Biological Molecules Notes

BIOLOGICAL MOLECULES

INTRODUCTION TO BIOLOGICAL MOLECULES

• Molecules essential for carrying out metabolic reactions (sum of all chemical reactions).
• Molecules under study include water, carbohydrates, fats, and proteins.

WATER

• Perhaps the most important biological molecule, with the molecular formula being H_2O.
• Almost 60-75% of the body is made up of water.
• Water is a universal solvent; almost all chemical reactions require or produce water.
• Water is the major component of cytoplasm.
• If cells dry out, all metabolic activity stops.

USES OF WATER

• Major component of blood.
• Dissolves glucose, enzymes, and nutrients.
• Production of urine.
• Maintains temperature.
• Major chemical reactions occur in water.

CARBOHYDRATES

• Consist of 3 elements: Carbon, Hydrogen, and Oxygen.
• The number of hydrogen atoms is always double in comparison with carbon and oxygen atoms.
• They are broken down by the enzyme Carbohydrase.
• Note: Glucose $C6H{12}O6$, Ribose $C5H{10}O5$.

TYPES OF CARBOHYDRATES

• MONOSACCHARIDES - SIMPLE SUGARS (Also called Reducing sugars).
• DISACCHARIDES - SIMPLE SUGARS.
• POLYSACCHARIDES.

SIMPLE SUGARS (MONOSACCHARIDES)

• The simplest form of carbohydrates is called simple sugars or monosaccharides.
• Monosaccharides are used as direct energy sources and are highly reactive!
• This includes:
  • GLUCOSE: Most important, involved in respiration.
  • FRUCTOSE.
  • GALACTOSE.

DISACCHARIDES

• When two sugar molecules combine to make a more complex molecule.
• They can dissolve in water and are extremely sweet-tasting!
• DISACCHARIDES are used as transport sugars.
  • Glucose + Fructose = SUCROSE.
  • Glucose + Glucose = MALTOSE.
  • Glucose + Galactose = LACTOSE.

COMPLEX SUGARS (POLYSACCHARIDES)

• When a chain of 10 or more simple sugars combine to make a more complex molecule.
• They are insoluble and do not taste so sweet!
• Polysaccharides are used as storage sugars; they are stored, and when the body runs out of fuel or energy, they are used again.
• For example:
  • CELLULOSE: used in cell wall.
  • STARCH: Storage food for plants (chloroplast).
  • GLYCOGEN: Storage food for animals (Liver and muscles cells).

CARBOHYDRATE SUBUNITS, FUNCTIONS, AND EXAMPLES

• Monosaccharide
  • Subunits: One
  • Main Function: Energy Source
  • Examples: Glucose, Galactose, Fructose
  • Mnemonic: Gives Good Flavour
• Disaccharide
  • Subunits: Two
  • Main Function: Transport Form
  • Examples: Lactose, Sucrose, Maltose
  • Mnemonic: Length Supports Movement
• Polysaccharide
  • Subunits: Many
  • Main Function: Storage Form
  • Examples: Cellulose, Glycogen, Starch
  • Mnemonic: Can Get Stored

MNEMONICS

• HONEY - Monosaccharides
• SUGAR - Disaccharides

FUNCTIONS OF CARBOHYDRATES

• Used in respiration to make energy.
• Main source of energy, are broken down first.
• Can be transported easily for immediate use.
• Can be stored as polysaccharides for later use.
• Used for making cell wall in plants.
• Carbohydrates can be converted into proteins and fats if the need arises.

HOW CAN WE TEST FOR CARBOHYDRATES? USING A BENEDICT'S TEST

PROCEDURE OF BENEDICT’S TEST

1. Approximately 1ml of sample is placed into a clean test tube.
2. 2 ml (10 drops) of Benedict’s reagent (CuSO_4) is placed in the test tube.
3. The solution is then heated in a boiling water bath for 3-5 minutes.
4. Observe for color change in the solution of test tubes or precipitate formation.

• Positive Benedict’s Test: Formation of a reddish precipitate within three minutes. Reducing sugars present. Example: Glucose
• Negative Benedict’s Test: No color change (Remains Blue). Reducing sugars absent. Example: Sucrose.

BENEDICT'S TEST (ONLY FOR SIMPLE SUGARS)

• Blue solution: None, Traces of reducing sugar.
• Green/yellow ppt: Moderate.
• Orange/red ppt: Large amount of reducing sugar.

STARCH TEST

• Just add iodine to starch, it turns brown into black color.

FATS

• Also called Lipids, fats are made up of Carbon, Hydrogen, and Oxygen.
• They are the second source of energy.
• They are broken down by the enzyme LIPASE.
• They are made up of two units: GLYCEROL & FATTY ACIDS.
• If fats are broken down, they release fatty acids which can turn Litmus paper red due to acidity.

FATTY ACID STRUCTURE

• Simple and molecular structures of glycerol and fatty acids.
• Structure of a triglyceride formed from glycerol and three fatty acids, releasing 3 water molecules (3H_2O).

FUNCTIONS OF FATS

• 2nd source of energy, are broken down after all sugars in the body have been used.
• Stored in adipose tissues, that cover muscles and insulate heat.
• Make hormones and cell membrane.
• Keeps the skin lubricated.

TESTING FOR FAT (THE EMULSION TEST)

• Add a few drops of cooking oil into a test tube.
• Add 2 cm³ ethanol and shake.
• Add 2 cm³ water and shake again.
• Observation: Emulsion forms.

PROTEINS

• Made of N, H, O, and C.
• Proteins are polymers, relatively large molecules made from many smaller molecules.
• Each protein molecule is built up from peptides → amino acids.
• They are digested by enzymes called PROTEASE.

FUNCTIONS OF PROTEINS

• Enzymes.
• Hemoglobin.
• Antibodies.
• Keratin (Hair and Nails).
• Hormones.
• Muscles.
• Chlorophyll.
• Third source of energy.

TEST FOR PROTEINS

• Add 2 cm3 of the liquid food sample to a clean, dry test tube.
• Add 2 cm3 of Biuret Reagent.
• Shake well and allow the mixture to stand for 5 minutes.
• POSITIVE RESULT: Color changes from blue to violet.
• NEGATIVE RESULT: No color change.

DCPIP TEST (VITAMIN C TEST)

TESTING FOR VITAMIN C

• Quantity of Vitamin C in food and drink determined by color test.
• Vitamin C decolorizes blue dye DCPIP.
• Vitamin C reduces the DCPIP.
• DCPIP changes color in presence of vitamin C from blue to colorless (or slightly pink).

DNA

• Basic unit of inheritance.
• Made up of:
  • Sugar - Ribose.
  • Phosphates.
  • Nitrogen bases: A, T, G, C
    • A = T
    • T = A
    • G = C
    • C = G

DNA STRAND EXAMPLE

• GGGGCCCAGTTCCGAT
• CCCCGGGTCAAGGCTA