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RELEVANT LEARNING OUTCOME:
(c) Describe the structures and properties of the following biomolecules and explain how these are related to their roles in living organisms: starch (including amylose and amylopectin), cellulose and glycogen (H2 only).
Starch and Glycogen
Starch and Glycogen
Starch is made of amylose and amylopectin. Glycogen is very similar to amylopectin.
Amylose is...
Amylose is...
helical and unbranched
made of alpha-glucose units linked by alpha-(1,4)-glycosidic bonds
hydrogen bonds form between hydroxyl groups of the glucose units within the helix
No cross-linking and insoluble in water
Most of the hydroxyl groups project into the interior of the helix
Amylopectin is...
Amylopectin is...
helical but branched
made of alpha-glucose units linked by alpha-(1,4)-glycosidic bonds
hydrogen bonds form between hydroxyl groups of the glucose units within the helix
also linked by alpha-(1,6)-glycosidic bonds, causing the branching
No cross-linking but slightly more soluble in water than amylose
Branching leads to free ends, making binding to water molecules easier.
Glycogen is...
Glycogen is...
very similar to amylopectin, but has more shorter branches and more glucose units.
Contains glycogenin protein.
🖊️Check Your Understanding
🖊️Check Your Understanding
Attempt Qns 7-10 of the Carbohydrates Learning Goals.
Cellulose
Cellulose
Cellulose is the most different from starch and glycogen.
Cellulose is...
Cellulose is...
straight and unbranched
made of beta-glucose units linked by beta-(1,4)-glycosidic bonds
alternate residues rotate 180 degrees of each other.
Cross-linking and insoluble in water
Straight cellulose chains lie parallel to one another via hydrogen bonding
Intermolecular and intramolecular hydrogen bonding hold the chains together, leading to cross linking.
Cellulose chains lie together to form microfibrils. Microfibrils lie together to form macrofibrils.
Contains other polysaccharides within its matrix like hemicellulose and pectin
Cellulose has intramolecular (in blue) and intramolecular (in red) hydrogen bonding.
🕹️Simulation!
🕹️Simulation!
Explore the structure of amylose and cellulose with the following simulation:
Click on amylose / cellulose at the top
Click on 'add α / β - glucose'
Align the OH group between carbon 1 and carbon 4(green in blue circle), once it turns green, you can let go and the bond should form.
For α-glucose:
Observe how the structure of amylose changes as more α-glucose are added
For β-glucose:
What did you have to do for each alternate monomer to algin the OH groups?
How is the structure of cellulose different from amylose?
🖊️Check Your Understanding: SLS Checkpoint
🖊️Check Your Understanding: SLS Checkpoint
Visit the following SLS to review the content and answer the questions provided.
🕹️Simulation
🕹️Simulation
Check in with your teacher for the following simulation.
Labster: Iodine Test for complex carbohydrates
🖊️Check Your Understanding
🖊️Check Your Understanding
Attempt Qns 11-15 of the Carbohydrates Learning Goals.
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