Chemical Composition Analysis in Living Tissues MCQ - Practice Questions with Answers

Analysis of Chemical Composition in Living Tissues
 It can be done by the following two methods:

1. Chemical Analysis: 

• By grinding any living tissue (like a piece of vegetable) with trichloroacetic acid (CCl3COOH) using a mortar and pestle. 
• A thick slurry obtained is strained with a cheesecloth. 
• Two fractions would be obtained as:
• Filtrate or acid soluble pool
• Retentate or acid insoluble fraction
• The acid soluble pool consisted of micromolecules.
• Their molecular weight is less than 1000 Da. 
• Amino acids, sugars, nucleotides are micromolecules. 
• The acid insoluble pool consisted of macromolecules whose molecular weight is more than 1000 Da. 
• Carbohydrates, nucleic acids, proteins are macromolecules. 
• The acid insoluble fraction also included lipids. However, lipids are micromolecules as they never weigh more than 800 Da. This happened because the lipid components of the plasma membrane and organelle membranes form vesicles which are insoluble. So, they appear along with acid insoluble fraction despite being a micromolecule.

2. To study inorganic elements and compounds:

• The weight of living tissue is called its wet weight. 
• When the tissue is dried and the water is evaporated, the resultant weight is called dry weight. Upon burning the dry tissue, carbon compounds are oxidized to release CO2 and H2O. 
• The remaining portion after burning is called ash. 
• The chemical analysis of the ash reveals the presence of inorganic elements like calcium, magnesium, sodium, potassium and other compounds.