Biological Molecules - Monomers, Polymers & Carbohydrates

Question 1

Define Monomer & Give Some Examples

Answer 1

Small Units That Join Together To Form Larger Molecules, eg:

• Monosaccharides
• Amino Acids
• Nucleotides

Question 2

Define Polymer - Give Some Examples

Answer 2

Molecules Formed From Many Monomers Joining Together, eg:

• Polysaccharides
• Proteins
• DNA/RNA

Question 3

What Happens In A Condensation Reaction?

Answer 3

Chemical Bond Forms Between 2 Molecules And A Molecule Of Water Is Produced

Question 4

What Happens In A Hydrolysis Reaction?

Answer 4

Water Molecule Used To Break A Chemical Bond Between 2 Molecules

Question 5

Name The 3 Hexose Monosaccharides

Answer 5

• Glucose
• Fructose
• Galactose

All With Chemical Formula C6H12O6

Question 6

Name Bond Formed When 2 Monosaccharides Join Together

Answer 6

Glycosidic Bond

1,4 or 1,6

2 Monomers With 1 Chemical Bond = Disaccharide
Many Monomers With Many Chemical Bonds = Polysaccharide

Question 7

Name The 3 Disaccharides & Describe How They Form

Answer 7

• Maltose : Glucose + Glucose
• Sucrose : Glucose + Fructose
• Lactose : Glucose + Galactose

Condensation Reactions - Forms Glycosidic Bonds Between The 2 Monosaccharides

All Have Chemical Formula of C12H22O11 (Removed Water)

Question 8

Describe The Structure Of Alpha Glucose

Answer 8

Hexagon With HOH (Hydroxide) At 4 Corners - At First Corner Orientated H-OH -, H-CH2OH at 5th and Oxygen at 6th

Question 9

Describe The Structure Of Beta Glucose

Answer 9

Hexagon With HOH (Hydroxide) At 4 Corners - At First Corner Orientated OH-H -, H-CH2OH at 5th and Oxygen at 6th

Question 10

Describe The Structure and Functions of Starch

Answer 10

Storage Polymer of All Plant Cells

Is:

• Insoluble : No Osmotic Effect On Cells
• Large : Does Not Diffuse Out of Cell

Made From Amylose or Amylopectin:
Amylose:
- 1,4 Glycosidic Bonds
- Helix With Intermolecular Hydrogen Bonds - Compact
Amylopectin:
- 1,4 and 1,6 Glycosidic Bonds
- Branched : Many Terminals Ends For Hydrolysis Into Glucose

Question 11

Describe The Structure and Functions of Glycogen

Answer 11

Main Storage Polymer of Alpha Glucose In Animal Cells (and also sometimes 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

Question 12

Describe The Structure and Functions of Cellulose

Answer 12

Polymer of Beta Glucose - Gives Rigidity To Plant Cell Walls (Prevents Any Bursting & Holds Stem Up)

• 1,4 Glycosidic Bonds
• Straight Chain : Unbranched
• Alternate Glucose Molecules : Rotated 180 Degrees After Each Glucose Molecule
• Hydrogen Bond Crosslinks Between Parallel Strands Form Microfibrils : High Tensile Strength

Question 13

Describe The Benedicts Test For Reducing Sugars

Answer 13

• Add An Equal Volume of Benedicts Reagent To A Sample
• Heat Mixture In Water Bath At 100 Degrees Celsius for 5 Minutes
• Positive Result Will Show A Colour Change From Blue To Orange/Brick Red : Precipitate Formed

Question 14

Describe The Benedicts Test For Non-Reducing Sugars

Answer 14

• Negative Benedicts Test For Reducing Sugars : Solution Remains Blue
• Hydrolyse Non-Reducing Sugars - eg: Sucrose Into Glucose + Fructose - by adding 1cm3 of HCl. Heat In Water Bath at 100 Degrees Celsius For 5 Minutes
• Neutralise Mixture Using Sodium Carbonate Solution
• Proceed With Benedicts Test - Blue-> Orange/Brick Red = Non-Reducing Sugars Present

Question 15

Describe Test For Starch

Answer 15

• Add Iodine Solution

- Colour Change From Orange to Blue/Black = Starch Present

Question 16

Outline How Many Colorimetry Could Be Used to Give Qualitative Results For The Presence of Sugars and Starch

Answer 16

1. Make Standard Solutions With Known Concentrations. Record Absorbance or % Transmission Values
2. Plot Calibration Curve: Absorbance or Transmission % (Y-axis) against Concentration (X-axis)
3. Record Absorbance/% Transmission Values of Unknown Samples. Use Calibration Curves to Read Off Concentration