BIOLOGY 415 PLANT CONSTITUENTS AND THEIR FUNCTIONS

Final (Second) Exam, Apr. 24, 2001


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200 points total

PART I. 80 points. 20 points each.

Answer 4 of the following 5 questions (1-5):

Each of these answers is restricted to about 1/2 page.

1. Although a number of foods (plant) have been accepted as part of our diet for many years, some may be detrimental. Explain this using 3 specific examples.

2. Explain what flavor is. Use specific examples where appropriate.

3. Take one example of a botanical folk medicine and explain its chemical and physiological basis.

4. What are mycotoxins and what do you think their natural role is?

5. Discuss the flower pigments in terms of their chemical makeup and their natural roles.


PART II. 30 points.

Answer 1 of the following 2 questions (6-7):

Each of these answers is restricted to about 1/2 page.

6. Using information from this course, explain in chemical and ecological terms what is going on in the figure. To enlarge this image, click on it, and to return to the original figure with the question, click on the BACK button in your web browser.




















7. Explain in chemical terms how the insects in the figure utilize the host plant also shown in the figure. To enlarge this image, click on it, and to return to the original figure with the question, click on the BACK button in your web browser.


















PART III. 40 points. 10 points each.

Each of these answers is restricted to about 4 lines.

8. Briefly, explain the meaning (and if appropriate, give an example) of any 4 of the following 5 terms:

8a. Analgesics (plant compounds)

8b. Honey

8c. Doctrine of signatures

8d. Astringency

8e. Kairomones


PART IV. 20 points. 10 points each.

Each of these answers is restricted to about 4 lines.

9. Briefly, explain the function (s) of 2 of the 3 following terms:

9a. Phycobilins

9b. Latex

9c. Semiochemicals


PART V. 30 points. 15 points each.

Each of these answers is restricted to about 4 lines.

10. Briefly, explain the mode of action (how they work) of 2 of the 3 following terms:

Note that these answers may be at the molecular level or higher levels as seems appropriate.

10a. Aflatoxin

10b. Lectins

10c. Capsaicin


ANSWERS to the Final (Second) Exam

Apr. 24, 2001

Do not scroll through the answers; use the links provided.

 


















AnswerI_1

1. Although a number of foods (plant) have been accepted as part of our diet for many years, some may be detrimental. Explain this using 3 specific examples.

There are far too many examples to cover more than a small fraction here.

One example would be spinach which may contain large amounts of oxalic acid which may chelate Ca+2 and aggravate Ca-deficiency problems.

Another could be the caffeine present in coffee and many other beverages. This may cause nervousness, stress and sometimes cardiac arrhythmias.

The isoflavones present in many soybean products certainly are beneficial dietary factors; however they are also estrogen mimics and thereby can cause problems in both men and women.

Pickled (putrified) foods rank high on our culinary scale, yet the monoamines (e.g. histamine, tryptamine) in them can cause vasoconstriction, increased blood pressure and headaches in many consumers.

Go back to question 1 or go on to question 2.

 














2. Explain what flavor is. Use specific examples where appropriate.

Flavor is a combination of taste, odor, texture and common chemical sense.

Taste is the perception of higher molecular weight, hydrophilic, nonvolatile compounds usually requiring fairly direct contact with the source. In humans, this takes place in the oral cavity, mainly on the tongue.

Odor is the sensing of lower molecular weight, hydrophobic, volatile compounds usually not requiring direct contact with the source. In humans, this takes place in the nasal cavity.

Texture, the feel of food (e.g., rough, smooth, etc.) is also an important facet of flavor.

The common chemical sense is a sensation, most often perceived in the delicate lining of the oral cavity. Pungency and astringency would be examples.

Go back to question 2 or go on to question 3.

 



















3. Take one example of a botanical folk medicine and explain its chemical and physiological basis.

As in question #1 above, there are many many possible examples here. Two examples are:

Opium. Opium and opium poppy extracts have been used as analgesics. One of the main active ingredients is morphine, an analog of endorphins (ent-kephalins) which serve to stimulate a pleasure response and suppress pain responses.

Willow extract. Willow teas have been important in pain relief in most cultures across the northern hemisphere. The active ingredient is salicylic acid, which is derived from salicin ( a glycoside), an it inhibits the COX-1 (cyclo-oxygenase) enzyme that converts arachidonic acid to prostagladins. This diminishes inflammation and pain.

Go back to question 3 or go on to question 4.

 




















4. What are mycotoxins and what do your think their natural role is?

Mycotoxins are toxins produced by nonmushroom fungi, and examples would include aflatoxin and possibly even penicillin.

The most probable function is to combat other microorganisms that compete for the same food source, e.g., antibiotic action.

One can also imagine other possible roles such as protecting a food source by deterring animals that might consume the food source or by providing protection for a plant symbiont as some mycorrhizal fungi seem to do.

Go back to question 4 or go on to question 5.

 












5. Discuss the flower pigments in terms of their chemical makeup and their natural roles.

This has the potential to be a more complex question than necessary.

The main flower pigments are the carotenoids and flavonoids. In some groups, the betalains are important and occasionally chlorophyll. Flowers usually do not carry on photosynthesis, so the photosynthesis pigments are usually not significant. The flower pigments are hydrophilic (flavonoids and betalains) or hydrophobic (cartenoids), and this influences their subcellular location, i.e., vacuolar or membranes and lipid droplets respectively.

The role of these pigments is to attract animal pollinators, and that can be somewhat selective with certain colors attracting particular groups of pollinators, e.g., red often attracts birds and UV-absorbing pigments are visible mainly to bees. Sometimes, special pigment patterns guide the pollinators, i.e., nectar guides.

Go back to question 5 or go on to question 6.

 
















6. Using information from this course, explain in cheical and ecological terms what is going on in the figure.

The diagram shows an example of allelopathy, one plant species inhibiting others by producing inhibitary cheicals, a non competitive mechanism.

The roots of the walnut release a glycoside which split and oxidized yielding the inhibitor juglone. Juglone inhibits the growth of tomato plants and many other species and may even kill them.


Go back to question 6 or go on to question 7.

 
















7. Explain in chemical terms how the insects in the figure utilize the host plant also shown in the figure.

The insects feed on the milkweed which is toxic to most animals due to cardiac glycosides. These insects have evolved resistance to the cardiac glycosides and are actually able to accumulate them in specific parts of their body (aposomatic). This provides them with some protection and they are brightly colored to warn potential predators. Interestingly, cardiac glycosides accumulated by the monarch butterfly caterpillars are passed along through metamorphosis to the butterfly

Go back to question 7 or go on to question 8a.

 














8a. Analgesics are pain killers. Examples include morphine and codeine from opium poppy and salicylic acid from willow.

Go back to question 8a or go on to question 8b.

 
























8b. Honey is nectar processed by bees. After the bees collect the nectar from flowers, they store and partially process it in their honey sacs. Honey may also contain pigments and scents.

Go back to question 8b or go on to question 8c.

 






















8c. Doctrine of signatures This is an ancient philosophy that holds that plants contain a sign or signature which reveals how they can be used by people. For example, walnut resembles a human brain and therefore should provide brain remedies.

Go back to question 8c or go on to question 8d.

 
















8d. Astringency is a sensation or feeling, a dry, puckery feeling in the mouth. It is caused by tannins binding to the lubricating proteins (mucin) in saliva and also to the lining of the mouth.

Go back to question 8d or go on to question 8e.

 

















8e. Kairomones are chemical signals between different species where the signal mainly benefits the producers. Examples include the insect pheromones released by some flowers, flavonoids released by legume roots to attract the N2-fixing symbiotic bacteria and the semiochemicals released by corn leaves under attack by caterpillars.

Go back to question 8e or go on to question 9a.





















9a. Phycobilins harvest light for photosynthesis or sense light. Phycocyanin and phycoerythrin harvest light and pass the energy along to the photosynthetic apparatus. Phytochrome senses light.

Go back to question 9a or go on to question 9b.

 

























9b. Latex helps to heal wounds and to deter herbivores. In addition to containing toxins, in many cases, latex may gum up the mouth parts of the herbivores.

Go back to question 9b or go on to question 9c.

 
























 



9c. Semiochemicals are calls for help from plants under attack by herbivores. The plant being eaten releases volatile chemicals that attract the predators of the herbivore.

Go back to question 9c or go on to question 10a.

 

























10a. Aflatoxin is bioactivated to a form that binds to DNA, and this results in cell damage and cancer formation.

Go back to question 10a or go on to question 10b.

 


























10b. Lectins are proteins (excluding antibodies) that specifically bind polysaccharides or sugars. This may inhibit cell functions or cause agglutination of cells

Go back to question 10b or go on to question 10c.

 

























10c. Capsaicin binds to heat-sensing cells causing a sensation of pain, but eventually it exhausts them deadening pain.

Go back to question 10c or to question 1 or to the top of this exam .





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