Carbohydrates

Question 1

what is the general formula for a monosaccharide

Answer 1

(CH20)n

Question 2

what is the formula for a hexose sugar

Answer 2

C6H1206

Question 3

when do the carbon atoms of carbs form a ring

Answer 3

when the sugar is dissolved in water

Question 4

state the 4 functions of monosaccharides

Answer 4

1. energy in respiration- C-H and H-H bonds broken to release energy, which is transferred to make ATP
2. building blocks for larger molecules- glucose used to make starch, glycogen, cellulose and chitin
3. intermediates in reactions e.g triose in respiration and photosynthesis
4. constituents of nucleotides e.g deoxyribose in DNA, ribose in RNA, ATP and ADP

Question 5

how are two monosaccharides bonded together

Answer 5

formation of a 1-4 glycosidic bond and elimination of water (condensation reaction)

Question 6

what is maltose made of and what is its function

Answer 6

glucose+glucose
germination seeds

Question 7

what is sucrose made of and what is its function

Answer 7

glucose+fructose
transport in phloem of flowering plants

Question 8

what is lactose made of and what is its function

Answer 8

glucose+galactose
milk

Question 9

what is a reducing sugar

Answer 9

a sugar that can donate an electron
-with benedicts, the sugar donates an electron to reduce copper ions, and they change colour

Question 10

how to test for a non reducing sugar

Answer 10

a non reducing sugar like sucrose must be broken down first by heating with HCl, and alkali must be added to the benedicts

Question 11

what is glucose converted to in plant cells and animal cells and why

Answer 11

starch (plant) and glycogen (animal).
{storage polysaccharides}
This is because glucose is soluble so it would increase the conc of the cell contents and draw in water by osmosis

Question 12

why must glucose be converted into storage polysaccharides

Answer 12

-they are insoluble so have no osmotic effect
-they cannot diffuse out of the cell
-compact molecules so can be stored in a small space
-carry lots of energy in C-H and C-C bonds

Question 13

what polymers does starch consist of

Answer 13

amylopectin and amylose

Question 14

describe the structure of amylose

Answer 14

linear molecule with 1-4 glycosidic bonds that repeat to form a chain which coils into a helix

Question 15

describe the structure of amylopectin

Answer 15

chains of glucose monomers joined with 1-4 glycosidic bonds. They are cross linked with 1-6 glycosidic bonds (side branches) and fit inside amylose

Question 16

describe the structure of glycogen

Answer 16

similar to amylopectin, it has 1-4 and 1-6 glycosidic bonds, except it contains more branches than amylopectin

Question 17

what is cellulose

Answer 17

structural polysaccharide found in cell walls

Question 18

describe the structure of an individual cellulose molecule

Answer 18

long chain of beta glucose units joined by 1-4 glycosidic bonds. The beta-link rotates adjacent glucose molecules by 180

Question 19

describe the structure of cellulose

Answer 19

hydrogen bonds between OH groups of adjacent chains. Many of these bond chains together to form microfibrils.
The microfibrils are all held together and called fibres

Question 20

what is chitin

Answer 20

a structural polysaccharide found in the exoskeleton of insects and fungal cell walls

Question 21

describe the structure of chitin

Answer 21

similar to cellulose with 1-4 beta glucose molecules, but has amino acid groups added to make a heteropolysaccharide. It also forms microfibrils.

Question 22

what are the properties of chitin

Answer 22

strong, waterproof and lightweight