In the second-messenger system, what serves as the first messenger?

Which type of epithelial tissue forms the most superficial layer of the skin?

a) Simple squamous epithelium b) Simple cuboidal epithelium c) Stratified squamous epithelium d) Stratified cuboidal epithelium e) Simple columnar epithelium

Which part of the brain works with the medulla oblongata to regulate respiration?

A. Reticular formation B. Pons C. Hippocampus D. Midbrain

The pancreas has both exocrine and endocrine tissue.

a. true b. false

Distinguish between hydrophilic and hydrophobic molecules

A) Hydrophilic molecules are attracted to water, whereas hydrophobic molecules do not interact with water molecules. B) Hydrophilic molecules do not interact with water molecules, whereas hydrophobic molecules are attracted to water. C) Hydrophilic molecules are inorganic, whereas hydrophobic molecules are organic. D) Hydrophilic molecules are organic, whereas hydrophobic molecules are inorganic. E) Hydrophilic molecules are monomers, whereas hydrophobic molecules are polymers.