Week 6 Online Lecture Discussion Assignment-Lectures 7 and 8

For the questions below, please choose just one or two highlighted questions from each lecture (one or two question froms ‘protein’ and one or two questions from ‘metabolism and energy’) that is interesting to you that you would like to discuss.

Protein

Did you know that breakfast cereal was first mass marketed in the United States in the early 1900s by the Kellogg brothers?

The Crusade Against Protein

Isn’t it interesting that protein used to be considered the ‘bad’ component of food, and these days we consider carbohydrate to be ‘bad’ or negative? Our food choices and consumption are certainly influenced by trends in our society! What do you eat for breakfast? (List some common food choices). Do you think your breakfast choices are influenced by family tradition? Why? Was there a shift to ‘carbs’ for breakfast in your family at some point?

Do you think that the current trend in protein consumption and dramatically reduced carbohydrate consumption might affect our health? Why or why not?

Notice that protein has 4 levels of structure and many functions in our body. Can you name some of these functions? Considering your answer to the last question, can you think of some reasons why we would want to conserve protein for other uses besides as energy?

Protein, unlike lipid and carbohydrate, contains nitrogen. When we break down amino acids, we must find a way to process nitrogen as higher concentrations of nitrogen in the blood can cause toxicity. We must process the nitrogen and remove it, placing a load on our kidneys. If you have ever tried a high protein, low carb diet you may have noticed that you need to urinate more often. Can you think of a reason why this might cause an issue for some people?

Did you notice that some amino acids are essential (9)? What makes them essential? Do you need to worry about consuming enough of the essential amino acids if you are vegan? Why?

How would you describe the concept of a ‘limiting’ amino acid to a friend?

When you review the process of protein synthesis (be sure to review this before the next exam), how does this process relate to the concept of a limiting amino acid? Which RNA molecule is responsible for building (attaching) the next amino acid in a chain of protein? If an essential amino acid (like lysine) is not consumed in enough quantity, it will not be present in the cell for this amino acid to attach to. What will happen to protein synthesis if the cell is missing lysine? You can use these ideas to elaborate in your answer to the question above regarding limiting amino acids. You can also watch a short video that explains limiting amino acids by selecting the link below:

Limiting Amino Acids

Did you notice that not only are we consuming more protein than necessary in the U.S., we are also consuming much more protein from animal sources than most other countries. Can you name five (5) good reasons why we should transition to plant protein? (hint: these should affect our health)

Notice that the RDA for protein is actually an equation (0.8 gm of protein / kg of healthy body weight). Can you calculate your RDA? Do you think you are consuming over or under your RDA for protein? Or just right?

From your review of the textbook and lectures, do you think that consuming protein powders, shakes and other supplements is necessary to build muscle? Can you think of any health issues you might face if you consume too much protein? You can view this link for more information.

What happens when you eat too much proteinLinks to an external site.

 

Metabolism and Energy

Here we begin our review of some key concepts related to metabolism and energy balance including basal metabolic rate, laws of thermodynamics and anabolic/catabolic pathways. We focus on ATP, the energy currency of the cell. A discussion of ATP structure and hydrolysis, along with the important work that the energy from ATP provides the cell. We review the processes of photosynthesis and cellular respiration, with three main steps occurring in the process of cellular respiration. Please describe these steps in detail including where they occur in the cell ( inside vs. outside the mitochondrial networks), are they aerobic vs. anaerobic, what are the products of each?

Did you notice in the last question I referred to ‘mitochondrial networks’ rather than ‘mitochondria’? Take a look at slide 40 and observe that rather than a single, kidney shaped membranous organelle that we are used to seeing (slide 29), our mitochondria exist as a matrix that is very closely associated with and in constant communication with the endoplasmic reticulum. Did you know that your mitochondrial matrix can grow and develop depending on the needs of the cell?

Take a look here:

Play media comment.

You should be able to see an entire mitochondrial matrix here, with fission and fusion events occurring based on the needs of the cell. This understanding of the true nature of mitochondria is very important when we begin to discuss the use of lactate by cells as a superfuel! Based on this understanding of mitochondrial networks, you should now be aware that when we exercise, our mitochondrial networks grow and when we suffer from couch-potato syndrome our mitochondrial networks shrink. This is yet another reason why exercise is so important for our health (including the health of our cells). Can you think of some reasons (or situations) in which having healthy mitochondrial networks would be important for a person’s health and/or survival? See if you can explain how having a healthy, established network of mitochondria would contribute to recovery from injury or disease.

Now lets move on to a discussion of lactate. Notice that in slide 37 we begin a discussion of lactate as a ‘super fuel’ for the cells. For example, according to the work of George Brooks at UC Berkeley, “The ‘lactate shuttle’ and mitochondrial network prefer lactate for fuel over glucose and fatty acids.” Professor Brooks has also established that cells produce lactate as a super fuel for the brain and tissues in response to stress, regardless of the presence of oxygen in the cell (slide 44). Review this article (and the information posted on the slides for this lecture) and tell us what you think!:

Rehabilitating Lactate: From poison to fuel

You can also find a nice, informative interview with Professor Brooks here if you are interested in hearing him talk about his theory:

Lactate Shuttle Theory

Finally, notice how protein, carbohydrate, lipid and alcohol are used for the production of ATP. Briefly describe the main differences you notice between the major macronutrients in the process of ATP production (ex. gluconeogenesis, beta-oxidation and ketogenesis).

That’s all for these two chapters. I will be very interested, as always, to hear your thoughts. Thank you all for such great discussions in our Bio 45 class. It is fantastic to see your ideas and how you can share them with each other in this format.

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