Expert: John Locke - 10/16/2009

Question
1. The phospholipid molecules of most membranes have a :
A - hydrophobic head and a hydrophilic tail
B - hydrophobic head and a hydrophobic tail

2. The glucose transport mechanism is an example of:
A. simple diffusion
B. facilitated diffusion
C. osmosis
D. active transport
E. more than one answer is correct

3. Which statement is true?
A - The movement of solvent occurs from a hypotonic solution to an isotonic solution.
B - The net movement from an isotonic to a hypotonic solution involves the movement of solute molecules only.
C - The concentration of the solute is greater in an isotonic solution than in a hypertonic solution.
D - Osmosis involves only hypertonic solutions.

4. The net direction that an ion or molecule moves is:
A - dependent upon the size of the molecule
B - unpredictable because movement is random
C - influenced by the temperature of the medium
D - influenced by the membranes in the vicinity
E - the result of concentration differences

5. Wilting of a plant occurs:
A - if the plant is placed in an isotonic solution
B - if there is a rise in turgor pressure
C - as a result of facilitated diffusion
D - when a plant with flexible cell walls is placed in a hypertonic solution

6. White blood cells use ______ to get rid of foreign particles in the blood:
A - osmosis
B - bulk flow
C - simple diffusion
D - phagocytosis
E - facilitated diffustion

These questions were not in the book, and i need help with them very much!! Anything you can answer will help me.

Answer
Sorry for the long delay in answering your question. The answers are given as follows, along with a short explanation:

1. Neither answer is correct. The phospholipid molecules of most membranes have hydrophilic heads and hydrophobic tails.
2. E. Glucose is transported by multiple methods, including facilitated diffusion (as in the intestine, where the co-transport of sodium and glucose takes place) and active transport. See here: http://www.medbio.info/Horn/Time%203-4/glucose_transport_proteins.htm
3. A. The solvent moves from a hypotonic solution (where concentration is lower) to an isotonic solution (where concentration is higher).
4. E is probably the most correct, although A is also correct.
5. D. The plant loses water from its cells in a hypertonic solution and subsequently wilts; the flexible cell walls will produce a physical deformation.
6. D. Phagocytosis is used specifically by macrophages to engulf and destroy foreign objects within the body.