뒤로Foundations of Biochemistry: Body Fluids and pH
스터디 가이드 - 스마트 노트
자료에 맞춘 맞춤형 노트, 핵심 정의, 예시, 맥락을 확장해 제공합니다.
Foundations of Biochemistry
Body Fluids and pH
This study guide covers the foundational concepts of biochemistry related to body fluids, their composition, and the regulation of pH. Understanding these principles is essential for grasping the chemical basis of life and physiological processes.
Key Elements in the Human Body
Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N) are the four most abundant elements, comprising approximately 96% of body mass.
Relative abundance: Oxygen (65%), Carbon (18%), Hydrogen (9.5%), Nitrogen (3.2%).
These elements are fundamental to the structure and function of biomolecules.
Composition of the Human Body
Water: 60% of body mass; most abundant inorganic compound.
Protein: 16%.
Triglycerides (lipids): 13%.
Salts: 6.2%.
Carbohydrates: 1.5%.
Nucleic acids: 0.2%.
Inorganic vs Organic Components
Inorganic: Water and salts.
Organic: Carbohydrates, lipids (triglycerides), proteins, nucleic acids.
Organic molecules contain carbon and are typically larger and more complex.
Body Fluids: Classification and Examples
Intracellular Fluid (ICF): Located within cells; main example is cytosol.
Extracellular Fluid (ECF): Located outside cells; includes interstitial fluid, plasma, lymph, cerebrospinal fluid, synovial fluid, digestive fluids, and other transcellular fluids.
Fluid Balance
Maintained when intake equals output.
Intake: Beverages, food, metabolic water.
Output: Urine, skin/lungs (insensible loss), sweat, feces.
Imbalance: Dehydration (excessive loss) and water intoxication (excessive gain) can be life-threatening.
Properties of Water
Polar molecule: Unequal sharing of electrons creates partial charges.
Excellent solvent: Dissolves ionic and polar substances.
High heat capacity: Absorbs and releases heat slowly.
High heat of vaporisation: Requires significant energy to change from liquid to gas.
Cohesive and adhesive: Water molecules stick to each other and to surfaces.
Participates in chemical reactions: Hydrolysis and dehydration synthesis.
Lubricates and cushions tissues: Essential for joint and organ function.
Solutions and Solubility
Solution: Homogeneous mixture of solute(s) in a solvent.
Solvent: The dissolving medium (usually water in biological systems).
Solute: The substance dissolved.
Dissolve: To disperse within a solvent.
Dissociate: To separate into ions in solution.
Water as the Universal Solvent
Water's polarity enables it to dissolve many ionic and polar substances.
Surrounds charged particles, keeping them in solution.
Electrolytes vs Non-Electrolytes
Electrolytes: Substances that dissociate into ions and conduct electricity (e.g., NaCl, KCl).
Non-electrolytes: Substances that dissolve but do not form ions (e.g., glucose).
Major Electrolytes in Body Fluids
Fluid Compartment | Major Cation | Major Anion |
|---|---|---|
Intracellular Fluid (ICF) | K+ (Potassium) | Additional info: Phosphate, proteins |
Extracellular Fluid (ECF) | Na+ (Sodium) | Cl- (Chloride) |
pH and Acid-Base Balance
pH: Measure of hydrogen ion concentration; lower pH = more acidic, higher pH = more alkaline.
pH 7: Neutral.
Pure water: pH 7.
Acids: pH < 7.
Bases: pH > 7.
Neutral salts: Generally produce solutions around pH 7, but some may shift pH.
Common Acids and Bases in Physiology
Acids: Carbonic acid, hydrochloric acid (stomach).
Bases: Bicarbonate ion, phosphate ion.
Physiological Significance of pH
Protein structure, enzyme activity, ion transport, and cellular metabolism depend on maintaining a narrow pH range.
Buffer Systems
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system
Buffers resist changes in pH by neutralizing excess acids or bases.
Normal Plasma pH
Normal range: 7.35–7.45.
Factors Influencing Body pH
Respiratory function: CO2 levels affect pH.
Kidney function: Regulates H+ and HCO3-.
Metabolism, disease, exercise, fluid/electrolyte disturbances also impact pH.
Acid-Base Imbalance
Occurs when body pH moves outside the normal physiological range.
Acidosis: Blood pH < 7.35.
Alkalosis: Blood pH > 7.45.
Major Acid-Base Disorders
Disorder | Cause |
|---|---|
Respiratory Acidosis | Impaired CO2 removal (e.g., hypoventilation) |
Respiratory Alkalosis | Excessive CO2 removal (e.g., hyperventilation) |
Metabolic Acidosis | Excess acid production or loss of bicarbonate |
Metabolic Alkalosis | Excess bicarbonate or loss of acid |
Key Equations
pH Calculation:
Bicarbonate Buffer System:
Quick Revision Points
OCHN = four major elements.
Water is the most abundant inorganic compound.
ICF is inside cells; ECF is outside cells.
K+ is the major intracellular cation; Na+ is the major extracellular cation.
Normal plasma pH: 7.35–7.45.
Buffer systems: bicarbonate, phosphate, proteins.
Four acid-base disorders: respiratory/metabolic acidosis and respiratory/metabolic alkalosis.
Example: The bicarbonate buffer system is crucial for maintaining blood pH. During intense exercise, increased CO2 production can lead to acidosis, which is compensated by increased respiration to remove CO2.
Additional info: The phosphate and protein buffer systems are especially important in intracellular and plasma environments, respectively. Protein buffers include hemoglobin in red blood cells.
