The major virulence factor produced by C. diphtheriae is diphtheria toxin. The production of diphtheria toxin during infection is controlled by a repressor, DtxR. The activity of DtxR is regulated by iron, which acts as a corepressor. During an infection, the levels of iron available in the tissues for use by C. diphtheriae are low. What effect will the decreased iron availability have on the production of diphtheria toxin

Which statement best explains how cellular respiration maintain homeostasis in animals? it maintains body temperature by absorbing energy. it breaks glucose into energy required by the organism. it speeds up metabolism by making oxygen. it produces energy from hormones present in the organism.

The eruption of a nearby volcano causes a prairie ecosystem to receive a lot less sunlight. which of these is the most likely effect on the ecosystem? a-an increase in biodiversity. b-an increase in immigration to the area. c-a decrease in available water. d-a decrease in plant growth.

You decide that the introduction should also discuss the extremophiles that are referred to as the archaea. these single-cell organisms are considered "extremophiles" due to their ability to survive and reproduce in environmental conditions that would be hostile for most living organisms. archaea species have been isolated from highly acidic sulfur springs, ocean floor thermal vents with temperatures that exceed boiling, and subarctic ice well below freezing. while still considered to be prokaryotic, the archaea have numerous differences that place them apart from the bacteria. choose the characteristics that separate the archaea from other prokaryotic cells. select all that apply. view available hint(s) select all that apply. archaea lack true peptidoglycan in their cell walls. the morphology of the cell is rigid and is geometric in shape, similar to a sphere or cylinder. the cytoplasmic membrane lipids of archaea have branched or ringform hydrocarbon chains. all currently identified and characterized archaea have been linked as the causative agent to an animal or human disease.