Biochemistry I: Minerals

Biochemistry I: Minerals

• Course Title: Biochemistry I
• Course Code: FM 104
• Department: Biochemistry
• Lecturer: Ass. Prof. Dr. Omnia Safwat El-Deeb
• Lecture Title: Minerals

Lecture Objectives

• Know the biochemical classification of minerals
• Recognize the functions of important minerals
• Identify the signs of clinical deficiency and overproduction of important minerals and their absorption mechanisms

Contents

• Classification of minerals
• Calcium (functions and deficiency)
• Phosphorus (functions)
• Iron (absorption, functions, and deficiency)
• Zinc (important enzymes require calcium)
• Fluoride and tooth decay

Definition of Minerals

• Inorganic compounds essential for normal body growth and maintenance

Classification of Minerals

• A-Macrominerals (Bulk Elements): Required in amounts greater than 100 mg/day.
• B-Microminerals (Trace Elements): Required in amounts less than 100 mg/day.

Classification of Minerals List

I-Calcium

• Sources: Milk, milk products, cheese, almonds, green beans, enriched breads and grains, broccoli, soybeans, sardines, oranges, yogurt, okra, and dried apricots are rich sources of calcium.
• Daily Requirements: Adults need 500 mg/day, children about 1200 mg/day. Requirements increase to 1500 mg/day during pregnancy and lactation.
• Absorption & Excretion: Absorption occurs in the duodenum's first and second parts. Calcium absorption requires a carrier protein and energy (calcium-dependent ATPase). Adults excrete 400 mg in the stool and 100 mg through urine.
• Distribution in the body: 99% of calcium is in bones and teeth, 1% is in body fluids and other tissues. Plasma calcium levels range from 9-11 mg/dL.
• Forms: Diffusible Calcium (50% of total serum calcium) is ionized (essential for blood clotting). Non-diffusible calcium is combined with albumin and cannot cross the cell membrane.
• Functions:
  • Strong bones and teeth.
  • Aids in muscle contraction.
  • Cellular metabolism.
  • Neural transmission.
  • Plays a key role in blood clotting.
  • Normalizes heart rhythm.
• Calcium and Enzymes Activity: Calmodulin is a calcium-binding regulatory protein that binds to 4 calcium ions. Calcium binding activates enzymes, including various regulatory kinases. Other enzymes (e.g., pancreatic lipase, coagulation enzymes, rennin) can be directly activated by calcium without calmodulin's involvement.
• Factors affecting calcium absorption:
  • Enhancers: High protein diet, acidic pH, high dietary lactate or citrate, vitamin D (calcitriol), parathormone
  • Inhibitors: Excess fat in the diet, alkalinity, high phosphate, oxalate, and phytates in the diet, vitamin D deficiency, parathormone.
• Regulation: A complex regulatory system maintains normal calcium and phosphate levels in the body. Key hormones include parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol (calcitriol), and calcitonin. These hormones act on the intestinal tract, bone, and kidneys.

II-Phosphorus

• Sources: Milk, milk products, fish, meat, liver, kidney, leafy vegetables, and egg yolks are good sources. Phospho-proteins (e.g., casein in milk, vetillin in eggs).
• Daily Requirements: Adults: 800-1000 mg/day. Pregnant women: 1500-2000 mg/day.
• Absorption: Absorbed by active transport as phosphate.
• Absorption Function: Helps filter waste in the kidneys and stores/releases energy.
• Distribution in the body: 600g of phosphorus is in skeletons (bones/teeth)
• Plasma Phosphorous levels: Normal range is 3-5 mg/dL.
• Relationship with Calcium: Phosphorus and Calcium have an inverse relationship. High phosphorus can cause calcium excretion by the kidneys.
• Function:
  • Bone formation
  • Phosphate buffers
  • Cellular components (nucleic acids, phospholipids, phosphoproteins, coenzymes, high-energy phosphate compounds).

III-Sodium & Potassium

• Sodium: Affects cardiac muscle activity, maintains heart beat, maintains acid-base balance of the body
• Potassium: Maintains intracellular osmotic pressure, plays a role in protein biosynthesis, transmits nerve impulses.

IV-Iron

• Source: Meat, liver, kidney, nuts, beans, and dates are good sources of iron.
• Requirements: Adults: 10 mg/day. Pregnant/lactating women: 30 mg/day.
• Absorption: Iron absorption occurs in the duodenum and upper jejunum. Diet contains approximately 10-20 mg of iron per day. Only about 10-20% is absorbed.
• Mechanism (Mucosal Block theory): Absorbed as ferrous (Fe++), oxidized to ferric (Fe+++), and combines with apoferritin to form ferritin. Ferritin releases ferrous ions to capillaries, and apoferritin is regenerated based on body needs. Intestinal apoferritin gets saturated with iron, absorption is blocked.
• Iron-containing proteins: Hemoglobin, myoglobin, cytochromes, catalase, peroxidase, Ferritin, transferrin, hemosiderin
• Factors affecting iron absorption:
  • Enhancers: Vitamin C (ascorbic acid), meat, poultry & fish (amino acids), gastric acid, cooking in iron vessels, low body stores of iron.
  • Inhibitors: Calcium, some antacids, oxalate (spinach), animal products(milk, egg), tannins (tea, coffee), Zn/Cu containing foods.

Clinical Abnormalities

• Iron Deficiency Anemia: Causes: Decreased intake/absorption, increased loss (hemorrhage, menstruation), increased requirements (pregnancy, lactation), parasitic worm infestations
• Iron Overload: Causes: Repeated blood transfusions, intravenous iron administration. Hemochromatosis: a hereditary disease characterized by abnormal iron absorption. Iron is deposited as hemosiderin in the liver (causing cirrhosis), pancreas (fibrosis, diabetes), and skin (bronze discoloration).

II-Zinc

• Sources: Meat, liver, eggs, seafood, milk, whole-grain cereals
• Absorption: Primarily in the small intestine
• Functions: Essential for growth, reproduction, tissue repair, wound healing; forms a complex with insulin for storage/release in the pancreas

Questions

• Classify minerals
• Enumerate factors affecting calcium absorption
• Function of phosphorus