Respiration (CIE A Level Biology)

Fig.1 below shows the respirometer apparatus used by a teacher for measuring the rate of oxygen consumption of seeds during aerobic respiration.

Fig. 1

For the first 12 minutes, the tap attached to tube 1 was left open and the syringe from tube 2 was removed.

Suggest two reasons why this was done.

A temperature of 25^°C was used during the experiment. One of the students suggested using a temperature of 35^°C.

Explain why the teacher did not do this.

After 12 minutes, the tap connected to tube 1 was closed and the syringe was attached to tube 2. Every 60 seconds, the syringe plunger was moved to make the levels in the U-tube identical. The reading on the volume scale of the syringe was then recorded. The results are shown in Table 1 below.

Predict which tube the coloured liquid in the U-tube moves towards during the experiment. Justify your answer.

The mass of the seeds was 1.8 g.

Using the information provided in Table 1, calculate the rate of oxygen consumption in cm³ g^-1 hour^-1 by the seeds. Show your working and give your answer to two decimal places.

Describe the mechanism by which ATP is formed in the mitochondria.

Mitochondrial diseases in humans cause their mitochondria to malfunction. Individuals that suffer from mitochondrial disease are only able to endure intense exercise for a short period of time.
 
Explain the reason for this.

Fig. 1 below shows a mitochondrion.

Fig. 1

Identify the structures labelled A and B in the diagram.

Some forms of mitochondrial dysfunction result in mitochondria that lack fully formed cristae as shown in Fig. 2 below.

Suggest, with a reason, the effect of this on the production of ATP.

Fig. 3 below shows glycolysis.

Fig. 3

State the net production of ATP and reduced NAD during glycolysis.

The Krebs cycle, which takes place in the mitochondrial matrix, releases hydrogen ions.
These hydrogen ions provide a source of energy for the synthesis of ATP, using coenzymes.

Describe the role of the coenzymes in the synthesis of ATP.

Explain why the link reaction is described as an oxidative decarboxylation reaction.

Fig.1 below shows the Krebs cycle.

Fig. 1

Identify the number of carbon atoms (e.g. 1C) in the compounds at each stage of the Krebs cycle (A to D).

Reduced NAD and FAD are produced throughout the stages of respiration. 

Table 1

Complete Table 1 above to show how many molecules of reduced NAD and FAD are produced at each stage per molecule of glucose.

During a sporting event, an athlete carries out aerobic respiration.

Structures and compounds involved in aerobic respiration are listed, 1 to 10.

Complete Table 1 by matching each description with one number chosen from 1 to 10, to show the correct structure or compound.

You may use each number once, more than once or not at all.

Table 1

Sometimes the muscle cells of an athlete need to carry out respiration in anaerobic conditions.

Explain why the respiration of glucose in anaerobic conditions produces less ATP than in aerobic conditions.

Fig. 1 outlines some of the steps of glycolysis.

Fig. 1

State the precise location of glycolysis in the cell.

[1]

(ii)

With reference to Fig.1:

• State the steps where phosphorylation occurs

• State the step where oxidation occurs

• Name the type of reaction by which ATP is made during step 5.

[3]

Some cancer cells have different metabolic requirements from normal cells. These cancer cells obtain most of their ATP from glycolysis, even if oxygen is available.

State how the glucose and oxygen requirements of these cancer cells differ from normal cells.

The link reaction and Krebs cycle take place in the mitochondrion.

The main stages of the link reaction and Krebs cycle are listed in Table 1.

They are not listed in the correct order.

Table 1 

Complete Table 2 to show the correct order of the stages.

Three of the stages have been done for you.

Table 2

Outline the role of NAD in respiration in aerobic conditions.

Carbon dioxide is removed from compounds in the link reaction and Krebs cycle by decarboxylation.

(i)

State the total number of molecules of carbon dioxide removed in the link reaction and Krebs cycle for each molecule of glucose respired.

(ii)

In a mammal, carbon dioxide diffuses from cells into the blood to be transported to the lungs.

Suggest why carbon dioxide is transported in the blood mainly as hydrogen carbonate ions and not as carbonic acid.

A researcher investigated the use of a new carbohydrate source (substance L) for the production of ethanol as biofuel. She wanted to find the optimum length of time to leave a mixture of yeast and substance L to produce ethanol. They set up an airtight container containing yeast and substance L.  The oxygen, carbon dioxide and ethanol concentrations were measured over 10 hours. The results of this experiment are shown in Fig.1 below. The researcher used a sealed container that was airtight.

Fig. 1

Give three reasons why the container had to be airtight. 

Describe and explain the relationship seen between the concentration of oxygen and the concentration of carbon dioxide between 0 and 2.5 hours.

A student concluded that the yeast started to respire anaerobically when the oxygen concentration fell below a certain concentration.

Suggest at what time in the experiment this occurred. Justify your answer.

A biofuel company wanted to know how long they should let the reaction go on for when commercially producing ethanol for biofuels using substance L .

Use Fig.1 to suggest a length of time (to the nearest hour). Justify your answer.

Compare and contrast aerobic respiration and anaerobic respiration.

Extreme rainfall and flooding can create major problems when growing crops. As water levels rise, fields can become waterlogged causing crops to be submerged underwater.

Suggest how waterlogged conditions may negatively impact the growth of crops.

A species of rice plant Oryza sativa (commonly known as Asian rice) possesses adaptations to maximise aerobic respiration in flooded fields. It demonstrates an increased rate of upward growth which allows the leaves to remain above the waterline. Fig.1 below shows a cross-section of an Oryza sativa stem, near the tip.

Fig. 1

Using Fig.1, identify an additional adaptation present in the stems of Oryza sativa that aids aerobic respiration in flooded fields. Justify your answer.

The West Indian manatee (Trichechus manatus) is a large, aquatic mammal found in the warm coastal waters of the Caribbean. They mainly feed on sea grass and other aquatic plants, that requires them to spend an extended amount of time underwater.

Fig. 1 shows an image of a West Indian manatee.

Image courtesy of U.S. Fish and Wildlife Service Headquarters, Public domain, via Wikimedia Commons

Fig. 1

During feeding, there is an increase in the lactate concentration in their blood.

Suggest a reason for this.

Fig. 2 shows changes in the lactate concentration in the blood of a manatee before, during and after a dive.

Fig. 2

Calculate the percentage change in the lactate concentration between 10 and 15 minutes after the dive was completed.

Show your calculations.

Explain the change in lactate concentration calculated at part (b).

Manatees prefer to live in warm waters around coastlines and in rivers. If they are exposed to extremely cold water for prolonged periods of time, they develop a condition called 'cold water stress syndrome', which may be fatal.

With reference to respiration, suggest a reason why cold water stress syndrome may be fatal to manatees.