Module 2 - All cells arise from other cells

Question 1

2 marks

Describe and explain 2 specialisations of the root hair cell that enable it to absorb water from the soil

Answer 1

1. Many mitochondria provide ATP for active transport of mineral ions into the cell
2. Root hair increase surface area for absorption
3. Permanent vacuole containing sap, to store sap to keep water potential low
4. Thin walls reduces diffusion distance for osmosis

Question 2

2 marks

Bacteria are often used in industry as a source of enzymes. One reason is because bacteria divide rapidly, producing a large number of them in a short time.
Describe how bacteria divide.

Answer 2

1. Binary fission
2. Replication of circular DNA
3. Division of cytoplasm to produce 2 daughter cells
4. Each with a single copy of circular DNA

Question 3

Cyclin D undergoes DNA replication faster

Some tumour cells contain higher than normal concentrations of cyclin D.
Suggest why higher than normal concentrations of cyclin D could result in a tumour.

Answer 3

1. Shortens interphase/ DNA replication starts faster
2. Uncontrolled cell division
3. Resulting in a mass of abnormal cells

Question 4

Explain interphase

Answer 4

• Increase in volume of cell
• DNA replication
• Organelles replication
• Energy stores increase (ATP, protein synthesis)

Question 5

Explain prophase

Answer 5

• Chromosomes condense and become visible
• Nuclear envelope disappears

Question 6

Explain metaphase

Answer 6

• Chromosomes arrange themselves at the equator of the cell
• Spindle fibres attach to centromere

Question 7

Explain anaphase

Answer 7

• Centromeres divide
• Spindle fibres contracts/ shortens
• One of each sister chromatid pulled to poles of the cell

Question 8

Explain telophase

Answer 8

• Chromosomes uncoil
• Spindle fibres disintegrates
• Nuclear envelope reforms

Question 9

Explain cytokineses

Answer 9

• Cytoplasm splits
• Cell membrane forms between 2 cells

Question 10

1 mark

Cells lining the human intestine complete the cell cycle in a short time. Explain the advantage of these cells completing the cell cycle in a short time

Answer 10

Form / replace cells quickly / rapidly / divide / multiply / replicate rapidly

Question 11

6 marks

Explain how the structure of DNA is related to its functions.

Answer 11

1. Sugar-phosphate backbone strength
2. Long molecule so can store lots of information
3. Double helix (helical) so compact
4. Base sequence codes for amino acids / protein
5. Double stranded so replication can occur semi-conservatively / complementary base pairing / A-T and G-C so accurate replication
6. Weak hydrogen bonds for replication