Practice Paper 2 (HL IB Biology)

State the features of RNA that mean it is presumed to have been the first genetic material. 

Scientists investigated the effect of ribozyme on population growth in yeast, Saccharomyces cerevisiae.

Describe ribozyme.

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(ii)

State the specific role of ribozyme. 

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A growth curve analysis of S. cerevisiae was carried out; S. cerevisiae cells were treated with a control substance (pGAD), with ribozyme (pGADRz) or with a mutant ribozyme (pGADmRz) at 30 °C. The results are shown in the graph below.

Note that N is number of cells after the given time period and N₀ is the initial number of cells.

Describe the effect of ribozyme on the growth of the S. cerevisiae population at 30 °C.

A student suggested that the results of the experiment shown in part (c) were surprising. 

Explain why the student came to this conclusion. 

Carbon dioxide is one of the main greenhouse gases in the atmosphere. The graph below shows the changes of carbon dioxide levels in the atmosphere, as well as the change in global temperatures over a period of time.

Describe the general trends in the data.

Suggest possible causes of the trends in the data presented in part (a).

Discuss the importance of greenhouse gases, such as carbon dioxide, in the atmosphere.

The image shows a representation of a neurone.

Identify structures X-Z in the image.

Branching from structure X of the neurone in part a) are structures known as dendrites.

State the role of dendrites in the nervous system.

Describe the structure of Y from the image in part a).

It has been estimated that a neurone without structure Y present can conduct nerve impulses at speeds of 0.5 m s^-1 whereas a neurone with structure Y present can conduct impulses at speeds of 150 m s^-1.

Calculate how many times faster impulse conduction is in the presence of structure Y than without structure Y.

The graph below shows the effect of light intensity, carbon dioxide, and temperature on the rate of photosynthesis.

 A - 0.04 % carbon dioxide at 15 °C

B - 0.04 % carbon dioxide at 25 °C

C - 0.04 % carbon dioxide at 35 °C

D - 0.1 % carbon dioxide at 25 °C

State three factors that could be measured to allow an estimate of the rate of photosynthesis in this experiment.

A commercial farmer growing peppers keeps her greenhouses at 25 °C and circulates air around the greenhouses. Air has a CO₂ concentration of 0.04 % and the ambient light intensity is 3 000 lux.

Use the graph in part a) to state whether the farmer would be more likely to achieve higher pepper yields by raising the carbon dioxide concentration to 0.1 % or by raising the temperature to 35 °C.

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Explain your answer to part i).

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There are two types of chlorophyll in chloroplasts, chlorophyll a and chlorophyll b. Researchers created a genetically-modified (GM) vine plant with an allele that caused them to synthesise higher levels of chlorophyll b than wild-type vine plants. They investigated the effect of this new allele on the rate of plant growth.

The researchers grew wild-type and GM vines. They grew some of each in low light intensity and grew others in high light intensity. They extracted chloroplasts from mature plants of both types. Finally, they measured oxygen production at different light intensities by the chloroplasts they had extracted from the plants.

Oxygen production here is used as a measure of the rate of photosynthesis.

State why this is possible.

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Calculate the percentage improvement in oxygen production caused by the genetic modification for vines grown at high light intensity at an experimental light intensity of 20 mmol photons m^-2 min^-1. Give your answer to 3 significant figures.

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The researchers suggested that GM plants producing more chlorophyll b would grow faster than wild-type plants in all light intensities.

Explain how the data in part c) support this suggestion.

 The diagram below depicts a section of the human gas exchange system.

 Figure 1

State the name of Organ 1 and describe its role in breathing out.

The graph below shows the changes in the volume of air in a woman’s lungs while breathing.

Explain how the graph shows that the woman was breathing out between times W and X.

Muscle action during ventilation is described as antagonistic.

Outline what this means with reference to one example during ventilation.

One mark is available for clarity of communication throughout this question.

Outline how changes in substrate concentration affects the rate of enzyme action. 

Sometimes the active site of enzymes can be blocked or "inhibited" by substances that aren't the specific substrate for that enzyme. 

Suggest how this would affect the rate of reaction of an enzyme-catalysed reaction as well as some possible uses of enzyme inhibitors in medicine. 

Plan an investigation to determine how changing the temperature of amylase affects the rate of reaction of the digestion of starch to maltose. 

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One mark is available for clarity of communication throughout this question.

Compare and contrast aerobic respiration and anaerobic respiration.

During sprint exercise or weight lifting, the body relies on anaerobic respiration to maximise the power of muscle contraction.

Explain why anaerobic respiration can only be sustained for short periods of time.

Describe and explain the use of yeast in baking.

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