Give three examples of structures whose formation involves molecular interactions that either increase or decrease contact with water molecules, explaining how they are similar and how they differ from each other. (Hint: They all involve molecules that have both polar and nonpolar portions.)
What will be an ideal response?
Phospholipids have a polar portion that is attracted to water and a nonpolar portion that repels water. The molecules orient in water such that water is excluded from contacting the nonpolar portions. This is seen in: the bilayer arrangement of phospholipids in cell membranes, in which hydrophobic tails are in the middle of the layer; micelles, in which a single layer of phospholipids forms a sphere with the hydrophobic tails in the middle; and liposomes, which are hollow spheres made from phospholipid bilayers that can be filled with water-soluble
molecules.
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Balance is the responsibility of which sensory organ?
A) Throat B) Eye C) Nose D) Ear
Answer the following statements true (T) or false (F)
1. There are four major types of teeth. 2. Another name for baby teeth is deciduous teeth. 3. The terms gastroesophageal sphincter and pyloric sphincter refer to the same structure. 4. The ileum of the small intestine empties into the transverse colon of the large intestine. 5. The names of many enzymes end in “The names of many enzymes end in “ase.”ase.”
Bile acts on
a. distention of the stomach b. gastrin c. carbohydrate in the stomach d. fat in the duodenum e. fat in the stomach
Looking into a microscope, you notice cells swimming, propelled by a long tail. What cell structure must these cells have in order to be mobile?
A) ribosomes B) smooth ER C) flagella D) peroxisomes E) cytoplasm