1.1-> 1.3 Carbohydrates

Question 1

Hydrogen bonding

Answer 1

electrons within a (polarized) molecule are not evenly distributed but tend to spend more time at one position- region is more negatively charged

negative region and positive region attract one another, so weak electrostatic bonds form between the two

Question 2

Polymer

Answer 2

Long chain molecule made up of monomer sub-units joined together

Question 3

Condensation reaction

Answer 3

Each time a new sub-unit is attached to a polymer, a molecule of water is formed

Question 4

2 examples of condensation reaction

Answer 4

1. polypeptide from amino acid
2. polysaccharide starch from monosaccharide glucose

Question 5

Hydrolysis

Answer 5

When water molecules are used to break bonds that link sub-units of a polymer, whereby splitting the molecule into its constituent parts

Question 6

2 examples of hydrolysis

Answer 6

1. polypeptides into amino acids
2. starch into glucose

Question 7

One mole

Answer 7

Contains same number of particles as there are in 12g of Carbon12 aroms
6.022 x 10^23

Question 8

Molar solution

Answer 8

Contains one mole of solute in each litre of solution

Question 9

Carbon atom unusual feature

Answer 9

readily form bonds with other carbon atoms
this allows a sequence of carbon atoms of various lengths to be built up
these form a backbone which other atoms can be attached

Question 10

Carbohydrates

Answer 10

made up of carbon and water

Question 11

Single monomer of carbohydrates

Answer 11

monosaccharide(sugar) - soluble sweet-tasting substances

Question 12

Monosaccharide basic formula

Answer 12

general formula (CH2O)n

Question 13

Formula of glucose

Answer 13

C6H12O6

Question 14

examples of monosaccharide

Answer 14

glucose
fructose
galactose

Question 15

Test for reducing sugars

Answer 15

1. Add 2cm3 of food sample to be tested into a test tube
2. Add an equal volume of blue Benedict’s reagent(copper II sulphate)
3. Heat the mixture in a gently boiling water bath for 5 minutes
4. If reducing sugar is present, it forms an insoluble red/orange-brown precipitate of copper I oxide

Question 16

Reducing sugar

Answer 16

sugar that can donate electrons to another chemical
e.g glucose, galactose and fructose

Question 17

Disaccharide

Answer 17

When two monosaccharides are combined in a pair

Question 18

3 examples of disaccharides

Answer 18

1. glucose + glucose -> maltose
2. glucose + fructose-> sucrose
3. glucose + galactose-> lactose

Question 19

What happens when monosaccharides join together

Answer 19

Condensation reaction - a molecule of water is removed
a glycosidic bond is formed

Question 20

Test for non- reducing sugars

Answer 20

1) Grind up sample into liquid form
2) Add 2cm3 of food sample to be tested and an equal volume of blue Benedict’s reagent(copper II sulphate) into a test tube
3) Filter the mixture
4) Heat the mixture in a gently boiling water bath for 5 minutes. If the solution doesn’t change colour, then a reducing sugar isn’t present
5) Add another 2cm3 of food sample to2cm3 of dilute hydrochloric acid in a test tube in a gently boiling water bath for 5mins. The dilute HCl will hydrolyse any disaccharide present into its constituent monosaccharides
6) Slowly add some sodium hydrogen carbonate solution to the test tube in order to neutralise the HCl(Benedict’s reagent won’t work in acidic conditions). Test with pH paper to check solution is alkaline
7) Re-test solution by heating it with 2cm3 of Benedict’s reagent in gently boiling water bath for 5mins
8) If non-reducing sugar is present in original sample, solution will now turn orange-brown.

Question 21

Example of non-reducing sugar

Answer 21

sucrose

Question 22

Polysaccharide

Answer 22

polymers formed from many repeating monosaccharide sub-units
joined by glycosidic bonds formed from condensation reaction
very large molecule so is insoluble- suitable for storage