Nutrition Biochemistry Notes PDF

Nutrition and metabolism Fat sol vitamins Vitamins Vitamins are organic nutrients that are: 1- Required in small amounts 2- Cannot be synthesized by the body and must be supplied by the diet 3- They are essential for a variety...

Nutrition and metabolism Fat sol vitamins Vitamins Vitamins are organic nutrients that are: 1- Required in small amounts 2- Cannot be synthesized by the body and must be supplied by the diet 3- They are essential for a variety of biochemical functions which are required for the normal growth, development and maintenance of life. 4- Not provide energy Classification of vitamins: The solubility of vitamins was used as a basis for their classification, Vitamins are divided into two main groups: 1. Fat soluble vitamins: Vitamins K, E, D, A. 2. Water soluble vitamins: Vitamins B group and C. 1  Nutrition and metabolism Fat sol vitamins Fat-soluble vitamins K E D A 1-Vitamin K (Anti-haemorrhagic vitamin) Sources : K1 in plants as cabbage, cauliflower, spinach K2 in egg yolk & liver. It is synthesized by the bacteria in the gut. K3 is synthetic. Function: 1- Essential for clotting of blood. - Vitamin K is essential for synthesis of blood clotting factors II, VII, IX and X in the liver - Conversion of prothrombin to thrombin - Formation of fibrinogen to fibrin, leading to clot formation 2- Stimulates bone formation and decreases bone resorption. Deficiency of vit K: It is rare but may occur in : ✓ New born because there is no intestinal bacteria. ✓ Biliary obstruction and liver diseases ✓ Prolonged use of antibiotics which kills the intestinal bacteria. ✓ Decrease intake. Manifestation of vitamin K deficiency: -Hemorrhage and bleeding. -Prolonged prothrombin time Hypervitaminosis K (Toxicity): rare 2  Nutrition and metabolism Fat sol vitamins 2-Vitamin E (Tocopherol) (Anti-sterility vitamin) Sources :Excellent sources are vegetable oils e.g. cotton seed oil, sunflower oil, wheat germ oil, soybean oil, pean nut, olive oil while Moderate sources like liver, milk, egg yolk. Function: 1- It is the most important natural anti-oxidant. ( It protects the RBCs from toxic haemolysis particularly in patients with reduced glucose-6-phosphate dehydrogenase ) 2- Important in reproduction in rats and some animals (Anti-sterility vit.). Manifestations of vit E Deficiency: ✓ Haemolytic anaemia (due to oxidation of polyunsaturated fatty acids (PUFAs) ✓ Sterility in mice. Hypervitaminosis E (Toxicity): rare 3  Nutrition and metabolism Fat sol vitamins 3- Vitamin D (Anti-rachetic vitamin): Sources : Fishes liver oils, cod liver oil and halibut liver oil, liver and egg yolk. (7-dehydrocholesterol in animal and man is derived from cholesterol and passes to skin where by the effect of UV rays converted to vitamin D ) Vitamin D activation: Vitamin D2 and D3 are not biologically active. They are converted in vivo to the active form by two hydroxylation reactions: I- Hydroxylation of vitamin D3 at the 25-position in the liver results in the formation of 25-OH D3. II- 25 OH D3 is further hydroxylated at the one in the kidney resulting in the formation of 1-25 OH D3 (Calcitriol). 4  Nutrition and metabolism Fat sol vitamins Vitamin D function: Maintains adequate serum level of calcium by: 1. Increasing absorption and uptake of calcium by intestine. 2. Decreasing loss of calcium by the kidney. 3.Stimulate resorption of bone and mobilization of Ca and PO4 from bone when parathyroid hormone (PTH) is released in response to low serum calcium. Causes of vitamin D deficiency: intake Absorption (due to biliary obstruction) exposure to sunlight. activation of vitamin D ( liver and kidney diseases). Manifestations of vitamin D deficiency: In Children: Rickets ✓ Failure of bones to grow properly ✓ Delay setting, walking & teething. ✓ Deformed bones (skull, chest and legs) ✓ Decrease of Ca & P in the blood In Adult: Osteomalacia. Bone deformation, fracture, Decrease of Ca & P in the blood. 5  Nutrition and metabolism Fat sol vitamins Vitamin D toxicity: Vitamin D is the most toxic of all vitamins. Manifestations of Vitamin D of toxicity: Loss of appetite, nausea, thirst. Calcification of soft tissue: Hypercalcemia may lead to calcium deposit in Lungs, heart, blood vessels Hardening of arteries Stone formation in kidneys ✓ Does not occur from sunlight or dietary sources ✓ Does occur with supplementation 4- Vitamin A (Anti-xerophthalmic vitamin): Sources : present only in animal sources as liver, kidney, butter, milk and egg yolk. Fishes liver oil as cod liver oil, halibut liver oil. Carotenes (provitamin A) are present in yellow and green vegetables and fruits as spinach, lettuce, potato, carrots and tomatoes. 6  Nutrition and metabolism Fat sol vitamins Function: 1- Vision: Colored vision and night vision 2. Normal growth important for normal growth 3. Reproduction 4. Necessary for healthy skin & hair growth 5. Maintenance of integrity of epithelial tissues as skin, mucus membranes. 6. Antioxidant (carotene) 7. anticancer activity Manifestations of vit A deficiency: 1. Defective night vision. 2. Failure of growth. 3. Reproductive disorders. 4. Loss of health and integrity of epithelial tissues as the skin and mucus membrane. 5. Dryness of the eye (Xerosis). Manifestations of Vitamin A toxicity: Due to excessive use of vitamin A supplements. 1. headache 2. drowsiness 3. nausea 4. skin & bone abnormalities 5. Congenital malformations. 6. Dry itchy skin 7. Hair loss 7  Nutrition and Metabolism Water sol vitamins Water soluble vitamins Water soluble vitamins includes: Vitamins B group and vitamin C. A-Vitamin C (L-Ascorbic acid) Sources: citrus fruits e.g. lemon, orange &tangerine. Functions: 1- It is required for the biosynthesis of collagen. 2- Absorption, transport and storage of iron. 3- Activation of folic acid to tetrahydrofolic acid (active form). 4- Act as hydrogen carrier : in oxidation-reduction reactions. 5- Act as an antioxidant. Vitamin C deficiency Scurvy: * It is due to collagen synthesis which is indicated by:1- Soft swollen gums and loose teeth. 2- Bleeding tendency and subcutaneous hemorrhage. 3- Swollen joints and muscle weakness 4- Delayed wound healing. Iron deficiency anemia: due to absorption of iron. 1 Nutrition and Metabolism Water sol vitamins B-Vitamin B-complex B-complex are made up of 8 water soluble vitamins: B1(Thiamine), B2 (Riboflavin), B3(Niacin), B5 (Pantothienic acid), B6 (Pyridoxine), B7 (Biotin), B9 (Folic acid)and B12 (Cobalamine). 1-Vitamin B1(Thiamine) (Anti Beri beri) Function: ❖ TPP (The active form of vit B1) serves as a coenzyme in the oxidative decarboxylation of α keto acids. Thiamine Deficiency ( production of ATP) : leads to Beri-beri which is present in two forms. 1- Dry Beri beri: produce neurological disorders. 2- Wet Beri beri: produce cardiovascular and gastrointestinal disorders. 2 Nutrition and Metabolism Water sol vitamins 2-Vitamin B2 (Riboflavin) Functions: The active forms are 2 coenzymes 1- FMN. 2- FAD. FMN and FAD serve as hydrogen carrier in oxidation reduction reactions Deficiency: ✓ Angular stomatitis ✓ Glossitis. ✓ Photophobia. 3-Vitamin B3 (Niacin)(Pellagra Preventing factor) Functions: ❖ Enter in the formation of 3coenzymes 1- NAD= co-enzyme I 2-NADP = co-enzyme II Both are hydrogen carrier in oxidation reduction reactions. 3-NMN = co-enzyme III (Important for the synthesis of bile salts) ❖ Nicotinic acid: -CNS stimulant. - Vasodilator. -↓ blood lipids. 3 Nutrition and Metabolism Water sol vitamins Niacin Deficiency: (Pellagra) 3D 1- Dermatitis 2 - Diarrhoea 3- Dementia 4- Vitamin B5 (Pantothienic acid) important in formation of Co-ASH which is a carrier in many enzymatic reactions in metabolism 5-Vitamin B6 (Pyridoxine) Functions: 1- It gives pyridoxal phosphate (PLP) which is the co-enzyme of enzymes of amino acid metabolism: a) Transamination. b) Deamination. 4 Nutrition and Metabolism Water sol vitamins c) Decarboxylation: Formation of Gama amino butyric acid (GABA) 2- Synthesis of haemoglobin. 3- Conversion of amino acid tryptophan into niacin (B3). Manifestations of vitamin B6 deficiency: 1. Impaired growth: due to altered amino acid metabolism. 2. Iron deficiency anemia due to impaired haemoglobin formation. 3. Neurologic disorders as convulsion ( due to formation of GABA). 4. Pellagra as a result of impaired niacin synthesis from tryptophan. 6- Vitamin B7 (Biotin) 5 Nutrition and Metabolism Water sol vitamins 7- Vitamin B 9 (Folic Acid ) Tetrahydrofolate (THF or H4 Folate) is the active form of folic acid Functions of THF: ✓ Essential for erythropioesis. ✓ Essential for DNA synthesis. Deficiency of folic acid : Impaired growth: due to inhibition of DNA synthesis. Megaloblastic anemia: due to defective erythropoisis. 8- Vitamin B12 (Cobalamin) Sources: It is not present in plants, It is present in liver, eggs, fresh shrimp, meat, chicken and milk (animal origin). It is synthesized by intestinal bacterial flora. Absorption Needs intrinsic factor (IF)(glycoprotein) secreted by parietal cells of the stomach. 6 Nutrition and Metabolism Water sol vitamins Vitamin B12 Functions: ✓ It act as carrier of methyl group (CH3) in transmethylation reactions ✓ Reduction of ribose to deoxyribose : conversion of ribonucleotide to deoxyribonucleotide ✓ Amino acid activation for protein synthesis. ✓ Essential for erythropoisis ✓ Regeneration of nerve fibers in the spinal cord and peripheral nerves. Vitamin B12 deficiency Causes: ✓ lack of intrinsic factor secreted from stomach leads to absorption of vitamin B12 as in: gastrectomy, gastritis and gastric malignancy. ✓ Vegetarians are at risk of vit B12 deficiency because the vitamin is present only in food of animal origin. 7 B12 deficiency Leads to: Pernicious anemia Its characterized by: a) Megaloblastic anemia b) Neurological manifestations. 8  Minerals According to body needs, minerals are divided into: A- Major elements [Macronutrients]: They are required in amounts > 100 mg / day. They include: calcium, phosphorus, sodium, potassium, chloride and magnesium B- Trace elements [Micronutrients]: They are required in amounts < 100 mg / day. They include: iron, copper, zinc, selenium, chromium, cobalt, iodine, fluoride, manganese and molybdenum A- Major elements [Macronutrients] 1- Calcium Normal Blood Calcium level: 9 – 11 mg/dl Sources: Milk and its product, egg yolk, cabbage, cauliflower Function: Bone mineralization: Ca is an essential element in bone and teeth. Ionized Ca (free Ca): 1- Blood coagulation and milk clotting. 2- Membrane permeability. 3- Muscle and Nerve excitability 4- Second messenger of many hormones 5- For activity of many enzymes eg: lipase, phosphorylase and amylase enzyme. 8 Factors affecting Ca absorption 1- Calcitriol (1, 25 dihydroxycholecalciferol): 2- PTH: through activation of vit D. 3- pH of intestinal contents. Alkaline pH leads to decrease Ca solubility and absorption. Acidic pH leads to increase Ca solubility and absorption. 4- Dietary factors: Lactose and high protein diet the absorption. Phytate, oxalate and fatty acids Ca absorption 2- Phosphorus Normal Blood level: 4 – 7 mg/dl in children 3– 4.5 mg/dl in adult Function: 1. Bone and teeth mineralization. 2. Phosphate ester compounds for transfer and storage of energy. 3. Nucleic acids formation. 4. Coenzymes [TPP, NADP]. Ca : P ratio is important in ossification In serum, the ionic product of Ca P is about 50 mg/dl in children(decrease in rickets). 3  Control of blood calcium & phosphorus: by action of Calcitriol (active vitamin D3), PTH and calcitonin on intestine, kidney and bone. 1- Calcitriol: produced in kidney in response to low calcium & phosphorus level. It increases their levels by: Increasing their intestinal absorption. Decreasing renal excretion of Ca. Stimulate bone resorption. 2- PTH: Secreted in response to low plasma calcium level. It calcium & phosphorus levels 3- Calcitonin: Lowers both plasma calcium and phosphorus 4 Disorders of blood calcium level: Hypocalcemia: Blood level < 8.8 mg/dl. < 7.5 mg/dl→ tetany [ neuro-muscular irritability] → muscle &Laryngeal spasm. Chronic ↓→ bone deformity (Rickets and osteomalacia). Hypercalcemia: Blood level > 11 mg/dl Calcification of soft tissue: Ca deposit in: - Lungs, heart, Kidney, blood vessels - Hardening of arteries, stone formation in kidneys 3- Sodium Blood sodium level 132-146 mEq/L is the major cation in the extracellular fluid of the body Function of Na 1- Regulation of acid base balance 2- Maintenance of osmotic pressure of the body 3-Conduction of nerve impulse 4- Maintain normal irritability of the muscle 5- Maintain cell permeability. Source: Table salt (NaCl) in food is the main source. Also, cheese, bread and spinach. 5 4- Potassium - Main cation of intracellular fluid - plasma K level 3.5-5 mEq/L Function 1- Essential for many metabolic processes - protien synthesis - glycogenesis - glycogenolysis 2- Maintain normal cardiac muscle excitability 3- Maintain acid base balance, osmotic pressure, water content. 5- Magnesium Mg Distribution: 21 g. 70% with calcium & phosphrus in bones. 30% in all tissues and body fluids (intracellular and extracellular). Mg ions are activators for: 1. Phosphate transferase enzymes e.g. Kinases, phosphorylase. 2. Co factor in RNA & DNA synthesis 3. Important in Nerve Impulse conduction 6- Chloride Function: Regulation of acid base balance. Maintenance of osmotic pressure of body fluids and water balance. Activates salivary amylase. 6  B- Trace elements [Micronutrients] The trace elements are classified according to their biological role into three groups: Essential trace elements: Iron, copper, selenium, zinc, manganese, iodine, chromium, fluoride, molybdenum and cobalt. Possibly essential: Nickel, vanadium and silicon. Non essential trace element: Aluminum, lead..etc Trace Function Deficiency element Iron enters in the structure of: Decrease serum iron: - Hemoglobin & myoglobin. Iron deficiency anemia. - Respiratory cytochromes. Increased serum iron: Iron (Fe) Haemosiderosis - Cytochrome P450. - Peroxidases and catalases. +Factors affecting iron absorption Essential for: 1. Growth retardation - Reproduction, tissue repair 2. Delayed wound healing Zinc and wound healing. 3. Impaired sexual - Insulin storage & release development Copper (Cu) Essential for: 1- Hb synthesis, 2- Bone formation, 3-Maintenance of myelin. 7  Essential for normal bone structure Manganese Function of CNS and (Mn) spermatogenesis. Involved in activation of many enzymes Iodine Formation of thyroid hormones Goitre (If prolonged deficiency) Fluoride Distribution: Bone, teeth and very low amount in soft tissues Functions: - protective against dental caries - protective against osteoporosis & osteomalacia. Selenium (Se) -Component of: glutathione peroxidase, - Essential for: Antioxidant activity Cobalt (Co) As a constituent of vitamin B12, it is involved in Erythropoiesis NB: Factors increasing iron absorption: Vitamin C (lemon juice – orangejuice) Factors decreasing iron absorption: Ca- high phytate, oxalate, phosphatein diet