A reaction that joins two molecules together with the formation of a chemical bond and involves the elimination of water
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What is a hydrolysis reaction?
A reaction that breaks a chemical bond between two molecules and involves the use of a water molecule
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How strong are hydrogen bonds?
They are quite weak but strong in large numbers
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Give 3 features of mono/disaccharides
Low molecular weight, soluble in water, sweet to taste
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Give 3 features of polysaccharides
High molecular weight, insoluble in water, tasteless
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What are monosaccharides used for?
Release of energy in respiration and as building blocks for polysaccharides
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Give the general formula of a monosaccharide
(CH2O)n
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What is an isomer?
When the chemical structure of the same molecule is slightly different
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Give an example of 2 isomers of each other
Alpha and beta glucose
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What bond is formed between 2 monosaccharides in a condensation reaction?
A glycosidic bond
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What is maltose?
A disaccharide formed from 2 glucose molecules
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What is lactose?
A disaccharide formed from 1 glucose and 1 galactose molecule
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What is sucrose?
A disaccharide formed from 1 glucose and 1 fructose molecule
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Describe the test for starch
1) Add a few drops of iodine solution to the solution/solid you are testing. 2) If the colour of the iodine changes from reddish black to a blue-black colour, starch is present
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What is a reducing sugar?
Sugars which can reduce a chemical as they can donate electrons
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Describe the test for reducing sugars
1) Add 2cm3 of the sample to be tested in a test tube, make sure you have grinded it up in water if not already a liquid. 2) Add an equal volume of benedicts solution. 3) HEAT the mixture gently in a water bath for 5 minutes. 4) Observe the colour
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Describe the results of the reducing sugars test
If there is no reducing sugar present, the Benedict's solution will remain blue. Any colour change indicates the presence of a reducing sugar, with brick red being the strongest positive
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What should you do to test for a non-reducing sugar?
1) If the Benedict's test was negative, add 2cm3 of the sample to 2cm3 of dilute hydrochloric acid in a test tube. This will hydrolyse any present disaccharides. 2) Slowly add sodium hydrogen carbonate to neutralise the HCl, and repeat the test
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What types of sugars are reducing sugars?
All monosaccharides and some disaccharides
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What type of molecule is glycerol?
An alcohol
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What is the general formula of a fatty acid?
R.COOH and the 'R' represents a hydrocarbon chain
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What are triglycerides made up of?
3 fatty acids for every 1 glycerol
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What is the bond called between a fatty acid and glycerol?
Ester bond
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What are saturated fatty acids?
Hard fats, e.g. butter, with single c-c bonds only.
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Are saturated fatty acids solid at room temperature?
Yes, saturated = solid
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What are unsaturated fatty acids?
Liquids, e.g. olive oil, contain some double c-c bonds
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Are unsaturated fatty acids solid at room temperature?
No, unsaturated = liquid
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Give 3 functions of lipids
Store fat soluble vitamins, protect kidneys and other organs, store of energy (1g of fat stores the same as 2g carbohydrates), waterproofing- they are insoluble (plant leaves)
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What is the test for lipids?
The emulsion test
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Describe the emulsion test
1) Add 5cm3 of ethanol to 2cm3 of the sample you're testing. 2) Shake the tube thoroughly to dissolve any lipid. 3) Add 5cm3 of water and shake. 4) A cloudy-white colour indicates the presence of a lipid
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Other cards in this set
Card 2
Front
What is a condensation reaction?
Back
A reaction that joins two molecules together with the formation of a chemical bond and involves the elimination of water
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