1.1 Monomers and Polymers & 1.2 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 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.
Condensation reaction forms glycosidic bond between 2 monosaccharides
- maltose: glucose + glucose
- sucrose: gluctose + fructose
- lactose: glucose + galactose
all have molecular formula C12H22O11
Describe difference in structures of alpha and beta glucose
alpha: OH group on right carbon in downwards position
beta: OH group on right carbon in upwards position
Describe structure and functions of starch
- storage polymer of a-glucose in plant cells
- insoluble= no osmotic effect on cells
- large= does not diffuse out of cells
made from amylose:
- 1,4 glycosidic bonds
- helix with intermolecular H-bonds= compact
and amylopectin:
-1,4 & 1,6 glycosidic bonds
- branched= many terminal ends for hydrolysis into glucose
Describe structure and functions of glycogen
main storage polymer of a-glucose in animal cells
-1,4 & 1,6 glycosidic bonds
- branched= many terminal ends for hydrolysis
- insoluble= no osmotic effect and does not diffuse out of cells
- compact
Describe structure and function of cellulose
polymer of b-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 degrees
- H-bonds crosslinks between parallel strands form microfibrils= high tensile strength
Describe Benedict’s test for reducing sugars
- Add an equal volume of Benedict’s reagent to a sample
- Heat mixture in an electric water bath at 100*c for 5 mins
- Positive result: colour change from blue to orange & brick-red precipitate forms
Describe 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 water bath for 5 mins.
- Neutralise mixture using sodium carbonate solution
- Proceed with the Benedict’s test as usual
Describe 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 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.
