Week 3 Online Lecture Discussion Assignment-Lectures 3 and 4

Directions

To respond to the discussion questions below, please choose one or two of the highlighted questions from each lecture and respond. Don’t forget to check back and review the posts of at least three other students to complete your assignment.

Lecture 3-Food Supply, Safety, and Contaminants

When we begin to look at our lecture on food supply, we find that 1 in 6 people are food insecure (do not have confidence in their next meal). When we talk about the food security in developing countries (60% to just 14% undernourished) we find much improvement, with an increasing food supply that has developed as the world population has expanded. But we are still facing malnutrition or undernutrition world-wide, with diseases related to protein insufficiency (Kwashiorkor and Marasmus). Did you notice that Kwashiorkor occurs when a child is suddenly weaned and abruptly loses the protein in its diet? When this occurs, many underlying health issues can surface. Did you know that Kwashiorkor also occurs in the U.S. in communities that have very little nutrition education?

But we are also finding diseases from ‘over’nutrition (obesity) now, as our diet shifts to heavily processed food with high sugar and fat content and very little micronutrients or fiber. This is particularly prevalent in poverty-stricken communities. The obesity epidemic we are facing in the southern states is not a result of fried food! It is a result of poverty and lack of access to grocery stores. These locations are called ‘food deserts’. Take a look now at the youtube link for Will Allen’s “Growing Power” by selecting the link below:

 

Will Allen: Growing PowerLinks to an external site.

 

What do you notice about his farming technique. Is it energy efficient? why or why not? How does he provide nutrients to his plants? Does he use pesticides? Do you notice that he can provide fresh fish to local restaurants? What are the aspects of his gardening technique that you find most interesting?

Notice that his ‘polyculture’ technique is very different from the ‘monoculture’ farming that we use primarily for food production (think of the corn fields in the midwest). Now take a look at slide 15 and the outline of the ‘Green Revolution’. Do you notice that this is a revolution in monoculture farming? How would you describe the Green Revolution to a friend? This farming technique requires large inputs of water, fertilizers and pesticides. Although it has allowed us to increase our food supply to match our population explosion, we are now reaching a production limit related to limited water supply, manufactured fertilizers and pesticides! Our industrialized, monoculture food production system also relies heavily on fossil fuel.

Notice that as countries rapidly transition to a western diet they can go from producing all the grain they need to importing most grain within a few decades. Why?

When we review the slides related to genetic engineering and GMOs we find that the FDA does not require foods to be labeled as ‘GMO’. Did you know that most of Europe has now completely banned GMO foods (New Scientist: Half of European Union votes to ban growing GM cropsLinks to an external site.)? Do you think that genetically modified foods are safe to eat? Why or why not?

Do you think that eating organic food is ‘the answer’ to avoid GMOs and pesticides? why or why not?

Now take a look at polyculture farming (slide 60). Do you notice that many different kinds of crops are grown together in the same plot? This is a traditional form of food production that creates habitat for predators, increases local biodiversity and resistance to disease. Roots that reach to varying depths help to retain water in the system (less water required). Biodiversity also allows nutrients to remain in the soil, mimicking natural ecosystems. Trees planted in the vicinity of these crops can hold water in the system and actually improve the climate for farming. Notice that when we evaluate these systems, polyculture is much more productive per unit of energy required than monoculture. Now take a look at this youtube link for an introduction to Wangari Maathai:

Wangari MaathaiLinks to an external site.

This clip relates back to one of our first slides in this talk–>”Recognizing the role of women in food production is an important step forward”

After viewing the link, were there any aspects of it that you found interesting? What were they? Do you think it relates to recognizing the role of women in food production? how?

Food Safety

Please note: Our study of food safety and contaminants will be covered in a separate online discussion assignment. Please be sure to study the slides provided in this lecture to supplement the information that you learn from other students’ presentations.

Now take a look at this excerpt from a PBS Frontline presentation on a Salmonella outbreak in the United States:

Frontline: When Chicken SickensLinks to an external site.

 

What do you find interesting about how the FDA, EPA and USDA work with the Centers for Disease Control (CDC) to manage outbreaks and keep our food supply safe? Were there any surprises for you?

 

Lecture 4-Digestive System

Notice the various components of the digestive system with accessory organs (this should be a review for many of you in our class as you may have already covered these topics in Bio 40C, We will focus in our class primarily on how the digestive system functions rather than anatomy) . What are the components of the digestive system? How do the accessory organs aid in digestion? Notice that our digestive system is basically one long, uni-directional tube, with valves at each juncture to keep contents moving in the right direction (which sphincters do you remember? What do the pyloric and esophageal sphincters do for us?). This body plan evolved very early in our evolutionary history. Can you name all of the main components from the mouth to the large intestine? Observe the main function of each part of the digestive system…in brief:

 

Mouth: chewing and enzymatic breakdown of some components of your food What are the enzymes secreted here and what do they do? Are there any other components of saliva?

Esophagus: Notice how peristalsis moves the bolus of food down to the stomach. Is swallowing voluntary? How does it work?

Stomach: Which macronutrient is first digested in the stomach. Which hormones and enzymes are involved? How does the stomach avoid digesting itself? The stomach is also acidic! The acid protects us from contents in our food that might harm us (enzymes, bacteria, etc.). The acid in our stomach also enters, as chyme, with pre-digested food to our small intestine. Which sphincter regulates this? Did you notice that the acid content in chyme helps us to absorb minerals? Do you remember that vitamins are also classified as water soluble or lipid soluble? This will be important when we need to address how these micronutrients are actually absorbed in the small intestine.

Small Intestine: This is where MOST of the digestion and absorption of food takes place. What are the enzymes and hormones here that are necessary for carbohydrate, lipid and protein digestion? Where in the small intestine does most absorption take place? Which accessory digestive organs are involved?

What components of the macronutrients we consume can actually be absorbed by the cells lining the small intestine? How are they absorbed (active, facilitated, passive)? Why do you think we don’t absorb intact protein?

Did you notice that the small intestine greatly increases surface area? Which components does the small intestine use to increase surface area? This large surface area (as large as a tennis court!) in the small intestine helps us to absorb all of the nutrients we are digesting.

Take a look at lipid digestion. Did you notice that the pathway is different? Why do you think lipid is packaged as chylomicrons and enters the lymph system? Why can the components of carbohydrate and protein enter the hepatic portal system directly? Where is the hepatic portal system going? Why?

What is bile (where is it made and stored)? Do you see how bile increases the surface area for pancreatic enzymes to digest lipid?

What is our large intestine used for (primarily)? Why is it called the ‘large’ intestine?

When reviewing the digestive system and the accessory organs, was there a particular aspect of digestion that surprised you? Which aspect of digestion did you find most interesting?

There are many questions for the digestive system review, but just a few for discussion. Be sure to thoroughly review the digestive system with special emphasis on the steps in digestion and absorption of macronutrients.

 

Don’t forget to comment on at least three (3) other students’ posts for full credit!