CHAPTER 4 BIOLOGY

• All organic molecules contain carbon.
• Examples of organic molecules/compounds are carbohydrates, proteins and lipids.
• Carbohydrates

  Simple Sugars (Monosaccharide) : Glucose, Fructose, Galactose

  Double Sugars (Disaccharide) : Maltose, Sucrose, Lactose

  Complex Sugars (Polysaccharide) : Cellulose, Starch, Glycogen
• Condensation process


  Glucose (mono) + Glucose (mono) -----> Maltose (Di) + water

  Glucose (mono) + Fructose (mono) -----> Sucrose (Di) + water

  Glucose (mono) + Galactose (mono) -----> Lactose (Di) + water
• Hydrolysis process

  Maltose (Di) + water ----> Glucose (Mono) + Glucose (Mono)

  Sucrose (Di) + water ----> Glucose (Mono) + Fructose (Mono)

  Lactose (Di) + water ----> Glucose (Mono) + Galactose (Mono)
• Polysaccharide ( Starch, Glycogen, Cellulose)

  • All made of many glucose molecules joined together.

  A) Found in plants

  B) Carbohydrate storage in plants

  C) Found in yeast and animals

  D) Carbohydrate storage in yeast and animals

  E) Found in plants

  F) Components of cell wall

  
• Fats / Lipids

  • made up of triglycerides
  • Their basic unit is 1 glycerol molecule chemically bonded to 3 fatty acid chains
  • Lipids are divided into fats (solid at r.t.) and oils (liquid at r.t.)
• Proteins

  • Long chains of amino acids
  • When amino acids are joined together a protein is formed
  • Amino acids -> polypeptide ->protein
• Deoxyribonucleic acids (DNA)

  • Carries the genes or genetic information for the development and functions to the body
  • Two strands in DNA are twisted to form a double spiral or double helix.
  • Basic unit of DNA : Nucleotide
  • 1 Nucleotide contain Phosphate, Sugar, Nitrogenous base
• Nitrogenous Base

  Adenine --> Thymine

  Cytosine --> Guanine
• Basic units of

  1. Starch, Cellulose, Glycogen : Glucose
  2. Fats and Oil : Fatty acids and Glycerol
  3. Proteins : Amino acids
  4. DNA : nucleotide
• Test for glucose (reducing sugar)

  • Add Benedict’s solution into sample solution in test tube

  • Heat at 60 – 70 °c in water bath for 5 minutes

  • Take test tube out of water bath and observe the colour

  • A positive test will show a colour change from blue to orange or brick red
• Test for starch using iodine

  • Add drops of iodine solution to the food sample

  • A positive test will show a colour change from orange-brown to blue-black
• Test for protein

  • Add drops of Biuret solution to the food sample

  • A positive test will show a colour change from blue to violet / purple

  • Biuret reagent is a blue solution made up of sodium hydroxide and copper sulfate.
• Test for lipids


  • Food sample is mixed with 2cm^3 of ethanol and shaken

  • The ethanol is added to an equal volume of cold water

  • A positive test will show a cloudy emulsion forming
• Test for Vitamin C

  • Add 1cm^3 of DCPIP solution to a test tube

  • Add a small amount of food sample (as a solution)

  • A positive test will show the blue colour of the dye disappearing(decolourise / turn colourless)
• Food Test

  A) Reducing sugar

  B) Vitamin C

  C) Starch

  D) Protein

  E) Lipid

  F) Benedict’s solution

  G) DCPIP solution

  H) Iodine solution

  I) Biuret solution

  J) 2cm^3 of ethanol

  K) Blue to orange / brick red

  L) Blue colour of the dye disappearing (decolourise)

  M) Orange-brown to blue-black

  N) Blue to violet / purple

  O) Cloudy emulsion

  
• Why do we need food?

  (a) Food provides energy for cell activities

  (b) Food substances are needed to make new cells for growth such as proteins

  (c) Food helps us stay healthy

  • Calcium -> keep our bones and teeth strong
  • Iron -> Make new red blood cells (lack of iron become anaemic)
• Nutrients include carbohydrates, fats, proteins and water.

  Carbohydrates, fats and proteins are three major types of biological molecules in living organisms.
• Why is water important?


  (a) Water is an important solvent

  • Used to dissolve solute during chemical reactions

  (b) Water helps in controlling body temperature

  • water in sweat evaporates, remove excess heat from our bodies, prevent overheating

  (c) Water is needed for photosynthesis in plants

  • need water to manufacture carbohydrates during photosynthesis
• Carbohydrates are organic molecules made up of elements carbon, hydrogen and oxygen.
• Starch

  • Made up of several thousand glucose molecules joined together
  • Unbranched molecule gives a blue-black colour with iodine solution
  • Branched molecule
  • Storage form of carbohydrates in plants, can be digested to provide energy for cell activities
  • found in grains and storage organs of plants
• Cellulose

  • Made up of many glucose molecules joined together
  • Cellulose cell wall protect plant cells from bursting or damage
  • Cellulose fibres can't be digested, it serves as dietary fibre to prevent constipation
  • Cell walls in plants made of cellulose
• Glycogen

  • Branched molecule that made up of many glucose molecules joined together
  • Storage form of carbohydrates in mammals
  • Can be digested to glucose to provide energy for cell activities
  • Stored in liver and muscles of mammals
• Carbohydrates are needed

  • as a source and store of energy
  • to form supporting structures
  • for the formation of nucleic acids like DNA
  • to make lubricants
  • to make nectar in flowers, which attracts insects for pollination
• Fats like carbohydrates are organic molecules made up of the elements, carbon, hydrogen and oxygen.
• Fats functions as:

  • a source and store of energy, especially for animals
  • an insulating material that prevents excessive heat loss
  • a solvent for fat-soluble vitamins and many other vital substances, such as hormones
  • an essential part of cells, especially in cell membranes
  • reduce water loss from the skin surface
• Proteins are organic molecules made up of the elements carbon, hydrogen, oxygen and nitrogen. Sulfur may not be present.
• Protein molecules must be broken down by enzymes during digestion.
• Proteins are used

  • to make new cytoplasm, used for growth and repair of worn-out tissues
  • to make enzymes and some hormones
  • for the formation of antibodies to combat diseases
  • to make chromatin in chromosomes
• Children that is not enough protein have protein deficiency disease called kwashiorkor.