carbohydrates

Question 1

draw the structure of alpha glucose

Answer 1

OH on right at bottom

Question 2

what are monosaccharides giving 3 examples

Answer 2

monomers from which larger carbohydrates are made

glucose,fructose,galactose

Question 3

draw the structure of beta glucose

Answer 3

OH on right at the top

Question 4

what are disaccharides and how are they formed

Answer 4

two monosaccharides joined together with a glucosidic bond
formed by a condensation reaction releasing a water molecule

Question 5

list 3 common disaccharides and monosaccharides in which they are made

Answer 5

glucose + glucose –> maltose
glucose + fructose –> sucrose
glucose + galactose –> lactose

Question 6

draw a diagram to show how two monosaccharides are joined together

Answer 6

two OH form glycosidic bond releasing water H2O

Question 7

what are polysaccharides and how are they formed

Answer 7

dmany monosaccharides joined together with glycosidic bonds
formed by many condensation reactions, releasing water molecules

Question 8

describe the basic function and structure of starch

Answer 8

energy store in plant cells
- polysaccharide of alpha glucose
- amylose- 1,4-glycosidic bonds unbranched
-amylopectin- 1,4 and 1,6-glycosidic bonds branced

Question 9

describe the basic function and struture of glycogen

Answer 9

energy store in animal cells
- polysaccharide made of alpha glucose
-1,4 and 1,6 glycosidic bonds branched

Question 10

explain how the structure of starch relates to its function

Answer 10

helical - compact for storage in cell
large and insolube - cant leave cell
insoluble in water - water potential of cell not affected

Question 11

explain how the structure of glycogen relates to its function

Answer 11

branched - compact
branched - more ends for faster hydrolysis - release glucose for respiration to make ATP for energy release
large and insoluble - cant leave cell
- insoluble in water - water potential of cell not affected

Question 12

describe the basic function and structure of cellulose

Answer 12

provides strength and structural support to plant
- beta glucose
- 1,4-glycosidic bonds straight unbrached chains
- chains linked parallel by hydrogen bonds forming microfibrils

Question 13

explain how the structure of cellulose relates to its function

Answer 13

• every other beta glucose inverted in a long straight unbranched chain
• many hydrogen bonds link parallel strands forming microfibrils
• hydrogen bonds strong in high numbers
• provides strength to cell walls

Question 14

desribe the test for reducing sugars

Answer 14

1. add benedicts solution to sample
2. heat in a boiling water bath
3. positive = red precipitate

Question 15

describe the test for non reducing sugars

Answer 15

1. do benedicts test and stays blue
2. heat in boiling water bath with acid
3. neutralise with alkali
4. heat in boiling water bath with benedicts
5. positive = red precipitate

Question 16

suggest a method to measure the quantity of sugar in a solution

Answer 16

carry out benedicts test then filter and dry precipitate
find mass

Question 17

suggest another method to measure the quanity of sugar in solution

Answer 17

1. make sugar solutions of known concentration
2. heat a set volume of each sample with a set volume of benedicts solution for same time
3. use colorimeter to measure absorbance of each known conc.
4. plot a calibration curve - conc. on x axis, absorbance on y and draw line of best fit
5. repeat with unknown sample and measure absorbance
6. read off calibration cure to find conc. associated with unknowwn samples absorbance

Question 18

decribe the biochemical test for starch

Answer 18

1. add iodine dissolved in potassium iodide
2. positive = blue black