1.1/1.2 Carbohydrates Flashcards
1) What is a polymer?
A polymer is many monomers joined together
2) Describe a condensation reaction
A condensation reaction joins two molecules together with the formation of a chemical bond and involves the production of a molecule of water
3) Describe a hydrolysis reaction
A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.
1) Define a monosaccharide. Name the three monosaccharides you need to know and give their formula.
Monosaccharides: a single carbohydrate unit which cannot be hydrolysed (broken down) to any simpler carbohydrate.
Glucose, galactose and fructose are examples – all have the formula C6H12O6
3) Describe the reaction which forms a disaccharide.
Formed when two monosaccharides join together. A condensation reaction occurs, a water molecule is removed and a glycosidic bond is formed between the two monosaccharides.
2) Draw the Structures of Alpha and Beta glucose
Check notes
4) Draw the reaction which forms maltose from its monosaccharides and circle the bond formed.
Check notes
5) For each of the disaccharides you need to know (there are 3), write the monosaccharides they are formed from and the chemical equation for each.
Lactose C12H22O11: made of glucose and galactose
Sucrose C12H22O11: made of glucose and fructose
Maltose C12H22O11: 2 a-glucose molecules joined together
6) What is a polysaccharide?
Polysaccharides: are long chains of many monosaccharides joined together in condensation reactions with the formation of glycosidic bonds
Functions and properties of starch
Found in plants
Storage molecule
Made of alpha glucose
Chains form a helical structure – some branches
Hydrogen bonding – holds starch in a helical shape
Mainly 1-4 glycosidic bonds and some 1-6 glycosidic bonds.
Functions and properties of Glycogen
Found in Animals
Storage molecule
Made of alpha glucose
Helical with lots of branches
Hydrogen bonding – holds glycogen in a helical shape
Mainly 1-4 glycosidic bonds and lots of 1-6 glycosidic bonds
Functions and properties of Cellulose
Found in Plants
Provides strength to cell walls
Made of beta glucose
Every other beta glucose is inverted
Long straight chains
MANY H-bonds between the long, straight chains forming microfibrils and fibrils
Only 1-4 glycosidic bonds
1) Describe the difference in structure between starch and cellulose
- Starch is made of alpha glucose whereas cellulose is made of beta glucose.
- Starch is made of mainly 1-4 glycosidic bonds and some 1-6 glycosidic bonds. Cellulose contains only 1-4 glycosidic bonds.
- Starch glucose monomers are the same way up. Cellulose glucose monomers are alternately inverted.
- Starch has a coiled, helical structure whereas cellulose is made of long straight chains.
- Many hydrogen bonds between long straight chains in cellulose, but no hydrogen bonds between chains in starch
1) How is the structure of starch related to its function?
- Compact storage molecule because of its helical structure
- Doesn’t affect osmosis/ water potential because it is insoluble
- Cannot leave cells because it is a large molecule
1) How is the structure of glycogen related to its function?
- Can be hydrolysed quickly because it has lots of branches, so enzymes can act at the end of each branch
- Doesn’t affect osmosis/ water potential because it is insoluble
- Compact storage molecule because its helical structure
1) How does the structure of cellulose relate to its function?
Long straight chains are joined together by MANY hydrogen bonds forming microfibrils. This provides strength to the cell wall.
1) Describe the test for Reducing sugars
- Heat with Benedict’s solution. Brick red precipitate shows the presence of a reducing sugar
1) Describe the test for non-reducing sugars
- Heat with Benedict’s solution and stays blue/negative
- Add HCl and heat
- Add sodium hydrogen carbonate to neutralise the acid.
- Add Benedict’s solution and heat.
- Brick red precipitate shows the presence of a reducing sugar
1) Describe the test for starch
- Add iodine dissolved in potassium iodide.
- It turns Blue/Black if starch is present
1) Describe how you would use colorimetry to identify the concentration of glucose in an unknown solution
- Create a dilution series of glucose with known concentrations
- For all known glucose concentrations, add Benedict’s solution and heat
- Remove precipitate/ allow precipitate to settle and remove solution
- Use a colorimeter to measure the % light transmission of known samples of glucose
- Draw a graph with glucose concentration (units) on the x-axis and % light transmission on the y-axis
- Plot the points on the graph and draw a line of best fit (calibration curve)
- Carry out the Benedict’s test on sample of glucose with an unknown concentration add Benedict’s solution and heat
- Remove precipitate/ allow precipitate to settle and remove solution
- Measure the % light transmission using a colorimeter
- Find this % of light transmission on the y-axis and draw a horizontal line until you reach the calibration curve.
- Then draw a vertical line down and read the concentration of glucose from the x-axis
