Carbohydrates Flashcards
What are monosaccharides & 3 examples?
monomers from which larger carbohydrates are made
- glucose
- fructose
- galactose
What is the difference between alpha & beta glucose?
- isomers are molecules with the same molecular formula but differently arranged atoms
OH group is below carbon 1 in alpha glucose whilst it’s above in beta glucose
What are disaccharides and how are they formed?
2 monosaccharides joined together with a glycosidic bond by a condensation reaction which releases a molecule of water
Give 3 examples of disaccharides and what monosaccharides they are made from
maltose = glucose + glucose
sucrose = fructose + glucose
lactose = galactose + glucose
What are polysaccharides and how are they formed?
many monosaccharides joined with a glycosidic bond formed by a condensation reaction which releases molecules of water
What is the structure and function of starch?
function: energy store in plant cells
structure:
- polysaccharide made of alpha-glucose
- amylose - 1,4 glycosidic bonds & unbranched
- amylopectin - 1,4 & 1,6 glycosidic bonds & branched
How does structure of starch relate to its function?
- helical - compact for storage in cells
- large - can’t diffuse out of cells
- insoluble - doesn’t affect cell’s water potential
What is the structure & function of glycogen?
function: energy store in animal cells
structure:
- polysaccharide made of alpha-glucose
- 1,4 & 1,6 glycosidic bonds - branched
How does the structure of glycogen relate to its function?
- branched - more can fit in a small area & more ends for faster hydrolysis which releases glucose for respiration to produce ATP faster
- large - can’t diffuse out of cell
- insoluble - doesn’t affect cell’s water potential
What is the structure & function of cellulose?
function: provides strength & structural support to plant cells
structure:
- polysaccharide made of beta-glucose
- 1,4 glycosidic bonds - straight unbranched
- chains linked in parallel by hydrogen bonds forming microfibrils
How does the structure of cellulose relate to its function?
- straight unbranched chain - every other beta-glucose is inverted
- many hydrogen bonds link parallel strands forming microfibrils
- many H bonds together are very strong which provides strength to plant cell walls
What are examples of reducing sugars & the test for them?
e.g. monosaccharides, maltose & lactose
1. add Benedict’s solution to sample
2. heat in boiling water bath
3. positive result produces red precipitate
What is an example of a non-reducing sugar and the test for them?
e.g. sucrose
1. do Benedict’s test and stays blue
2. heat in boiling water bath with HCl
3. Neutralise with sodium hydrogen carbonate (alkali)
4. heat in a boiling water bath with Benedict’s solution
5. positive result produces red precipitate
What is a method to measure the quantity of sugar in a solution?
- carry out Benedict’s test then filter & dry precipitate
- find the mass
What is another method to measure the quantity of sugar in a solution?
- make sugar solutions of known conc
- heat a set volume of each sample with a set volume of Benedict’s solution for the same time
- use colorimeter to measure absorbance of each known conc
- plot calibration curve = conc on x axis & absorbance on y axis and draw line of best fit
- repeat Benedict’s test with unknown sample & measure absorbance
- read off calibration curve to find conc associated with unknown sample’s absorbance
What is the biomedical test for starch?
- add iodine dissolved in potassium iodide and shake
- positive result produces blue/black colour of sample
