BIOCHEM LAB

Study Notes

pH and pOH

pH measures the acidity/basicity of a solution; scale ranges from 0 to 14.
pH values:
- Below 7 indicates an acidic solution.
- Equal to 7 indicates a neutral solution.
- Above 7 indicates a basic solution.
pH stands for "potential of hydrogen"; pOH stands for "potential of Hydroxide".

Definitions of Acids and Bases

Acids donate hydrogen ions (H+), while bases accept hydrogen ions.
Svante Arrhenius: Acids produce H+ ions in aqueous solution; bases produce OH- ions.
Gilbert N. Lewis: Acids are electron-pair acceptors; bases are electron-pair donors.
Bronsted-Lowry theory: Current accepted classification for acids and bases.

pH Scale and Buffers

S.P.L. Sørensen introduced the pH scale to measure the strength of acidic/basic solutions.
Buffers resist changes in pH when acids/bases are added, composed of weak acid/alkali + salt (e.g., acetic acid + sodium acetate).
Le Chatelier's Principle explains buffer equilibrium shifts due to condition changes.
Carbonic acid acts as a primary buffer in blood.

Litmus Testing

Litmus tests identify acids/bases using litmus paper:
- Blue litmus turns red in acidic solutions.
- Red litmus turns blue in basic solutions.
- No color change indicates a neutral solution.
Indicator paper changes color at specific pH levels, compared to a standard.

pH Meter Calibration

pH meters must be calibrated before use.
Calibration involves using three standard pH solutions: 7, 4, and 10.

Carbohydrates Overview

Carbohydrates are one of the three main macronutrients (alongside proteins and fats).
Structural classifications include:
- Aldehydes: Carbonyl group at the end of the carbon chain.
- Ketones: Carbonyl group within the carbon chain.
Monosaccharides are the simplest form of sugar, further classified:
- Pentoses: Five carbon atoms (e.g., ribose and xylose).
- Hexoses: Six carbon atoms (e.g., glucose, galactose, and fructose).

Tests for Carbohydrates

Selwanoff’s Test: Detects ketohexoses; distinguishes ketosis from aldoses.
Molisch’s Test: Identifies presence of carbohydrates.
Bial’s Test: Differentiates pentoses/pentosans from hexoses.
Benedict’s Test: Determines presence of reducing sugars; all monosaccharides are reducing sugars.
Barfoed’s Test: Detects reducing monosaccharides; distinguishes them from disaccharides.
Fehling’s Test: Analyzes reducing sugars in solution.
Tollens’ Test: Distinguishes between aldehydes and ketones.
Mucic Acid Test: Specifically detects galactose and lactose.

Fermentation and Sucrose Inversion

Fermentation occurs in yeast, bacteria, and animal muscles.
Sucrose inversion is the chemical breakdown of sucrose into glucose and fructose.

Lipids

Lipids are amphipathic molecules, including fatty acids, diglycerides, triglycerides, phospholipids, and cholesterol.
Acrolein Test: Used to detect glycerol or fat.
Liebermann-Burchard Test: Identifies the presence of cholesterol.

Description

This quiz explores the concepts of pH, acidity, and basicity in chemistry. Learn about the significance of pH levels, the definitions of acids and bases, and the contributions of Svante Arrhenius to the field. Test your understanding of these fundamental chemical principles.