1.1-Monomers and Polymers + 1.2-Carbohydrates Flashcards

1.1 + 1.2

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1
Q

Define Polymer. Give some examples.

A

Molecules formed when many monomers join together.
- Polysaccharides
- Proteins
- DNA/RNA

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1
Q

Define Monomer. Give some examples

A

Smaller units that join together to form larger molecules.
- Monoscaccharides (glucose, fructose,galactose)
- Amino acids
- Nucleotides

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2
Q

What happens in a condensation reaction?

A
  • A chemical bond forms between 2 molecules
  • A molecule of water is formed
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3
Q

What happens in a hydrolysis reaction?

A

A water molecule is used to break a chemical bond between 2 molecules.

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4
Q

Name the 3 hexose monosaccharides.

A
  • Glucose
  • Fructose
  • Galactose
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5
Q

Name the type of bond formed when monosaccharides react.

A

Glycosidic Bonds (1-4, 1-6)

2 monomers = 1 chemical bond = disaccharide
Multiple monomers = many chemical bonds = polysaccharides

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6
Q

Name 3 disaccharides. Describe how they form.

A

Condensation reaction forms glycosidic bond between 2 monosaccharides
- Maltose: glucose + glucose
- Sucrose: glucose + fructose
- Lactose: glucose + galactose

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7
Q

Describe the structure and functions of starch.

A

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.

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8
Q

Describe the structure and functions of glycogen.

A

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

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9
Q

Describe the structure and functions of cellulose.

A

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

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10
Q

Describe the Benedict’s test for reducing sugars.

A
  1. Add an equal volume of Benedict’s reagent to a sample.
  2. Heat the mixture in an electric water bath at 100*C for 5 mins.
  3. Positive result: colour will change from blue to orange & brick-red precipitate forms.
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11
Q

Describe the Benedict’s test for non-reducing sugars.

A
  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.
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12
Q

Describe the test for starch.

A
  1. Add iodine solution.
  2. Positive result: colour change from orange to blue-black.
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13
Q

Outline how colorimetry could be used to give qualitative results for the presence of sugars and starch.

A
  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 the absorbance or % transmission values of unknown samples. Use calibration curve to read off concentration.
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