BIO 243 Lecture Homework Chapter 2

Which parts of atoms can interact (react) to form chemical bonds?

• protons

• valence electrons

• the orbitals

• the nucleus of each atom

Atoms of oxygen have a total of 8 electrons. Are these atoms stable, and why or why not?

• Yes, because the Octet Rule says stable atoms have 8 electrons.

• No, because only atoms with 2 valence electrons are stable.

• No, because the atoms have only 6 valence electrons, but need 8 for stability.

• Yes, because oxygen is in the air we breathe and it doesn’t hurt us.

Carbon atoms have four valence electrons. Are they likely to react with other atoms, and why or why not?

• No, because they have an even number of valence electrons so they are already stable.

• Yes, but only with other stable atoms.

• No, because they do not have enough valence electrons.

• Yes, because they can become more stable by doing so.

Which of the following is not produced through chemical bonding?

• adipose (fat) tissue

• cells

• the heart

• atoms

Foods are broken down into their building blocks by adding water. This would be an example of which characteristic of water?

• Water acts as a lubricant.

• Water has a high heat of vaporization.

• Water acts as a cushion.

• Water acts as a reactant.

Water acts to dissolve molecules in the body. How does water dissolve the salt (NaCl) in your mouth from a salty pretzel?

• Water acts as a cofactor for enzymes that dissolve the salt.

• When water is added to the NaCl, NaCl is broken down by adding OH^- to one element and H⁺ to the other. This is known as hydrolysis.

• Water acts as a solvent because the partial negative charge on the oxygen in water attracts sodium, while the partial positive charge on hydrogen attracts chloride. This results in the separation of sodium from chloride, thus breaking the ionic bond.

In plasma, a typical body fluid, protein floating around would be considered to be which of the following?

• a solute, specifically both a colloid and a nonelectrolyte

• a solute, specifically both a colloid and an electrolytea solvent

• a solvent

Electrolytes are charged particles called ions that are dissolved in body fluids. Which of the following ions would be considered a major anion in the body?

• potassium

• sodium

• calcium

• chloride

Which pH is more acidic, a pH of 3, a pH of 7, or a pH of 9?

• pH of 3

• pH of 7

• pH of 9

Cortisol is a type of lipid hormone. Which type of lipid would cortisol be classified as?

• triglyceride

• phospholipid

• steroid