BIOCHEM EXPERIMENT NO.1

Background

Water is essential to all living systems. It is one of the most abundant molecules and the one most critical to life on Earth. Water is a highly polar molecule with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This polarity makes water an excellent solvent as its molecules can form electrostatic interactions with other polar molecules (e.g., alcohol and sugars) and ions including salts.

In biochemistry, water is a crucial component since most biochemical reactions occur in an aqueous environment. Nutrients such as glucose, inorganic salts, and water-soluble vitamins dissolve in water which enable their transport throughout the body. Most metabolic waste products also dissolve in water for excretion. Approximately 70 percent of the human body is made up of water. Without it, life as we know it simply would not exist.

Besides being a solvent, water also could move across semi-permeable membranes. Semi-permeable membranes allow small molecules (including water) to pass through but restrict the passage of larger molecules such as proteins and blood cells. This principle of selective permeability enables the body to regulate its fluid and waste balance.

Objective

To determine the properties of water that make it suitable for sustaining life in biological systems.

Materials and Reagents

Materials

  • Dialysis bag

  • Cellophane

  • Beakers (250-mL)

  • Thistle tube

  • Test tubes

  • Test tube rack

  • String or rubber band

  • Iron stand

  • Iron clamp

  • Clamp extension

  • Digital balance (if necessary)

Reagents

  • NaCl (solid)

  • Glucose (solid)

  • Gelatin (solid)

  • Copper (II) Sulphate (solid)

  • Ethanol

  • Ethyl acetate

  • Citric acid powder (solid)

  • Sodium bicarbonate (solid)

  • 1% NaCl in starch solution

  • 0.1 M Silver Nitrate

  • 10% Sucrose solution

Procedure

I. Water as Universal Solvent

A. Deposit 0.5 grams into separate test tubes: NaCl, Glucose, Gelatin, Copper (II) Sulphate, and Ethanol. Add around 2 mL of water to each test tube and shake vigorously. If the reagent does not dissolve, add 2 mL of water and shake again.

B. Repeat solubility test with the use of Ethyl Acetate instead of water.

C. Describe the solubility of the substances in both solvents as soluble, slightly soluble, and insoluble. Record your observations on the table below.