Chapter 7: Biological Molecules

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What is a carboxyl group?
-COOH this groups readily ionises to form -COO- and H+ so it is acidic.
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What is a fatty acid?
A molecule containing a hydrocarbon chain with a carboxyl group at one end.
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Define 'Glycosidic Bond'
The bond that links sugar molecules together in a disaccharide or polysaccharide.
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What is a hydrolysis reaction?
A reaction in which two molecules are separated from each other, involving the combination of water.
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What happens in a hydrogen bond?
An attractive force between a slight negative charge on one atom and a slight positive charge on another.
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What is a polysaccharide?
A substance whose molecules are made of many sugar units linked together in a long chain.
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What does the secondary structure of a polypeptide look like?
A regular repeating pattern.
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Water can form weak bonds between other molecules due to polarity. What are these bonds called?
Hydrogen bonds.
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The density of most substances as they cool ___. What happens to the density of water as it cools to 0ºc?
Increases, decreases.
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Glucose, galactose and fructose are all ___ of each other as all C6H12O6.
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Why is water dipolar?
Oxygen nucleus attracts the electrons more than the hydrogen nucleus, resulting in an uneven distribution of charge, therefore it is dipolar.
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Glucose, galactose and fructose are all _saccharides, whereas maltose, lactose and sucrose are all _saccharides.
Mono; Di
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What are the properties of monosaccharides?
Are all in C-H-O 1:2:1 ratio, contain a carbonyl (reactive) group, contain at least two OH (hydroxyl) groups,.
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What are the similarities between a triglyceride and a phospholipid?
Contain glycerol, fatty acids, ester bonds and Carbon, Hydrogen and Oxygen.
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What are the differences between a triglyceride and a phospholipid?
T has 3 fatty acids whereas P only has 2. Triglyceride has 3 ester bonds whereas P has 2. P contains phosphate whereas T does not.
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What is the test used to test the presence of lipids?
Emulsion Test.
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Describe how to carry out an emulsion test.
Add ethanol to sample, shake it and then add to cold water. Expected mixture to be a cloudy, milky white colour.
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What are the roles of lipids in the body?
Make up membranes, energy store, respiratory substrate, thermal insulation, buoyancy, vitamin D, waterproofing and protection of organs.
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Name the polymer formed from a chain of amino acids
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Name the bond that is formed when two amino acids are joined together. Describe the formation of this bond.
A peptide bond between amine groups. A hydrogen from an amine combines with an OH from a carboxyl group. This is a condensation reaction.
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List examples of where hydrogen bonds are found in biological molecules
Between water molecules, in a proteins secondary or tertiary structure, between strands of DNA and chains of cellulose.
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Describe ways in which the physical properties of water allow organisms to survive over a range of temperatures.
High latent heat of evaporation means sweat cools you down, high SHC means it is a thermally stable environment for aquatic organisms so use less energy and their reactions work well. Ice is less dense that water so provides a habitat.
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In a benedicts solution if there is a brick-red precipitate there is a presence of ___?
A reducing sugar.
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How do you test for a reducing sugar?
Place 10cm3 of glucose solution in a test tube. Add a few drops of Benedicts solution. Stand the tube in a water bath at 100ºc for 5 minutes. RS present if brick-red precipitate is formed as it reduces the copper (II) ions inthe B's to copper(I)oxide
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How do you test for a non-reducing sugar?
Place about 10cm3 of sucrose solution in test-tube. Add 3 drops of h.chloric acid. Shake. Place in water bath at 100ºc for 5. Remove and allow to cool. Add 3 drops of dilute sodium hydroxide and mix to neutralise acid, then repeat reducing sugar test
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How do you test for starch?
Using a pipette, place a drop of starch solution in a depression in a spotting tile. Add a drop of iodine. If present, a blue/black colour is formed.
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How do you test for protein?
Place about 5cm3 of protein solution in a test tube. Add an equal amount of biuret solution. if present a lilac solution is formed.
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Describe the structure of a triglyceride molecule
One glycerol connected to 3 fatty acids in a ester bond.
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DNA is found in the nucleus. The molecule is twisted into a __ __ in which each of the strands are__ . It has two __ backbones attached to one another by complementary bases. These bases pair in the centre of the molecule by means of __ bonds.
double helix ; anti-parallel ; sugar-phosphate ; hydrogen
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Describe how the concentration of a reducing sugar can be measured using a colorimeter.
Using known concentrations of a reducing sugar, heat with benedicts solution keeping conditions constant, changes colour and remove precipitate. use colorimeter on red filer and read result.More transmission, less absorbance means more RS.
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Explain why glycogen makes a good storage molecule
Insoluble, does not affect water potential, can be broken down, lots of branches for enzyme to attach and compact
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State the differences in structures of glycogen and cellulose.
C has H bonding, G does not. G has 1,4 and 1,6 glycosidic bonds, but C only has 1,4. G is branched, C is not. G has no fibres, C does. G has granules, C does not.
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What are the common properties of mono/disaccharides?
Are in a crystallised form, have carbonyl groups, are solid and soluble in water.
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What structural features of carbohydrates account for the wide variety of polysaccharide?
Type of glucose means the glycosidic bonds form different shapes, vary on their function depending on the mono.s. it is formed from. Whether it is in a ⍺ or β form. And its hydrogen bonding.
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Describe glucose.
Formed by a 1,4 glycosidic bond, structure does not coil but exists in straight lines. H bonding exists between adjacent strands. They make fibrils which then form larger bundles called fibres.
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Describe Proteins
Contain C H O N, building blocks are amino acids, test via biuret and can be used in channel proteins, antibodies, enzymes and carriers.
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Describe Glycogen
Energy store only in animals, made from ⍺ glucose, have 1,4 glycosidic but occasionally 1,6 and are branched molecules.
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What type of reaction breaks down a glycosidic bond?
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Primary structure is _____. Secondary is the___. Tertiary structure is the ___. Quaternary structure is the ___.
Sequence of amino acids in a polypeptide; formation of a alpha helix or beta pleating; could form ionic or hydrogen bonding; is two or more tertiary structures connected and non-protein structures.
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Card 2


What is a fatty acid?


A molecule containing a hydrocarbon chain with a carboxyl group at one end.

Card 3


Define 'Glycosidic Bond'


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Card 4


What is a hydrolysis reaction?


Preview of the front of card 4

Card 5


What happens in a hydrogen bond?


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