P1: bio-molecules: poly, mono and carbs

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Define monomer

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Paper 1 Topic 2 biological molecules. If it’s helpful feel free to save or check the other sets :)

20 Terms

1

Define monomer

Smaller units that join together to form larger molecules

Eg. monosaccharides (fructose, glucose and galactose)

Amino acids

nucleotides

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2

Define Polymer

molecules formed when many monosaccharides join together

eg. Polysaccharides

proteins

DNA/RNA

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3

What happens in a condensation reaction?

A chemical bond forms between 2 molecules and a molecule of water is produced

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4

What happens in a hydrolysis reaction?

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

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5

Name 3 hexose monosaccharides

glucose, fructose and galactose

All have molecular formula C6H12O6

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6

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

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7

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

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8

Draw the structure of B-glucose

OH on carbon 1 is above the ring

<p>OH on carbon 1 is above the ring</p>
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9

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 of cells

Made from amylose:

  • 1,4 glycosidic bonds

  • Helix w intermolecular H-bonds=compact

Made from Amylopectin:

  • 1,4 and 1,6 glycosidic bonds

  • Branched=many terminal ends for hydrolysis into glucose

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10

Describe the structure and functions of glycogen

Main storage polymer of a-glucose in animal cells (but also found in plant cells)

  • 1,4 and 1,6 glycosidic bonds

  • Branched=many terminal ends for hydrolysis

  • Insoluble=no osmotic effect & does not diffuse out of cells

  • compact

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11

Describe the 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 cross links between parallel strands on oxygen molecules form microfibrils=high tensile strength

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12

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 degrees C for 5 mins

  3. Positive result: colour change from blue to orange & brick-red precipitate forms

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13

Describe the Benedict’s test for non-reducing sugars

  1. Negative result: Benedict’s reagent remains blue

  2. Hydrolyse non-reducing sugars eg. Sucrose into their monomers by adding 1cm³ of dilute acid e.g HCL. Heat in a boiling water bath for 5 mins

  3. Neutralise the mixture using an alkali

  4. Proceed with the Benedict’s test as usual

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14

Describe the test for starch

  1. Add the iodine solution

  2. Positive result: colour change from orange to blue-black

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15

Outline how colorimetry could be used to give quantitative 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

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16

Exam Q: Cellulose is a polysaccharide of B-glucose molecules. Describe how two B-glucose molecules are able to join together

  • OH group on carbon 1 is above the ring but OH group on carbon 4 of adjacent B-glucose molecule is below the ring (1)

  • only hydrogen available to form water with OH so no oxygen available to form glycosidic bond (1)

  • Every other B-glucose ‘flips’ through 180 degrees to place two OH groups adjacent to each other (1)

  • 1,4 glycosidic bonds are formed to created unbranched chains

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17

draw the shorthand structural formula of alpha-glucose

note that the5 corners of the corners of the hexagon are C atoms while one is O. each of the C atoms is designated by a number, increasing by 1 starting at the O atom.

<p>note that the5 corners of the corners of the hexagon are C atoms while one is O. each of the C atoms is designated by a number, increasing by 1 starting at the O atom. </p>
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18

differences between beta and alpha glucose?

carbon 1 hydroxyl (OH) group lies below the ring

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19

What is the general formula of monosaccharides?

(CH2O)n

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20

name the 3 key polysaccharides:

glycogen, starch and cellulose.

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