Biological Molecules

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What two types of glucose are there?
Alpha glucose and Beta glucose
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Give some examples of a polysaccharides
Starch, glucose, cellulose
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What is the general formula for monosaccharides?
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What is an isomer?
The name given to chemicals with the same chemical formula but different structural formula
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Describe the Benedict's test for reducing sugars(RS)
RS can 'reduce' Copper (II) Sulphate (blue) to Copper (I) Oxide (orange). Add Benedict's reagent to a sample and heat it in a water bath that has been brought to the boil. Stays blue= no RS present. Green, yellow, orange or red precipitate=RS present
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How does the concentration of RS affect the colour change in the reaction?
The higher the concentration of RS, the further the colour change goes (i.e. green= low concentration, brick red= high concentration)
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How can a colorimeter be used to compare colour change?
Can provide an accurate way of comparing. Filter the solution to remove the precipitate . The colorimeter will measure the aborption of light
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Give an example of a non-reducing sugar
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How do you test for non-reducing sugars? (N-RS)
First break them down into monosaccharides. Neutralise by adding sodium hydrogencarbonate. Then carry out Benedict's test like you would for RS. If the sample stays blue then there is no N-RS present. Green, yellow, orange, red= N-RS present
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What is polymerisation?
The process of reacting monomer molecules together in a chemical reaction to form polymer chains
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What is a condensation reaction?
A chemical reaction in which 2 molecules combine to form a larger molecule with the loss of a smaller molecule (water)
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Define hydrolysis reaction
A chemical process in which a molecule of water is added to a substance which causes the substance and the water molecule to split
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Which monosaccharides form the disaccharide lactose?
Glucose and galactose
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What type of glycosidic bond is formed in lactose?
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What monosaccharides form maltose?
2 alpha glucose
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Which monosaccharides form sucrose?
Glucose and Fructose
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What type of glycosidic bond is formed in sucrose?
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Why is it called a 1,2 bond?
Bond fomed between Carbon 1 and Carbon 2 of the constituent monosaccharides
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What bonds hold polysaccharides together?
Covalent bonds
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What reaction forms polysaccharides?
Condensation polymerisation
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How are glucose molecules held together?
Glycosidic bonds
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What do plants store excess glucose as?
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What is starch formed of?
Two polysaccharides of alpha glucose- amylose and amylopectin
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Amylose is branched/unbranched
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What is the structure of amylose?
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What are the benefits of this structure?
Makes it compact so you can fit more of it into a small space
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Amylopectin is branched/unbranched
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Why are its side branches useful?
Allow enzymes that breakdown the molecule to get at the glycosidic bonds easily so glucose can be released quickly
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Why is starch good for storage?
Insoluble in water+ doesnt affect water potential so it doesn't allow water to enter the cell by osmosis so the cell doesn't swell (more compact)
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What are amyloplasts?
Found in the cytoplasm of plant cells. Starch molecules are built up into starch grains in amyloplasts
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How do animals store excess glucose?
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What kind of glycosidic bonds are in glycogen?
1,4 and 1,6
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Why does glycogen have a very compact structure?
Branches off frequently (more so than amylopectin)
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Where is glycogen often found?
Liver cells and muscle tissue
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Why is glycogen well suited to its function?
Compact so doesn't take up much space and prevents too high a conc of glucose in cells. Can be readily hydrolysed to glucose to use a a respiratory substrate
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Lipids are hydrophilic/hydrophobic
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What do lipids dissolve well in?
Organic solvents (e.g. propanone)
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What do lipids dissolve poorly in?
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Fats and oils are mostly T__________
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What are triglycerides composed of?
3 fatty acid residues bonded to a 3 carbon molecule called glycerol
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Cellulose is made of unbranched alpha/beta glucose
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What is formed when beta-glucose bonds?
Straight cellulose chains linked together by hydrogen bonds between the hydroxyl groups to form microfibrils
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How do microfibrils provide structural support?
Have great tensile strength enabling them to resist pulling forces
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Describe the iodine test for starch
Add iodine dissolved in potassium iodide solution to the test sample. If starch is present the sample changes from browny-orange to a blue-black colour
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What are the two kinds of fatty acids?
Saturated and unsaturated
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Do saturated fatty acids contain any double bonds between their carbon atoms?
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What causes the unsaturated fatty acid chains to 'kink'?
Double bonds between carbon atoms
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How many carbons are there in glycerol?
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Which group are fatty acids in?
Carboxylic Acid group (-COOH)
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What bonds link carbon atoms in saturated fatty acids?
Single covalent bonds
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Can more carbon atoms be added to an unsaturated fatty acid?
Yes bc it contains at least 1 C-C double bond
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Why are unsaturated fatty acids more fluid?
They contain a 'kink' which makes them more fluid compared to the rigidity of saturated fatty acids in which the lack of kink makes them solid
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Give examples of saturated fatty acids
Palmitic acid and stearic acid
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Give an example of unsaturated fatty acid
Oleic acid (found in plant oils and some animal fats)
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What combines to form a triglyceride?
Fatty acids and glycerol
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What reaction causes a triglyceride to form?
Condensation reaction
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What bonds are formed in a triglyceride?
Ester bonds
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What does the R group of a triglyceride represent?
A fatty acid residue
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How is a phospholipid produced?
If one fatty acid from a triglyceride is replaced with a phosphate containing group
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Why is the 'head' of a phospholipid hydrophilic?
It contains glycerol and a phosphate group so os polar
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Why are are hydrocarbon tails of a phospholipid hydrophobic?
They are non-polar so don't mix with water
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Describe the emulsion test for fats and oils
Add a few drops of the liquid sample to a test tube. Add ethanol and shake thoroughly. Add distilled water. A layer of cloudy white suspension forms which is called an emulsion
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What is the polarity of water and why?
It is polar and have an uneven distribution of charge as the electrons have orientated themselves closer to the oxygen atom so they are delta negative (therefor hydrogen atoms are delta positive)
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What bond is formed between oxygen and hydrogen atoms?
Hydrogen bonds
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Hydrogen bonds are weak which means...
... they can be easily broken but also easily reformed
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Name 6 properties of water
Good solvent, high specific heat capacity, high latent heat of vapourisation, less dense as a solid, high surface tension/adhesion/cohesion and important metabolite
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Why is water a good solvent?
Water molecules gather closely around any substance that has an electrical charge so the ion will dissolve.
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Define specific heat capacity
The heat energy needed to raise the temperature of 1kg of water by 1oC
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Why does water have a high specific heat capacity?
Water can absorb large amounts of heat energy before its temp increases by any significant amount. A lot of heat energy is needed to overcome the hydrogen bonds and make the water molecules free to move so less energy available to heat the water
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Water acts as a t.... b...... in large bodies of water and terrestrial organisms
thermal buffer
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What is latent heat?
While changing state a substance will either take in or expel heat energy without changing temperature which is called latent heat
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How does latent heat allow organisms to cool down without losing much water?
It takes a lot of heat to change water from a liquid to a gas which means that organisms can use water loss through evaporation to cool down without losing much water
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Why is water less dense as a solid?
When water freezes into ice, it crystallizes into a rigid lattice that increases the space between molecules, with each molecule hydrogen bonded to 4 other molecules. Water expands when it freezes so its density (mass per unit of volume)will decrease
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What causes water to be cohesive and adhesive?
Its polarity
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Define cohesive
Water molecules stick to other water molecules by hydrogen bonding
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Define adhesive
Water molecules stick to other polar molecules by hydrogen bonding
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How does cohesion allow transport in xylem vessels?
With hydrogen bonding water has large cohesive forces which allow it to be pulled up through a tube e.g. in a xylem vessel
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How is water used to break down molecules?
In hydrolysis reactions water is used to break down complex molecules (e.g. proteins to amino acids)
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What is an inorganic ion?
Does not contain carbon
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Which ion does haemoglobin contain?
Fe2+ ion (Iron ion)
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What is the structure of haemoglobin?
4 polypeptide chains each with an Fe2+ ion prosthetic group in the centre
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How does Fe2+ ions assist haemoglobin in its function?
Each Fe2+ ion can combine with a single oxygen molecule so each haemoglobin molecule can carry 4 O2 molecules
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What is the pH of a solution?
The measure of its hydrogen ion concentration
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The more H+ ions present....
the lower the pH (more acidic)
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What are sodium ions used for?
The co-transport of glucose and amino acids across cell membranes (sodium-potassium pump)
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What are the components of a phosphate group?
A phosphate ion (PO43-) attached to another molecule
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What molecules contain a phosphate group?
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How do phosphate groups help store energy in ATP?
The bonds between phosphate groups store energy
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What are amino acids?
The building blocks of proteins?
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What do proteins contain?
Oxygen, carbon, hydrogen and nitrogen (the components of amino acids)
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What causes amino acids to join together?
Condensation reactions
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What is a polypeptide?
Formed when 2 or more amino acids join together
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What bonds link amino acids?
Peptide bonds
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What is the one part of the amino acid structure that can change?
The residual group which determines what bonds it can make
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Describe the Biuret Test
Determines if a substance contains protein. The test solution needs to be alkaline so add a few drops of sodium hydroxide and mix carefully. Then add some copper (II) sulphate. Do not shake the solution. positive=purple/lilac negative=blue
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Other cards in this set

Card 2


Give some examples of a polysaccharides


Starch, glucose, cellulose

Card 3


What is the general formula for monosaccharides?


Preview of the front of card 3

Card 4


What is an isomer?


Preview of the front of card 4

Card 5


Describe the Benedict's test for reducing sugars(RS)


Preview of the front of card 5
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