You're viewing 2 free preview questions for Biology HL — subscribe to unlock 55 more, plus the Full Question Bank, Mock Papers & Worksheets.Upgrade

Cell Specialization · Paper 2 — Free Biology HL Practice Questions

What this topic covers

This theme is built on one repeated argument: structure exists because it does a job, and you can predict the job from the structure. Examiners test this exact logic at every scale — a motor protein's shape tells you which way it walks a microtubule, a red blood cell's missing nucleus tells you why it can pack more haemoglobin, a gill's countercurrent geometry tells you why it out-performs a lung-style parallel flow. Several chunks here — muscle and motility, enzyme kinetics, endosymbiotic theory, detailed phloem loading — exist only on the HL paper, and they're flagged below. Get the mechanism words right (troponin, not tropomyosin; ATP-binding, not hydrolysis) because that's where the marks actually sit.

Read the full Form and Function lesson notes →

1MasterySAQ-SStem cells and differentiation5 marksPaper 2~8 min

A research team studies the differentiation of neural stem cells (NSCs) isolated from a mouse brain. NSCs are cultured for 7 days in the presence of the growth factor FGF-2. After 7 days, 150 of the original 200 NSCs have differentiated into neurons; the remainder are still undifferentiated NSCs. In a separate experiment, the same NSCs are cultured with BMP4 instead of FGF-2. After 7 days,

95\%

of cells have differentiated into astrocytes and

5\%

into neurons.

(a)

State what is meant by differentiation in the context of these neural stem cells. [1 mark]

(b)

Calculate the percentage of NSCs that differentiated into neurons in the FGF-2 experiment. [2 marks]

(c)

Using the results from both experiments, explain how growth factors direct the fate of NSCs during differentiation. [2 marks]

Solutions

2MasterySAQ-SStem cells and differentiation5 marksPaper 2~8 min

Scientists are studying the use of stem cells to repair damaged heart muscle after a heart attack. They compare two sources of stem cells: (i) mesenchymal stem cells (MSCs) from bone marrow, and (ii) induced pluripotent stem cells (iPSCs).

(a)

State one difference between MSCs and iPSCs in terms of their origin. [1 mark]

(b)

The scientists treat groups of mice with a chemical that causes heart damage, then inject either MSCs or iPSC-derived cardiomyocytes into the damaged area. After 4 weeks, they measure the percentage of the damaged area repaired. Treatment — Mean repair (%) — Standard deviation (%) MSCs — 12 — 4.1 iPSC-derived cardiomyocytes — 45 — 3.8 Deduce whether the difference in repair between the two treatments is likely to be significant. [2 marks]

(c)

Despite the greater effectiveness of iPSC-derived cardiomyocytes, some mice in the iPSC group developed tumours. Explain a possible reason for this observation, linking it to the properties of iPSCs. [2 marks]

Solutions

Questions 3-57

Unlock these questions with Premium

That's every free question here — 2 of 57.

+55 more questions, plus Mock Papers & Worksheets, are waiting in Premium.

Upgrade