought its volume up to 50 ml with fresh
medium?
Oh, the fascinating world of bacteria and oxygen consumption! Let's dive right into these questions and inject some humorous answers:
1. What could explain the gradual consumption of oxygen, even though no glucose has yet been added to the culture?
Well, maybe the bacteria are running on "power-saving mode" until the glucose arrives. They're just taking a little breather before getting all energized!
2. If the DO levels drop by 0.5 mg/l in a period of 1 min, and by 1.0 mg/l during the following 2 mins, do those represent different rates of O2 consumption?
Ah, it seems like the bacteria had a little weekend getaway during those two minutes and their oxygen consumption got extra efficient. I guess they had a productivity boost!
3. You may have observed that after injecting glucose, there was a slight delay before the rate of O2 consumption changed significantly. What might be responsible for that delay?
Well, maybe the bacteria had a little debate on whether they should consume the glucose or throw a party with it first. It took them a moment to decide, you know, bacteria have social lives too!
4. If the cells in your culture grow and increase in number during the course of the lab period, how might your measurements of oxygen consumption rate be affected?
Ah, those multiplying bacteria must've realized that sharing is caring and decided to split the workload. So, your measurements might see an increase in oxygen consumption as more bacterial employees join the workforce!
5. If you have 10 ml of a culture of cells that has an absorbance of 0.5 A650 units, what would its absorbance be if you brought its volume up to 50 ml with fresh medium?
Ah, dilution, our old friend! If you dilute it with fresh medium, the absorbance will be as clear as a superhero's conscience! It'll be reduced to 0.1 A650 units, giving you more room for new adventures!
I hope these humorous answers bring a smile to your face as you unravel the mysteries of oxygen consumption and bacterial culture. Happy experimenting!
To answer the questions about oxygen consumption by a growing culture of Escherichia coli bacteria, let's go through each question and explain the concepts involved.
1. What could explain the gradual consumption of oxygen, even though no glucose has yet been added to the culture?
One possible explanation for the gradual consumption of oxygen without the addition of glucose is that the bacteria are utilizing other carbon sources present in the culture media. Bacteria can have metabolic pathways that allow them to break down alternative carbon sources, such as amino acids, organic acids, or other carbohydrates, to generate energy in the absence of glucose. This process could still result in the consumption of oxygen.
2. If the DO levels drop by 0.5 mg/l in a period of 1 min, and by 1.0 mg/l during the following 2 min, do those represent different rates of O2 consumption?
Yes, the change in dissolved oxygen (DO) levels indicates the rate of oxygen consumption. In this case, the rate of oxygen consumption can be calculated by dividing the change in DO levels by the corresponding time interval. Therefore, the rate of oxygen consumption for the first minute would be 0.5 mg/l per minute, and for the following two minutes, it would be 1.0 mg/l per minute. These rates represent different rates of oxygen consumption because there is a difference in the amount of oxygen consumed per unit of time.
3. You may have observed that after injecting the glucose, there was a slight delay before the rate of O2 consumption changed significantly. What might be responsible for that delay?
The delay observed before a significant change in the rate of oxygen consumption can be attributed to the time required for the bacteria to metabolize the injected glucose. Once glucose is added to the culture, the bacteria need to transport it across the cell membrane and initiate the appropriate metabolic pathways to utilize glucose as an energy source. This process takes some time, which causes the initial delay before the rate of oxygen consumption changes significantly.
4. If the cells in your culture grow and increase in number during the course of the lab period, how might your measurements of oxygen consumption rate be affected?
As the cells in the culture grow and increase in number, the overall oxygen consumption rate will likely increase. More bacterial cells will result in increased metabolic activity and higher demand for energy, leading to a greater consumption of oxygen. Therefore, the measurements of oxygen consumption rate would reflect the increased metabolic activity due to cell growth.
5. If you have 10 ml of a culture of cells that has an absorbance of 0.5 A650 units, what would its absorbance be if you brought its volume up to 50 ml with fresh medium?
Absorbance is a measure of the amount of light absorbed by a sample. In this case, the absorbance of the culture is given as 0.5 A650 units for a volume of 10 ml. If you were to dilute the culture to 50 ml with fresh medium, the absorbance would not change. Absorbance is a property that depends on the concentration of the absorbing material, not the volume. Therefore, the absorbance of the culture would still be 0.5 A650 units even after dilution.