Biological compunds

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What are the names given to the large organic compounds formed by monomers?
Macromolecules or polymers
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What is the name of the process that joins many monomers to make a polymer?
Polymerisation
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What type of compound is water?
Inorganic
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Describe the polarity of water
It is made up of 2 positively charged hydrogen atoms and one negatively charged oxygen atom
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Water is a polar molecule, what other name is given for this?
A dipole
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How do water molecules join?
Via hydrogen bonding between the slight positive of the H and the slight negative of the O
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Name the 7 properties of water
Cohesion, Solvent, Density, High specific heat capacity, High latent heat of evaporation, Transparency, Water is a metabolite
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Explain cohesion and its biological importance
Water molecules have the property of cohesion and they 'stick' together. As a result water can be pulled up through the xylem
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Explain water as a solvent and its biological importance
It dissolves many ionic/polar substances. It is used to transport substances like glucose in the blood and it allows chemical reactions to occur in cells
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Explain density and its biological importance
Ice is less dense than water so floats on the surface. Lakes and ponds freeze from the top downwards, the layer of ice helps to insulate the water, allowing organisms below to survive
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Explain high specific heat capacity and its biological importance
Water requires large amounts of heat energy to warm up and large amounts of heat energy are released when it cools down. Aquatic environments take longer to cool down in winter and longer to heat up in the summer allowing a suitable environment for
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Explain high latent heat of evaporation and its biological importance
Large amounts of heat energy are needed to make water evaporate. Evaporation of water via sweating helps to cool down humans and maintain a constant body temp.
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Explain transparency and its biological importance
Water allows light to pass through it. This is essential as aquatic plants wouldn't be able to photosynthesise.
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Explain water as a metabolite and its biological importance
Water is either used or released in many metabolic reactions. It's a reactant in photosynthesis, released when polysaccharides, lipids and proteins are made via condensation reactions
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What are the 3 main types of carbohydrates
Monosaccharides, Disaccharides and Polysaccharides
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Describe Monosaccharides
Made up of 1 sugar, sweet, soluble in water, low molecular mass
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Name 3 types of monosaccharides
Triose sugars, Pentose sugars and hexose sugars
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What is meant by structural isomerism?
All monosaccharides exhibit structural isomerism. For example, all hexoses have exactly the same molecular formula but they have different structures.
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How many carbon atoms do trioses have in their skeleton?
3
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What are 2 examples of trioses?
Glyceraldehyde and Dihydroxyacetone
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What group does Glyceraldehyde contain and therefore what is it known as?
Aldehyde group, an aldotriose
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What group does dihydroxyacetone contain and therefore what is it known as?
Ketone group, a ketotriose
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How man carbons to hexoses have?
6
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Name 3 examples of hexoses
Glucose, Fructose and Galactose
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Hexoses possessing an aldehyde group (e.g. glucose) form what when dissolved in water?
A six-sided ring called a pyranose ring
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Hexoses possessing a ketone group (e.g. fructose) form what when dissolved in water?
A five-sided ring called a furanose ring
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In ALPHA glucose where does the hydroxyl group (-OH) on carbon 1 lie?
Below the plane of the ring
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In BETA glucose where does the hydroxyl group (-OH) on carbon 1 lie?
Above the plane of the ring
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How many carbons do pentoses have?
5
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Name 2 examples of pentoses
Deoxyribose and ribose
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Why are pentoses needed?
For the synthesis of nucleic acids.
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What type of rings do pentoses form in solution?
Furanose rings
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How are disaccharides formed?
By a condensation reaction between two monosaccharides
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What is a condensation reaction?
It is the removal of a water molecule to form a bond and join 2 compounds
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What is the name of a bond joining two monosaccharides together?
A glycosidic bond
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Where is the glycosidic bond normally formed?
Between carbon 1 of one monosaccharide and carbon 4 of the other
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How can a condensation reaction be reversed?
Via a hydrolysis reaction, this involves the chemical addition of a water molecule to break a bond
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How is maltose formed?
By two ALPHA glucose molecules.
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Where is maltose found?
Germinating seeds
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How is sucrose formed?
ALPHA glucose and fructose
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How is sucrose used?
It's the form in which sugar is transported around a plant
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How is lactose formed?
ALPHA glucose and galactose
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Where is lactose found?
It is the sugar found in milk
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What are polysaccharides?
They are polymers
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Are polysaccharides soluble in water?
NO
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What are the functions of polysaccharides?
Glucose storage or they have structural roles
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Why are polysaccharides good glucose storage molecules?
They are easily converted back into glucose by hydrolysis and their large size makes them insoluble in water so they exert no osmotic or chemical effect on the cell
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What is the glucose storage polysaccharide in plant cells?
Starch
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What are the names of the two different polysaccharides starch is a mixture of?
Amylose and amylopectin
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Describe amylose
Made entirely out of ALPHA (A) glucose, only has A 1,4 bonds, no side branches so folds up into a spiral shape
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Describe amylopectin
Made entirely out of ALPHA (A) glucose, has A 1,6 bonds as well as A 1,4 bonds. Highly branched structure because of the numerous side links
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How is the structure of amylose and amylopectin related to the function of starch?
The ALPHA glycosidic bonds in these 2 are very easily hydrolysed. This means starch is ideal as both types easily release glucose when the plant cells are short of it.
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Is there more amylose or amylopectin in starch?
More amylose
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What is the glucose storage polysaccharide in animals?
Glycogen
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How is glucose converted into glycogen?
In the liver by the hormone insulin
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Describe the structure of glycogen
It is similar in structure to amylopectin but has more side branches i.e every eight glucose
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What does the structure of glycogen allow?
It allows for a more rapid hydrolysis of starch which is important as animals need glucose faster than plants.
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What are the 2 structural polysaccharides?
Cellulose and chitin
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What is the main function of cellulose?
Plant cell walls
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What are some commercial uses of cellulose?
Cotton, Fabrics + Paper
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Describe the structure of cellulose
Cellulose consists of un-branched, straight chains of thousands of BETA (B) glucose molecules. There are only B 1,4 bonds, the linkage of adjacent B glucose molecules is only possible if adjacent molecules are rotated by 180'
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What does the structure of a cellulose chain allow to happen?
Cross links via hydrogen bonding between different chains, therefore cellulose is made up of many chains of BETA glucose molecules linked together by hydrogen bonding to form rope-like bundles of microibrils
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Describe the structure of chitin
It's very similar to cellulose however the only difference is that some of the -OH groups are replaced with amino acids containing the element nitrogen.
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Due to its structure, what property does cellulose have?
It is very rigid with great mechanical strength
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What are lipids made up of?
Fatty Acids and alcohol (usually glycerol)
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Why are fatty acids so called?
Because they contain a carboxyl group (COOH)
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What is an example of a saturated fatty acid?
Palmitic Acid - C15H31COOH
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What is the fatty acid tail made up of?
Hydrogen and carbon atoms, it is known as the hydrocarbon chain
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Why is Pamitic acid a saturated fatty acid?
There are no C=C double bonds in the hydrocarbon chain
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Give an example of an unsaturated fatty acid
Oleic Acid
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Why are unsaturated fatty acids so called?
Because they contain C=C double bonds in the hydrocarbon chain
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What is the alcohol found in nearly every lipid?
Glycerol
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What is glycerol's formula?
C3H8O3
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Name 2 lipids
Triglycerides and phospholipids
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What do triglycerides consist of?
They consist of a glycerol backbone where the three hydroxyl groups have joined with a fatty acid via a condensation reaction
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What is the name of the bond formed in the formation of a triglyceride?
Ester bond
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What are the functions of triglycerides?
Energy storage molecules, Source of metabolic water from respiration, thermal insulation, mechanical protection, buoyancy and waterproofing
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Why are triglycerides good energy storage molecules?
The oxidation of 1 gram of triglyceride yields nearly two and a half as much energry as 1 gram of carbohydrate
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Explain what happens to triglycerides to make them a source of Metabolic water and why is this useful?
When they are oxidised during respiration instead of carbs, over twice as much metabolic water is produced. This is useful for organisms that don't have much access to water.
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Why is carbohydrate the main respiratory substrate in most cells if triglycerides yield more energy?
This is because far less oxygen has to be consumed to release energy from carbs like glucose
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Explain triglycerides being used for thermal insulation
Fat conducts heat slowly and therefore triglycerides which are stored under the skin are important for preventing heat loss or heat gain
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Explain mechanical protection
Internal organs like the kidneys are protected from physical damage by fat
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Explain buoyancy as a function
As fat is less dense than water, fat reserves provide buoyancy for aquatic organisms
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Explain why triglycerides are used in waterproofing
Triglycerides are needed to form the waxy cuticle that waterproofs leaves and fats waterproof skin and fur
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What are the implications of saturated and unsaturated fat on human health?
Arteries can be narrowed by fatty deposits, leading to a reduction in blood flow in the affected artery. This could lead to a heart attack if said artery is the coronary artery.
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How do phospholipids differ from fats and oils?
One of the 3 fatty acids is replaced by a phosphate group
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What is special about the phosphate group?
It is hydrophilic i.e. it's polar and is soluble in water
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What are phospholipids a component of? (Function)
All cell membranes
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What is formed when a thin layer of phospholipid is spread over the surface of water?
A single monomolecular layer
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What happens if the phospholipid is present in large amounts and is shaken up with the water?
The hydrophobic fatty acid tails mix up and project inwards from the water with the hydrophilic phosphate groups surrounding them. This is known as a micelle
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What is the plasma membrane of a cell known as?
It is known as the phospholipid bilayer
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Who came up with the most recent theory about plasma membranes?
Singer and Nicholson
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What was the name of the model of the plasma membrane created?
Fluid Mosaic model
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Why is the fluid mosaic model so called?
Fluid - Everything is moving, Mosaic - The proteins are present in the membrane as a mosaic, Model - It is just an idea
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What does the amount that the protein penetrates the membrane depend on?
It depends on how large the hydrophobic portions on the protein are. Charged parts will associate with the hydrophilic phosphate heads and uncharged parts will associate with the fatty acid tails
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What is protein called that is found on the outside of a plasma membrane?
An extrinsic protein
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What is a function of an extrinsic protein?
They can act as hormone receptors and are involved in cell recognition
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What is the name given to proteins that span and penetrate the phospholipid bilayer?
Intrinsic proteins
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What is a function of intrinsic proteins?
They can act as carrier proteins and allow the passage of molecules by facilitated diffusion
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Name 4 proteins
Enzymes, Hormones, Antibodies, Membrane proteins
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What 4 things are amino acids made up of?
A carboxyl group, A basic amino group, A hydrogen atom and a variable R group
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What is the significance of the R group?
The properties of an amino acid depend on its R group. One of the most important properties Of the R group is whether it's attracted to water or not
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How are amino acids linked together?
Via condensation reactions
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What are two amino acids linked together known as?
A dipeptide
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What is the bond formed between two dipeptides?
A peptide bond
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What are many amino acids joined together known as?
A polypeptide
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What determines the order of amino acids in a polypeptide chain?
A gene
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What is the Primary structure of a protein?
The primary structure is the sequence of amino acids in a polypeptide chain
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What is the secondary structure of a protein?
The secondary structure is the predictable shape that the PP chain folds up into e.g. A Helix or B sheet due to hydrogen bonding
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Which is the most common secondary structure?
Alpha helix
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Give 2 examples of globular proteins
Enzymes, hormones
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Give 2 examples of fibrous proteins
Collagen, keratin
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What is the difference in the sequences of amino acids of globular and fibrous proteins?
Globular proteins have a highly irregular sequence, Fibrous proteins have a regularly repeating sequence
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Describe the structure of a fibrous protein
Fibrous proteins are made up of several pp chains linked by hydrogen bonds. The PP chains are made up entirely of A helix or B sheet, if all PP chains are A helices, the molecule will be rope like
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What is Keratin?
Keratin is made up of many PP chains each being an A helix. The PP chains are closely bound by bonds including hydrogen bonds. Keratin is found in wool, hair, nails, claws and beaks.
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What is Collagen?
Collagen is made up of three PP chains each being an alpha helix. The PP chains are closely bound and are held together by hydrogen bonds. Collage is a structural protein found in tendons.
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What is the tertiary structure of a protein?
The tertiary structure is the specific 3D shape the PP chain folds up into due to hydrogen, ionic and disulphide bonding between amino acids
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Name the 3 bonds in the tertiary structure starting from the weakest
Hydrogen, Ionic and disulphide
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What is the tertiary structure determined by?
It is determined by the primary structure
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What happens if there is a change in the specific 3D shape of the protein?
It will become denatured
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What does denaturation of a protein mean?
The substrates will no longer fit into the enzyme's active sites, antibodies don't recognize antigens, hormones don't fit into receptor sites
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What can cause denaturation of proteins?
Heat, changes in pH and heavy metals
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What is the quaternary structure of a protein?
The quaternary structure is the association of 2 or more PP chains (in tertiary form) to create a functional protein
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What does haemoglobin consist of?
Four PP chains, 2 Alpha chains and 2 beta chains. Haemoglobin also has a non protein group attached i.e. 'haem' made of iron
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Describe a positive test result with Benedict's solution
The test reagent is heated to 70->90'c + the Benedict's solution will turn green/orange/red depending on the concentration of the reducing sugar
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How do you test for a non reducing sugar like sucrose?
Boil the sucrose with HCL to hydrolyse the sucrose into glucose and fructose. The HCL is then neutralized with NaOH and the sucrose needs to be heated to 70-90'c with Benedict's.
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What colour does Biuret turn if protein is present?
Purple
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Card 4

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Describe the polarity of water

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Water is a polar molecule, what other name is given for this?

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