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OCR

Respiration Questions

12

© OCR 2008

4 (a) The first stage in respiration involves the conversion of one molecule of glucose into two molecules of a 3C compound that can enter mitochondria when oxygen is present.

State:

(i) the name of this stage ................................................................................................. [1]

(ii) where this stage occurs in the cell .............................................................................. [1]

(iii) the name of the 3C compound formed ........................................................................ [1]

(iv) the total number of ATP molecules formed during this stage ..................................... [1]

(b) In this question, one mark is available for the quality of spelling, punctuation and grammar.

Reduced NAD is another product of the first stage of respiration.

Describe the role and fate of reduced NAD in respiring yeast cells, both in the presence and absence of oxygen.

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Quality of Written Communication [1]

(c) In mammals, anaerobic respiration in muscle tissue results in the production of molecules of lactate.

Describe how the production of lactate in muscle tissue differs from anaerobic respiration in yeast.

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[Total: 15]

2

© OCR 2008

Answer all the questions.

1 (a) Fig. 1.1 is a high power electronmicrograph of some mitochondria.

P

Q

R

© Dr Gopal Murti / Science Photo Library

Fig. 1.1

Identify P, Q and R.

P ...............................................................................................................................................

Q ...............................................................................................................................................

R .......................................................................................................................................... [3]

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(b) Mitochondria are variable in shape and size. They may be spiral, spherical, elongated, cup-shaped and even branched. Their length varies from 1.5 to 10.0 μm and their width from 0.25 to 1.00 μm. However, their diameter does not exceed 1.0 μm.

(i) Suggest why the diameter of mitochondria must not exceed 1.0 μm when the length and

shape is so variable.

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(ii) Explain why structure Q on Fig. 1.1 is so highly folded.

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(c) During respiration, exchange of materials takes place between the cytoplasm and mitochondria.

Complete the table below listing three chemical substances that enter mitochondria from the cytoplasm during respiration and three that leave mitochondria during respiration.

Chemical substance that enters mitochondria from cytoplasm

Chemical substance that leaves mitochondria and enters cytoplasm

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2........................................................ ........................................................

3........................................................ ........................................................ [6]

(d) Fatty acids are important energy sources contributing at least half the normal energy requirements of cardiac muscle, the liver and kidneys.

Explain why fatty acids release more energy per gram than carbohydrates.

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4

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(e) Tripalmitin is a triglyceride. The chemical equation for the aerobic respiration of tripalmitin is:

2 C51H98O6 + 145 O2 102 CO2 + 98 H2O (i) Calculate the RQ value for tripalmitin. Show your working.

Answer = .......................................................... [2]

(ii) Explain why the usual RQ value for respiration in humans is between 0.7 and 1.0.

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[Total: 18]

2

© OCR 2009

Answer all the questions.

1 Respiration is the process by which chemical energy in organic molecules is released by oxidation. This energy is then made available to living cells in the form of ATP (adenosine triphosphate).

Fig. 1.1 represents the structure of ATP.

E

G

F

Fig. 1.1

(a) Name the parts of the molecule labelled E, F and G.

E ...............................................................................................................................................

F ................................................................................................................................................

G .......................................................................................................................................... [3]

(b) ATP can be converted to ADP (adenosine diphosphate) and Pi (inorganic phosphate). This reaction releases energy.

(i) Name the molecule that reacts with ATP to release energy and state the type of reaction taking place.

molecule ............................................................................................................................

type of reaction ............................................................................................................. [2]

(ii) State the amount of energy released in this reaction for every mole of ATP broken down.

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(c) ATP is often described as the ‘universal energy carrier’.

Explain why it is described in this way.

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(d) Parasites, such as tapeworms, can survive in the gut in anaerobic conditions.

Suggest how they obtain ATP under these conditions.

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[Total: 12]

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© OCR 2009

3 Fig. 3.1 shows a simple respirometer that can be used to measure the uptake of oxygen and the production of carbon dioxide during respiration of germinating mung beans.

germinatingmung beans

sodalime

capillarytube

colouredwater

plunger

meniscus

Fig. 3.1

The position of the meniscus was marked on the capillary tube after each minute so that the distance, d, moved during each minute could be measured.

The results are shown in Table 3.1.

Table 3.1

time / min 1 2 3 4 5

distance, d, moved by meniscus each minute / mm 2 3 2 2 3

(a) (i) The internal diameter of the capillary tube is 0.4 mm. Using the formula �r2d, where � = 3.14, calculate the average volume of oxygen taken up in mm3 min–1.

Show your working.

Answer = ...................................... mm3 min–1 [2]

(ii) Explain how you would adapt the apparatus to measure the volume of carbon dioxide produced per minute and to calculate the respiratory quotient (RQ) of the germinating mung beans.

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(iii) A student calculated the RQ value of germinating mung beans to be 0.8.

Explain what this value indicates about the type of substrate being respired.

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(b) The role of oxygen in respiration is to act as the final acceptor of hydrogen atoms. These hydrogen atoms will have been involved in oxidative phosphorylation.

(i) Explain where the hydrogen atoms that are involved in oxidative phosphorylation come from.

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(ii) State where in the mitochondrion oxidative phosphorylation occurs.

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(iii) Explain what is meant by the term chemiosmosis.

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[Total: 15]

2

© OCR 2010

Answer all the questions.

1 Fig. 1.1 shows some of the reactions in a cell which occur during aerobic respiration.

glucose

pyruvate

NAD ATPCO2

reducedNAD

ADP + inorganic phosphate

P

acetyl coenzyme A

Q

Fig. 1.1

(a) (i) Name the reaction pathways P and Q.

P ........................................................................................................................................

Q .................................................................................................................................. [2]

(ii) State where reaction pathway P occurs.

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(b) One of the enzymes involved in the conversion of pyruvate to acetyl coenzyme A is called pyruvate dehydrogenase.

Explain why this enzyme is given this name.

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(c) State what is meant by the term decarboxylation.

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(d) The respiratory quotient (RQ) is a measure of the ratio of carbon dioxide given out to the oxygen consumed by an organism over a given period.

(i) State what information is gained from determining RQ values.

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(ii) Table 1.1 shows RQ values of seeds and seedlings at different stages of germination and growth.

Table 1.1

stage of germination and growth RQ

seeds soaked in water 5.6

seeds after 12 hours in soil 0.8

seedlings after 21 days 1.0

Suggest an explanation for each of the RQ values shown in Table 1.1.

seeds soaked in water .......................................................................................................

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seeds after 12 hours in the soil .........................................................................................

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seedlings after 21 days .....................................................................................................

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[Total: 15]

16

© OCR 2010

7 (a) State what is meant by the term respiratory quotient (RQ). ...................................................................................................................................................

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(b) Complete and balance the following equation for the aerobic respiration of compound A, C55H100O6.

C55H100O6 + 77 O2 � …………………… + …………………… [2]

(c) Calculate the RQ for this reaction.

Answer = .............................................. [2]

(d) Identify, from the RQ value calculated in (c), the type of molecule to which compound A belongs.

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© OCR 2010

(e) After surface sterilisation, some seeds were soaked in water for four hours before being left in moist air to germinate. The RQ values of these seeds are shown in Table 7.1.

Table 7.1

time RQ

immediately after soaking 6.34

after 12 hours in air 2.22

after 36 hours in air, radicles appearing 1.02

Explain the changes in RQ values of these germinating seeds.

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[Total: 10]

END OF QUESTION PAPER