sbch322: unit 4 prof khajamohiddin syed room no. 247 ... · micronutrients vitamins a vitamin is an...
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SBCH322: UNIT 4
Prof Khajamohiddin Syed
Room no. 247, Department of Biochemistry & Microbiology,
University of Zululand
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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