1.2 Carbohydrates ( biological molecules ) Flashcards
what are monosaccharides give 3 examples
- monomers from which larger carbohydrates are made
- glucose , fructose , galactose
describe the structure of alpha glucose
- OH at the bottom of shape
- H at the top
- O in between
describe the differences between structures of alpha and beta glucose
- isomers => same molecular formula but differently arranged atoms
- OH group is below carbon 1 in a alpha glucose but above carbon 1 in beta glucose
what are disaccharides and how are they formed
- two monosaccharides joined together with a glycosidic bond
- formed by a condensation reaction releasing a water molecule
list 3 common disaccharides and monosaccharides from which they’re made
Maltose => glucose + glucose
Sucrose => glucose + fructose
Lactose => glucose + galactose
what are polysaccharides and how are they formed
Many monosaccharides joined together with glycosidic bonds
- formed by many condensation reactions releasing many water molecules
describe the basic function and structure of starch and glycogen
starch - energy store in plant cells
• polysaccharide of alpha glucose
• some has 1,4 glycosidic bonds so is unbranched
• some has 1,6 glycosidic bonds so is branched
Glycogen - energy store in animal cells :
• polysaccharide made of alpha glucose
• 1,4 and 1,6 glycosidic bonds => branched
explain how the structures of starch and glycogen relate to their functions
Starch :
• helical => compact for storage in cell
• large , insoluble polysaccharides molecule => cant leave cell
• insoluble in water => water potential of cell not affected
Glycogen :
• branched => compact
• branched => more ends for faster hydrolysis to release glucose for respiration to make ATP for energy release
• large , insoluble polysaccharides molecules => can’t leave cell
• insoluble in water => water potential of cell not affected
describe the basic function and structure of cellulose
- provides strength and structural support to plant / algal cell walls
• polysaccharides of beta glucose
• 1,4 glycosidic bonds so forms straight , unbranched chains
• chains linked in parallel by hydrogen bonds forming microfibrils
explain how the structure of cellulose relates to its function
- every other beta glucose molecule is inverted in a long straight unbranched chain
- many hydrogen bonds links parallel strands to form microfibrils
- hydrogen bonds are strong in high numbers
- so provides strength to plant cell wall
describe the test for reducing sugars
( monosaccharides, maltose , lactose )
1) add benedict’s solution to sample
2) heat in a boiling water bathe
3) positive result = red ppt
describe the test for non reducing sugars
non reducing = sucrose
1) do benedict’s test and stays blue
2) heat in a boiling water bath with acid
3) neutralise with alkali
4) heat in a boiling water bath with benedict’s solution
5) positive result = red ppt
suggest a method to measure the quantity of sugar in solution
- carry out benedict’s test as above , then filter and dry ppt
- find mass / weight
suggest another method to measure the quantity of sugar in a solution
1) make sugar solutions of known conc e.g dilution series
2) heat a set volume of each sample with a set of volume of benedict’s solution for the same time
3) use colorimeter to measure absorbance of each known concentration
4) plot calibration curve => conc on x axis , absorbance on y axis and draw line of best fit
5) repeat benedict’s test with unknown sample and measure absorbance
6) read off calibration curve to fine conc associated with unknown samples absorbance
describe the biochemical test for starch
- add iodine dissolved in potassium ipdide
- positive result = blue - black
