CARBOHYDRATES 2 - POLYSACCHARIDES

Question 1

What are oligosaccharides?

Answer 1

Molecules with 3-10 monosaccharide units.

Question 2

What is hydrolysis?

Answer 2

A reaction in which bonds are broken by the addition of a water molecule

Question 3

What is amylose?

Answer 3

A complex carbohydrate containing only glucose monomers joined together by 1,4-glycosidic bonds so the molecule form long unbranched chains.

Question 4

What is amylopectin?

Answer 4

A complex carbohydrate made up of glucose monomers joined by both 1,4-glycosidic bonds and 1,6-glycosidic bonds so the molecules branch repeatedly.

Question 5

What is the structure of glycogen?

Answer 5

Made up of many α-glucose units joined by 1,4-glycosidic bonds but also has 1,6-glycosidic bonds, giving it many side branches.

Question 6

What is cellulose’s structure?

Answer 6

A complex carbohydrate with β-glucose monomers held together by 1,4-glycosidic bonds where one of the monomer units has been inverted.
-It is very important in plant cell walls.

Question 7

When are glycosidic bonds broken?

Answer 7

With the addition of a molecule of water in hydrolysis reactions.

Question 8

Where does hydrolysis occur?

Answer 8

During digestion in the gut, and also in the muscle and liver cells when the carbohydrate stores are broken down to release sugars for use in cellular respiration.

Question 9

Why does the structure of polysaccharides make them ideal as storage molecules?

Answer 9

• They can form very compact molecules, so large numbers can be stored in cells.
• Glycosidic bonds are easily broken, allowing rapid release of monosaccharide units for cellular respiration.
• They are not very soluble in water, so have little water potential within a cell and cause no osmotic water movements.

Question 10

The sugars produced by photosynthesis are…

Answer 10

rapidly converted into starch, which is insoluble and compact but can be broken down to release glucose when needed.

Question 11

Starch is made of long chains of…

Answer 11

α-glucose.

Question 12

Starch is made of what two compounds?

Answer 12

Amylose and amylopectin .

Question 13

As the chain length of amylose lengthens the molecule…

Answer 13

forms a spiral, which makes it more compact for storage.

Question 14

In amylopectin the branching chains have…

Answer 14

terminal glucose molecules that can be broken off rapidly when energy is needed.

Question 15

Starch is the combination of what chains?

Answer 15

Straight and branched.

Question 16

Like starch glycogen is very compact, but…

Answer 16

glycogen has more 1,6-glycosidic bonds, giving it many side branches. So, it can be broken down more rapidly. Making it ideal for active tissue with a constantly high rate of cellular respiration.(muscle & liver.)

Question 17

What is the cell wall in plants made over?

Answer 17

Insoluble cellulose.

Question 18

What is cross linking in cellulose?

Answer 18

the linking of β-glucose molecules means that the hydroxyl (-OH) groups stick out on both sides of the molecule. Resulting in hydrogen bonds forming between the partially +ve charged H atoms of the -OH & the partially -ve charged oxygen in other areas of the glucose molecules.

Question 19

Why can some animals digest cellulose and others can’t?

Answer 19

Some animals have bacteria and fungi that live in their gut which produce cellulose-digesting enzymes.

Question 20

A typical starch grain contains how much amylopectin and amylose?

Answer 20

amylopectin = 70-80%
amylose = 20-30%

Question 21

How do you test for starch?

Answer 21

Add a few drops of iodine solution to a solid sample or a sample in solution, when starch is present the solution will turn blue-black.