EXAM 2

Question 1

Explain two ways in which the structures of amylose and glycogen make them
suitable for energy storage.

Answer 1

1. Contain glucose and are compact and large so large numbers of glucose can fit into a small volume
2. They are insoluble so they do not affect osmosis

Question 2

Describe how insulin is modified, packaged and secreted by the cell

Answer 2

1. In the Rough endoplasmic reticulum insulin is folded the insulin is then packaged into transport vesicles by the RER.
2. Vesicles then fuse with the golgi apparatus and the golgi apparatus modifies the insulin.
3. Insulin is then transferred in vesicles from the golgi apparatus to the cell surface membrane which then fuse with the membrane and insulin exits the cell via exocytosis

Question 3

Describe the process of meiosis

Answer 3

1. Prophase 1 - Sister chromatids condense, homologous pairs line up forming bivalents, crossing over occurs at the chiasma
2. Metaphase 1 - Nuclear membrane breaks down, spindle fibres form, spindle fibres pull bivalents to the equator.
3. Anaphase 1 - Spindle fibres contract, bivalents are separated and one pairs of chromatids are pulled to opposite poles.
4. Telophase 1 - Nuclear membrane reform, spindle fibres break down, chromosomes decondense
5. Prophase 2 - Sister chromatids condense and centrioles duplicate.
6. Metaphase 2 - Nuclear membrane breaks down, spindle fibres form, spindle fibres pull sister chromatids to the equator of the cell.
7. Anaphase 2 - Spindle fibres contract, centromere splits separating sister chromatids, chromosomes are pulled to opposite poles
8. Telophase 2 - Chromosomes decondense, nuclear membrane reforms, spindle fibres break down and cytokinesis occurs

Question 4

Explain how meiosis leads to variation

Answer 4

1. Independent/random assortment - bivalents line up at the equator completely at random
2. Crossing over - sections of DNA are exchanged at the chiasmata between non-sister chromatids within a homologous pair

Question 5

Explain how meiosis can give rise to genetic variation in the gametes produced.

Answer 5

Crossing over which is the swapping of chromosomes at the chiasmata and independent assortment which produces a new combination of alleles

Question 6

Describe the structure of glycogen and explain why it is a suitable molecule for
storing energy

Answer 6

1. Consists of alpha glucose that are joined together by 1,4/1,6 glycosidic bonds
2. Glycogen is very compact meaning that there are lots glucose in a small volume
3. As it contains 1,6 glycosidic bonds it is easily hydrolysed
4. Glycogen has a low solubility so it has no osmotic effect

Question 7

Describe two ways in which the structure of starch is related to its function.

Answer 7

1. Strach is made up of many glucose monomers meaning that it can store lots of energy
2. Starch is very large so it is insoluble and has no osmotic effect
3. Starch is compact so more energy can be stored in a small space

Question 8

What is the role of DNA helicase

Answer 8

Unzips the DNA double helix by breaking hydrogen bonds between bases

Question 9

What is the role of DNA polymerase

Answer 9

DNA polymerase catalyses the reactions between nucleotides and forms phosphodiester bonds

Question 10

What is the role of DNA ligase

Answer 10

Joins okazaki fragments on the lagging strand due to DNA polymerase catalyzing the reactions between nucleotides in the 3’ to 5’ direction