Lab Notes and Procedures-02 Biology 1004

North Arkansas College

Topic: Chemical Basis of Life

All living organisms/cell are made of four major classes of chemical compounds.

1. Carbohydrates
2. Proteins
3. Lipids
4. Nucleotides

These compounds are responsible for both the similarity and diversity among the species. What types of components are present?

We can detect these molecules with reagents that change color in the presence of protein.

1. Proteins are chains of compounds called amino acids which have basic structure.
2. Amino acids link together by forming peptide bonds to make a protein. They will share the acid portion of one amino acid with the NH₂ group of another amino acid. Carbon needs 8 to be stable, nitrogen need 8 to be stable. Link the two together and they share carbon and nitrogen ~ formed a bond this way and is now stable.
3. Biuret reagent contains copper which forms complexes with NH₂ (amino groups) to form a deep violet color (purple to violet). Water is a control. Albumin is most abundant protein in cells. Pepsin is an enzyme (small amount of protein). Enzymes - biological catalyst that speeds up chemical reactions. Enzymes do not actually change, but they speed the process. Pepsin is an enzyme that breaks down proteins. Pepsin is commonly found in stomach where the pH is 1-3 (acid). Pepsin works best in the presence of hydrochloric acid. To break down protein into peptides - add pepsin, hydrochloric acid and water.

Carbohydrates are chemical compounds that contain carbon, hydrogen and oxygen (three basic units; may have others too). There are three major classes of carbohydrates:

1. Simple sugars - monosaccharides (e.g. glucose, fructose).
2. Disaccharides - two sugars bound together:

1. e.g. sucrose - glucose and fructose (table sugar)
2. e.g. lactose - glucose and Galactose (milk sugar)
3. e.g. maltose - two glucose molecules

3. Complex sugars - polysaccharides are long chains of sugars linked together:

1. e.g. starch (seeds, stems of plants); most starch is a straight chain of glucose up to about 5,000 glucose molecules linked together making amylose : g-g-g-g-g. Amylase is enzyme that breaks down amylose (long straight chains of starch). Sometimes chains of glucose show branching called amylopectin. Cellulose and chitin are polysaccharides with different bonding associated with them. Starch reacts readily with iodine to produce a deep blue-black color.

1. Benedict’s regent (light blue) combines with free reducing sugars (-OH groups) to form colors ranging from a brick red to orange to light green based on the amount present.

Effect of Amylase on Starch (Page 28)

If you have starch and H₂0 and add amylase - maltose.

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