Chemistry 106University of Nebraska – Lincoln

Spring 2009

25 March, 2009

NUTRIENTS

• Carbohydrates• Lipids• Proteins• Vitamins• Minerals

Proteins

• Why eat proteins?– To provide amino acids for new protein synthesis– As a source of nitrogen and sulfur

• Most abundant macromolecules (large molecules) in the cell

• Excess amino acids cannot be stored in the body (nitrogen is converted to ammonia and excreted as urea)

• However, protein deficiency is very rare in the U.S.

• Biological catalysts (enzymes)

• Antibodies that fight antigens (bacteria and viruses)

• Transport molecules and ions

• Regulate cell function (hormone)

• Provide structural support and mechanical strength

• Necessary for all forms of movement

• Sources of amino acids for growth

Proteins

The high-quality protein of eggs contains essential amino acids in nearly the same ratios found in human protein.

Essential Amino Acids-KNOW F OR TEST:LeucineIsoleucineLycineMethioninePhenylalanineThreonineTryptophanValine

Grams of the essential amino acids per 100 g of hens’ eggscompared to that of cornmeal (approximate values).

Protein Quality

Dates, lima beans, cornmeal, and peanuts represent plant foods that are deficient in one or more essential amino acids – these are considered low-quality protein.

-High quality protein have high levels of essential amino acids, low quality proteins do not…Know for test

-More essential amino acids from animal protein

In general, plants are relatively poor sources of protein.

Animal foods (beef, poultry, seafood, dairy products, eggs) provide our best source for protein.

Complementary proteins can be obtained by a varied diet.(These are proteins that individually are incomplete or low quality but when taken together provide the amount and ratios of protein required)- choose foods so that each one has high values of different amino acids, so that a proficient amount of each amino acid is eaten (for vegetarians)

Proteins

Macronutrients

• Macronutrients include carbohydrates, proteins, and fats and oils

• They make a major portion of food we eat in volume and weight

Micronutrients• Vitamins and minerals (and additives?)• not normally converted into energy_-• make up very small mass of body (except calcium and

phosphorus)

Minerals• Nutritionally important elements except C, O, H, N, S• Not synthesized by the body• Used by body in ionic form• Toxic if ingested in excess

• Plants provide a good source of minerals

Major Minerals

• Calcium (1.5-2% of body weight)– Most abundant mineral in body– 99% in body found in bones and teeth– Required for nerve transmission,

muscle contraction, and blood

clotting

Major Minerals

• Phosphorous (1-1.5% of body weight)– Required for optimum Ca packing (increasing

density) in bones and teeth-– Used in DNA and RNA

Major Minerals

• Sodium, potassium, chloride– Maintenance of salt levels in body fluids

(required by many enzymes)– Nerve Transmission: intercellular (outside of

the cell) sodium and intracellular potassium (inside the cell itself)

– Chloride used in HCl as stomach acid

Major Minerals

• Magnesium– Found in teeth and bones, helps protein

formation, and intercellular electrical transmission promoter

Minor Minerals (trace elements)

• Similar to vitamins in that• required in small amounts (<100 mg/day)• food usually only contains a small amount

• Most used in enzymes and hormones

• Exact function of many trace elements remains unknown

Minor Minerals (trace elements)• Iron• contrary to many trace elements its

function is well known• used in the protein hemoglobin• binds to and transports oxygen to cells• Anemia – iron deficiency (reduced oxygen)• too much iron can cause cirrhosis of the

liver

Minor Minerals (trace elements)

• Iodine• concentrated in thyroid gland• required in the hormone thyroxine which regulates metabolism

• too much or too little can lead to Goiter (swelling of thyroid gland)

Minor Minerals (trace elements)

• Fluorine• hardens enamel of teeth• some communities add fluorine to drinking water• many toothpastes contain sodium fluoride

• Zinc• involved with growth via enzyme function• healing of wounds

• Copper• critical component of some enzymes• interacts with iron in hemoglobin

• Chromium• glucose metabolism• efficient use of insulin

Vitamins• A group of naturally occurring organic compounds found in the diet and essential to good health • Not used for energy or body muscle/bone• “vitamin” originally from the phrase “vital amine”• minerals are from the soil, vitamins are from plants and other animals (produced from plants and animals)• like minerals they are required in small amounts

Vitamins

• Categories of vitamins• Fat-soluble: soluble in non-polar solvents (fats,

oils, hydrocarbons, etc.)• Vitamin A, D, E, K

• Water soluble: soluble in water and other polar solvents

• B vitamins and vitamin C

Vitamins

Differences between fat and water soluble vitamins

– Many water soluble vitamins have several hydroxyl groups (OH-) – allows hydrogen bonding with water.

– Fat soluble vitamins need not be taken daily: stored in fat and liver tissue (can build up to toxic levels)

– Water soluble vitamins (generally) are not stored so must be consumed frequently & in small quantities.

Fat Soluble Vitamins

Water Soluble Vitamins

Vitamin A

• Chemical name: Retinol• Characteristics

• Fat-soluble vitamin – accumulates in fats and liver• important for skin, eyes, mucous membranes• food sources – meat (liver) (not found in plants)• overdose symptoms

• headache, dizziness, nausea, death• birth defects

• orange/yellow vegetables contain no retinol but do containb-carotene which is easily converted to retinol

• eating excess “carrots” will not give overdose of retinol but may impart an orange/yellow color to the skin

b-carotene molecule

***be able to recognize both for test!!!!

2 retinol molecues