Explain how temperature and pH levels can influence microbial infections in the human body.
What will be an ideal response?
All microbes have particular ranges of temperature and pH within which they thrive. When the temperature or pH of their environment falls outside this range, their growth is inhibited, and they may even die as a result of the adverse conditions. Therefore, only those microbes whose pH and temperature requirements match those conditions found in the human body will be able to grow and reproduce there. For example, because the temperature of the human body is 37°C, only mesophiles can reproduce there. In addition, the pH of most tissues and fluids in the body is 6.5-7.5, which matches the pH requirements of neutrophiles. Therefore, it is not surprising that most human pathogens are mesophiles and neutrophiles. However, this is not always the case. Some microbes have adapted to environments that would otherwise be extremely hostile to most microbes. A good example is the bacterium Helicobacter pylori, which is able to live in the extremely acidic conditions of the stomach by secreting substances that help to neutralize the acid. The result is an infection that can lead to stomach ulcers.
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Which of the following is not considered to be part of an adaptive immune response?
a. phagocytic cells e. antigen receptors b. antigen-presenting cells f. complement activation c. histamines g. antibodies d. cytokines h. none of these
Which functional group is incorrectly matched with its structure?
A) ether: R-CH3 B) amino: R-NH2 C) phosphate: R-PO42- D) carboxyl: R-COOH E) alcohol: R-OH
Which of the following is not a process that regenerates ATP?
A. reductive phosphorylation B. substrate-level phosphorylation C. oxidative phosphorylation D. photophosphorylation
You fertilize egg cells from a healthy plant with pollen (which contains the male germ cells) that has been treated with DNA-damaging agents
You find that some of the offspring have defective chloroplasts, and that this characteristic can be passed on to future generations. This surprises you at first because you happen to know that the male germ cell in the pollen grain contributes no chloroplasts to the fertilized egg cell and thus to the offspring. What can you deduce from these results?