biological molecules

Question 1

compare and contrast triglycerides and phospholipids (5 marks)

Answer 1

similarities:
1. both have ester bonds
2. both have glycerol
3. both are insoluble in water

differences:
1. triglycerides have 3 fatty acids, phospholipids have 2 and a phosphate group
2. phospholipids form a bilayer in water
3. phospholipids have hydrophobic tails and a hydrophilic head

Question 2

what is maltose composed of?

Answer 2

glucose and glucose

Question 3

what is lactose composed of?

Answer 3

glucose and galactose

Question 4

what is sucrose composed of?

Answer 4

glucose and fructose

Question 5

what is the function of starch?

Answer 5

• found in plants and is a major carbohydrate store
• made from excess glucose created during photosynthesis
• if more glucose is made than needed it is converted into starch for storage

Question 6

describe the structure of starch

Answer 6

• made up of alpha glucose
• alpha glucose monomers joined by condensation reactions
• made from polymers amylose and amylopectin
• 1-4 glycosidic bonds in amylose results in spiral shaped polymer
• 1-6 glycosidic bonds in amylopectin results in branches

Question 7

what is the function of glycogen?

Answer 7

• made from excess glucose that has been eaten or absorbed
• if more glucose is eaten than required, it is converted into glycogen
• mainly stored in liver and muscle cells (liver removes toxins, muscles responsible for movement) so need glucose to respire

Question 8

describe the structure of glycogen

Answer 8

• polymer made from alpha glucose
• glycogen contains more 1-6 bonds so is more branched than starch

Question 9

what are some properties of glycogen?

Answer 9

1. insoluble - can be stord within cells and won’t dissolve –> doesnt affect water potential
2. highly branched - larger SA for enzymes to attach to –> readily hydrolysed into glucose

Question 10

what is the function of cellulose?

Answer 10

to provide strutural strength in plants

Question 11

describe the structure of cellulose

Answer 11

• made of beta glucose
• joined y 1-4 glycosidic bonds only so is unbranched
• long, straight chains of beta glucose accumulate and lie parallel to each other –> parallel chains held by hydrogen bonds
• –> fibril - slign in parallel, held by more H bonds to form a cellulose fibre

Question 12

what are some properties of fibre?

Answer 12

1. insoluble - won’t change water potential
2. very strong - large number of hydrogen bonds in and between fibrils
   3.