Biological molecules (2.3-2.4)

• All organic molecules contain carbon and hydrogen atoms; Hydrocarbons

• Organic molecules can be large and show a wide variety of chain and ring structures

• Organisms need organic molecules to:

  • Provide energy to drive life processes
  • Provide raw materials for the growth and repair of tissues

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• Main organic molecules used by organisms are:

1. Carbohydrates

2. Lipids

3. Proteins

4. Nucleic Acids

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• Biochemistry: The study of the organic and inorganic molecules that make up living organisms
• Metabolism: Sum of all the chemical reactions in an organism
• Large organic molecules are made of many simmilar smaller molecules (subunits/isomers)
• Subunits can be split apart by Hydrolisis
  • Hydrolisis: Reaction that uses water to break apart subunits
  • They can be joined together again by condensation

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• Living organisms can obtain molecules from their environment and rearrange them into shapes that suit their own particular requirements
  • Large molecules are made from smaller ones

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Carbohydrates

• Carbohydrates: Organic compounds containing Carbon, Hydrogen and Oxygen
  • Sources: rice, wheat, oats, maize barley
• Carbohydrates are long chains of simple sugars (glucose)
• Simple sugars are also called monosaccharides; made of one sugar molecule
• When 2 glucose molecules join together they form maltose (a disaccharide)
• Many glucose molecules can join together to form starch, cellulose or glycogen (polysaccharides)

Example:

Glucose (monosaccharide) →Glycogen (polysaccharide)

Importance of Carbohydrates

• Good sources of energy
• Plants store excess carbohydrates as starch
• Animlas store excess carbohydrates as glycogen in the liver and muscles
• Eating excess carbohydrates causes obesity
• Defiency of carbohydrates causes ‘Marasmus’

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Protein

• Proteins: Organic compounds containing Carbon, Hydrogen, Oxygen and Nitrogen (and sometimes sulphur)
  • Sources: Milk, eggiwhite, fish, peas, beans and meat
• Made up of the basic subunit (monomer) amino acids
  • 20 types amino acids are naturally occuring
  • 8 are essential (from food) 12 are non-essential (present in your body)

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• Amino acids are soluble in water; can be transported in organisms
• The sequence of amino acids determines the shape of the protein molecule
  • Shape determines the function of the protein
  • Different sequences of amino acids causes the polypeptide chains to fold in different ways and form differently shaped proteins

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Examples

• Enzymes have active sites where substrate molecules bind for a reaction to take place

  • Since enzymes are substrate specific the shape of the active site has to match the shape of the molecule
  • The shape of the active site determines which molecules will bind and react using the enzyme

• Antibodies are proteins produced by WBCs which bind to antigens on the surface of antibodies

  • The shape of the anitbody has to match the shape of the antigen so it can bind to it and signal for destruction

• In proteins there are four components attached to a central carbon

  

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Importance of proteins

• Proteins are body builders and they are used in tissue growth and tissue repair

• They are used to make antibodies, enzymes, hormones, and plasma proteins

• Excess proteins are not stored in the body, they are converted into urea in the liver -deamination of amino acids

• Lack of protein causes' ‘Kwashiorkor’

  

• Hydrolisis breaks down proteins into amino acids by adding water

• Condensation reactions synthesise protein molecules and water from amino acids

Lipids

• Lipids: Organic compounds containing chemical elements Carbon, Hydrogen, Oxygen

  • Sources: Cream, ghee, oil, nuts, butter, dairy

• One molecule of lipid is made of 1 glycerol and 3 fatty acids and is made by condensation

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Importance of lipids

• Acts as an energy store
• Provides insulation
• Less dense than water
• Harvesting animals store food in bodies as fat as a source of energy
  • (fats- solid, oils- liquid)

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Nucleic Acids

• The 2 nucleic acids are DNA and RNA

• DNA contains the instruction for the growth and development of organisims and is made of 2 strands wrapped around eachother forming a double helix

  

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• Nucleotides: individual units of DNA
  • They all have the same phosphate and sugar ‘backbone’ but have different bases attached
  • Adenine, Cytosine, Thymine and Guanine
• The bases on each strand form cross links (hydrogen bonds) and form base pairs holding the two strands of DNA in the double helic together
  • Adenine always pairs with Thymine (A-T)
  • Cytosine always pairs with guanine (C-G)

Apple Tree and Car Garage to remember ;)

• The sequence of base pairs holds the code for the formation of proteins

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Food tests

• Reducing sugars

1. Add Benedicts solution into sample in test tube
2. Heat at 60-70 C in a water bath for 5 minutes
3. Take test tue out
4. Positive test; Blue → orange/brick red

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• Starch

1. Add drops of iodine to sample
2. Positive test; Orange/brown → Blue/black

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• Protein

1. Add drops of Biuret solution to sample
2. Positive test; Blue →Purple

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• Lipids

1. Mix 2cm3 of Ethanol with food sample
2. Add equal volume of water
3. Positive test; Cloudy emulsion

OR

3. Take a sample of oil and add water and shake; forms an emulsion (bubbles)

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• Vitamin C

1. Add 1cm3 of @@DCPIP@@ solution to test tube
2. Add food sample to solution
3. Positive test; @@Blue color of the dye will turn colorless @@

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Water

• Water is an important solvent; many substances can dissolve in it , making it essential for life on earth

Importance of water

• Water allows substances to be easily transported arounf organisms

• Digested food molecules in the alimentary canal are moved around the body using water as a solvent

• Toxic substances (eg. urea) and substances in excess (eg. salts) are dissolved in water to be removed from the body (as urine)

• Water is an important part of the cytoplasm and is involved in ensuring metabolic reaction can take place in cells

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