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Option A
A.1.1 Define nutrient: a chemical substance found in food that is used in the human body.
This includes all the 4 major macromolecule groups: carbohydrates, proteins, lipids and nucleic acids. It
also includes co-enzymes ( vitamins), co-factors ( elements).
A 1.2 List the type of nutrients that are essential in the human diet, including amino acids, fatty acids, minerals,
vitamins, and water.
Of the 20 amino acids used in all living things, 9 of them cannot be made by humans. They are called
essential amino acids because it is essential that we obtain them in our diet. One of them is only used while we
are within our mothers.
Note that most societies have diets that include legumes and a grain since the combination provides a complete
set of amino acids. Eat meat and you do not have to worry, all amino acids are in meat.
We also have an essential lipid- linoic acid, and various minerals, called co-factors such as Mg, Se, Fe. Cofactors are non-organic molecules, usually metals, that we need in trace amounts. Co-enzymes are organic
molecules that we cannot make, such as vitamin C and vitamin E. Co- enzymes and co-factors bind to enzymes
and activate them. Without them, we cannot perform certain metabolic functions because our specific enzymes
are not activated. Note that most mammals, but not primates, can make their own vitamin C. Some long lost
ancestor had a mutation that eliminated our ability to make vitamin C.
A.1.3 State that non-essential amino acids can be synthesized in the body from other nutrients.
Eleven of the 20 amino acids essential to life we can make by converting other amino acids and
molecules into them. It is a very complex process that you do not need to know unless you major in nutrition.
Note that all babies born in the U.S. are tested for a genetic disease called PKU. Babies with the mutation
cannot convert phenalanine into other amino acids and it builds up in the brain and destroys brain cells. The fix
is to limit the amount of phenalanine that those babies get in their diet. Phenalalanine is an essential amino acid,
we cannot make it, but we use it to make other amino acids.
A.1.4. Outline the consequences of protein deficiency malnutrition
Without getting the essential amino acids in our diet, certain proteins cannot be made, which causes a
number of diseases. This results in such diseases as kwashiorkor, which afflicts over 10 million children in
developing countries. It causes such things as mental retardation, apathy, and failure to grow. Early signs of low
protein are being tired when you should not be, slow healing and recovery from exercise, and hair falling out.
A.1.5 Explain the causes and consequences of phenylketonuria (PKU) and how early diagnosis and a special
diet can reduce the consequences
[Limit the causes to a mutation of a gene for an enzyme that converts the essential amino acid phenylalanine to
tyrosine. The consequences are an accumulation of phenylalanine in tissues, lack of normal skin pigmentation,
and mental retardation. Newborns can be tested for PKU and then placed on a low-phenylalanine diet that
prevents most of the effects of PKU.
All newborns in the U.S. are tested via a simple blood test. Untreated symptoms are a small head
size, jerky movements, seizures, and mental retardation. Treatment involves the elimination of such
foods as milk and eggs, which are rich in phenylalanine. A special infant formula, called Lofenalac, has
been made that is very low in phenylalanine. Note that this is a rare disease, but since it is easily identified
and treated, all babies are tested.
A.1.6 Outline the variation in the molecular structure of fatty acids, including saturated fatty acids, cis and
trans unsaturated fatty acids, monounsaturated and polyunsaturated fatty acids
We have covered this before in the structure of fatty acids. Saturated fatty acids have no double bonds
and are saturated with hydrogen. These are solids at room temperature such as butter, and lard. Unsaturated
fatty acids have at least one double bond that means that it has fewer hydrogen atoms than a saturated fat. The
double bond causes a bend in the fatty acid, which results in it taking up more space… hence, it is less dense.
Unsaturated fatty acids are liquids at room temperature. Cis and trans refer to the position of the single
hydrogens that are attached to the doubly bonded carbons in the fatty acid. If they are on opposite sides, they are
trans fats, which apparently stick together more than cis fats, which have the hydrogen on the same side. When
fats stick together, we are in danger of atherosclerosis, in which fats build up in arteries and eventually stop
blood flow through them. This results in either a stroke, or a heart attack. Omega-3 fatty acids are considered to
be most healthy, they have the double bonds between the 3rd and 4th carbon in the carbon chain. These are in
fish oils, etc.
A.1.7 Evaluate the health consequences of diets rich in the different types of fatty acid.
Unsaturated fatty acids are better than saturated fatty acids. The consequences may include cancer,
atherosclerosis – narrowing of arteries by fatty deposits, coronary heart disease – narrowing of the coronary
arteries with the associated risk of heart attacks, and high concentrations of LDL –bad cholesterol. Tests show
that some monounsaturated fatty acids help lower LDL levels. However, both fatty acids lead to cardiovascular
disease when consumed in large amounts.
A.1.8 Distinguish between minerals and vitamins in terms of their chemical nature.
[Limit this to minerals being elements in ionic form and vitamins being organic compounds.]
Minerals are inorganic molecules such as Fe, Mg, Se, Zn, Co, Cl, N, K, Na, Ca, P, I. Of the ones listed, we need
potassium in the greatest amount, Chlorine is the second most needed… for stomach acids.
Vitamins are organic compounds that act as co-enzymes, they activate particular enzymes. Some are water
soluble , and others are oil soluble. Water soluble are vitamin C and the B vitamins such as niacin, biotin,
riboflavin, and thiamin. Oil soluble are A, D, E and K
A.1.9 Outline two of the methods that have been used to determine the recommended daily intake of vitamin C.
Human subjects: During WWII, a vitamin C trial in England involved twenty volunteers. For six weeks all
volunteers were given a diet with 70 mg of vitamin C. For the next eight months, three volunteers continued on
the 70 mg diet, seven were placed on a 10 mg diet, and ten were given no vitamin C. All ten that were given no
vitamin C developed scurvy. The groups given 10 mg and 70 mg diets did not develop scurvy.
Small mammal subjects: Experiments for vitamin C requirements also have been conducted with real guineapigs. The collagen in the guinea-pigs with restricted vitamin C had less cross-linking between protein fibers and
lower strength than those with non-restricted vitamin C.
A.1.10 Discuss the amount of vitamin C that an adult should consume per day, including the level needed to
prevent scurvy, claims that higher intakes give protection against upper respiratory tract infections, and the
danger of rebound malnutrition.
Rebound malnutrition can occur when a normally adequate intake of a vitamin follows a period of excessive
intake and excretion.
Adults were found to require only about 10 mg of vitamin C per day, but the recommended daily allowances
that national governments have set are much higher – typically 30-60 mg for adults. The USDA recommends 50
mg of vitamin C per day. Linus Pauling claimed that higher intakes of vitamin C protect against upper
respiratory tract infections. Other scientists claim that high doses do not give protection and could even cause
deficiency problems when stopped. The body becomes used to excreting the excess. If the intake drops back
down to normal levels, symptoms of scurvy can develop. This is rebound malnutrition. Linus Pauling based his
high levels of recommended vitamin C ( 14,000 mg) on the fact that other mammals that produce their own
Vitamin C produce that level on a daily basis ( specifically, goats)
A.1.11 List the sources of vitamin D in human diets.
Vitamin D can be synthesized in human skin in the presence of light. Oily fishes, eggs, and liver are all sources
of vitamin D. Margarine and milk are artificially fortified with vitamin D.
A.1.12 Discuss how the risk of vitamin D deficiency from insufficient exposure to sunlight can be balanced
against the risk of contracting malignant melanoma.
Ultraviolet light can lead to skin cancer. Melanin in the skin intercepts and absorbs light, including the
ultraviolet wavelengths. Dark skins therefore give good protection against cancer, but they also reduce vitamin
D synthesis. In indigenous human populations, skin color balances the twin risks of vitamin D deficiency and
cancer or other damage due to ultraviolet light. After population migrations there can be problems. Immigrants
with dark skin from India living in the United Kingdom started to show symptoms of vitamin D deficiency.
Immigrants from northern Europe with light skin living in Australia were found to have high rates of malignant
melanoma.
A.1.13 Explain the benefits of artificial dietary supplementation as a means of preventing malnutrition, using
iodine as an example.
Artificial dietary supplementation is the addition of a dietary supplement into the diet of an individual to
prevent a deficiency of that particular nutrient and thus malnutrition. The addition of iodine to table salt helps
prevent thyroid gland problems, such as goiter. Iodine deficiency disorder (IDD) causes swelling of the thyroid
in the neck. This is goiter, which is most common in the Central African Republic and Syria, but can be found
in all parts of the world. Goiter is very serious. If women are affected during pregnancy, their children are born
with permanent brain damage. If children suffer from IDD after birth, their mental development and intelligence
are impaired.
A campaign to eliminate IDD by adding iodine in small quantities to salt sold for human consumption has
continued since the 1920s. By adding iodine to salt and providing it to populations suffering from IDD, the
number of those suffering diminished significantly. In 2000, iodized salt was reaching more than 3.3 billion
people throughout the world.
Iodine is the mineral in thyroxine, which is a metabolic hormone produced by the thyroid gland. Many
people are deficient in iodine, which is why the only recourse for exposure to radioactive elements is to take
iodine tablets. Radioactive iodine is one of the stable intermediates of the decay of heavy radioactive elements.
If you are deficient in iodine, your body will take up the radioactive iodine and hold it in the thyroid gland. This
results in cancer of the thyroid gland, a common malady after Hiroshima, Nagasaki, and Chernobyl.
A.1.14 Outline the importance of fiber as a component of a balanced diet.
Fiber cannot be digested by the small intestine. Cellulose from plant cell walls is the main component of dietary
fiber, but there are other components, such as chitin and lignin. Fiber has been shown to help prevent
constipation by increasing the bulk of material in the large intestine. The bulk from fiber also helps muscles
keep food and wastes moving through the digestive and excretory systems. Fiber may reduce the risk of
diseases of the large intestine including appendicitis, cancer, and hemorrhoids. It can prevent obesity by
increasing the bulk in the stomach, which reduces the desire to eat more food. Fiber may also increase the rate
of absorption of calcium. It also scrapes off the villi of the intestine, allowing them to diffuse materials into the
blood stream.