Question 1

Why do water molecules orient themselves with their oxygen atom pointing inward when surrounding a sodium ion ($$\mathrm{Na^+}$$)?

Accepted Answer

Because the oxygen atom in water is slightly negative due to its higher electronegativity, and is attracted to the positive sodium ion.

Question 2

What type of bond is found between the oxygen and hydrogen atoms in a water molecule?

Accepted Answer

Polar covalent bond

Question 3

Which container is more acidic: one with a higher concentration of $$\mathrm{H^+}$$ ions or one with a higher concentration of $$\mathrm{OH^-}$$ ions? Why?

Accepted Answer

The container with more $$\mathrm{H^+}$$ ions, because hydrogen ions increase acidity.

Question 4

If you add a base such as sodium hydroxide ($$\mathrm{NaOH}) to a $$solution, what happens to the concentration of $$\mathrm{H^+}$$ ions?

Accepted Answer

The concentration of $$\mathrm{H^+}$$ ions decreases.

Question 5

Wine has a pH of 3 and urine has a pH of 6. How many times more acidic is wine than urine?

Accepted Answer

$$1000$$ times more acidic

Question 6

Which has more $$\mathrm{H^+}$$ ions: pure water ($$\mathrm{pH} = 7) or $$seawater ($$\mathrm{pH} \approx 8$$)?

Accepted Answer

Pure water, because it has a lower pH.

Question 7

Why is carbon considered the basis for all biological macromolecules?

Accepted Answer

Because carbon has four valence electrons, allowing it to form up to four covalent bonds with other atoms.

Question 8

Which of the following is NOT a biological macromolecule?

Accepted Answer

Water

Question 9

Hydrocarbons are high in energy and consist of which elements?

Accepted Answer

Carbon and hydrogen

Question 10

Are hydrocarbons hydrophobic or hydrophilic, and why?

Accepted Answer

Hydrophobic, because they are nonpolar.

Question 11

Which functional group is responsible for stabilizing protein structure by forming disulfide bridges?

Accepted Answer

Sulfhydryl group ($$-\mathrm{SH})$$

Question 12

Which functional group is found in amino acids and is basic in nature?

Accepted Answer

Amino group ($$-\mathrm{NH_2$})$$

Question 13

Estradiol and testosterone differ by just a few chemical groups. What does this illustrate about functional groups in biological molecules?

Accepted Answer

Small changes in functional groups can greatly influence molecular function and properties.

Question 14

Which functional group can react with water to release energy and is commonly found in ATP?

Accepted Answer

Phosphate group ($$-\mathrm{$$OPO_4$$})$$

Question 15

A molecule contains both a carbonyl group ($$\mathrm{C=O}) $$and a hydroxyl group ($$-\mathrm{OH}). $$Which type of molecule is this most likely to be?

Accepted Answer

A carbohydrate

Question 16

Which of the following best describes the difference between a monomer and a polymer?

Accepted Answer

A monomer is a single building block; a polymer is a chain of monomers.

Question 17

Which functional group is nonpolar and can affect molecular properties such as gene expression?

Accepted Answer

Methyl group ($$-\mathrm{CH_3$})$$

Question 18

A solution has a pH of 5. What is the concentration of $$\mathrm{H^+}$$ ions in this solution?

Accepted Answer

$$1 	imes 10$$^{-5}$$ M

Question 19

Which of the following molecules contains a phosphate group and is essential for energy transfer in cells?

Accepted Answer

ATP (adenosine triphosphate)

Water, Acidity, and Introduction to Biological Macromolecules

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