Biology: Key Questions Essay

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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?


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
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When the two smaller reactants join together, water is produced and removed during the synthesis of the larger molecule. This is also called Dehydration Synthesis.
For example, molecules with projecting Hydrogen atoms bond with molecules with projecting Hydroxyl groups (-OH), forming water. The water molecule then leaves the reactants, allowing them to bond to form a larger, more complex molecule.

This type of reaction occurs continuously throughout the body in the joining of amino acids to form protein.

Amino acid + Amino acid  Protein + Water

Oxidation and Reduction (Redox)
A chemical reaction involving the transfer of electrons rather than molecules is classified as a Redox reaction. A reaction involving the loss of electrons is called Oxidation, and a reaction involving the gain of electrons is called Reduction. Oxidation and Reduction always occur together, as one reactant loses electrons, and the other gains them. This exchange often effects the physical states of molecules, as their solubility is changed with their charge. *Zn(s) + Cu2+  Cu(s) + Zn2+(aq)

Cellular respiration is a redox reaction that combines glucose & oxygen to produce carbon dioxide, water, and energy.

Neutralization reactions are those that involve the reaction of an acid and a base to form water and salt. A solution with a high hydrogen ion concentration is acidic, and a solution with a high concentration of hydroxide ions is
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