2. Major Concepts
A. Study and classify elements present in the
body.
B. Study in detail the minerals or principal
elements.
C. Study in detail the trace elements.
3. Introduction
• Minerals are inorganic compounds that are required for the body as
one of the nutrients.
• The inorganic elements (minerals) constitute only small proportion
of the body weight.
• Human body needs a number of minerals for its functioning.
FUNCTIONS
Minerals perform many vital functions which are essential for
existence of organism-
1. Calcification of bones
2. Blood coagulation
3. Neuromuscular irritability
4. Acid-base equilibrium
5. Fluid balance
6. Osmotic regulation
4. CLASSIFICATION OF MINERALS
1. Macrominerals
• Required in excess of 100mg/day
• Na, K, Ca++, Cl, P, S, Mg.
2. Microminerals
• Required in amounts less than 100mg/day
• Fe, Cu, Zn, Mo, I, Fl, Cr, CO, Mn
5. SODIUM
• Sodium is the chief electrolyte which is found in large conc.
in extracellular fluid compartment.
• Approx. body distribution of sodium is
• The sodium is found in the body mainly in associated form as
NaCl and NaHCO3.
Compartments Concentration (mmol/L)
Intracellular 10
Extracellular 140
Plasma 140
6. Sources:
• Sodium is widely distributed in food material
more in animal sources than plants.
• Major source is table-salt used in cooking.
• It is also found in cheese, butter.
Daily Requirement:
• 1-3.5 g of Na is required daily for adults.
• Infants need 0.1-0.5 g
• Children 0.3-2.5 g daily
7. Absorption of Sodium
• Sodium is absorbed by sodium pump
• situated in basal and lateral plasma
membrane of intestinal and renal cells.
• Na-pump actively transports Na into
extracellular fluid.
8. SODIUM PUMP
• Na-pump is an enzyme, Na+-K+-ATPase.
• It is a glycoprotein composed of 2 α and 2 β chains.
• Its activity depends on presence of Na+ and K+ and requires ATP
and Mg++ ions as cofactor.
• The enzyme hydrolyses a high energy phosphate bond of ATP .
• It uses the energy to transport three Na+ ions outside and
simultaneously two K+ ions inside across the cell membrane.
• The Na-pump is very active in those cells where activities depend
largely on transmembrane Na+ fluxes, e.g. nervous, muscle fibers,
renal tubules cells, intestinal mucosal cells.
CLASS ACTIVITY: What is the chemical nature of
sodium pump?
9. Forms of Sodium Pump and Mechanism
• Na+-K+ ATPase exists in two forms: E1 and E2.
The E1 form:
• E1 has an inward –facing high affinity Na+ binding site and
reacts with ATP to form the activated product E1~P only
when Na+ is bound.
• Presents its ion binding and phosphate binding sites on the
cytoplasmic surface of the membrane.
• Three sodium ions from cytoplasm bind with the ion
binding sites of E1.
• This leads to the phosphorylation of aspartate residue of E1
with the help of ATP and Mg++.
• This results in conformational change and E1 becomes E2.
10. • E2 form has an outward –facing high affinity K+ binding
site
• E 2 exposes both ion binding and phosphate binding
sites on the extracellular surface of the membrane.
• Lowers the affinity of the ATPase for Na+ and releases
it into the ECF.
• On the contrary, now the K+ ions from ECF bind to the
respective ion binding site of the pump.
• This lowers the affinity of E2 for phosphate.
• This dephosphorylation changes the conformation of
E2 to E1 again and lowers its affinity for K+ ions.
• This leads to release of the K+ ions from ATPase into
the cell.
• CLASS ACTIVITY: Why Na+-K+ pump is known as P-Type ion
transporter?
12. Regulation of Sodium Pump
• The Na/K+-ATPase is upregulated by cAMP.
• Substances causing an increase in cAMP upregulate the
Na+/K+-ATPase.
• These include the ligands of the Gs-coupled GPCRs.
• The regulation of Na(+)-K(+)-ATPase in various tissues is
under the control of a number of circulating hormones
like aldosterone, thyroid hormone, catecholamines.
• Catecholamines provides short term regulation while
aldosterone, thyroid hormone provides long term
regulation.
13. Inhibitors
• Ouabain: A glycoside of a steroid and digitalis
is the cardiotonic drug which inhibits the Na+-K+
pump by blocking the step of
dephosphorylation.
14. CLASS ACTIVITES
• Na+-K+ pump is a tetramer. On which
subunits are the binding sites for Na+ and
K+?
• What is the effect of steroids on Na+-K+
pump ?
• How is Na+-K+ pump regulated?
• When Na+-K+ pump is dephosphorylated?
• How E2 form of Na+-K+ pump is converted to
E1 form?
15. • The sodium transported actively by Na pump diffuses into the cell
• Active absorption of Na+ is coupled with glucose absorption or
amino acid absorption.
Excretion of Na:
• Every 24 hours approximately, 25000 mmol of sodium are filtered
by the kidneys.
• However, due to tubular reabsorption less than 1 per cent of this
sodium appears in the urine (100-200 mM/day).
• Approximately 70 per cent of the filtered sodium is
reabsorbed in proximal tubule.
• Further 20–30 per cent of filtered Na+ is reabsorbed by ascending
loop of Henle.
17. CLINICAL ASPECT
Clinical conditions related to sodium are of two major types:
I. Hypernatraemia
II. Hyponatraemia.
Hypernatraemia
• Deficit of water relative to sodium
Causes
Specific conditions in which hypernatraemia occurs are
• Simple dehydration
• Diabetes insipidus
• Osmotic loading
• Excess sodium intake
• Steroid therapy
Hyponatraemia
Causes
• Excessive sweating
• Kidney diseases
• Congestive heart failure
• Gastrointestinal loss
18. POTASSIUM
• Potassium is the major intracellular cation.
• It is widely distributed in the body fluids and
tissues as follows:
19. Source
• It is widely distributed in the vegetable foods.
• An average amount of 4 g of potassium is present in the diet.
• Potassium is easily absorbed.
• Metabolism
As soon as it is absorbed, potassium enters the cells.
• It is excreted in the urine.
• The conc. of intracellular K+ is 150 mEq/L which is roughly equal to
the conc. Of sodium outside the cell.
• The normal conc. of plasma potassium is 3.5-5 mEq/L.
• The Na+-K+ ATPase or sodium pump maintains this concentration
gradient.
• Potassium is continuously filtered by the glomeruli of the kidney
and reabsorbed by the cells of proximal convoluted tubules.
• Potassium ions are also secreted in distal tubule in exchange
for sodium
20. FUNCTIONS
• It influences the muscular activity.
• Involved in acid-base balance.
• It has an important role in cardiac function.
• Certain enzymes such as pyruvate kinase
require K+ as cofactor.
• Involved in neuromuscular irritability and
nerve conduction process.
21. CLINICAL ASPECT
Hyperkalaemia
Causes
• Kidney failure
• Tissue damage:
• Addison’s disease
• Diabetes mellitus
Hypokalaemia
Low serum K+ usually results from the depletion of total body K+
Causes
• Dietary deficiency
• Loss of K+ in GI secretions
• Loss of K+ in urine
• Loss of extracellular potassium into the intracellular
space
• inherited disorder called familial periodic paralysis
22. Suggested Readings
• MN Chatterjea and R.Shinde. Text
book of Medical biochemistry.
Eighth Edition, 2013.
