Biological Molecules Notes

Biological Molecules

Organic Molecules

• Always contain carbon and hydrogen.
• Usually large molecules with complex functions.
• Utilize covalent bonds.
• Carbon chains can vary in length, have double bonds, and be branched.
• Carbon chains can form rings of different sizes and have double bonds.

Monomers vs. Polymers

• A polymer is a long molecule consisting of many similar building blocks.
• Monomers are the building blocks of polymers.

Dehydration Synthesis

• Occurs when two monomers bond together through the loss of a water molecule.
• Dehydration removes a water molecule, forming a new bond.
• $H_2O$ is released during the formation of a polymer from monomers.

Hydrolysis

• Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction
• Hydrolysis adds a water molecule, breaking a bond.
• $H_2O$ is consumed during the breakdown of a polymer into monomers.

4 Classes of Organic Molecules

Carbohydrates

• Diverse group of substances formed from C, H, and O.
• Main function is as a source of energy.

Diversity of Carbohydrates

1. Monosaccharides:
   • monomers
2. Disaccharides:
   • two monomers linked, sweet taste
3. Polysaccharides

Lipids

• Formed from C, H, and O.
• Ratio of O is less than 1:2:1 (less oxygen atoms per molecule compared to carbohydrates).
• Hydrophobic.
• Triglycerides (fats) are a type of lipid.
• Provide twice as much energy as carbohydrates.

Fats/Triglycerides

• Fats are constructed from two types of smaller molecules:
  • Glycerol: a three-carbon alcohol.
  • Fatty acid: a carboxyl group attached to a long carbon skeleton.
• Ester linkage: bond between glycerol and fatty acids in a fat molecule.

Proteins

• Most abundant organic compound in the body.
• Made up of C, H, O, N, and a small amount of sulfur may be present.
• Perform many functions:
  • Support
  • Movement
  • Transport
  • Buffering
  • Defense
  • Catalysis (Enzymes): speed up chemical reactions

Proteins: Structure

• Monomers: amino acids
• Primary Protein Structure: sequence of a chain of amino acids

Protein: Enzymes

• Catalyze (speed up) chemical reactions such as hydrolysis and dehydration synthesis.
• Enzymes speed up reactions by properly orienting colliding molecules.
• Enzymes usually end in suffix -ase and are named for the types of chemical reactions they catalyze.
  Enzymes activity can be affected by temperature and pH; chemicals that specifically influence the enzyme.
• If the enzyme loses the right shape/structure, it becomes DENATURED.

Experiment 1: Hydrolysis of milk fat by pancreatic lipase

• Lipase breaks down the milkfat into Fatty acid and Glycerol.
• Litmus cream is blue: basic when no lipase is present.
• Lipase digestion: Litmus cream turns pink: acidic.
• Fats are made from 1 glycerol and 3 fatty acids

Experiment 2A: Hydrolysis of starch by pancreatic amylase

• Amylase is an enzyme that breaks down polysaccharides into smaller oligosaccharides, maltose, and with enough time eventually into glucose.
• We can use indicators to determine:
  • The absence of starch (once it has been digested by amylase).
  • The presence of simple sugars (the products of starch digestion).

Using (i) iodine as indicator (Lugol’s iodine) to test for starch

• Yellow/brown color turns Blue/black in the presence of starch.

Using (ii) Benedict reagent as indicator

• Indicates presence of simple (monosaccharides and some disaccharides) sugars.
• Turns Blue to green/yellow/orange/red.
• Requires heat for reaction.

Denaturing Amylase

• Starch, Amylase, Denatured. Then use iodine to know if amylase is denatured.

Starch Digestion by Amylase Effect of Temperature

• Different Temperatures: 0° C, 37° C, 90° C, Room Temp.

Starch Digestion by Amylase Effect of pH

• Different pH: pH 4, pH 7, pH 9.