Fundamental Macromolecules and Concepts

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Biochemistry › Fundamental Macromolecules and Concepts

Questions 1 - 10
1

Which of the following statements about water is incorrect?

Because of hydrogen bonding, water has a low heat of vaporization.

Water has a tetrahedral structure when considering lone pairs and a bent molecular structure when not considering lone pairs.

Water has the potential to form a maximum of 4 hydrogen bonds.

Ice is a hexagonally packed network of water molecules and is less dense than water.

Explanation

Because of hydrogen bonding, water has a low high heat of vaporization. In other words, it takes more energy to free up water molecules from a hydrogen-bonded liquid state to a gaseous state.

2

What percentage of the human body is composed of interstitial water?

15%

5%

65%

60%

90%

Explanation

Interstitial water is the fluid on the outside of cells, and surrounds the cells of the human body. While estimates vary, the best answer is that 15% of the entire human body is composed of interstitial water. Overall, about 60% of the body (42L) is composed of water. Additionally, about two-thirds of the total body water is intracellular water. Finally, about 5% of the entire body is composed of plasma.

Remember that these percentages are estimates, and vary by individual. Sex and muscle mass are two factors that can significantly alter these estimates.

3

Which of the following statements about water is incorrect?

Because of hydrogen bonding, water has a low heat of vaporization.

Water has a tetrahedral structure when considering lone pairs and a bent molecular structure when not considering lone pairs.

Water has the potential to form a maximum of 4 hydrogen bonds.

Ice is a hexagonally packed network of water molecules and is less dense than water.

Explanation

Because of hydrogen bonding, water has a low high heat of vaporization. In other words, it takes more energy to free up water molecules from a hydrogen-bonded liquid state to a gaseous state.

4

What percentage of the human body is composed of interstitial water?

15%

5%

65%

60%

90%

Explanation

Interstitial water is the fluid on the outside of cells, and surrounds the cells of the human body. While estimates vary, the best answer is that 15% of the entire human body is composed of interstitial water. Overall, about 60% of the body (42L) is composed of water. Additionally, about two-thirds of the total body water is intracellular water. Finally, about 5% of the entire body is composed of plasma.

Remember that these percentages are estimates, and vary by individual. Sex and muscle mass are two factors that can significantly alter these estimates.

5

Which of the following statements about water is incorrect?

Because of hydrogen bonding, water has a low heat of vaporization.

Water has a tetrahedral structure when considering lone pairs and a bent molecular structure when not considering lone pairs.

Water has the potential to form a maximum of 4 hydrogen bonds.

Ice is a hexagonally packed network of water molecules and is less dense than water.

Explanation

Because of hydrogen bonding, water has a low high heat of vaporization. In other words, it takes more energy to free up water molecules from a hydrogen-bonded liquid state to a gaseous state.

6

A biochemist is studying two metabolic reactions at constant temperature and pressure. Reaction 1 is found to have a G value of . Reaction 2 has a G value of . Which statement is true about these reactions?

None of the other answers are true

Reaction 1 proceeds at a faster rate than reaction 2

Reaction 1 proceeds at a slower rate than reaction 2

Reaction 1 and reaction 2 proceed at equally fast rates

Reaction 1 and reaction 2 proceed at equally slow rates

Explanation

The G values given in the question relate to the reactions' thermodynamics. A negative G value means that a reaction is thermodynamically spontaneous. A spontaneous reaction can occur without further energy input. This does not tell us anything about the reaction's rate (kinetics). A spontaneous reaction may be slow or it may be fast.

7

A biochemist is studying two metabolic reactions at constant temperature and pressure. Reaction 1 is found to have a G value of . Reaction 2 has a G value of . Which statement is true about these reactions?

None of the other answers are true

Reaction 1 proceeds at a faster rate than reaction 2

Reaction 1 proceeds at a slower rate than reaction 2

Reaction 1 and reaction 2 proceed at equally fast rates

Reaction 1 and reaction 2 proceed at equally slow rates

Explanation

The G values given in the question relate to the reactions' thermodynamics. A negative G value means that a reaction is thermodynamically spontaneous. A spontaneous reaction can occur without further energy input. This does not tell us anything about the reaction's rate (kinetics). A spontaneous reaction may be slow or it may be fast.

8

What percentage of the human body is composed of interstitial water?

15%

5%

65%

60%

90%

Explanation

Interstitial water is the fluid on the outside of cells, and surrounds the cells of the human body. While estimates vary, the best answer is that 15% of the entire human body is composed of interstitial water. Overall, about 60% of the body (42L) is composed of water. Additionally, about two-thirds of the total body water is intracellular water. Finally, about 5% of the entire body is composed of plasma.

Remember that these percentages are estimates, and vary by individual. Sex and muscle mass are two factors that can significantly alter these estimates.

9

A biochemist is studying two metabolic reactions at constant temperature and pressure. Reaction 1 is found to have a G value of . Reaction 2 has a G value of . Which statement is true about these reactions?

None of the other answers are true

Reaction 1 proceeds at a faster rate than reaction 2

Reaction 1 proceeds at a slower rate than reaction 2

Reaction 1 and reaction 2 proceed at equally fast rates

Reaction 1 and reaction 2 proceed at equally slow rates

Explanation

The G values given in the question relate to the reactions' thermodynamics. A negative G value means that a reaction is thermodynamically spontaneous. A spontaneous reaction can occur without further energy input. This does not tell us anything about the reaction's rate (kinetics). A spontaneous reaction may be slow or it may be fast.

10

Is water an acid or a base?

Both

Acid

Base

It is impossible to predict.

Explanation

Water, , is an amphoteric substance--it can act as either an acid or a base. In certain circumstances, water can act as a Bronsted-Lowry acid by donating a proton.

As seen above, donated one of its hydrogen atoms, becoming .

In other cases, water can act as a Bronsted-Lowry base by accepting a proton.

As seen above, accepted a hydrogen atom to become .

Therefore, water can act as either an acid or a base depending on the situation. There are other amphoteric substances, but water is definitely the most common.

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