Biological Molecules -carbohydrates

Question 1

N- acetylglucosamine is chitin’s monomer (it closely resembles beta glucose) using your knowledge of the formation of structural polysaccharides describe the formation of a chitin molecule and predict its structure.

Answer 1

• Chitin is formed via condensation polymerisation where a water molecule,N-acetyluglucosamine is similar to beta glucose so in chitin every N-acetyluglucosamine is flipped due to the position of its C1.

Question 2

Describe and explain how the structure and properties of different carbohydrate and lipid molecules suit them to their role as energy storage molecules in plants and animals

Answer 2

-starch-insoluble so it doesn’t effect osmotic balance as water potential isn’t changed
-amylose has many 1,4 glucosidic bonds making it easy to break into monomers- not rapidly released but that’s not required for plants.
Amylose is also coiled making it take up less space
-glycogen has many 1,6 glycosidic bonds this means there’s a more rapid release of glucose for animals
-fats have more c-c bonds which store lots of energy -more energy stored in less space
In fats there’s hydrocarbon chains that store lots of energy in the c-h bonds so when it’s broken down lots of energy is released

Question 3

Explain why mammals store glycogen instead of glucose

Answer 3

-glycogen is insoluble so it doesn’t change water potential of a cell.
-glycogen has lots of branching so glucose can be released quickly

Question 4

What does lactose consist of?

Answer 4

Glucose and galactose

Question 5

What does maltose consist of?

Answer 5

2 alpha glucose

Question 6

Structural similarities between lactose and maltose

Answer 6

-Two hexose
-1,4 glycosidic bond
-2 CH2OH groups

Question 7

Differences between lactose and maltose

Answer 7

Lactose consists of a glucose monomer and a galactose monomer whereas maltose is a disaccharide of glucose
Lactose consists of a beta glycosidic bond whereas maltose consists of an alpha glycosidic bond
Lactose has sugars of opposite orientation whereas maltose consists of ones in the same orientation

Question 8

Explain how the structure of galactose allows it to be used as a respiratory substrate

Answer 8

Galactose must be broken down by enzymes
Galactose OH and H groups form hydrogen bonds making it soluble

Question 9

E-coli usually grow in conditions where the extracellular concentration of lactose is low. In such conditions lactose does not easily cross the bacterial cell surface membrane
Suggest and explain why lactose is unable to cross membranes.

Answer 9

-too large to fit through the phospholipid bilayer |
-the lactose concentration is too low for diffusion to occur across the membrane

Question 10

Three properties of cellulose that makes it suitable as the basis of plant cell walls

Answer 10

-insoluble
-Unreactive
- flexible
-high tensile strength

Question 11

State two similarities and two differences between the caricatures of chitin and glycogen

Answer 11

-similarities :
Both polymers , both have CH2OH, both have 6 carbon sugars, both have 1,4 glycosidic bonds
-difference:
Chitin has beta glycosidic bonds , no 1,6 glycosidic bonds in chitin, chitin contains nitrogen, no branching

Question 12

State a property of glucose that allows it to be easily transported

Answer 12

Soluble/polar

Question 13

Explain how the structure of glycogen differs from amylopectin’s to make it better suited as an energy store in animals

Answer 13

-glycogen is more branches meaning hydrolysis can be sped up and more glucose can be released
-more coiled so it’s more compact and better for storage

Question 14

Is amylose soluble?

Answer 14

Yes