Carbohydrates

Question 1

why do large molecules often contain carbon

Answer 1

carbon atoms readily form bonds with each other that form a backbone that other atoms can be attached

Question 2

Monosaccharides

Answer 2

Simplest form of sugar and are water soluble

Question 3

Reducing sugars

Answer 3

Can donate electrons to a molecule (benedict’s reagent)

Question 4

What 3 elements are found in monosaccharides

Answer 4

carbon, hydrogen, oxygen

Question 5

What are the 3 monosaccharides

Answer 5

Glucose, galactose, fructose

Question 6

What are the isomers of glucose

Answer 6

-alpha
-beta

Question 7

Glycosidic bond

Answer 7

the bond that forms between two monosaccharides during condensation to form a disaccharide

Question 8

Maltose

Answer 8

glucose + glucose

Question 9

Lactose

Answer 9

Galactose + glucose

Question 10

Sucrose

Answer 10

fructose + glucose

Question 11

Disaccharide

Answer 11

form when 2 monosaccharides chemically react together

Question 12

polysaccharides

Answer 12

formed by the condensation of many glucose units

Question 13

Why are polysaccharides good for storage

Answer 13

they are large molecules that are insoluble

Question 14

Test for starch-iodine

Answer 14

-add sample to spotting tile
-add drops of iodine and stir
-starch is indicated by a colour change from orange to blue-black

Question 15

Test for reducing sugars

Answer 15

Benedicts

Question 16

Why does benedict’s reagent turn red when heated with a reducing sugar

Answer 16

sugar donated electrons that reduce blue copper 2 sulfate to orange copper 1 oxide

Question 17

Benedict’s test

Answer 17

1. grind up food and filter solids
2. Add solution to boiling tube and add benedict’s solution
3. heat for 5 minutes
   4.If it remains blue there are no reducing sugars present if it turns red there are

Question 18

How do you test for a non-reducing sugar

Answer 18

-Add sample and benedicts to water bath for 5 minutes
-if no colour change then a reducing sugar is not present
-Heat another sample with acid and neutralise;
- Heat with Benedict’s (solution);
-Red precipitate/colour;

Question 19

Starch

Answer 19

made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reactions

Question 20

What type of glucose is starch and glycogen made from ?

Answer 20

Alpha glucose

Question 21

What type of glucose is cellulose made from?

Answer 21

Beta glucose

Question 22

Structure of starch

Answer 22

Made up of amylose which is unbranched, coiled and compact. And amylopectin which is branched so enzymes can work simultaneously.

Question 23

Structure of glycogen

Answer 23

Very similar structure to starch but has shorter chains and is more highly branched

Question 24

Structure of Cellulose

Answer 24

-Long, straight unbranched chains of beta glucose joined by glycosidic bonds
-Microfibrils are strong threads that made of long cellulose chains that run parallel joined by hydrogen bonds (cross-linkage)

Question 25

What bonds cellulose together

Answer 25

Hydrogen bonds

Question 26

What two molecules is starch made from ?

Answer 26

Amylose and amylopectin

Question 27

What makes starch suited to its role as an energy store

Answer 27

• it’s insoluble and therefore doesn’t affect water potential
  -it’s compact so a lot of it can be stored in a small space
  -it’s large and insoluble so doesn’t diffuse out of cells

Question 28

What makes glycogen suited to its role as an energy store

Answer 28

-it’s insoluble and therefore doesn’t tend to draw water into cells
-it doesn’t diffuse out of cells
-it’s compact so lot can be stored in a small space
-highly branched so more enzymes can work simultaneously

Question 29

What is starch used for

Answer 29

energy store in plant

Question 30

What is glycogen used for

Answer 30

energy store in animals

Question 31

What is cellulose used for

Answer 31

Component of plant cell walls and provides rigidity to the wall, prevents the cell from bursting

Question 32

What makes cellulose suited to its role as an energy store

Answer 32

-made of beta glucose and so form long straight, unbranched chains
-cellulose molecular chains run parallel to each other and are cross linked by hydrogen bonds which add collective strength