1.1-Monomers and Polymers + 1.2-Carbohydrates Flashcards
1.1 + 1.2
Define Polymer. Give some examples.
Molecules formed when many monomers join together.
- Polysaccharides
- Proteins
- DNA/RNA
Define Monomer. Give some examples
Smaller units that join together to form larger molecules.
- Monoscaccharides (glucose, fructose,galactose)
- Amino acids
- Nucleotides
What happens in a condensation reaction?
- A chemical bond forms between 2 molecules
- A molecule of water is formed
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
Name the type of bond formed when monosaccharides react.
Glycosidic Bonds (1-4, 1-6)
2 monomers = 1 chemical bond = disaccharide
Multiple monomers = many chemical bonds = polysaccharides
Name 3 disaccharides. Describe how they form.
Condensation reaction forms glycosidic bond between 2 monosaccharides
- Maltose: glucose + glucose
- Sucrose: glucose + fructose
- Lactose: glucose + galactose
Describe the structure and functions of starch.
Storage Polymer of a-glucose in plant cells
- Insoluble = no osmotic effect on cells
- Large = does not diffuse out cells
Made from amylose:
- 1,4 glycosidic bonds
- Helix with intermolecular H-bonds = compact
Amylopectin:
- 1,4 and 1,6 glycosidic bonds
- Branched = many terminal ends for hydrolysis into glucose.
Describe the structure and functions of glycogen.
Main storage polymer of a-glucose in animal cells but can also be found in plant cells.
- 1,4 and 1,6 glycosidic bonds
- Branched = many terminal ends for hydrolysis
- Insoluble = no osmotic effect and does not diffuse out of cells
- Compact
Describe the structure and functions of cellulose.
Polymer of b-glucose gives rigidity to plant cell walls (prevents bursting under turgid pressure, holds the 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*C for 5 mins.
- Positive result: colour will 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 1cm^3 of HCl. Heat in a boiling water bath for 5 mins.
- Neutralise the mixture using sodium carbonate solution.
- 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 the absorbance or % transmission values of unknown samples. Use calibration curve to read off concentration.