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Revising A-level Biology: Plants ‘r’ mint

Revision pack 2: Exchange surfaces and breathing; health & disease; excretion; photosynthesis; transport in plants; respiration.

In this revision pack, you will revise information you’ve studied at AS and A2. You’ll look at one particular living organism, and see how this can be linked to the topics that you’ve already studied.

This is the second of five revision packs, covering the A2 syllabus.

Aims

1.  To develop your breadth of knowledge (including AS topics) and your ability to apply both AS and A2 knowledge in new contexts.

2.  To help you make links between different topics and modules to encourage synoptic thinking.

Exchange Surfaces & Breathing (AS-1.2.1)

Health & Disease (AS-2.2.2)

L-menthol is a major component of peppermint oil and cornmint oil. It is widely used to produce medicines such as decongestants and cough sweets, and to make “menthol cigarettes”. According to the Food and Drugs Administration (FDA) in the USA, the cooling and anaesthetic effects of L-menthol reduce the harshness of cigarette smoke, which could facilitate deeper and more prolonged inhalation of tobacco smoke, resulting in greater smoke intake per cigarette.

Source:http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/TobaccoProductsScientificAdvisoryCommittee/UCM244975.pdf

With reference to the structure of alveoli, suggest three reasons why L-menthol from cigarette smoke is absorbed into the bloodstream quickly. (3 marks)

(1) 

(2)  )

(3) 

Image Source: http://wikieducator.org/File:

Gas_exchange_in_the_alveolus_unlabeled_diagram.JPG

Outline three health risks of smoking which could be increased by smoking “menthol cigarettes”. (3 marks)

Excretion (A2-4.2.1)

Inhaled L-menthol is absorbed into the blood via the lungs, ingested L-menthol is

absorbed into the blood via the stomach and small intestine.

The liver is responsible for converting L-menthol in the blood into an excretory product. Most of the L-menthol which arrives at the liver is converted to menthol glucuronide. This molecule (RMM = 332) is transported to the kidneys, where it is filtered out of the blood by nephrons and is eventually excreted in urine.

Name the following blood vessels associated with the liver:

(a) The artery entering the liver which carries L-menthol absorbed from smoking (inhaled).

(1 mark)

(b) The vein entering the liver which carries L-menthol absorbed from the gut (ingested).

(1 mark)

(c) The vein that carries L-menthol glucoronide out of the liver.

(1 mark)

With reference to the structure of the glomerulus capillaries and Bowman’s capsule, describe how nephrons filter menthol glucuronide out of blood by nephrons. (3 marks)


Photosynthesis (A2-4.3.1)

Transport in Plants (AS-1.2.3)

In 1771 Joseph Priestley, an English Chemist and clergyman, put a sprig of mint into a transparent closed space with a candle that burned in the air until it soon went out. After 27 days, he relit the extinguished candle again by focusing sunlight beams with a mirror onto the candle wick and it burned perfectly well in the air that previously would not support it. In carrying out several other experiments, scientists such as Priestley and his contemporaries (Karl Scheele from Sweden and Antoine Lavoisier from France) discovered oxygen.

Source: http://www.juliantrubin.com/bigten/oxygenexperiments.html

Explain in detail why oxygen is a bi-product of non-cyclic photophosphorylation. (4 marks)

Although most mint plants are green, they contain a range of photosynthetic pigments.

Name three photosynthetic pigments found in mint plants. (3 marks)

Explain why plants with several photosynthetic pigments can make more starch than plants with just one photosynthetic pigment. (3 marks)


In relation to photosynthesis, what is a limiting factor? (2 marks)

* Limiting factor is that factor which limits the rate of photosynthesis.

* If that factor is increased, then the rate of photosynthesis increases.

Explain fully how each of the following factors can limit the rate of photosynthesis:

(a) Low temperature (3 marks)

(b) Low light intensity (3 marks)

(c) Low CO2 concentration (3 marks)

Suggest why, on a hot day, the rate of photosynthesis may be less at 12 noon (when light intensity peaks) compared to at 10 a.m. (3 marks)

Respiration (4.4.1)

A box of twelve chocolate peppermint creams contains 200g net of creams. The creams contain glucose syrup, cocoa butter, emulsifier, soya lecithin, invertase and peppermint oil.

Table 3: Nutritional information Table 4: Approximate standard energy values

for peppermint creams for different respiratory substrates

Standard Energy Values
Carbohydrates 16 kJg-1
Fats 39 kJg-1
Proteins 17 kJg-1
Nutritional Information
Content per 100g
Energy 1886 kJ
Carbohydrates 76.9 g
Fats 14.4 g
Proteins 2.7 g

Use the information in tables 3 and 4 to work out the % difference between the energy content per 100g as stated on the box, and the energy value calculated using standard energy values and nutritional information. Show your working. (5 marks)

Suggest two reasons for any difference between the two values. (3 marks)

According to the Rowett Research Institute, the average daily energy intake in the UK is 10250kJ for men and 7030kJ for women. Source:http://www.rowett.ac.uk/edu_web/sec_pup/energy_expenditure.pdf

Given that a box of 12 peppermint creams has a net weight of 200g and an energy content of 1886 kJ per 100g, how many peppermint creams could the average man and woman eat per day before exceeding their average daily intake? (3 marks)


Explain why different respiratory substrates have different energy values, with reference to ATP production by mitochondria. (4 marks)

Finally, back to Joseph Priestley and his mint.

“I took a quantity of air, made thoroughly noxious, by mice breathing and dying in it, and divided it into two parts; one of which I put into a phial immersed in water; and to the other (which was contained in a glass jar, standing in water) I put a sprig of mint. This was about the beginning of August 1771, and after eight or nine days, I found that a mouse lived perfectly well in that part of the air, in which the sprig of mint had grown, but died the moment it was put into the other part of the same original quantity of air; and which I had kept in the very same exposure, but without any plant growing in it”.

Source: Priestley ‘Observations on Different Kinds of Air', Philosophical Transactions (1772), 62, 193-4.

Explain Priestley’s findings:

(a) With reference to the role of oxygen (supplied by the mint plant) in aerobic respiration.

(3 marks)

(a) With reference to anaerobic respiration (in the absence of the mint plant).

(3 marks)

*

Science & Plants for Schools: www.saps.org.uk (2013)

Revising A-level biology – revision pack 2