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Chemical Indicator Tests: Iodine and HCl Reactions

Like many journeys, study can be boring and tiresome and often you wonder if you are getting anywhere at all. But eventually you will reach a place where you not only can see how far you have gone, but a place where you can see things that you couldn't see before, or maybe you reach a place where things that you' ve seen before now look different and perhaps more under­ standable. Fundamentally, this is a biology book. Why study biology? Living things are fas­ cinating for a wealth of reasons—their diversity, their complexity combined with a fundamental simplicity, their function­ ing that begs for explanation, the multiple ways that living things exhibit organiza­ tion, the multiple interrelationships between different living things.

Key Points

  • During iodine titrations, concentrated iodine solutions must be reacted with some titrant, often thiosulfate, in order to remove most of the iodine before the starch is added.
  • Many bacteria like Bacillus subtilis can produce such an enzyme to help scientists identify unknown bacterial samples – the starch–iodine test is one of many tests needed to identify the exact bacterium.
  • Two important cell wall materi­ als, calcium carbonate and silica dioxide, are most commonly found as minerals in rocks.
  • Starch, the main component of flour, is made up of long chains of glucose molecules bound together.
  • Carboxylation occurs when carbon dioxide is added to a metabolite called ribu­ lose bisphosphate (RuBP), a five-carbon sugar with two phosphates, in a reaction cat­ alyzed by an enzyme called ribulose bisphosphate carboxylase (rubisco).

Terms

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