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ACTIVE READING WORKSHEETS

CHEMISTRY OF LIFE

Water and Solutions

Read the passage below, which covers topics from your textbook. Answer the questions that follow. TEK 3E, 4B, 9A

1 A solution is a mixture in which one or more substances are uniformly distributed in another substance. 2 Solutions can be mixtures of liquids, solids, or gases. 3 A solute is the substance dissolved in the solution. 4 The solvent is the substance in which the solute is dissolved. 5 For example, when sugar, a solute, and water, a solvent, are mixed, a solution of sugar water results. 6 Though the sugar dissolves in the water, neither the sugar molecules nor the water molecules are altered chemically.

7 Solutions can be composed of various proportions of a given solute in a given solvent. 8 Thus, solutions can vary in concentration. 9 The concentration of a solution is the measurement of the amount of solute dissolved in a fixed amount of solution. 10 For example, a 2 percent saltwater solution contains 2 g of salt dissolved in enough water to make 100 mL of solution. 11 The more solute dissolved, the greater the concentration of a solution. 12 A saturated solution is one in which no more solute can dissolve.

Read each question and write your answer in the space provided.

SKILL: Identifying Main Ideas

1. What is the difference in a solution and a solute?

2. What is a saturated solution?

Circle the letter of the phrase that best completes the statement.

3. The greater the amount of solute dissolved in a solvent, the greater the

a. number of ions in the solution.

b. volume of the solution.

c. number of charged molecules in the solution.

d. concentration of the solution.

ACTIVE READING WORKSHEETS

BIOCHEMISTRY

Molecules of Life

Read the passage below, which covers topics from your textbook. Answer the questions that follow.

Lipids are divided into categories according to their structure. Three classes of lipids important to living things contain fatty acids: triglycerides, phospholipids, and waxes. A triglyceride is composed of three molecules of fatty acid joined to one molecule of the alcohol glycerol. Saturated triglycerides are composed of saturated fatty acids. They typically have high melting points and tend to be hard at room temperature. In contrast, unsaturated triglycerides are composed of unsaturated fatty acids and are usually soft or liquid at room temperature.

Phospholipids have two, rather than three, fatty acids joined to a molecule of glycerol. The cell membrane is composed of two layers of phospholipids, which are referred to as the lipid bilayer. The inability of lipids to dissolve in water allows the membrane to form a barrier between the inside and outside of the cell. This bilayer arrangement of molecules produces a stable and effective barrier for a cell.

A wax is a type of structural lipid. A wax molecule consists of a long fatty-acid chain joined to a long alcohol chain. Waxes are highly waterproof, and in plants, waxes form a protective coating. Waxes also form protective layers in animals.

Fill in the blank to complete each sentence.

SKILL: Completing Sentences

One reading skill is the ability to complete an incomplete sentence by logically determining what will complete the unfinished thought.

1. Lipids are divided into categories according to their .

2. The three classes of lipids are .

3. Saturated triglycerides are composed of .

4. At room temperature, unsaturated triglycerides are .

5. The two layers of phospholipids that form the cell membrane are called the .

6. Lipids cannot dissolve in .

7. The bilayer arrangement of molecules in a cell membrane gives the cell a .

8. Waxes form a protective coating on the outer surfaces of .

Write your answers in the spaces provided.

SKILL: Vocabulary Development

Write “T” on the line if the statement describes triglycerides. Write “P” on the line if the statement describes phospholipids. Write “W” on the line if the statement describes waxes.

9. They consist of a long fatty-acid chain joined to a long alcohol chain.

10. Two categories of these are saturated and unsaturated.

11. They consist of two molecules of fatty acids joined by a molecule of glycerol.

12. Two layers of these enclose a cell.

13. They consist of three molecules of fatty acids joined to one molecule of glycerol.

14. They form a protective layer in animals.

Read the question and write your answer in the space provided.

15. The prefix lipo- is derived from a Greek term meaning “fat.” The suffix -oid means “resembling” or “having the appearance of.” What can you infer about a substance that is described as being lipoid?

Circle the letter of the phrase that best completes the statement.

16. A main structural difference between the three categories of lipids is the number of

a. fatty-acid molecules present.

b. alcohol molecules present.

c. oxygen molecules present.

d. Both (a) and (b)

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