Specimen 2014

Question 1

Describe how you could use cell fractionation to isolate chloroplasts

Answer 1

Break open cells and remove debris

Solution cold/isotonic/buffered

Second pellet chloroplasts

Question 2

Describe what has happened during division 1

Answer 2

Chromosomes in homologous pair

One of each into daughter cells

Question 3

Sugar in DNA nucleotide

Answer 3

Deoxyribose

Question 4

Explain why the arrows point in different directions

Answer 4

DNA has antiparallel strands

Shape of nucleotides is different

Enzymes have active sites with specific shapes

Only substrates with complementary shape can bind with active site

Question 5

Advantage of different percentage of cholesterol in RBC

Answer 5

RBC free in blood so cholesterol helps maintain shape

Question 6

ecoli has no cholesterol in its cell-surface membrane

Despite this the cell membrane has a constant shape

Why

Answer 6

Cell unable to change shape due to cell wall

Question 7

Describe how you would use a 1.0moldm-3 solution of sucrose to produce 30cm of a 0.15mol dm3 solution of sucrose

Answer 7

Add 4.5cm solution to 25.5 distilled water

Question 8

Describe how you would use a students results to find water potential of potato tissue

Answer 8

Plot a graph with conc on x axis and percentage change in mass on y axis

Find conc where curve crosses x-axis

Use another resource to find water potential of sucrose concentration

Question 9

Explain why HSV only infects nerve cells

Answer 9

Outside of virus has antigens/proteins

With complementary shape to receptor

Receptor only found on membrane of nerve cells

Question 10

Explain why this virus can be described as inactive

Answer 10

No more nerve cells infected

As virus is not replicating

Question 11

Explain how microRNA allows HSV to remain in the body for years

Answer 11

MicroRNA binds to cells mRNA

Via complementary base pairing

So prevents mRNA being read by ribsomes

So prevents production of proteins that cause cell death