Carbohydrates

Question 1

2 forms of glucose

Answer 1

-alpha + beta
-isomers

Question 2

3 major polysaccharides

Answer 2

-starch, glycogen and cellulose

Question 3

The shape of glucose

Answer 3

-sugars with 6 carbon atoms = hexose
-monosaccharide
-glycosidic bonds - 1’4, 1’6 bonds
-condensation join + H2O up
-galactose + fructose

Question 4

Properties of monosaccharides

Answer 4

-soluble in water
-contains lots of OH groups - they form H bonds with water molecules

Question 5

Pentose monosaccharides

Answer 5

-contain 5 carbons
-eg. Ribose + deoxyribose
-form RNA and DNA

Question 6

Formation of disaccharides + polysaccharides

Answer 6

-monosaccharides can be chemically joined to form larger carbs

Question 7

The 2 isomers

Answer 7

-beta - OH at top
-alpha - OH at the bottom

Question 8

What is a disaccharide?

Answer 8

-2 glucose molecules reacting together
-also form water - from a H from one, and a OH from another
-condensation

Question 9

What is maltose made of?

Answer 9

2 alphas

Question 10

What is sucrose made from?

Answer 10

Glucose + fructose

Question 11

What is lactose made from?

Answer 11

Glucose + galactose

Question 12

What is a glycosidic bond?

Answer 12

-chemical bond between 2 molecules of glucose
-carbon 1’4 glycosidic bond
-if water is added to DS - GS bond is broken
-converts back into OG MS
(Hydrolysis)

Question 13

What is starch made from?

Answer 13

-contains dissolved glucose - water moves in - plant stores starch
-grains are found in plastids - chloroplasts + colourless amyloplast
-2 molecules; amylose + amylopectin
-when cells need glucose - water is used to break GS bonds

Question 14

What is amylose made of?

Answer 14

-polymer of alpha
-lots of alpha = polysaccharide chain of amylose
-can twist into helix = H bonds form between glucose along the chain

Question 15

Why can’t amylose + amylopectin diffuse through a cell membrane?

Answer 15

-too large

Question 16

Structure of starch

Answer 16

-amylopectin - polymer of alpha with branches every 25-30 glucose molecule
-branch connected to main chain by GS bond - 1’6

Question 17

Why do we need starch?

Answer 17

-need glucose - enzymes break GSB in starch - hydrolysis - needs water
-enzyme breaking down starch acts at end of molecule
-lots of branches = lots of ends = enzyme can break down starch quickly

Question 18

What is glycogen?

Answer 18

-animal store of glucose
-in liver + muscle cells
-polymer of alpha 1’4 - contains branches 1’6
-more branched than amylopectin = compact
-insoluble in water - doesn’t draw water in

Question 19

Importance of glycogen

Answer 19

-lots of free ends - enzymes convert glycogen to glucose fast
-high rate of respiration - sudden spike - glycogen can be converted to glucose to be used

Question 20

What is cellulose?

Answer 20

-polymer of beta glucose -OH on top
-can’t form between 1’4 - every 2nd beta is flipped
-unbranched polysaccharide - no branches - can be close together
-H bonds can form between neighbouring chains = strong

Question 21

Grouping of cellulose

Answer 21

-(microfibril) - group together to make large microfibrils
-group make a cellulose fibre = plant cell wall
-impermeable to molecules