1.1- 1.2 Monomers, Polymers, And Carbohydrates Flashcards
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 C6H12O6
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.
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 C12H22O11
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
- Add an equal volume of Benedict’s reagent to a sample.
- Heat the mixture in an electric water bath at 100℃ for 5 mins.
- Positive result: colour change from blue to orange & brick-red precipitate forms.
Describe the Benedict’s test for non-reducing sugars
- Negative result: Benedict’s reagent remains blue
- Hydrolyse non-reducing sugars e.g. sucrose into their monomers by adding 1cm3 of HCl. Heat in a boiling water bath for 5 mins.
- Neutralise the mixture using sodium carbonate solution. 4. Proceed with the Benedict’s test as usual.
Describe the test for starch.
- Add iodine solution.
- 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.
- Make standard solutions with known concentrations. Record absorbance or % transmission values.
- Plot calibration curve: absorbance or % transmission (y-axis), concentration (x-axis).
- Record absorbance or % transmission values of unknown samples. Use calibration curve to read off concentration.
