3.1.2 Carbohydrates Flashcards
Name the 3 Hexose monosaccharides
- Galactose
- Glucose
- Fructose
all have the molecular formula C6H12O6
What are Monosaccharides?
The monomers from which larger carbohydrates are made
Name the type of bond formed when monosaccharides react
Glycosidic bond
What does Disaccharide mean?
2 monomers so 1 chemical bond
What does Polysaccharide mean?
Multiple monomers so many chemical bonds
How are Disaccharides formed?
Condensation reaction of 2 monosaccharides
Name 3 Disaccharides
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose
all have the molecular formula C12H22O11
Glucose has..
2 Isomers
- Alpha glucose
- Beta glucose
How are Polysaccharides formed?
Condensation of many glucose units
How are Glycogen and Starch formed ?
By the condensation of alpha glucose
How is Cellulose formed?
By the condensation of beta glucose
Describe the structure of Cellulose
- Straight unbranched chain
- Alternate glucose molecules are rotated 180°
- Hydrogen bonds form cross links between parallel strands, forming microfibrils, which give high tensile strength
Function of Cellulose
Polymer of beta glucose and gives rigidity to plant cell walls, preventing bursting under turgor pressure holding the stem up
Describe the structure of Starch
- Insoluble so no osmotic effect on cells
- Large so doesn’t diffuse out of cells
- Compact
- Branched so many terminal ends for hydrolysis into glucose
Function of Starch
Major energy source in diets and storage of polymer alpha glucose in plant cells
Describe the structure of Glycogen
- Compact
- Insoluble so no osmotic effect and doesn’t diffuse out of cells
- Branched so many terminal ends for hydrolysis
Function of Glycogen
Main storage polymer of alpha glucose in animal cells (liver and muscle cells) and is also found in plant cells
Describe the test for Starch
- Add iodine solution
- Positive result: colour change from orange to blue-black
Describe the Benedict’s test for reducing suguars
- Add an equal volume of Benedict’s reagent to a sample
- Heat the mixture in an electric water bath at 100 degrees for 5 mins
- Positive result: colour change from blue to orange and brick red precipitate forms
Describe the Benedict’s test for non-reducing suguars
Negative result: Benedict’s reagent remains blue
- Hydrolyse non reducing suguars into their monomers by adding by adding 1cm cubed of HCL
- Heat in a boiling water bath for 5 mins
- Neutralise mixture using sodium carbonate solution
- Proceed with the benedict’s test as usual