Respiration

Fig. 7.1 shows a diagram of part of a mitochondrion in section.

Feb/March 2016

An athlete carries out aerobic respiration while taking part in a sporting event.

Feb/March 2017

For respiration, the relevant structures and compounds are listed below: 1 coenzyme A, 2 cytoplasm, 3 pyruvate, 4 NAD, 5 outer mitochondrial membrane, 6 carrier protein, 7 inner mitochondrial membrane, 8 intermembrane space of mitochondrion, 9 ADP, 10 acetyl group.

Feb/March 2018

Fig. 8.1 is a transmission electron micrograph showing a mitochondrion.

Feb/March 2021

Giant axonal neuropathy (GAN) is an uncommon autosomal recessive disorder that affects neurones. Mitochondria are able to move freely inside the axons of neurones. In GAN, the axons of neurones enlarge and become obstructed by the build-up of particular proteins. This stops mitochondria moving freely and interferes with the transmission of action potentials along the axon membrane.

Feb/March 2022

During aerobic respiration, ATP is made by substrate-linked reactions and by oxidative phosphorylation.

Feb/March 2022

Fig. 6.1 shows a diagram of part of a mitochondrion in section. The four arrows, A, B, C and D, indicate how molecules and ions move.

Feb/March 2023

A respirometer is apparatus used to measure the respiration rate of living tissue, such as germinating peas. A simple respirometer is shown in Fig. 6.1. A student investigated how temperature affects the respiration rate of germinating peas. The student assembled the respirometer as in Fig. 6.1 and put it in a water-bath at $10^\circ\text{C}$. After five minutes, the student used the syringe to move the coloured liquid on the right-hand side of the U-shaped tube until it was level with $0\ \text{cm}$ on the ruler. The timer was started immediately. As the germinating peas used up oxygen, the coloured liquid in the U-shaped tube moved. The student measured how far the coloured liquid moved after 20 minutes. The experiment was repeated at $20^\circ\text{C}$, $30^\circ\text{C}$, $40^\circ\text{C}$ and $50^\circ\text{C}$.

Feb/March 2024

Different respiratory substrates can possess different energy values, so they release different amounts of energy when respired.

Feb/March 2025

In the link reaction, pyruvate is turned into a two-carbon acetyl group. This acetyl group is then passed to coenzyme A, forming acetyl coenzyme A (acetyl‑CoA). State the terms used for the two chemical changes that happen in the link reaction as pyruvate is converted into an acetyl group.

Feb/March 2025

In the early stages of respiration, 1 molecule of glucose is converted into 2 molecules of a 3C compound.

May/June 2010

Cereal crops, for example sorghum and rice, supply a large share of nutrients worldwide.

May/June 2010

Fig. 7.1 is a simplified sketch of the Krebs cycle. A two carbon acetyl group enters the cycle by joining with a molecule of oxaloacetate. This produces a molecule of citrate, which is then decarboxylated and dehydrogenated to regenerate the oxaloacetate. The letters $P$ to $V$ indicate steps in the cycle.

May/June 2010

Cereal crops, including sorghum and rice, are an important source of nutrients worldwide.

May/June 2010

Fig. 7.1 shows a simplified outline of the Krebs cycle. A two carbon acetyl group enters the cycle by joining with an oxaloacetate molecule. Citrate is produced, then it is decarboxylated and dehydrogenated so that oxaloacetate is regenerated. The letters $P$ to $V$ indicate the steps in the cycle.

May/June 2010

The Krebs cycle takes place in the matrix of the mitochondrion. Fig. 6.1 presents the steps in the Krebs cycle.

May/June 2011

The Krebs cycle takes place in the matrix of the mitochondrion. Fig. 6.1 sets out the sequence of steps in the Krebs cycle.

May/June 2011

Section B. Answer one question.

May/June 2012

Section B. Answer any one question.

May/June 2012

Section B. Choose one question to answer.

May/June 2012

An investigation was done to find out how temperature affects oxygen consumption in the lizard, Sauromalus hispidus. Because this lizard’s body temperature changes with the surrounding temperature, several lizards were fitted with small airtight masks that covered their heads. Air was passed into the mask through one tube and removed through another. By comparing the oxygen concentration of the inhaled air with that of the exhaled air, the researchers could determine the lizards’ oxygen consumption rate. Each lizard’s oxygen consumption rate was measured while it was resting and while it was running. The measurements were taken at a range of temperatures from $15^\circ\text{C}$ to $40^\circ\text{C}$. Fig. 4.1 presents the results.

May/June 2013

The filamentous fungus Fusarium venenatum is cultivated in continuous culture inside fermenters so that mycoprotein can be produced for human consumption.

May/June 2013

ATP is generated by oxidative phosphorylation along the electron transport chain within a mitochondrion.

May/June 2013

An investigation was undertaken to find out how temperature affects the rate of oxygen consumption in the lizard, Sauromalus hispidus. A lizard’s body temperature changes with the surrounding temperature. A number of lizards were fitted with small airtight masks over their heads. Air was passed into the mask through one tube and removed through another. Differences in oxygen concentration between the air supplied for inhalation and the air breathed out allowed the researchers to determine the lizards’ rate of oxygen consumption. Each lizard’s oxygen consumption rate was measured both at rest and while it was running. The measurements were carried out at a range of temperatures from $15^\circ \text{C}$ to $40^\circ \text{C}$. Fig. 4.1 presents the findings.

May/June 2013

A mitochondrion has DNA and ribosomes and is the organelle where aerobic respiration occurs. Suggest the roles of the DNA and ribosomes in a mitochondrion.

May/June 2014

A mitochondrion has DNA and ribosomes, and it is the organelle where aerobic respiration occurs. Suggest the roles of the DNA and the ribosomes in a mitochondrion.

May/June 2014

Outline how glycolysis proceeds in a mammalian cell.

May/June 2015

Every cell requires ATP for energy-demanding processes in the body. Fig. 7.1 displays the molecular structure of ATP.

May/June 2015

Outline how glycolysis occurs in a mammalian cell.

May/June 2015

ATP and NAD each have key functions in respiration. Both substances are nucleotides. Fig. 1.1 shows the molecular structures of ATP and NAD.

May/June 2016

Section B. Answer a single question.

May/June 2016

ATP and coenzyme A each have important roles in respiration. Fig. 1.1 shows the molecular structure of coenzyme A.

May/June 2016

Section B. Choose and answer one question.

May/June 2016

ATP and NAD each have key roles in respiration. Both are nucleotides. Fig. 1.1 shows the molecular structures of ATP and NAD.

May/June 2016

B section

May/June 2016

ATP may be consumed or generated at different points during glucose respiration under aerobic conditions. Complete the table to indicate whether ATP is consumed or generated at each stage of respiration. Enter either YES or NO in each box.

May/June 2017

Fig. 1.1 shows the link reaction.

May/June 2017

ATP is consumed or made at different points during glucose respiration in aerobic conditions. Fill in the table to indicate whether ATP is used or produced at each stage of respiration. Write either YES or NO in each box.

May/June 2017

Fig. 6.1 presents a transmission electron micrograph of a cross-section through a mitochondrion.

May/June 2018

Section B. Answer only one question.

May/June 2018

Fig. 6.1 is a line diagram that shows two stages of aerobic respiration.

May/June 2018

Fig. 6.1 shows part of a mitochondrion in diagram form, illustrating several of the events that take place during oxidative phosphorylation.

May/June 2018

A striated muscle contains many fibres, and each fibre is built from myofibrils. The striped look of the muscle fibre comes from the way two kinds of protein filaments, thick filaments and thin filaments, are organised within the sarcomeres of the myofibril.

May/June 2018

The link reaction and Krebs cycle occur in the mitochondrion. Table 4.1 gives the main stages of the link reaction and Krebs cycle, but they are jumbled rather than set out in the correct order.

May/June 2019

Oxidative phosphorylation occurs in the mitochondrion. Table 8.1 presents the different stages of oxidative phosphorylation. The stages are not arranged in the correct order.

May/June 2019

Describe the process by which ATP is made by oxidative phosphorylation.

May/June 2019

Table 8.1 presents several stages of glycolysis and respiration in anaerobic conditions in yeast. The stages are shown in the wrong sequence.

May/June 2019

By the end of glycolysis in mammalian muscle tissue, pyruvate is produced. Pyruvate may then be broken down through two separate pathways, pathway 1 and pathway 2. Fig. 6.1 shows the two pathways.

May/June 2020

What does the term respiratory quotient (RQ) mean?

May/June 2020

Fig. 7.1 illustrates part of respiration inside a mitochondrion.

May/June 2020

The elephant seal, Mirounga angustirostris, lives in the ocean for most of its life. Fig. 7.2 shows an elephant seal. Elephant seals are able to remain underwater for up to two hours. Respiration continues during this period. Fig. 7.3 shows the mass of blood in the body, as a percentage of total body mass, for the elephant seal and for three other mammals.

May/June 2020

All living organisms carry out respiration to release energy from energy-rich compounds such as glucose.

May/June 2021

Section B. Answer just one question.

May/June 2021

All living organisms carry out respiration. The ATP formed during respiration acts as the cell’s energy currency.

May/June 2021

Describe how a mitochondrion’s structure is connected to its function.

May/June 2021

(a) In respiration, respiratory substrates such as glucose act as an energy source for making ATP molecules.

May/June 2021

Respiration is a process that leads to ATP synthesis. The ATP may then be used inside the cell for reactions and processes that require energy. Aerobic respiration has four stages: glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation.

May/June 2022

Aerobic respiration takes place when oxygen is present. It gives a much larger energy yield than respiration under anaerobic conditions.

May/June 2022

ATP is made from ADP and $\text{P}_i$ in a phosphorylation reaction. State the two different ways that this phosphorylation reaction takes place in aerobic respiration.

May/June 2022

Amino acids are the monomers from which proteins are made in organisms. Amino acids also carry out other roles in the body that are not related to proteins.

May/June 2023

Glycolysis is a metabolic pathway that takes place in the cytoplasm of cells. During glycolysis, one glucose molecule is converted into two pyruvate molecules. Fig. 1.1 shows the sequence of events.

May/June 2023

A striated muscle cell (muscle fibre) contracts after stimulation by a motor neurone at a neuromuscular junction. Air temperature can influence the temperature of striated muscle cells. Investigations have shown that the efficiency of contraction of striated muscle cells falls as air temperature falls. Suggest reasons why lower temperature can reduce the efficiency of contraction of striated muscle cells.

May/June 2023

The Krebs cycle takes its name from the biochemist Sir Hans Krebs, who established the sequence in 1937. Fig. 1.1 provides a simplified outline of the Krebs cycle.

May/June 2023

Oxygen is required for aerobic respiration in cells. In eukaryotic cells, aerobic respiration takes place in the mitochondrion.

May/June 2024

Fig. 6.1 shows part of a mitochondrion.

May/June 2024

Figure 8.1 shows a mitochondrion diagram.

May/June 2024

Organisms require an energy source for many cellular activities. In respiration, energy is released from energy-rich molecules so that ATP molecules can be synthesised. ATP is known as the energy currency of cells.

May/June 2025

A respirometer may be used to find out how temperature changes the rate of respiration in woodlice. Woodlice are tiny invertebrate animals. Fig. 2.1 shows one woodlouse. Fig. 2.2 shows a basic respirometer.

May/June 2025

Fig. 1.1 shows part of the inner membrane of a mitochondrion in diagram form.

May/June 2025

The grey seal, Halichoerus grypus, is an aquatic mammal found in the North Atlantic Ocean. It eats fish, which it catches at depths of up to 70 metres. Fig. 10.1 displays a grey seal. Diving to catch fish affects the respiration of the grey seal. A study measured the blood lactate concentration of a grey seal before, during and after a dive in deep water.

May/June 2025

Fig. 1.1 shows part of a liver cell in diagram form.

May/June 2025

The respiratory quotient (RQ) is used to show which substrate is being broken down in respiration.

May/June 2025

Rice, Oryza sativa, is a staple food in many regions across the world. It is often cultivated in fields that are inundated with water for part of the growing season.

Oct/Nov 2010

In many regions of the world, rice, Orzya sativa, is a staple food. It is often cultivated in fields that stay flooded with water for part of the growing season.

Oct/Nov 2010

Describe the structure of ATP and explain the function of ATP as the energy currency in all living organisms.

Oct/Nov 2010

Maize, Zea mays, is a cereal crop adapted for growth at high temperatures. Even so, it is less drought-tolerant than some other crops, for example sorghum. An investigation examined the effect of low water availability on mitochondria taken from maize seedlings. Young seedlings were uprooted and kept in dry air for different lengths of time so that the water potential of their tissues fell.

Oct/Nov 2010

The earliest diagnostic test strip to use immobilised enzymes was a dip stick for estimating glucose concentration in urine. It is a narrow plastic strip with a cellulose pad at one end that contains two enzymes and a colour reagent (chromogen). When the strip is dipped into a urine sample that contains glucose, the pad changes colour. The colour is then compared with a graded colour chart to give a ‘semi-quantitative’ estimate of glucose concentration in the sample, as shown in Fig. 2.1. The chart displays a negative result ($-$) and three progressively more positive results ($+$, $++$ and $+++$).

Oct/Nov 2011

In glycolysis, glucose is broken down through a sequence of reactions to produce two pyruvate molecules. Fig. 6.1 presents glycolysis.

Oct/Nov 2011

The earliest diagnostic test strip to use immobilised enzymes was a dipstick for estimating glucose concentration in urine. It is a narrow plastic strip with a cellulose pad at one end that contains two enzymes and a colour reagent (chromogen). When the pad is dipped into a urine sample containing glucose, it undergoes a colour change. The colour is then compared with a graduated colour chart to provide a ‘semi-quantitative’ estimate of the glucose concentration in the sample, as shown in Fig. 2.1. The chart includes the colours for a negative result ($-$) and for three progressively more positive results ($+$, $++$ and $+++$).

Oct/Nov 2011

During glycolysis, glucose is broken down through a sequence of reactions to yield two pyruvate molecules. Fig. 6.1 shows the pathway of glycolysis.

Oct/Nov 2011

Fig. 6.1 summarises anaerobic respiration in yeast cells.

Oct/Nov 2011

Fig. 8.1 shows an electron micrograph of a mitochondrion in section. Name X and Y.

Oct/Nov 2012

Fig. 8.1 shows an electron micrograph of a slice through a mitochondrion. Name X and Y.

Oct/Nov 2012

Fig. 8.1 shows several stages of glucose metabolism in mammalian cells.

Oct/Nov 2012

Fig. 3.1 shows the components that make up a molecule of ATP (adenosine triphosphate).

Oct/Nov 2013

Outline the part played by oxygen in aerobic respiration.

Oct/Nov 2013

Fig. 5.1 illustrates the arrangement of an ATP molecule.

Oct/Nov 2014

Fig. 5.1 illustrates the structure of an ATP molecule.

Oct/Nov 2014

Every living organism needs a constant energy supply. Outline the need for energy in living organisms.

Oct/Nov 2014

The molecules named below are all connected with respiration: ATP synthase, glucose, ATP, NAD, oxaloacetate, pyruvate, citrate, oxygen.

Oct/Nov 2015

The molecules named here are all linked with respiration: ATP synthase, glucose, ATP, NAD, oxaloacetate, pyruvate, citrate, oxygen.

Oct/Nov 2015

Yeast cells sometimes carry out anaerobic respiration. Figure 1.1 shows the pathway of anaerobic respiration in yeast cells.

Oct/Nov 2015

When water is taken up by a dormant seed, germination begins and the respiration rate rises.

Oct/Nov 2016

If a dormant seed absorbs water, germination starts and its respiration rate rises. Name the plant growth regulator that triggers the start of seed germination.

Oct/Nov 2016

A respirometer may be used to determine the respiration rate of small invertebrates, for example the common woodlouse, $\textit{Oniscus asellus}$. Fig. 8.1 shows a common woodlouse and Fig. 8.2 shows a respirometer.

Oct/Nov 2016

Chemiosmosis is the name given to ATP synthesis that uses a proton gradient across a membrane in a mitochondrion or chloroplast. Peter Mitchell first showed this in 1961.

Oct/Nov 2017

Describe how ATP is synthesised in substrate-linked reactions.

Oct/Nov 2017

Section B. Choose one question to answer.

Oct/Nov 2017

Chemiosmosis refers to ATP synthesis driven by a proton gradient spanning a membrane in a mitochondrion or chloroplast. Peter Mitchell demonstrated this first in 1961.

Oct/Nov 2017

Fig. 6.1 shows some of the stages of glycolysis.

Oct/Nov 2018