HNE25306
Problem set 4: Protein, Energy Homeostasis and Weight Management
Instructor: Sander Kersten
Protein and Health
1. Dietary proteins are composed of ___________. ___________ can be synthesized in
the body from carbohydrates and amino nitrogen source. The major role of dietary
protein is to supply amino acids for the synthesis of ___________ needed in the body,
although dietary protein can also serve as a ______________source
2. What chemical element in present in proteins yet absent in triglycerides and
carbohydrates?
3. Match the following:
a) enzyme 1. chain of amino acids
b) antibody 2. main protein in human hair
c) hormone 3. a chemical messenger present in blood
d) polypeptide 4. accelerates a chemical reaction
e) collagen 5. main contractile protein in muscle
f) actin 6. inactivates invading microorganisms
g) keratin 7. main structural protein in the body
4. Why is the low pH of the stomach necessary for efficient protein digestion?
5. In the following list of food, indicate whether the particular food item has a protein
content that is higher or lower than 5%
Lower Higher
Cauliflower
Beer
Soft cheese
Soy milk
Avocado
Boiled white rice
Whole wheat bread
Banana
Peanuts
Bacon
Egg yolk
Wine
Cow’s milk
Butter
Chicken nuggets
Milk chocolate
, Mushrooms
Cassava
Salmon
6. Describe the factors that determine the quality of dietary protein?
7.
a) Explain the concept of limiting amino acid.
b) What amino acids are limiting in grains?
c) What amino acids are limiting in legumes?
d) Is there any rationale behind consuming rice and beans or corn bread and beans?
8. Gelatin is a very poor quality animal protein. It is one of the few foods that cause a net
loss of protein if eaten exclusively. Gelatin is derived from an animal protein that serves
important structural functions in numerous tissues.
a) Which one?
b) Which amino acids are lacking or absent in gelatin?
c) Why would the exclusive consumption of gelatin cause a net loss of protein (=negative
N balance)?
9. The synthesis of body proteins is often compared to building a house, with the bricks
signifying amino acids. However, a fundamental difference separates the two. Explain.
10. Amino acids are not secreted into the urine as such but are first converted into a
metabolite rich in nitrogen. What is the name of this metabolite and where is it produced?
11. Explain the similarities between the concept of nitrogen balance and energy balance.
What group of individuals should have a positive nitrogen balance?
12. Protein turnover is not constant throughout the day. When are we in a state of net
protein synthesis (anabolic) and when in a state of net protein breakdown (catabolic)
13. Wheat and corn protein are inherently poor in lysine. Look up what actions breeders
have taken to try to improve the nutritional value of wheat and corn in terms of protein
quality?
14. The recommended daily allowance (RDA) for protein is 0.8 g per kg of bodyweight.
Some bodybuilders reach a daily protein intake that is 4 times higher than the RDA. How
is this possible? What are the purported benefits of such a high intake?
Energy homeostasis and Weight management
1. PAR (Physical Activity Ratio) is defined as the energy cost of physical activity as a
ratio of BMR. Give an estimate of the PAR of the following group of activities: dressing,
Problem set 4: Protein, Energy Homeostasis and Weight Management
Instructor: Sander Kersten
Protein and Health
1. Dietary proteins are composed of ___________. ___________ can be synthesized in
the body from carbohydrates and amino nitrogen source. The major role of dietary
protein is to supply amino acids for the synthesis of ___________ needed in the body,
although dietary protein can also serve as a ______________source
2. What chemical element in present in proteins yet absent in triglycerides and
carbohydrates?
3. Match the following:
a) enzyme 1. chain of amino acids
b) antibody 2. main protein in human hair
c) hormone 3. a chemical messenger present in blood
d) polypeptide 4. accelerates a chemical reaction
e) collagen 5. main contractile protein in muscle
f) actin 6. inactivates invading microorganisms
g) keratin 7. main structural protein in the body
4. Why is the low pH of the stomach necessary for efficient protein digestion?
5. In the following list of food, indicate whether the particular food item has a protein
content that is higher or lower than 5%
Lower Higher
Cauliflower
Beer
Soft cheese
Soy milk
Avocado
Boiled white rice
Whole wheat bread
Banana
Peanuts
Bacon
Egg yolk
Wine
Cow’s milk
Butter
Chicken nuggets
Milk chocolate
, Mushrooms
Cassava
Salmon
6. Describe the factors that determine the quality of dietary protein?
7.
a) Explain the concept of limiting amino acid.
b) What amino acids are limiting in grains?
c) What amino acids are limiting in legumes?
d) Is there any rationale behind consuming rice and beans or corn bread and beans?
8. Gelatin is a very poor quality animal protein. It is one of the few foods that cause a net
loss of protein if eaten exclusively. Gelatin is derived from an animal protein that serves
important structural functions in numerous tissues.
a) Which one?
b) Which amino acids are lacking or absent in gelatin?
c) Why would the exclusive consumption of gelatin cause a net loss of protein (=negative
N balance)?
9. The synthesis of body proteins is often compared to building a house, with the bricks
signifying amino acids. However, a fundamental difference separates the two. Explain.
10. Amino acids are not secreted into the urine as such but are first converted into a
metabolite rich in nitrogen. What is the name of this metabolite and where is it produced?
11. Explain the similarities between the concept of nitrogen balance and energy balance.
What group of individuals should have a positive nitrogen balance?
12. Protein turnover is not constant throughout the day. When are we in a state of net
protein synthesis (anabolic) and when in a state of net protein breakdown (catabolic)
13. Wheat and corn protein are inherently poor in lysine. Look up what actions breeders
have taken to try to improve the nutritional value of wheat and corn in terms of protein
quality?
14. The recommended daily allowance (RDA) for protein is 0.8 g per kg of bodyweight.
Some bodybuilders reach a daily protein intake that is 4 times higher than the RDA. How
is this possible? What are the purported benefits of such a high intake?
Energy homeostasis and Weight management
1. PAR (Physical Activity Ratio) is defined as the energy cost of physical activity as a
ratio of BMR. Give an estimate of the PAR of the following group of activities: dressing,
