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
• $Carbohydrates are <strong>long chains of simple sugars</strong> (glucose)$
• 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
• $One molecule of lipid is <strong>made of 1 glycerol and 3 fatty acids</strong> and is made by condensation$

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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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