BM - Carbohydrates

Question 1

What are the isomers of Glucose?

Answer 1

Alpha-glucose
Beta-glucose

Question 2

What is a reducing sugar?

Answer 2

A sugar which is able to donate electrons to another chemical.

Question 3

What types of sugars are reducing?

Answer 3

All monosaccharides
Some disaccharides

Question 3

What is a non-reducing sugar?

Answer 3

A sugar which is not able to donate electrons to another chemical.

Question 4

What types of sugars are non-reducing?

Answer 4

All polysaccharides
Some disaccharides

Question 5

What is the test for identifying a reducing sugar?

Answer 5

1 - add 2cm³ of food sample to be tested into test tube. If the sample is not liquidised, grind it up in water before adding to test tube.
2 - Add an equal volume of benedict’s reagent
3 - Heat the mixture in a gently boiling water bath for 5 minutes.

Question 6

What is the test for identifying a non-reducing sugar?

Answer 6

1 - add 2cm³ of food sample to be tested into test tube. If the sample is not liquidised, grind it up in water before adding to test tube.
2 - Add an equal volume of benedict’s reagent
3 - Heat the mixture in a gently boiling water bath for 5 minutes.
4 - If there is no colour change, add acid and then alkali to the sample and repeat steps 1 - 3.

Question 7

What type of molecules are polysaccharides?

Answer 7

Macromolecules.
- Slightly/ insoluble in water
- formed by condensation reactions
- non-reducing sugars

Question 8

What are the polysaccharides of α-glucose?

Answer 8

Glycogen
Starch (amylose and amylopectin)

Question 9

What are the polysaccharides of β-glucose?

Answer 9

Cellulose

Question 10

Glycogen ((7))

Answer 10

• Insoluble
• Energy store in animals + fungi
• 1 - 4 & 1 - 6 linked glucose
• Coiled structure (good for storage)
• Polymer of α-glucose
• larger surface area for enzymes to hydrolyse glycosidic bonds & this allows glucose to be released quickly.
• similar to amylopectin but it has more branches

Question 11

Starch ((4))

Answer 11

• Polymer of α-glucose
• Made from amylose & amylopectin
• Insoluble
• Energy store in plants

Question 12

Amylopectin ((4))

Answer 12

• Polymer of α-glucose
• A component of starch alongside amylose
• Long branched chains (large surface area)
• Side chains

Question 13

Amylose ((5))

Answer 13

• Polymer of α-glucose
• 1 - 4 linked glucose molecules
• Coils into a helix for storage (compact for storage)
• Stabilised by H bonds
• Iodine can get ‘trapped’ in

Question 14

Cellulose

Answer 14

• Polymer of β-glucose
• Insoluble
• Long unbranched chains (straight chains)
• Cellulose + Cellulose form H bonds to create microfibrils (strong but flexible - valuable to structure)