pH

pH and Its Biological Significance (Page 1)

pH Scale Overview
- pH is a measure of how acidic or basic a solution is.
- Ranges from 0 to 14:
  - Neutral: pH of 7 (pure water)
  - Acidic: pH < 7 (more H⁺ than OH⁻)
  - Basic (Alkaline): pH > 7 (more OH⁻ than H⁺)
- At 25°C, pure water has:
  - [H⁺] = 0.0000001 M
  - [OH⁻] = 0.0000001 M
Biological Significance of pH
- Enzyme Activity
  - Enzymes have optimal pH ranges for activity.
  - Deviations can reduce activity or denature enzymes.
- Cellular Functions
  - Cells maintain specific internal pH for proper function.
  - Example: Cytoplasm is slightly basic; stomach is very acidic.
- Homeostasis
  - Organisms regulate internal pH.
  - Human blood maintains a pH around 7.4; deviations can cause health issues (acidosis or alkalosis).
- Metabolism
  - pH affects metabolic reaction rates and nutrient availability.
  - Soil pH influences nutrient availability to plants.
- Fundamental Role
  - pH is crucial for enzyme function, cellular health, and nutrient availability.
Definition of Bases
- Bases have a pH > 7 and can accept H⁺ ions.
- Example: Bleach (pH 12.6).

Definition of Acids
- Acids release H⁺ ions in water, resulting in a sour taste and a pH < 7.
- Examples:
  - Hydrochloric acid (HCl)
  - Sulfuric acid (H₂SO₄)
  - Nitric acid (HNO₃)
  - Citric acid
- Pure water is neutral with a pH of 7.
pH Scale Changes
- A change of 1 on the pH scale represents a tenfold change in H⁺ concentration.

Carbon Atom Prefixes and Suffixes
- Number of Carbon Atoms:
  - 1: meth- (single bond) -ane
  - 2: eth- (single bond) -ane
  - 3: prop- (double bond) -ene
  - 4: but- (double bond) -ene
  - 5: pent- (triple bond) -yne
  - 6: hex- (triple bond) -yne
Bond Strength and Types
- Bond Dissociation Energy
  - Energy required to break a bond between two atoms.
- Types of Bonds
  - Single Bonds: Share one pair of electrons; weakest bond type.
  - Double Bonds: Share two pairs of electrons; stronger than single bonds.
  - Triple Bonds: Share three