Vitamin C: Properties and Functions

Vitamin C Overview

• Also known as ascorbic acid and anti-scorbutic factor.
• Hexose derivative with structure closely resembling monosaccharides.
• Exists in two forms: L-ascorbic acid (reduced form) and L-dehydro ascorbic acid (oxidized form).
• Its acidic properties come from the enolic hydroxyl group.
• Strong reducing agent.
• L-ascorbic acid undergoes reversible oxidation to form dehydro ascorbic acid.
• Most plants and animals can synthesize it from glucose.
• Destroyed by heat.

Vitamin C Functions

• Collagen formation: Plays a key role in collagen formation
• Collagen is a fibrous protein in connective tissues.
• Collagen binds and supports cells and tissues within the body.
• Hydroxylation reactions involving proline and lysine are aided by vitamin C.
• Vitamin C deficiency leads to impaired collagen synthesis, delaying wound healing.
• Antioxidant Properties: works with vitamins A & E as a powerful antioxidant.
• Neutralizes free radicals.
• Iron absorption: Helps convert ferric iron to the more readily absorbed ferrous form.
• Other functions include bone formation, tryptophan metabolism, and steroid synthesis.

Minerals Overview

• The human body contains over 50 chemical elements which are all vital for body functions.
• Minerals fall into two categories: major minerals (more than 100mg) and trace minerals (less than 100mg).

Calcium Introduction

• Total body calcium ranges from 1 to 1.5 kg.
• 99% resides in bones and teeth with the remaining 1% distributed in body fluids and tissues.
• Calcium in teeth is not mobilized, while bone calcium is constantly mobilized.
• Blood calcium level is 10mg/dl and is regulated by thyroid hormone (calcitonin) and parathyroid hormone.
• Calcitonin decreases calcium levels.
• Parathyroid hormone increases calcium levels.

Calcium Functions

• Formation and maintenance of bones and teeth: Bone is a mineralized connective tissue composed of calcium and phosphate, along with organic (collagen) and inorganic (minerals) components. Bone serves as a reservoir for calcium.
• Muscle contraction: Ca2+ interacts with troponin C to initiate muscle contraction and activates ATPase to enhance actin and myosin interaction.
• Blood coagulation: Several reactions in the blood clotting process require Ca2+.
• Nerve transmission: Required for transmission of nerve impulses.
• Membrane integrity and permeability: affects the membrane structure and transport of water and ions.
• Activation of enzymes: Activates lipase (pancreatic), ATPase, and succinate dehydrogenase.
• Heart Action: Affects myocardium and prolongs systole.
• Hypercalcemia can lead to cardiac arrest during systole.
• Hormone Release: Facilitates the release of insulin, parathyroid hormone, and calcitonin.
• Absorption: Aids in the absorption of vitamin B12.

Factors Affecting Calcium Absorption

• Promoters: Vitamin D, parathyroid hormone, acidity (low pH), lactose, lysine and arginine.
• Inhibitors: Phytates and oxalates (form insoluble salts), high dietary phosphate, alkaline conditions (high pH), and high dietary fibre.

Phosphorus Introduction

• The adult human body contains about 1kg of phosphate found in every cell.
• Approximately 80% is combined with calcium in teeth and bone.
• The remaining phosphate is found in cells and extracellular fluid.
• Phosphorus and Calcium share similar functions.
• Their absorption and excretion depend on Vitamin D and parathyroid hormone.
• These two minerals are referred to as "metabolic twins.”

Phosphorus Functions

• Essential for the development of bones and teeth.
• Required for the formation of DNA and RNA.
• Present in cell membranes as phospholipids.
• Plays a key role in metabolism as well as activating proteins, enzymes, and vitamin B through phosphorylation.
• The phosphate buffer system is key for maintaining blood pH balance.

Potassium Introduction

• K+ serves as a major intracellular ion.
• About 98% of potassium is located inside cells, while only 2% is in the extracellular fluid (ECF).
• Accounts for only 5% of the total mineral content in the body.
• Maintains total body fluid volume and promotes acid and electrolyte balance, also aiding normal cell functions.

Potassium Functions

• Influences muscular activities.
• Supports acid-base balance.
• Lowers systolic and diastolic blood pressure in hypertensive patients.
• Certain enzymes like pyruvate kinase require K+ as a cofactor.
• Required for proper biosynthesis of protein.