Biology: Key Questions 
Biology Key Questions – Lesson #1
1. How many electrons does Mg2+ have?
Answer: Mg2+ has 10 electrons. A Magnesium atom has 12 electrons, 2 of which are valence electrons. The atom will lose the 2 outermost electrons in order to stabilize its electron shell. The nucleus maintains its 12 protons and becomes a Mg2+ ion.
2. Given that the half-life of the radioisotope carbon-14 is 5730 years, how useful do you think this isotope would be for dating bones that are over a million years old?
Answer:
Carbon-14 is incorporated in the tissues of plants and animals through their environment. When they die the incorporation of carbon-14 ends, and what remains in the specimen decays at a constant rate, with a half-life of 5730 years. That is, after 5730 years only half of Carbon-14 remains in the sample. (Measuring the ratio between C-14 & C-12 can give us a good idea about when an organism died.) This exponential decay continues and continues; however after about 40 000 years, less than 1% of Carbon-14 remains in the sample, so it is not useful for dating material much older than that.
Thus, given the half-life of the radioisotope Carbon-14, it would not be useful in dating a bone over a million years old.
3. Summarize the four major types of biochemical reactions studied in this lesson. For each type give its name, a word summary of what happens during the reaction, and an example of where the reaction might be biologically important.
Answer:
Hydrolysis:
Hydrolysis uses water (and various enzymes) to break down molecules into smaller, simpler molecules. This occurs by breaking a bond on the reactant and adding a hydrogen atom to one part, and a hydroxyl (-OH) to the other. The result is 2 simpler molecules.
Macromolecule + Water molecule + molecule
This process aids us in controlling blood sugar, by the hydrolysis of glycogen to glucose.
Glycogen + Water + (Enzymes) Glucose + Glucose
Condensation:
1. How many electrons does Mg2+ have?
Answer: Mg2+ has 10 electrons. A Magnesium atom has 12 electrons, 2 of which are valence electrons. The atom will lose the 2 outermost electrons in order to stabilize its electron shell. The nucleus maintains its 12 protons and becomes a Mg2+ ion.
2. Given that the half-life of the radioisotope carbon-14 is 5730 years, how useful do you think this isotope would be for dating bones that are over a million years old?
Answer:
Carbon-14 is incorporated in the tissues of plants and animals through their environment. When they die the incorporation of carbon-14 ends, and what remains in the specimen decays at a constant rate, with a half-life of 5730 years. That is, after 5730 years only half of Carbon-14 remains in the sample. (Measuring the ratio between C-14 & C-12 can give us a good idea about when an organism died.) This exponential decay continues and continues; however after about 40 000 years, less than 1% of Carbon-14 remains in the sample, so it is not useful for dating material much older than that.
Thus, given the half-life of the radioisotope Carbon-14, it would not be useful in dating a bone over a million years old.
3. Summarize the four major types of biochemical reactions studied in this lesson. For each type give its name, a word summary of what happens during the reaction, and an example of where the reaction might be biologically important.
Answer:
Hydrolysis:
Hydrolysis uses water (and various enzymes) to break down molecules into smaller, simpler molecules. This occurs by breaking a bond on the reactant and adding a hydrogen atom to one part, and a hydroxyl (-OH) to the other. The result is 2 simpler molecules.
Macromolecule + Water molecule + molecule
This process aids us in controlling blood sugar, by the hydrolysis of glycogen to glucose.
Glycogen + Water + (Enzymes) Glucose + Glucose
Condensation: