Biological Molecules

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What is a condensation reaction?
A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
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What is a hydrolysis reaction?
A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.
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What bonds form in carbohydrates?
a glycosidic bond
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What is reduction?
A chemical reaction involving the gain of electrons
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What is the test for reducing sugars?
The Benedicts test. 1. Add 2cm of the food sample to be tested to a test tube. 2. Add an equal volume of Benedicts reagent. 3. Heat the mixture in a gently boiling water bath for 5 minutes.If reducing sugar is present an orange-brown colour is formed
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What is the test for starch?
Place 2cm of the sample being tested into a test tube. Add 2 drops of iodine solution and shake or stir. The presence of starch is indicated by a blue-black colouration.
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How are amino acids joined together?
By condensation reaction between the carboxyl group of one and amine group of another, leaves a bond between carbon and nitrogen (called a peptide bond) forming a dipeptide
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Define the primary structure of proteins?
Sequence of amino acids, polypeptide chain held by peptide bonds
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Define the secondary structure of proteins?
The primary structure (polypeptide chain) coils to form a helix, held by hydrogen bonds
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Define the tertiary structure of proteins?
Secondary structure folds again to form final 3D structure, held together by hydrogen,ionic, disulfide bonds
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Define the quaternary structure of proteins?
Made of more than one polypeptide chain
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What is the test for proteins?
The biuret test. Place the sample of the solution to be tested in a test tube and add sodium hydroxide solution at room temperature. Add a few drops of dilute copper sulfate solution and mix gently. A purple colouration indicates a protein
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What is the structure of collagen?
Primary structure- Unbranched polypeptide chain. secondary structure- The polypeptide chain is very tightly wound. tertiary structure- The chain is twisted into a second helix. Quaternary structure- Made up of 3 such polypeptide chains wound together
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What is the test for lipids?
Take a completely dry and grease free test tube. Add 5cm of ethanol. Shake the tube thoroughly. Add 5cm of water and shake gently. A cloudy white colour indicates the presence of a lipid
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What is starch?
Starch is a polysaccharide that is found in many parts of a plant. Starch is made up of chains of a-glucose monosaccharides linked by glycosidic bonds.
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What is glycogen?
Glycogen is the major carbohydrate storage product of animals. It has a similar structure to starch but has shorter chains and is more highly branched
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What is cellulose?
Cellulose is made of monomers of b glucose therefore differs to glycogen and starch. Cellulose has straight, unbranched chains. Cellulose is a major component of plant cell walls
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What are qualitative tests?
Tests that indicate the presence or absence of a variable. e.g the test for reducing sugars and starch are qualitative tests
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What are quantitative tests?
The benedicts test can also be quantitative in that it can also indicate how much/the concentration of reducing sugars
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Describe the characteristics of lipids?
Lipids contain C, H and O. Lipids are non polar molecules so are insoluble in water. They are soluble in organic solvents. They are hydrophobic. Building blocks are fatty acids and glycerol. Do not form polymers.
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What are the roles of lipids?
An energy source/Waterproofing/ Insulation/ Protection/ Fat as a buoyancy aid
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What is the difference between saturated and unsaturated fatty acids?
In saturated fatty acids all the linkages between the carbon atom in the hydrocarbon chain are single bonds. Unsaturated fats contain unsaturated fatty acids and thus possess a number of double bonds.
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What is the difference between Cis unsaturated fats and Trans unsaturated fats?
In the Cis arrangement, the hydrogens are on the same side of the double bond. In the trans arrangement, the hydrogens are on opposite sides of the double bond.
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How does a triglyceride form?
A condensation reaction occurs between the carboxyl group (COOH) of the fatty acid and the hydroxyl group (OH) of the glycerol. An ester bond is formed
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What are the functions of triglycerides?
Energy source and metabolic water source/ Fat as a buoyancy aid/ Heat insulation/ Waterproofing/ Electrical insulation
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Which 2 substances are formed when two amino acid molecules join together?
dipeptide and water
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Explain one way in which starch molecules are adapted for their function in plant cells?
Starch is insoluble and therefore it does not tend to draw water into the cells by osmosis
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Explain how cellulose molecules are adapted for their function in plant cells?
Cellulose is a major component of plant cell walls as it prevents the cell from bursting as water enters it by osmosis because cellulose has a rigid structure.
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What is the difference between a phospholipid molecule and a triglyceride molecule?
Phospholipids consists of a glycerol molecule with 2 fatty acids and a phosphate group. A triglyceride molecule consists of a glycerol with 3 fatty acids and a phosphate group
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Card 2

Front

What is a hydrolysis reaction?

Back

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

Card 3

Front

What bonds form in carbohydrates?

Back

Preview of the front of card 3

Card 4

Front

What is reduction?

Back

Preview of the front of card 4

Card 5

Front

What is the test for reducing sugars?

Back

Preview of the front of card 5
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