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What is a monomer?
Smaller units from which larger molecules are made up of
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What is a polymer?
Polymers are molecules made from a large number of monomers joined together
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What is an example of a monomer?
- Any of the three;
- Monosaccharides
- Amino acids
- Nucleotides
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What is a condensation reaction?
A condensation reaction is one which joins two molecules together with the formation of a chemical bond and involves elimination of a water molecule.
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What is a hydrolysis reaction?
A hydrolysis reaction is one which breaks a chemical bond between two molecules and involves the use of a water molecule.
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Glucose, galactose and fructose are examples of what?
Monomers (of which larger carbohydrates are made up of)
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What do monomers join together to form?
Polymers
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What process joins monomers together?
Condensation Reactions
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What are polymers broken down into?
Monomers
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What breaks down polymers into monomers?
Hydrolysis reactions
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What elements do proteins contain?
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
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What is a protein made up from?
Proteins are polymers made up of one or more chains of amino acid monomers known as polypeptides.
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What are amino acids made up from? (3)
- An amino group
- a carboxylic group
- A Variable group
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What makes an amino acid unique?
The R group/variable group
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What does the variable group affect on an amino acid?
It's properties it has
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Two amino acids join together to form what?
dipeptide
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What is the bond between the amino acids called?
peptide bond(s)
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What is a peptide bond?
a strong covalent bond
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What is the general structure of an amino acid?
Amino group ; R Group ; carboxylic acid group
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Many amino acids link together by condensation to form what?
a polypeptide chain
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What are the four levels of protein structure?
- 1. Primary structure
- 2. Secondary Structure
- 3. Tertiary Structure
- 4. Quaternary Structure
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What is the primary structure of a protein?
This is the sequence of amino acids in a polypeptide chain
(amino chain)
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What is the secondary structure of a protein?
This is further folding of the polypeptide chain. As they fold they allow the formation of weak H-bonds which produce particular secondary structures
(hydrogen bonds between amino acids)
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Give two examples of secondary structures.
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Where would you find alpha helical structures of proteins?
fibrous proteins such as keratin (hair and nails)
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Where would you find B-pleated sheets?
globular proteins such as enzymes
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What is the tertiary structure of a protein?
further folding where the whole chain (including secondary structures) folds into a specific shape.
It is stabilised by ionic bonds, hydrogen bonds and disulphide bonds.
(alpha helix and beta-pleated sheets attract)
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What is a disulphide bond?
A covalent bond between sulphur-containing amino acids
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What can cause a protein to become denatured?
high temperatures and extremes of pH
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How does a protein become denatured?
Hydrogen bonds break first, as they are very weak bonds. The disulphide bonds are stronger and can withstand higher temperatures.
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What happens when the bonds break in a protein?
When the bonds break, the tertiary structure is lost and the protein loses its function.
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What is it that determines the function of a protein?
The specific shape of the tertiary structure of the protein
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What is the quaternary structure of a protein?
This is found in proteins made up of more than one polypeptide chain -----> 2 alpha chains or 2 beta chains
(more than one chain joined together)
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What are the different shapes of proteins?
Fibrous and globular
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What are fibrous proteins?
These form long chains running parallel to each other with cross-bridges between the chains. This produces very stable molecules.
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What is collagen?
Collagen is a protein found in tendons which join muscle to bone
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Describe Collagen's primary structure?
unbranched polypeptide chain
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Describe Collagen's secondary structure?
the polypeptide chain forms an a-helix.
lots of amino acid glycine helps close packaging
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What is the tertiary structure of collagen?
the polypeptide chain is further twisted
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What is the quaternary structure of collagen?
3 polypeptide chains are wound together with covalent bonds between amino acids of adjacent chains
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Why does the quaternary structure of collagen make it a suitable molecule for a tendon?
- Collagen is found in tendons which join muscle to bone.
- Tendons need to be very strong and not elastic.
- Cross-links between adjacent polypeptide chains in the fibres proved strength and stability.
- The points where one collagen molecule ends and another one starts are spread throughout the fibres, rather than being at the same point
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Give two examples of globular proteins
Enzymes and haemoglobin
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What do globular proteins carry out?
metabolic functions
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What is the Biuret test for proteins?
- add potassium hydroxide and copper sulphate (buret solution) to a sample of the solution to be tested
- if the solution turns lilac then a protein is present
- if the sample does not contain protein, only the pale blue colouration of the copper sulphate is seen
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What elements are carbohydrates composed of?
carbon, hydrogen and oxygen
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What are monosaccharides?
basic molecular units/monomers of which other carbohydrates are composed
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Give three examples of carbohydrates
glucose, galactose and fructose
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What properties do monosaccharides have?
soluble and sweet
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What type of sugar is glucose?
hexose
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What is meant by a hexose sugar?
It contains 6 carbon atoms
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What is the formula of glucose?
C6H12O6
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What is the formula of a pentose sugar?
C5H10O5
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What is the formula of a triose sugar?
C3H6O3
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What is glucose a product of?
Photosynthesis
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What is glucose a major substate of?
respiration
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What does the term 'isomers' mean?
different structural form
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what are the different forms/isomers of glucose?
a-glucose and B-glucose
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What is the difference between a-glucose and B-glucose?
The hydroxyl group points down in a-glucose and points upwards in B-glucose
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