Molecular Fundamentals - Vitamins

what are vitamins?

organic compounds that an organism requires for normal metabolism and physiological functions of the body

what kind of vitamins can our body not store?

water-soluble vitamins

water-soluble vitamins are excess vitamins that are excreted in what?

urine

what vitamins can our body store (mainly in liver)?

fat-soluble vitamins

an excess of fat-soluble vitamins can cause what?

toxicity (hypervitaminosis)

what are the water-soluble vitamins?

• vitamin B complex group

• vitamin C

what are the fat-soluble vitamins?

• vitamin A

• vitamin D

• vitamin E

• vitamin K

what is the active form of thiamin B1?

thiamin diphosphate (TDP)

thiamin diphosphate (TDP) is a what?

a coenzyme for several enzymes in the carbohydrates, amino acids, and lipid metabolism

what are examples of enzymes that thiamin diphosphate is a coenzyme for?

• pyruvate dehydrogenase

• α-Ketoglutarate dehydrogenase

• transketolase

what is the main common source of thiamin in the US diet?

cereals and bread

what is the rare effect of thiamin deficiency?

beriberi

what is beriberi characterized by?

mainly by peripheral neuropathy and wasting

what is the cure for beriberi?

administration of supplemental thiamin

what is the more common effect of thiamin deficiency in the United states?

Wernick-Korsakoff syndrome

Wernicke-Korskoff syndrome is more common in people with what?

chronic alcoholism

what are the symptosm of Wernicke-Korsakoff syndrome?

• confusion

• lack of energy, hypothermia, low blood pressure, or coma

• lack of muscle coordination that can affect posture and balance

• loss of memory

what is the treatment for Wernicke-Korsakoff syndrome?

intravenous vitamin B1

what are the active forms of riboflavin B2?

flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)

flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are coenzymes for what?

several dehydrogenase enzymes

riboflavin B2 is involved in what kind of reactions?

oxidation-reduction

the coenzymes involved with riboflavin B2 is important for what?

• energy production

• cellular function

• growth and development

• metabolism of fats, drugs, and steroids

Riboflavin B2 deficiency can cause what?

• corneal neovascularization (invasion of new blood vessels into the cornea)

• cheilosis (swollen, cracked lips)

• glossitis (inflammation of the tongue)

• stomatitis (lesions at the corners of the mouth)

• magenta-colored tongue

what is the active form of Niacin B3?

nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP)

what are required most metabolic redox process in cells where substrates are oxidized or reduced, involved in cellular respiration, glycolysis, and fatty acid oxidation?

NAD and NADP

niacin or tryptophan deficiency leads to what?

pellagra

what are the characterizations of pellagra?

• pigmented rash or brown discoloration on the skin

• skin develops a roughened, sunburned-like appearance

what are the signs of niacin deficiency?

(4 Ds)

• diarrhea

• dermatitis

• dementia

• death (if not treated)

what is the main function of pantothenic acid B5?

synthesis of CoA

CoA is a component of what?

acyl carrier protein of fatty acid synthase

what describes the deficiency of pantothenic acid B5?

rare deficiences only in sever malnutrition

vitamin B6 is mostly concerned with what?

protein metabolism (synthesis of non-essential amino acids)

what vitamin contributes to hemoglobin (heme biosynthesis) and neurotransmitter formation?

vitamin B6

what is a deficiency in vitamin B6?

sideroblastic anemia

biotin B7 is a coenzyme for and involved in what?

carboxylation enzymes involved in the metabolism of fatty acids, glucose, and amino acids

a rare deficiency of biotin B7 could be due to what?

excessive ingestion of raw egg white, as avidin (protein) can bind strongly to biotin and prevent its absorption

what is the active form of folic acid B9?

tetrahydrofolate (THF)

tetrahydrofolate (THF) is a coenzyme in what?

single-carbon transfers in the synthesis of nucleic acids (DNA and RNA) and metabolism of amino acids

folate could be depleted and lead to deficiency due to what?

• alcoholism

• pregnancy

what is folate important for in pregnancy?

the growth of the fetus spinal cord and brain; deficiency causes neural tube defects

folate deficiency anemia can lead to what?

cells unable to divide and leads to abnormal large red blood cells

what is the active form of vitamin B12?

cobalamin

B12 is a cofactor for enzymes, such as methionine synthase which does what?

converts homocysteine to methionine which is required to produce SAM (essential for hormone synthesis)

people with gastritis have weak stomach lining due to what?

they can’t produce intrinsic factor which is essential to bind to B12 for absorption

what can B12 deficiency lead to?

• hyperhomocysteinemia

• neurological dysfunction

• pernicious anemia

what is vitamin C known as?

ascorbic acid

vitamin C (ascorbic acid) is considered what?

an antioxidant, a reducing agent

vitamin C is required for what?

maintenance of normal connective tissue as well as for wound healing

what facilitates the absorption of iron?

vitamin C

scurvy disease is due to what?

vitamin C deficiency

vitamin A includes what?

retinal, retinol, and retinoic acid

what is the role of vitamin A?

• critical for vision

• differentiation of epithelial cells to specialized tissue such as pancreatic cells

what are examples of vitamin A deficiency?

• night blindness

• corneal degeneration

• prolong deficiency leads to irreversible loss of visual cells

what are symptoms of excess of vitamin A?

nausea, vomiting, blurred vision

an excess of vitamin A during pregnancy can lead to what?

teratogenic effect significant congenital malformation to the developing fetus

what are the two hydroxylation in the body that vitamin D must undergo for activation?

1. liver converts vitamin D to calcidiol

2. kidney forms the physiological active calcitriol

what is vitamin D essential for?

• helps normalize serum calcium levels

• increase intestinal absorption of calcium and phosphate

• increase bone mineralization

• increase bone resorption

what are examples of vitamin D deficiency?

• rickets (bowed legs) in children

• osteomalacia in adults (bone pain and muscle weakness)

what are examples of excess of vitamin D?

• hypercalcemia (high calcium concentration in the blood)

• hypercalciuria (excess calcium excretion in the urine)

what is the role of vitamin E?

• antioxidant (protects RBCs and neuronal membranes from free radical damage)

• helps prevent LDL oxidation that is involved in atherosclerotic plaque formation

what is a vitamin E deficiency?

hemolytic anemia (RBCs become fragile, premature death)

how is an excess of vitamin E toxic?

can interfere with Vitamin K metabolism and lead to excess bleeding (hemorrhage)

the active form of vitamin K (menaquinones or K₂) is produced by what?

bacteria of the intestinal flora

vitamin K is a cofactor for the glutamate carboxylase enzyme that is essential for synthesis of what?

prothrombin and coagulation factors II, VII, IX, X

a vitamin K deficiency causes what?

glutamate carboxylase activity decreases clotting factors and cannot function

vitamin K deficiency is most common in what population and due to what?

newborns due to insufficient intestinal bacteria

in acute fat malabsorption, what is the first fat-soluble vitamin to be deficient?

vitamin K