24.4–24.5
24.4–Hormones are produced in glands throughout the body.
Endocrine glands throughout the body are responsible for detecting and responding to signals that reflect an organism’s internal and external environments.
Q
Which of the following statements, if true, best supports the suggestion that endocrine systems in living things might have evolved earlier than nervous systems?
- a) Nervous systems are more complex than endocrine systems, so they obviously must have evolved later.
- b) Endocrine systems can provide all of the same functions that nervous systems can provide.
- c) The oldest organism we know of was capable of producing hormones.
- d) Plants have endocrine systems but they don’t have nervous systems.
- e) Simple animals that lack brains do have endocrine systems.
Human sex hormones are classified as which type of biological molecules?
- a) enzymes
- b) lipids
- c) proteins
- d) carbohydrates
- e) nucleic acids
Why are steroid hormones able to directly bind to DNA to influence gene expression, whereas peptide hormones must influence gene expression indirectly?
- a) Peptide hormones are made from amino acids, which are also used to make proteins, and proteins cannot bind to DNA. Steroid hormones are not made from amino acids and therefore can directly interact with DNA.
- b) Steroid hormones are lipid-
based, allowing them to pass through the lipid- composed cell membrane and nuclear membrane and directly bind to DNA. Peptide hormones are not lipid- based and therefore cannot pass through the cell membrane. - c) Steroid hormones are smaller than peptide hormones and can enter the cell through the holes in the cell membrane.
- d) Steroid hormones are cholesterolbased and therefore can block arteries, causing cardiovascular disease. Directly binding to DNA allows them to complete their function and to be removed from the circulatory system as soon as possible.
- e) Neither steroid nor peptide hormones directly bind to DNA; both influence gene expression indirectly.
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