Building blocks of protein
Structure of Proteins
Amine group, Acid Group, & Side Chain
gives amino acid its identity. attached to center carbon.
Stomach: Stomach acid denatures proteins, protein uncoils and is broken down into smaller pieces.
Small Intestine: Protein-digesting enzymes from pancreas and intestine keep working until all are broken into single, double, or tri peptides.
Cells along small intestine absorb single amino acids.
Amino acids can be metabolize to protein, nitrogen, plus energy, glucose, or fat. They will be metabolize to protein only if sufficient energy is present from other sources. The nitrogen part is removed from each amino acid, and the resulting fragment is oxidized for energy. No storage form of amino acids exists in the body.
Roles of Body Proteins
1. Provide structure and movement (muscle tissue - 40%)
2. Building enzymes, hormones, etc.
3. Building Antibodies
4. Transporting substances
5. Maintaining Fluid and Electrolyte Balance
6. Maintaining Acid-Base Balance
7. Blood Clotting
8. Providing Energy and Glucose
Calculate DRI for Protein Intake
.8 grams per each 2.2 pounds of body weight.
AMDR for Protein
10 - 35%
The amount of nitrogen consumed compared with the amount excreted in a given time period.
Positive: Nitrogen consumed > Nitrogen excreted: growing child, pregnant woman, body builder- anyone gaining mass
Neutral: Nitrogen consumed = Nitrogen excreted: adults who are in normal circumstances: healthy college student and a young retiree
Negative: Nitrogen consumed < Nitrogen excreted: someone who is sick, astronaut (muscle or other protein tissue is broken down and lost)- anyone losing mass
Neccesary to get all amino acids - why?
In order to make the required proteins, the cells need a full array of amino acids. If a nonessential amino acid (that is, ones the cell can make:) is unavailable from food, the cell synthesizes it and continues attaching amino acids to the protein strands being manufactured. If the diet fails to provide enough essential amino acids (ones that it can't make), the cells
break down more internal proteins to liberate the needed essential amino acids and
conserve the essential amino acid by limiting their synthesis of proteins.
As the deprivation continues, the tissues make one adjustment after another to survive.
Characterize food in protein amount
Quality Proteins: Provide enough of all the essential amino acids in relatively the same amounts that the body requires. More digestible=higher quality. Cook with moist heat, instead of frying
High quality protein sources: Animal. Contain all essential AA's
Mid quality sources: Legumes, soybeans
Low quality sources: grains/nuts (they're missing some AA)
Complementary: legumes and grains balance each other. (black beans and rice, tortillas and beans, pita bread and hummus, bread and peanut butter)
Complementary Proteins: Two or more proteins whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other.
Consequences for Protein Excess
It's wasted because you can't store protein. Heart disease, kidney disease (though excess protein does not cause kidney disease, it has been proven to accelerated preexisting conditions such as kidney stones), osteoporosis (also caused by low protein), and possibly cancer.
Consequences for Protein Deficiency
Protein-energy malnutrition (PEM):
Marasmus (skin and bones): similar to malnutrition; the person is shriveled and lean all over; most often in young children/infants. Muscles (including heart) weaken. Brain development stops. Body temp is subnormal, with no insulation. Need love. No growth, don't heal, no energy to even cry. Digestive tract stops working. Killed by disease (table 6-4 pg 212)
Kwashiorkor (big belly): sufficient calories with not enough protein; edema and fatty liver; swollen belly and skin rash; found in older children. The Liver swells because there isn't enough protein to export the fats into the body and so it expands to accommodate the fats. (table 6-4 pg. 212)
It has to do with functions. Muscle, bone, antibodies, fluid balance (edema, usually in feet and lower legs), working cells, organs, people become apathetic and listless.
apathy, loss of interest in women/men, loss of hair, edema, lack energy, food digestion decrease
Strengths of Veg & Vegan
Benefits of vegetarian:
Maintain healthier body weight
Reduced levels of chronic disease, particularly heart and arterial diseases
Lower levels of heart disease
Lower levels of cancer
Defense against high blood pressure, cancers, heart disease
On average, vegetarians usually abstain from alcohol and cigarette use opposed to other adults.
Fiber, fruit, and vegetables higher in diet
Less sat fats (most come from animal products)
Benefits of omnivorous:
Sufficient amounts of B12, calcium, iron, zinc
Meets energy needs for children
More reliable nutritionally
Limitations of vegetarianism
Limitations of vegetarian:
Needs to be a well planned vegetarian diet or you may omit essential nutrients by omitting certain key foods and nutrients such as B12, calcium, among others (iron, protein). Children have low energy.
Nutrients of particular concern for vegetarians: