Applied Science AQA/Breathing

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Topic Title[edit | edit source]


Setting Applied context[edit | edit source]

An understanding of respiration is vital to many scientists and healthcare professionals. Biochemists can analyse the rates of cellular respiration in samples of tissues. Sport physiologists can determine whether an individual is respiring aerobically or anaerobically using non-invasive methods. Engineers use their understanding of cellular respiration to clean up contamination in the environment, using cells which convert contaminants into energy.

Syllabus Content What you need to do
•    the distinction between breathing and cellular respiration:

•    breathing as a physical, external process

•    cellular respiration as a chemical, internal process

•    methods of monitoring the respiratory system (breathing rate and volumes)

•    how, during cellular respiration, adenosine triphosphate (ATP) is produced by phosphorylation, in which a phosphate group is added to a molecule of adenosine diphosphate (ADP)

•    how ATP is used to release energy for cell activity

•    the stages in respiration of glucose that result in the production of ATP, and the site of each process:

•    glycolysis (in the cell cytoplasm)

•    Krebs cycle (in the mitochondria)

•    electron transfer chain (in the mitochondria) • the process of glycolysis, to include:

•    phosphorylation of glucose to glucose phosphate, using ATP

•    production of triose phosphate (TP)

•    oxidation of TP to pyruvate with a net gain of ATP and reduced nicotinamide adenine dinucleotide NAD (NADH)

•    the process of the Krebs cycle, to include:

•    pyruvate is converted to acetyl coenzyme A (acetyl-CoA) which enters the Krebs cycle

•    acetyl-CoA reacts with a four-carbon molecule, to form a six-carbon molecule

•    a series of oxidation-reduction reactions generates reduced coenzymes and ATP, and carbon dioxide is lost

•    the process of the electron transfer chain, to include:

•    reduced NAD (NADH) or reduced flavine adenine dinucleotide FAD (FADH2) release hydrogen atoms which provide electrons to transfer down the electron transfer chain

•    as electrons are passed down the chain, energy is released which is used to phosphorylate ADP to ATP

•    the final acceptor of the electrons is oxygen, which forms water

•    the amount of ATP that can be produced from aerobic and anaerobic pathways

•    what is meant by basal metabolic rate (BMR) and how it can be determined by direct or indirect methods

•    the differences in BMR for males and females, and for different age groups of both genders, using secondary data.

Exploration of key ideas (must be original text, not C&P) – level checked by AQA[edit | edit source]

In general, point students towards the approach to take, as opposed to just giving them information.

Concept 1[edit | edit source]


mad scientist
mad scientist

Glycolysis- splitting of glucose







2 Pyruvate- go to link reaction

2 redNAD- to electron transport chain

4ATP- used by cells for energy Net ATP= 2ATP (two used as reactant)

Concept 2[edit | edit source]

Link reaction Text BoxTakes place in the matrix of the mitochondria

ShapeText BoxShape

ShapeShape2 x Pyruvate (3C) [Symbol] 2 x acetyl CoA (2C)




2 Pyruvate



2 Acetyl CoA

2 ReducedNAD

2 CO2

Co-enzymes are substances that are required in addition to the substrate to allow Enzymes to function.



These enzymes are hydrogen acceptors and they mop up excess hydrogen ions- electron carriers when reducuced

Takes place in the matrix of the mitochondria

Concept 3[edit | edit source]

Krebs Cycle

The 2-carbon acerylcoenzyme A from the link reaction combines with a 4-carbon molecule to produce a 6-carbon molecule.

In a series of reactions this 6-carbon molecule loses carbon dioxide and hydrogen to give a 4-carbon molecule and a single molecule of ATP produced as a result or substrate-level phosphorylation (Topic 2.3).

The 4-carbon molecule can now combine with a new molecule of acetylcoenzyme A to begin the cycle again.


Oxaloacetate (4C)

Acetyl CoA (2C)





Citrate (6C)

4CO2- Waste

2 ATP- used by cell

6 NADH- to ETC

2 FADH2- to ETC (Per 2 turns of the kerb cycle)

Concept 4[edit | edit source]

Electron Transport Chain Generates 34 ATP molecules

Requires oxygen

Takes place on the inner mitochondrial membranes

Uses reduced electron carriers: NAD and FAD from the Krebs cycle, link reaction and glycolysis










Electrons are carried along the ETC by NADH and FADH. The H+ ions cannot get to the electrons, but they are attracted to them so are pulled through the H+ pump.

Study Task[edit | edit source]

Work to do to understand this topic e.g. research, analysis

Careers and Organisations[edit | edit source]

Carry out some research into these jobs in this area. (Feel free to add other jobs you find.)

Research these roles: What are the benefits of this role to society? What organisations would employ someone in this role? 

(Where would they work?)

What would someone in this role have to do within the organisation? What scientifically-related skills do they need to have? 

What techniques do they need to have mastered?

What experience is needed to undertake this role and its responsibilities within an organisation? What other science personnel will they work with in their organisation.
Job 1
Job 2

Relevant practical/s[edit | edit source]

– relating to criteria skills

Quick questions[edit | edit source]


quick questions


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Exam-style questions[edit | edit source]

– can we use old AQA qs… e.g. from more than 5 years ago? With Examiner comments


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Links[edit | edit source]

to other sections within this book

to good external websites (including AQA website, wikipedia, relevant applications / companies) - also considering links in spec

References / Bibliography[edit | edit source]

of recommended text books

including mapped refs to existing books

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