Biological Molecules

 There are many different types of biological molecules

 Most of them fall into the following categories:
o Carbohydrates
o Proteins
o Lipids
o DNA
 The main element that makes up all of these molecules is Carbon
 Carbon is the main element that makes up all living organisms, and so these molecules are
organic molecules

 Carbohydrates are made of Carbon, Oxygen and Hydrogen (CHO)

 Proteins are made of Carbon, Oxygen, Hydrogen, Nitrogen, and some other small amounts
of other elements (CHON)
 Lipids are made of Carbon, Hydrogen, Oxygen and small amounts of other elements (CHO)

 We use these molecules for energy, growth and repair

 They are all made of smaller molecules
 These molecules join together in reactions called condensation reactions
 They break apart in reactions called hydrolysis

Carbohydrates

 Carbohydrates are made of smaller molecules

 The building blocks of carbohydrates are glucose molecules
 It is the simplest sugar
 We call this a monosaccharide
 It has a hexagonal ring structure
 Glucose tastes sweet and is soluble and is easily transported in the blood
 Glucose is the main source of energy for cells
 2 glucose molecules joined together are called a maltose
 This is called a disaccharide
 When there is a lot of glucose molecules joined together it is called a polysaccharide.
 The bond between the glucose molecules is called a saccharide bond

 Glucose makes up many different types of molecules

o In plants it makes up cellulose
o In animals it makes up glycogen
o It makes starch that can be found in both plants and animals
 Polysaccharides are not sweet, are insoluble and so are good stores of energy and make
strong structures such as the cellulose cell walls.

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Biological Molecules
Fats (Lipids)

 These are made up of 2 different molecules: fatty acids and glycerol

 The glycerol is bonded to 3 fatty acids
 The fatty acids can be all the same, or different
 They vary in size and structure, and this gives us many different types of fats
 Lipids are called fats when they are solid at room temperature and oils when they are liquid
at room temperature.
 These are insoluble and are therefore good stores of energy and insulation
 They form barriers between watery environments – such as in the cell membrane.

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Biological Molecules
Proteins
 Proteins are made up of long chains of amino acids
 There are 20 different types of amino acid
 The general structure of an amino acid is shown below

 The R group is different in each type of amino acid

 The 20 different types of amino acid can be arranged in any order in the chain, and this
gives rise to a lot of different types of protein
 Just one difference in an amino acid will make a different protein

Some important proteins are:

Name Function
Haemoglobin

Biological catalysts for reactions in

the body
Antibodies

Nails, hair and skin

Bones and skin

Insulin

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Biological Molecules
 Protein Shape
 There are thousands of different proteins in the human body and other organisms
 The shape of the protein makes a difference to the function of the protein
 Example:
 Enzymes have an area called an active site – this is specially shaped so other molecules
fit into it
 If the active site shape does not match the molecule, no reaction will take place
 Antibodies are proteins that a made specifically to attach to an antigen
 An antigen is something on an invading organism’s cell that the body recognises
 The shape of the antibody has to be very specific to be able to attach to the antigen
 The sequence of amino acids is what causes the protein shape
 It makes the amino acid chain fold in certain ways
 In this way, each protein has a specific 3D shape.

Food Tests
 It is possible to test for the presence of each of the biological molecules
 The following describe the test used
Starch
 This is tested for by using Iodine
 Iodine is a reddish brown colour
 When it is in the presence of starch, it changes to a blue-black colour

Glucose
 Glucose is what is known as a reducing sugar
 The test is to use Benedicts Solution
 Benedicts solution is blue
 A small amount is added to the glucose and the test tube is heated in a water bath
 A brick-red colour indicates the presence of glucose

Proteins
 We use the Biuret test for proteins
 It is a blue colour to start with
 It is added to the protein and shaken
 A purple colour indicates the presence of protein

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Biological Molecules
Lipids
 The sample is mixed with ethanol and shaken
 Then drops of distilled water are added and the test tube is shaken
 A cloudy white colour indicates the presence of lipids

Vitamin C
 A DCPIP solution is used to test for Vitamin C
 It is dark blue
 The solution containing Vitamin C is added to it drop by drop and shaken
 If Vitamin C is present, the dark blue colour of the DCPIP solution turns to a colourless
solution

Substance Test Original colour Positive result Additional

details
Starch Iodine Orange brown Blue black
Reducing sugars Benedict’s Blue Brick red Must be heated
Solution in a water bath
Protein Biuret test Blue Purple Shaken
Lipids Emulsion test Colourless Cloudy white Ethanol first,
then distilled
water and shaken
Vitamin C DCPIP Blue Colourless Added dropwise
to the DCPIP

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Biological Molecules
 DNA
 DNA stands for deoxyribonucleic acid
 It is made up of the elements Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus
(CHONP)
 It is the molecule that is responsible for the growth and development of all organisms
 It is made up of 2 DNA strands wound around each other in a double helix

 The individual units are called nucleotides

 The structure of a nucleotide is shown below

 All nucleotides are identical except for the

base that is attached to the deoxyribose sugar.
 There are four bases:
o Adenine – A
o Guanine – G
o Cytosine – C
o Thymine – T
 They pair up along the double helix, keeping the strands together.
 Adenine always pairs with Thymine
 Guanine always pairs with Cytosine
 The deoxyribose sugar and phosphate form the backbone of the DNA, like the 2 poles of
a ladder
 The bases form the rungs of the ladder
 The order of bases is what gives us genes
 Genes are sections of the DNA that code for proteins

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Biological Molecules
Water
 Water is important in all living organisms
 This is because many substances can dissolve in it
 It is a universal solvent
 The test for water is:
o Anhydrous white copper sulfate turns blue in the presence of water
o Blue cobalt chloride paper turns pink in the presence of water

Role within Organisms

 Dissolved substances can be easily transported around organisms
o Example: phloem and xylem in plants, blood in humans
 Digested food molecules are in the alimentary canal, but need to be moved to cells.
Without water this would not happen
 Toxic substances such as urea, and other excess materials like mineral salts dissolve in
water so they can be removed as urine
 Water is an important part of the cytoplasm in making sure metabolic reactions can
happen

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Biological Molecules
U

Biomolecules. Carbs. Lipids. Proteins. Nucleic acids

Monomer glucose. Fatty accids Nuclutide

Pasta
Food
Am

Use

Elements
Wolf Brother by Michael Paver

Torak woke with a jolt from a sleep he d never meant to have.

The re had burned low. He crouched in the fragile shell of light and peered into the looming blackness of the Forest. He couldn't see anything. Couldn't hear anything. Had it come back?

Was it out there now, watching him with its hot, murderous eyes?

He felt hollow and cold. He knew that he badly needed food, and that his arm hurt, and his eyes were scratchy with tiredness, but he couldn't really feel it. All night he'd guarded the wreck of

the spruce bough shelter and watched his father bleed. How could this be happening?

Only yesterday - yesterday - they'd pitched camp in the blue autumn dusk. Torak had made a joke, and his father was laughing. Then the Forest exploded. Ravens screamed. Pines

cracked.And out of the dark beneath the trees surged a deeper darkness: a huge rampaging menace in bear form.
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