Please Use the Following Information to Answer the Question Below

question 48

Multiple Choice

Please use the following information to answer the question below.
Nitrogenase,the enzyme that catalyzes nitrogen fixation,is inhibited whenever free O₂ reaches a critical concentration.Consequently,nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂.Consider the colonial aquatic cyanobacterium Anabaena,whose heterocytes are described as having "a thickened cell wall that restricts entry of O₂ produced by neighboring cells.Intracellular connections allow heterocysts to transport fixed nitrogen to neighboring cells in exchange for carbohydrates."
Which of the following questions arise from a careful reading of this quotation and are most important for understanding how N₂ enters heterocysts and how O₂ is kept out of heterocysts?

• A)If carbohydrates can enter the heterocysts from neighboring cells via the "intracellular connections," how is it that O₂ doesn't also enter via this route?
• B)If the cell walls of Anabaena's photosynthetic cells are permeable to O₂ and CO₂,are they also permeable to N₂?
• C)If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation,how can these cells fail to perform nitrogen fixation?
• D)If the nuclei of the heterocysts contain the genes that code for photosynthesis,how can these cells fail to perform photosynthesis?
• E)If the cell walls of Anabaena's heterocysts are permeable to N₂,how is it that N₂ doesn't diffuse out of the heterocysts before it can be fixed?

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Fixing one's gaze on someone or something for a long period, often in a manner that can be perceived as intense or aggressive.

Confounding Variable

An outside influence that changes the effect of a dependent and independent variable being examined in an experimental or observational study.

Independent Variable

A variable in an experiment that is manipulated or changed by the researcher to observe its effects on the dependent variable.