Dr. Reichlerís Bio 301L  1-2pm  Print Name:________________ KEY________
In-class Exam #4  April 26, 2002

 Answer each question as succinctly as possible in the space provided.  If you need more space, use the back.  If you use a drawing as part of your answer, be sure to also include a written explanation.  Each question is worth 6 pts, unless otherwise noted, for a total of 100 points possible for this exam.  Read each question carefully and donít hesitate to ask if a question seems unclear.

1. a.  Could a person survive if they ate only proteins or only carbohydrates?  For each, why or why not?
Protein- yes, amino acids can be used to provide both building blocks and energy.
Carbs- no, there are eight essential amino acids that the human body can not produce.  Without eating proteins, the body will be unable to make protein.

b. Name three minerals that your body needs and describe what they are used for in the human body.
Any three of:  Sodium- needed for nerve signals or water balance.  Potassium- needed for nerve signals.  Calcium- needed for nerve signal or muscle contraction.  Iron- needed for oxygen transport.

2. a.  Why does the physical breakdown of food generally precede chemical digestion?
The surface area of the food must be increased so that digestive enzymes can have access to and thereby breakdown the food.

b. Is the small intestine of bears relatively longer or shorter than in humans?  Explain.
Bears have a short small intestine.  They are evolved from meat eaters, so their digestive system is suited to digesting high energy meat and then getting rid of the rest rapidly before it rots.

c. How do stomach acids play a role in both digestion and the immune system?
The acid helps to liquefy the food and the low pH kills most pathogens that might enter the stomach.

3. a.  Why does inhaling require energy while exhaling does not?  And while holding your breath saves energy, it is detrimental to gas exchange.  Why?
Inhaling involves muscle contraction which requires ATP, during exhalation, the muscle is relaxing.  Gas exchange is dependent on a concentration gradient.  Without a refreshing of the air in the lungs, the concentration gradient will equalize.

b. How is the production of carbon dioxide (CO2) related to the release of oxygen from hemoglobin?
When CO2 enters the blood it forms carbonic acid.  This lowers the pH and causes hemoglobin to bind oxygen less well.

4. a.  Blood moves from the small intestine to the liver and then back to the heart.  How does the blood move from the small intestine to the liver?  (In other words, what causes the blood to move from the small intestine to the liver?)
The blood is absorbing nutrients in the sm. int.  This blood is in capillaries.  Therefore there is low pressure.  So the blood must move through one-way valves by squeezing of muscles to go from the sm. int. to the liver.

b. Why are there so many capillaries, but relatively few arteries and veins?
This is where exchange takes place.  All of the body's cells must have access to nutrients, gases, etc.  So the capillaries must be extensive to be in contact with the cells all over the body.

5. a.  Diabetics have too much sugar in their blood.  One symptom of having diabetes is the presence of sugar in the urine.  How can the presence of excess sugar in the urine of diabetics be explained?
The kidneys function by filtering everything out and then reabsorbing the needed nutrients, etc.  The excess sugar can not be reabsorbed, and so it passes into the urine.

b. What are two waste products that need to be eliminated from the body, and where do they come from?
Any two of:  CO2- from cellular respiration.  Nitrogen/urea- from breakdown of amino acids.

6. a.  You are riding on the bus, and although you do not know it, the person sitting next to you has tuberculosis (which is caused by bacteria).  They cough on youÖDescribe how at least one component your non-specific immune system and one component of your specific immune system might protect you from getting sick?  (8pts)
Non-specific-  Any one of:  the skin is a barrier keeping the TB out.  Other bacteria will outcompete the TB on the skin.  The hairs and mucous in the nose will trap the TB.  Stomach acid will kill it.
Specific-  B-cells recognize TB as foreign, make antibodies that mark it for destruction by macrophages.

b. Would B-cells or T-cells help defend against the occurrence of cancer?  Explain.
Only T-cells.  B-cells recognize foreign particles.  T-cells recognize our own abnormal cells, such as cancerous cells.

7. Why might immuno-suppressing drugs be effective in treating some forms of diabetes, MS, or arthritis?
These are all auto-immune disorders where the body's own immune system is attacking itself.  By suppressing the immune system, the symptoms might be relieved.

8. a.  Would you expect to find calcium (Ca++) channels in one part of a neuron or all over?  Would a muscle cell have calcium (Ca++) channels in one part or all over?  Explain.  (8pts)
Neuron-  only at end of axon.  This is where the increased Ca triggers release of neurotranslitters.  Muscle-  all over.  CA is needed for muscle contraction.  The contraction takes place throughout the cell.

b. Why does thinking require energy?
ATP is needed to run the NA/K pump.  To maintain the NA?K gradient.