Biochem fluid and electrolyte (may.14.2010)Presentation Transcript
FLUID AND ELECTROLYTES May.14.2010
2e 2e 105˚ WATER[H2O]
97% - Seawater.
2.7% - Ice.
0.3 -Fresh water.
A water molecule is an irregular , slightly skewed tetrahedron with oxygen at its center.
O H H
(3 or 2 also)
LEWIS STRUCTURE OF A WATER MOLECULE • • • O H • H H • • + + H Covalent bond A covalent bond is a chemical bond formed by the sharing of a pair of electrons between two atoms. • O O • • • • • • • • • • • • • H H The approximate shape and charge distribution of water.
THE DIPLOE NAUTRE OF A WATER MOLECULE.
HYDROGEN BONDS BETWEEN WATER MOLECULES Hydrogen bonds Hydrogen bonds between water molecules. The oxygen atoms are shown in blue.
RELATIVE BOND ENERTY (ionic) Bond strength increases left to right.
Carries nutrients and waste products.
Actively participates in chemical reactions.
Serves as a solvent for minerals, vitamins, amino acids glucose, and other small molecules.
Serves as a lubricant and cushion around joints.
Acts as a shock absorber(eyes, spinal column, amniotic sac)
Aids in maintaining body’s temperature.
BODY WATER CONTENT Its about 75% in the newborn. Total water content declines throughout life. Healthy males are about 60% water; healthy females are around 50% This difference reflects females’: Higher body fat Smaller amount of skeletal muscle Less than 50% in older individual. Water content is greatest in brain tissue (about 90%) and least in adipose tissue (10%).
DAILY WATER BALANCE Daily Balance of Water Intake and Production in Sedentary Healthy Adults In a Temperate Climate At least 500 ml of urine per day is required just to excrete urea, creatinine, and other Solutes. Insensible losses from the skin and from the lungs can occur even when resting at normal room temperature.
FLUIDS COMPARTMENTS Fluid between the cells (intercellular or interstitial) Cell membrane Nucleus ICF Blood vessel
FLUIDS COMPARTMENTS Water occupies two main fluid compartments. Intracellular fluid (ICF) – about two thirds by volume, contained in cells Extracellular fluid (ECF) – consists of two major subdivisions Plasma – the fluid portion of the blood Interstitial fluid (IF) – fluid in spaces between cells Other ECF – lymph, cerebrospinal fluid, eye humors, synovial fluid, serous fluid, and gastrointestinal secretions.
ECF AND ICF FLUID
Each fluid compartment of the body has a distinctive pattern of electrolytes
Extracellular fluids are similar (except for the high protein content of plasma)
Sodium is the chief cation
Chloride is the major anion
Intracellular fluids have low sodium and chloride
Potassium is the chief cation
Phosphate is the chief anion
COMPOSITION OF BODY FLUIDS Solutes are broadly classified into: Electrolytes – inorganic salts, all acids and bases, and some proteins Nonelectrolytes – examples include glucose, lipids, creatinine, and urea Electrolytes have greater osmotic power than nonelectrolytes Water moves according to osmotic gradients
ELECTROLYTES Nucleus The major components of plasma, intestitial fluid, and intracellular fluid. Crosshatching refers to other or minor components. Pr- , anionic proteins.
WATER DISORDERS Dehydration (loss of water) Edema(accumulation of water) Atypical accumulation of fluid in the interstitial space, leading to tissue swelling.
DEHYDRATION Cells lose H2O to ECF by osmosis; cells shrink 3 ECF osmotic pressure rises 2 Excessive loss of H2O from ECF 1 Mechanism of dehydration
BODY FLUID AND ELECTROLYTES Electrolytes are substances that become ions in solution and acquire the capacity to conduct electricity. Sodium. Potassium Chloride Bicarbonate Help keep fluids in proper compartments. -Intracellular water -Extracellular water
NORMAL VALUE mmol/L
SODIUM IN FLUID ANDELECTROLYTE BALANCE
Sodium holds a central position in fluid and electrolyte balance
Account for 90-95% of all solutes in the ECF
Sodium is the single most abundant cation in the ECF
Sodium is the only cation exerting significant osmotic pressure
Changes in plasma sodium levels affect:
Plasma volume, blood pressure
ICF and interstitial fluid volumes
SODIUM - FUNCTIONS
Accounts for 90 - 95% of osmolarity of ECF
Na+- K+ pump
exchanges intracellular Na+ for extracellular K+
creates gradient for co-transport of other solutes (glucose)
NaHCO3 has major role in buffering pH
SODIUM - IMBALANCE
plasma sodium > 145 mmol/L
from IV saline
water retension, hypertension and edema
plasma sodium < 136 mmol/L
result of excess body water, quickly corrected by excretion of excess water
POTASSIUM - FUNCTIONS
Most abundant cation of ICF
Determines intracellular osmolarity
Membrane potentials (with sodium)
90% of K+ in glomerular filtrate is reabsorbed by the PCT
DCT and cortical portion of collecting duct secrete K+ in response to blood levels
Aldosterone stimulates renal secretion of K+
POTASSIUM AND MEMBRANE
most abundant anions in ECF
required in formation of HCl
CO2 loading and unloading in RBC’s
major role in regulating pH
OSMOSIS AND WATER BALANCE
Is the movement of water across a semipermeable membrane
Is affected by the concentration gradient of dissolved substances
OSMOSIS Water can flow both ways across the divider, but has a greater tendency to move from side A to side B, where there is a greater concentration of solute. The volume of water becomes greater on side B, and the concentrations on side A and B become equal. With equal numbers of solute particles on both sides, the concentrations are equal, and the tendency of water to move in either direction is about the same. 3 2 1 Now additional solute is added to side B. Solute cannot flow across the divider (in the case of a cell, its membrane).23
OSMOSIS When immersed in water, raisins get plump because water moves toward the higher concentration of sugar inside the raisins.
When sprinkled with salt, vegetables “sweat” because water moves toward the higher concentration of salt outside the eggplant.
Is the ability of a solution to cause a cell to gain or lose water
IF A SOLUTION IS ISOTONIC
The concentration of solutes is the same as it is inside the cell, and water will move in and out of the cell at the same rate
IF A SOLUTION IS HYPERTONIC
The concentration of solutes is greater than it is inside the cell, and the cell will lose water
IF A SOLUTION IS HYPOTONIC
The concentration of solutes is less than it is inside the cell, and the cell will gain water
Hypertonic solution Hypotonic solution Isotonic solution Animal cell. An animal cell fares best in an isotonic environ- ment unless it has special adaptations to offset the osmotic uptake or loss of water. (a) H2O H2O H2O H2O Normal Shriveled Lysed H2O H2O H2O Plant cell. Plant cells are turgid (firm) and generally healthiest in a hypotonic environ- ment, where the uptake of water is eventually balanced by the elastic wall pushing back on the cell. (b) H2O Turgid (normal) Flaccid Plasmolyzed THE WATER BALANCE OF LIVING CELLS