1.1 - Monomers and polymers 1.2 - Carbohydrates

Define monomer. Give some examples.

smaller units that join together to form larger

molecules

● monosaccharides (glucose, fructose,

galactose)

● amino acids

● nucleotides

Define polymer. Give some examples.

molecules formed when many

monomers join together

● polysaccharides

● proteins

● DNA / RNA

What happens in a condensation

reaction?

A chemical bond forms between 2

molecules & a molecule of water is

produced

What happens in a hydrolysis reaction?

A water molecule is used to break a

chemical bond between 2 molecules.

Name the 3 hexose monosaccharides.

● glucose

● fructose

● galactose

all have the molecular formula C 6 H 12 O

Name the type of bond formed when

monosaccharides react.

(1,4 or 1,6) glycosidic bond

2 monomers = 1 chemical bond = disaccharide

multiple monomers = many chemical bonds =

polysaccharide

Name 3 disaccharides. Describe how

they form.

condensation reaction forms glycosidic bond

between 2 monosaccharides

● maltose: glucose + glucose

● sucrose: glucose + fructose

● lactose: glucose + galactose

all have molecular formula C 12

H 22

O 11

Draw the structure of ⍺-glucose.

Draw the structure of 𝛽-glucose.

Describe the structure and functions of

starch.

storage polymer of 𝛼-glucose in plant cells

● insoluble = no osmotic effect on cells

● large = does not diffuse out of cells

and amylopectin:

● 1,4 & 1,6 glycosidic bonds

● branched = many terminal

ends for hydrolysis into

glucose

made from amylose:

● 1,4 glycosidic bonds

● helix with intermolecular

H-bonds = compact

Describe the structure and functions of

glycogen.

main storage polymer of 𝛼-glucose in animal cells

( but also found in plant cells)

● 1,4 & 1,6 glycosidic bonds

● branched = many terminal ends for hydrolysis

● insoluble = no osmotic effect & does not diffuse

out of cells

● compact

Describe the structure and functions of

cellulose.

polymer of 𝛽-glucose gives rigidity to plant cell walls

(prevents bursting under turgor pressure, holds stem up)

● 1,4 glycosidic bonds

● straight-chain, unbranched molecule

● alternate glucose molecules are rotated 180°

● H-bond crosslinks between parallel strands form

microfibrils = high tensile strength

Describe the Benedict’s test for reducing

sugars.

1. Add an equal volume of Benedict’s reagent

to a sample.

2. Heat the mixture in an electric water bath at

100℃ for 5 mins.

3. Positive result: colour change from blue to

orange & brick-red precipitate forms.

Describe the Benedict’s test for

non-reducing sugars.

1. Negative result: Benedict’s reagent remains blue

2. Hydrolyse non-reducing sugars e.g. sucrose into their

monomers by adding 1cm 3 of HCl. Heat in a boiling

water bath for 5 mins.

3. Neutralise the mixture using sodium carbonate solution.

4. Proceed with the Benedict’s test as usual.

Describe the test for starch.

1. Add iodine solution.

2. Positive result: colour change from

orange to blue-black.

Outline how colorimetry could be used to

give qualitative results for the presence

of sugars and starch.

1. Make standard solutions with known concentrations.

Record absorbance or % transmission values.

2. Plot calibration curve: absorbance or % transmission

(y-axis), concentration (x-axis).

3. Record absorbance or % transmission values of unknown

samples. Use calibration curve to read off concentration.