Why will a radioactive rock never become completely stable?

1 answer:

8 0

Technically speaking, depending on the sample, the rock could become “stable.”

The radioactive decay of a radioisotope is expressed as a half-life equation; half-life is the colloquial term that describes how long it will take for half of the radioisotope to decay into another isotope or element. For example (if I remember correctly), Carbon-14 has a half life of 5,780 years. This means that in a 100% sample of C-14, after 5780 years passes, only 50% of that isotope would remain; another 5780 years, and only 25% would remain (half of half). Based on this principle, it seems like a sample could never fully decay because there’s always an amount that smaller than the current amount.

However, if the sample has a very short half life (milliseconds or nanoseconds) the sample would reach nigh-full decay eventually. At this point, it is considered “stable.”

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How does an animal cell react when there is no glucose available to carry out cellular respiration?

Verdich [7]

Answer:

B) It breaks down polysaccharides such as starch.

Explanation:

Polysaccharides are long chains of monosaccharides like glucose joined together with glycosidic linkages. While plants can simply make glucose via photosynthesis, animals rely on glucose sourced from their diet. In animals, glucose is stored as glycogen; however, plant storage polysaccharides like starch are regularly broken down through digestion using enzymes.

Enzymes are proteins which catalyze chemical reactions like the breakdown of large polysaccharides. Alpha amylase, an enzyme produced in the pancreas, is also found in human saliva; it catalyzes the hydrolysis, or breakdown of starch into glucose. Amylase acts on polysaccharides bonds at random points along the chain by splitting the α 1-4 glycosidic bonds. This produces maltose, dextrin and glucose; this glucose is used in ATP synthesis via <em>respiration, ethyl alcohol fermentation and lactic fermentation</em>.