After Reading the Paragraphs Below, Answer the Questions That Follow

question 20

Multiple Choice

After reading the paragraphs below, answer the questions that follow.
Recent studies have shown that the onset of puberty in American girls has decreased from an average of 12-13 years of age to as young as 8-10. Many scientists who study premature puberty suggest that steroids in our food and in the environment may be contributing factors, since steroids are known to cross cell membranes and bind to receptors inside cells.
Why are hormones present in our foods? Synthetic testosterone compounds (similar to those used by some athletes) make young animals gain weight faster so they are ready for market sooner. Female animals receive synthetic estrogen to inhibit the reproductive cycle and divert all energy into weight gain. In the United States, up to two-thirds of meat animals are raised using hormones. In addition, hormones are used to increase milk production in dairy cattle.
Scientific investigation of the exact effects of environmental steroids on humans is extremely difficult since there are multiple sources of hormones in the environment. A valid study would require a control group who hasn't been exposed to the chemicals being studied. Since everyone has had some exposure to environmental hormones, no control group is available to use as a reference.
-How are steroids able to cross cell membranes and enter cells?

• A)Steroids and cell membranes both contain receptor proteins.
• B)Steroids are able to pass through the phospholipid bilayer and bind to receptors inside the cell.
• C)Steroids can diffuse through open channel proteins in the membrane.
• D)Steroids move through cell membranes, such as water, by osmosis.