SBCH322: UNIT 4

Prof Khajamohiddin Syed

Room no. 247, Department of Biochemistry & Microbiology,

University of Zululand

SyedK@unizulu.ac.za

___________________________________________________________________

Important notice

The questions and answers provided in this file are only for students’ practice

purposes. The intention of providing this information is purely to educate and

make students aware of the correct way of answering the questions. All the

sources used in the preparation of this material are properly cited at the end of

this document. Students are requested not to regard this material as a reference,

but as guidance on how to answer questions. However, ultimately the onus rests

on the student to work hard and to read the books and other material on the

topics listed in the module.

Micronutrients

Vitamins

A vitamin is an organic molecule (or related set of molecules) which is an essential micronutrient,

meaning a substance which an organism needs in small quantities for the proper functioning of its

metabolism but cannot synthesize, either at all or in sufficient quantities, and therefore must obtain

through its diet.

Vitamins are organic compounds that are essential in the diet in small amounts to promote and

regulate the processes necessary for growth, reproduction, and the maintenance of health. When a

vitamin is lacking in the diet, deficiency symptoms occur. When the vitamin is restored to the diet the

symptoms resolve. There are 15 known vitamins, and they have traditionally been grouped based on

their solubility in water or fat. This chemical characteristic allows generalization to be made about how

they are absorbed, transported, excreted, and stored in the body. The water-soluble vitamins include

the B vitamin and vitamin C. The fat-soluble vitamins include vitamins A, D, E, and K (Table 1). The

vitamins were initially named alphabetically in approximately the order in which they were identified: A,

B, C, D, and E. The B vitamins were first thought to be one chemical substance but were later found to

be many different substances, so the alphabetical name was broken down by numbers; thiamin,

riboflavin and niacin were originally referred to as vitamin B1, B2, and B3, respectively. Vitamins B6, and

B12 are the only ones that are still commonly referred to by their numbers. Some people consider

choline and carnitine to be conditionally essential, water-soluble, vitamin-like compounds and thus

these two molecules were also included under water-soluble vitamins.

Table 1. Vitamins.

Water-soluble vitamins Fat-soluble vitamins

B Vitamins Vitamin A

B1 Thiamin Vitamin D

B2 Riboflavin Vitamin E

B3 Niacin Vitamin K

B5 Pantothenic acid

B6 Pyridoxine

B7 Biotin

B9 Folate

B12 Cobalamin

Vitamin C

Choline

Carnitine

Water-soluble vitamins function primarily as coenzymes in energy metabolism, the fat-soluble vitamins

are needed for cell growth, reproduction, and gene regulation.

Properties of water-soluble vitamins

One attribute that all water-soluble vitamins share is that they dissolve in water (as opposed to lipids).

Second, although there are exceptions, the body generally digests, absorbs, and transports the water-

soluble vitamins in similar ways. For example, they are absorbed mostly in the small intestines and, to

lesser extent, the stomach. Further, many water-soluble vitamins found in foods are bound to proteins

that enzymes must remove before the vitamins can be absorbed. In addition, their bioavailability (i.e.

absorption) can be influenced by many factors, including nutritional status, other nutrients and

substances in foods, medications, age, and illness. And, except for choline which is circulated away from

the gastrointestinal tract in the lymph, all of the water-soluble compounds are circulated directly to the

liver in the blood. Finally, because the body does not actively store water-soluble vitamins, they

generally do not have toxic effects when consumed in large amounts.

General characteristic of fat-soluble vitamins

Although each of the fat-soluble vitamins is chemically unique, this group of nutrients shares certain

general characteristics in terms of how they are absorbed and circulated (Table 2). For example, like the

water-soluble vitamins, fat-soluble vitamins are absorbed mostly in the small intestine. Unlike their

water-soluble counterparts, however, absorption requires the presence of dietary lipids as well as the

action of bile. In other words, if you were to eat a very low-fat diet, you might have difficulty absorbing

the fat-soluble vitamins. Unlike water-soluble vitamins, which are circulated in the blood, fat-soluble

vitamins are circulated away from the small intestine in the lymph via chylomicrons before eventually

entering the blood either as components of lipoproteins or bound to transport properties.

Like water-soluble vitamins, each fat-soluble vitamin has several forms, some of which are more

biologically active than others. Because the body can store most of the fat-soluble vitamins, consuming

large amounts of them (especially in supplement form) can results in toxicities, sometimes which serious

consequences. Once absorbed and circulated to cells in the body, the fat-soluble vitamins are involved

in many processes such as vision, blood coagulations, regulation of gene expression, cell maturation,

and stabilization of free radicals.

Table 2. General characteristics of the fat-soluble vitamins.

Food Sources Typically found in fatty portions of food

Some are easily destroyed by heat and light

Digestion Very little needed

Absorption Occurs mostly in small intestines

Requires incorporation into micelles and the action of bile

Once transported into the intestinal cell, vitamins and packaged with other lipids into chylomicrons

Circulation away from gastrointestinal tract Initially circulated in lymph, then in the blood

Functions Gene regulation and various other functions such as being antioxidants and participating in the blood-clotting casacade

Toxicity Except for vitamin K, toxicities are dangerous and sometimes fatal

Table 3. Major functions, deficiency diseases, toxicity symptoms, and food sources of the essential water-soluble vitamins, choline and carnitine.

Vitamin Major functions Deficiency Toxicity Food sources

Thamine (B1) Coenzyme (TPP)

Energy metabolism

Synthesis of DNA, RNA

Nerve function

Beriberi Pork; Whole grains; Legumes; Tune & Soy milk

Riboflavin (B2) Coenzyme (FAD and FMN)

Energy metabolism (redox reactions)

Metabolism of folate, vitamin A, niacin, Vitamin K

Neurotransmitter metabolism

Ariboflavinosis Liver; Mushrooms; Dairy products; Tomatoes; Spinach

Niacin (B3) Coenzyme (NAD+ and NADP+)

Energy metabolism (redox reactions)

Protein synthesis

Glucose homeostasis

Cholesterol metabolism

DNA repair

Pellagra Skin inflammation and flushin

Liver; Fish; Meat (including poultry); Tomatoes; Mushrooms

Pantothenic acid (B5) Coenzyme (CoA)

Energy metabolism

Heme synthesis

Cholesterol, fatty acid, steroid, and phospholipid

Burning feet syndrome (possibly)

Liver; Mushrooms; Sunflower seeds; Yogurt; Turkey

synthesis

Vitamin B6 Coenzyme (PLP)

Amino acid metabolism (transamination)

Neurotransmitter and hemoglobin synthesis

Glycogenesis

Regulation of steroid hormone function

Microcytic hypochromic anemia

Fish; Chickpeas; Liver; Potatoes; Bananas

Biotin Coenzyme

Energy metabolism (carboxylation)

Regulation of gene expression

Depression, loss of muscle control, and skin irritations

Peanuts; Almonds; Mushrooms; Egg yolk; Tomatoes

Folate Coenzyme (THF)

Single-carbon transfers

Amino acid metabolism

DNA and RNA synthesis

Macrocytic anemia, increased cardiovascular disease risk, increased risk for fetal malformations

Neurological problems Organ meats; Legumes’ Okra; Leafy vegatables; Orange juice

Vitamin B12 Coenzyme

Homocysteine metabolism

Energy metabolism

Macrocytic anemia Mollusks; Liver; Salmon; Meat; Cottage cheese

Vitamin C Antioxidant

Recharging enzymes

Collagen synthesis

Tyrosine, neurotransmitter, and hormone

Scurvy Gastrointestinal problems Peppers; Papayas; Citrus fruits; Broccoli; Strawberries

synthesis

Protection from free radicals

Choline Phospholipid synthesis

Neurotransmitter synthesis

Liver damage Fishy body odor Eggs; Liver; Legumes; Pork; Fish

Carnitine Phospholipid synthesis

Neurotransmitter synthesis

Muscle weakness, hypoglycemia, heart irregularities

Meat; Eggs; Dairy foods; Avocados

Abbreviations: TTP, thiamin pyrophosphate; FAD, Flavin adenine dinucleotide; FMN, Flavin mononucleotide; NAD+, Nicotinamide adenine

dinucleotide; NADP+, nicotinamide adenine dinucleotide phosphate; PLP, pyridoxal phosphate; THF, tetrahydrofolate

Below table help you to remember easily the general functions of the water-soluble vitamins, choline and carnitine.

Functions B1 B2 B3 B5 B6 B7 B9 B12 Vitamin C Choline Carnitine

Coenzyme

Energy metabolism

Antioxidant function

Interconversion or activation of nutrients

Blood health

DNA or RNA synthesis

Nerve/muscle function

Note that these vitamins are not, themselves, energy-yielding nutrients but are involved in energy metabolism via their coenzyme roles. The

roles that choline plays in the body are still being investigated.

Table 4. Functions, sources, deficiency, and toxicity diseases, and food sources of the essential fat-soluble vitamins.

Vitamin Major functions Deficiency Toxicity Selected food sources

Vitamin A Growth

Reproduction

Vision

Cell differentiation

Immune function

Bone health

Vitamin A deficiency disorder (VADD)

Night blindness

Xerophthalmia

Hyperkeratosis

Hypervitaminos A

Blurred vision

Birth defects

Liver damage

Osteoporosis

Liver; Pumpkin; Sweet potato; Carrot

Vitamin D Calcium homeostasis

Bone health

Cell differentiation

Rickets

Osteomalacia

Osteoporosis

Hypercalcemia

Calcification of soft tissues

Fish; Shiitake mushrooms; Fortified milk; Fortified cereals

Vitamin E Antioxidant properties

Cell membrane stability

Eye health

Heart health

Neuromuscular problems

Hemolytic anemia

Hemorrhage

Tomatoes; Nuts, seeds; Spinach; Fortified cereals

Vitamin K Coenzyme

Blood clotting

Bone health

Tooth health

Vitamin K deficiency bleeding (VKDB)

No known effects Kale; Spinach; Broccoli; Brussels sprouts

Minerals

Minerals are inorganic elements needed by the body as structural components and regulators of body processes. Because the body requires

them in very small amounts, dietary minerals are considered micronutrients. All minerals needed for health are essential nutrients because the

body cannot make them from other compounds. Thus, we rely on the foods we eat to provide us with these important substances. Minerals can

be neither created nor destroyed; even if you completely combust (burn) a food, the minerals will remain in the ash. This is true of the minerals

in our bodies as well.

Minerals have traditionally been categorized based on the amounts needed in the diet or present in the body. Essential minerals are divided up

into major minerals (macrominerals) and trace minerals (microminerals). The major minerals include those needed in the diet in amounts

greater than 100 mg per day or present in the body in amounts greater than 0.01% of body weight. These two groups of minerals are equally

important, but trace minerals are needed in smaller amounts than major minerals. The amounts needed in the body are not an indication of

their importance.

The body requires seven major minerals (calcium, phosphorus, magnesium, sodium, chloride, sulfur and potassium) and nine trace minerals

(iron, copper, iodine, selenium, chromium, fluoride, manganese, molybdenum, and zinc).

Mineral Sources Major functions Deficiency, diseases and symptoms

Groups at risk of deficiency

Toxicity

Calcium Dairy products, fish consumed with bones, leafy green vegetables, fortified foods

Bone and teeth structure, nerve transmission, muscle contraction, blood clotting, blood pressure regulation, hormone secretion

Increased risk of osteoporosis

Postmenopausal women, elderly, those who consume a vegan diet, are lactose intolerance, or have kidney disease

Elevated blood calcium, calcification of the kidney, kidney stones, reduced absorption of other minerals

Phosphorus Meat, dairy products, cereals, and baked goods

Structure of bones and teeth, membranes, ATP, and DNA; acid-base balance

Bone loss, weakness, lack of appetite

Premature infants, alcoholics, elderly

Calcium resorption from bone

Magnesium Greens, whole grains, nuts, seeds

Bone structure, ATP stabilization, enzyme

Nausea, vomiting, weakness, muscle

Alcoholics, those with kidney and

Nausea, vomiting, diarrhea, low blood

activity, nerve and muscle function

pain, irregular heartbeat

gastrointestinal disease

pressure

Sulfur High protein foods, preservatives

Part of amino acids, vitamins, acid-base balance

None when protein needs are met

None None likely

Sodium Table salt, processed foods

Major positive extracellular ion, nerve transmission, muscle contraction, fluid balance

Muscle cramps Those consuming a severely sodium-restricted diet, excessive sweating

Contributes to high blood pressure

Potassium Fresh fruits, and vegetables, legumes, whole grains, milk and meat

Major positive intracellular ion, never transmission, muscle contraction, fluid balance

Irregular heartbeat, fatigue, muscle cramps

Those consuming poor diets high in processed foods, those taking thiazide diuretics

Abnormal heartbeat

Chloride Table salt, processed foods

Major negative extracellular ion, fluid balance

Unlikely None None likely

Iron Red meats, leafy greens, dried fruit, whole and enriched grains

Part of hemoglobin, which delivers oxygen to cells, myoglobin, which holds oxygen in muscle, and electron carriers in the electron transport chain; needed for immune function

Iron deficiency anemia; fatigue, weakness, small pale red blood cells, low hemoglobin

Infants and preschool children, adolescents, women of childbearing age, pregnant women, athletes

Gastrointestinal upset, liver damage

Zinc Meat, seafood, whole grains, eggs

Regulates protein synthesis; functions in growth, development, wound healing, immunity, and antioxidant protection

Poor growth and development, skin rashes, decreased immune function

Vegetarians, low-income children, elderly

Decreased copper absorption, depressed immune function

Copper Organ meat, nuts, seeds, whole grains, seafood, cocoa

A part of proteins needed for iron absorption, lipid metabolism, collagen synthesis, nerve and immune function, and antioxidant protection

Anemia, poor growth, bone abnormalities

Those who over supplement zinc

Vomiting

Manganese Nuts, legumes, whole grains, tea

Functions in carbohydrate and lipid metabolism antioxidant protection

Growth retardation None Nerve damage

Selenium Organ meats, seafood, eggs, whole grains

Antioxidant protection as part of glutathione peroxidase, synthesis of thyroid hormones, spares vitamin E

Muscle pain, weakness, Keshan disease

Population in areas with low selenium soil

Nausea, diarrhea, vomiting, fatigue, hair changes

Iodine Iodized salt, salt water fish, seafood, dairy products

Needed for synthesis of thyroid hormones

Goiter, cretinism, mental retardation, growth and developmental abnormalities

Population in areas with low-iodine soil and iodized salt is not used

Enlarged thyroid

Chromium Brewers yeast, nuts, whole grains, mushrooms

Enhances insulin action

High blood glucose Malnourished children

None reported

Fluoride Fluoridated water; tea, fish, toothpaste

Strengthens tooth enamel, enhances remineralization of tooth enamel, reduces acid production by bacteria in the mouth

Increased risk of dental caries

Populations in areas with unfluoridated water

Mottled teeth, kidney damage, bone abnormalities

Molybdenum Milk, organ, meats, grains, legumes

Cofactor for a number of enzymes

Unknown in humans None Arthritis and joint inflammation

General functions of the essential major minerals

Major minerals

Function Calcium Phosphorus Magnesium Sodium\chloride potassium

Cofactor

Immune function

Bone and tooth health

Blood health

Energy metabolism

Fluid balance

Nerve and muscle function

Note that these minerals are not, themselves, energy-yielding nutrients but rather are involved in energy metabolism via other roles, such as

activation of enzymes or as a cofactor.

General functions of the required trace minerals

Trace minerals

Functions Iron Copper Iodine Selenium Chromium Manganese Molybdenum Zinc

Cofactors (metalloenzymes)

Regulation of gene transcription

Immune function

Antioxidant (redox) function

Bone/tooth health

Blood health

Energy metabolism

Note that these minerals are not themselves energy-yielding nutrients but are not involved in energy metabolism via other mechanisms.

References

Nutritional sciences from fundamentals to food, 3rd edition, by Michelle McGuire and Kathy A Beerman.

WADSWORTH cengage learning, ISBN-13:978-0-8400-5839-3; ISBN-10:0-8400-5839-X.

Nutrition science & applications, 2nd edition, by Lori A Smolin and Mary B Grosvenor, John Wiley & Sons,

Inc. ISBN: 13 978 -0-470-52474-9.

How do vitamins work? - Ginnie Trinh Nguyen: https://www.youtube.com/watch?v=ISZLTJH5lYg

Minerals - What Are Minerals - What Do Minerals Do: https://www.youtube.com/watch?v=i3GfrZR2DUE