Nutrition Ch 6
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1. What are proteins, and which element distinguishes them from other organic compounds?
polymers of amino acids
1. About how many amino acids are essential?
1. What does it mean when a protein is denatured? How does this play a role in digestion?
Loss of tertiary structure and function.
Stomach acid denatures proteins, allowing enzymes access.
Intestinal enzymes and pancrease further cleave it into di-andtri-peptides and single amino acids
1. You should know how/where proteins are digested and absorbed.
- di and tri-peptides are absorbed in the small intestine.
- larger fragments may act as hormones.
- different types of AA's are absorbed at
1. Why can an excess of one amino acid (i.e. a supplement) block absorption of others?
similar amino acids compete for similar receptors
1. Why is it wasteful for the body to use amino acids for energy?
Nitrogen/ amine groups are removed from the AA and excreted rather than being used for something under lack of energy from other sources, excess protein in the diet, excess of a single amino acid, low quality protein in the diet
1. What is ‘nitrogen balance’? Under what conditions is it positive or negative?
Healthy adults consume the same amount of nitrogen as they excrete
Positive N balance: more proteins are being built than lost (growing children, pregnant woemn, malnourished individuals replenishing tissues
Negative N balance: protein is being lsot from the body. illness/injury results in protein breakdown. AA's released into the blood provide energy for the immune response.
1. What are the two features of high quality protein?
It must be digestible, it must provide enough of all the essential amino acids
1. Why can it be a serious problem if even one amino acid is missing from the diet?
limits protein synthesis. like missing a letter from the alphabet.
1. How can we get all essential amino acids in our diet? What about if we are vegetarians/vegans?
Proteins from animals. Soybeans
1. How likely are protein/amino acid deficiencies in the US? What about in developing countries?
Rare. 2/3 of deaths of young children in developing countries
1. What are the two forms of PEM, and what are their causes?
Marasmus and Kwashiorkor
M: children living on weak cereal with low-quality protein.
K: babies weaned when the next is born to watery cereal with little protein. Proteins diminished.
1. Under what circumstances can PEM occur in developed countries?
Poor living in Indian reservations, inner cities and rural areas.
Hungry and homeless chidlren
Chidlren who's well-meaning parents replace their formula with low-protein "health food soy or rice drinks
patients with wasting diseases such as AIDs or cancer
1. What are some downsides of consuming excess protein on a regular basis?
Can crowd out other foods
Food high inprotein often adds saturated fat
Meat consumption often accompanies higher energy intakes (calories)
Increased workload for the kidneys
Read meat and processed meat inrease risk of colorectal cancer
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