4 of 58

2.8 Respiration

Syllabus Reference

	Statement	Guidance
2.8.U1	Cell respiration is the controlled release of energy from organic compounds to produce ATP.	Details of the metabolic pathways of cell respiration are not needed but the substrates and final waste products should be known.
2.8.U2	ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U3	Anaerobic cell respiration gives a small yield of ATP from glucose.
2.8.U4	Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
2.8.A1	Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
2.8.A2	Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
2.8.S1	Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.	There are many simple respirometers which could be used. Students are expected to know that an alkali is used to absorb CO2, so reductions in volume are due to oxygen use. Temperature should be kept constant to avoid volume changes due to temperature fluctuations.

5 of 58

	Statement	Guidance
8.2.U1	Cell respiration involves the oxidation and reduction of electron carriers.
8.2.U2	Phosphorylation of molecules makes them less stable.
8.2.U3	In glycolysis, glucose is converted to pyruvate in the cytoplasm.	The names of the intermediate compounds in gylcolysis is not required.
8.2.U4	Glycolysis gives a small net gain of ATP without the use of oxygen.	The names of the intermediate compounds in gylcolysis is not required.
8.2.U5	In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.
8.2.U6	In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.	The names of the intermediate compounds in the Krebs cycle is not required.
8.2.U7	Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.
8.2.U8	Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.
8.2.U9	In chemiosmosis protons diffuse through ATP synthase to generate ATP.
8.2.U10	Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation of water.
8.2.U11	The structure of the mitochondrion is adapted to the function it performs.

8.2 Respiration

Syllabus References

6 of 58

	Statement	Guidance
8.2.A1	Electron tomography used to produce images of active mitochondria.
8.2.S1	Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation reactions occur.
8.2.S2	Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

8.2 Respiration

Syllabus References

7 of 58

2.8 Respiration

Draw and annotate a molecule of ATP to show how it stores and releases energy

2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.

Mono = 1

Di = 2

Tri = 3

Pi =Inorganic Phosphate

8 of 58

2.8 Respiration

What happens when you burn sugar?

Do Now

All sugar molecules contain a lot of energy.
This energy is released rapidly in combustion,
the temperature can reach 300°C .
This energy release is too rapid for living cells .

9 of 58

Cell respiration is the controlled release of energy from organic compounds in cells to form ATP.

2.8 Respiration

What is cell respiration?

2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP

10 of 58

2.8 Respiration

Where does energy come from?

2.8.U1 Details of the metabolic pathways of cell respiration are not needed but the substrates and final waste products should be known

True or False: Glucose is the only molecule that can be broken down to release energy?

11 of 58

2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

2.8 Respiration

What is the equation for respiration?

2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.

12 of 58

2.8 Respiration

13 of 58

What do we use this energy for?

2.8 Respiration

List 6 cellular processes that use ATP as a source of energy

2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.

Muscle Contraction

Protein synthesis

DNA and RNA replication

Active Transport

Vesicle Transport

Cell Signaling

14 of 58

Anaerobic respiration involves the partial breakdown of organic molecules for a small yield of ATP (no oxygen required)
Aerobic respiration involves the complete break down of organic molecules for a larger ATP yield (oxygen required)

2.8 Respiration

2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.

2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

15 of 58

2.8 Respiration

2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.

2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.

16 of 58

•

2.8 Respiration

2.8.U11 The structure of the mitochondrion is adapted to the function it performs.

Intermembrane Space

Inner membrane

Matrix

Outer Membrane

Cristae

17 of 58

2.8 Respiration

2.8.U11 The structure of the mitochondrion is adapted to the function it performs. 2.8.S1Annotation of a diagram of a mitochondrion to indicate the adaptations to its function.

18 of 58

2.8 Respiration

2.8.A1 ectron tomography used to produce images of active mitochondria.

19 of 58

3. Characteristics of ATP

2. Processes where ATP is used

1. Definition of Respiration

2.8 Respiration

Complete the blast off

Checkpoint

Challenge: recite the exact definition word for word

20 of 58

	Oxidation	Reduction
Electrons	Loss	Gain
Oxygen	Gain	Loss
Hydrogen	Loss	Gain

2.8 Respiration

8.3.U1 Cell respiration involves the oxidation and reduction of electron carriers.

21 of 58

NAD⁺+ 2H⁺ + 2e^- 🡪 NADH + H⁺ (makes 3 ATP in the ETC)

FAD+ 2H⁺ + 2e^- 🡪 FADH₂(makes 2 ATP in the ETC)

2.8 Respiration

8.2.U1 Cell respiration involves the oxidation and reduction of electron carriers. 8.2.U7 Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and FAD.

22 of 58

The most common hydrogen carrier is NAD⁺ which is reduced to form NADH (NAD⁺ + 2H⁺ + 2e^– → NADH + H⁺)
A less common hydrogen carrier is FAD which is reduced to form FADH₂ (FAD + 2H⁺ + 2e^– → FADH₂)

2.8 Respiration

Explain when oxidation and reduction occur in respiration

23 of 58

2.8 Respiration

Reaction	Location	Purpose	ATP Yield
Glycolysis	Cytoplasm (cytosol)	Split organic molecules into small carbon compounds	2
Links Reaction	Matrix of the Mitochondrion	Convert pyruvate (3C) to acetyl CoA (2C)	0
Krebs Cycle	Matrix of the Mitochondrion	Reduce NAD+ and FAD with H+ and e- for electron transport chain	2
Electron Transport Chain	Inner Mitochondrial Matrix	Create an electrochemical gradient in the intermembrane space of the mitochondria	0
Oxidative Phosphorylation	Phosphorylate ADP + Pi	Use an electrochemical gradient to synthesis ATP as H+ move through ATP Synthase	34

25 of 58

A hexose sugar (typically glucose) is phosphorylated by adding two molecules of ATP (to form a hexose bisphosphate)
This phosphorylation makes the molecule less stable and more reactive, and also prevents diffusion out of the cell

2.8 Respiration

1. Phosphorylation

8.3.U2 Phosphorylation of molecules makes them less stable

Glucose

Glucose – 6 phosphate

Hexose bisphosphate

26 of 58

The hexose biphosphate (6C sugar) is split into two triose phosphates (3C sugars)

2.8 Respiration

2. Lysis

8.2.U3 In glycolysis, glucose is converted to pyruvate in the cytoplasm. 8.2U4 Glycolysis gives a small net gain of ATP without the use of oxygen.

Triose (3C) Phosphate

2 x ADP + Pi

2 x ATP

2 x ADP + Pi

2 x ATP

NAD+

NADH + H+

NAD+

NADH + H+

Pyruvate (3C)

•

27 of 58

Pyruvate (C₃H₄O₃) 🡪 Lactic Acid(C₃H₆O₃)

2.8 Respiration

8.2.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions

28 of 58

2.8 Respiration

The Links Reactions

8.2.U5 In aerobic cell respiration pyruvate is decarboxylated and oxidized, and converted into acetyl compound and attached to coenzyme A to form acetyl coenzyme A in the link reaction.

Pyruvate (3C)

Acetate (2C)

CO₂

Coenzyme A

NAD+

NADH + H+

NAD+

NADH + H+

Acetyl CoA (2C)

Pyruvate is transported from the cytosol into the mitochondrial matrix by carrier proteins on the mitochondrial membrane

29 of 58

Acetyl Co-enzyme A (2C)

Co-Enzyme A

Citric Acid (6C)

Oxaloacetate (4C)

5C Compound

Ketoglutarate

CO₂

NAD+

NADH

CO₂

2 NAD+

2 NADH

FAD

FADH2

Co-Enzyme A is recycled and reused in glycolysis

2 CO₂, 3 NADH, 1 FADH, 1 ATP per cycle

2 Cycles of the Krebs Cycle occurs

ATP

ADP

4 CO₂,

6 NADH, 2 FADH, 2 ATP

8.2 Respiration

The Krebs (Citric Acid) Cycle

8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

30 of 58

8.2.U6 In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.

2.8 Respiration

Acetyl CoA (2C)

Score Card

ATP

NADH

FADH

CO₂

Coenzyme A recycled

Citric Acid (6C)

CO₂

NAD+

NADH + H+

CO₂

NAD+

NADH + H+

FAD

FADH₂

ADP + Pi

ATP

NAD+

NADH + H+

31 of 58

Indicate where these processes are happening on the diagram below:
decarboxylation, oxidation, substrate level phosphorylation

2.8 Respiration

Describe the Kreb’s cycle

32 of 58

Pyruvate is transported from the cytosol into the mitochondrial matrix by carrier proteins on the mitochondrial membrane
The pyruvate loses a carbon atom (decarboxylation), which forms a carbon dioxide molecule
The 2C compound then forms an acetyl group when it loses hydrogen atoms via oxidation (NAD⁺ is reduced to NADH + H⁺)
The acetyl compound then combines with coenzyme A to form acetyl coenzyme A (acetyl CoA)

2.8 Respiration

33 of 58

Step 1 - In the first stage of the Krebs cycle, the carbon from acetyl CoA is transferred to a 4 carbon compound. This forms a six carbon compound.

2.8 Respiration

The Kreb’s Cycle

34 of 58

Step 2 - This six carbon compound then undergoes decarboxylation (CO₂ is removed) and oxidation (hydrogen is removed) to form a 5 carbon compound. The hydrogen is accepted by NAD+ and forms NADH + H⁺.

2.8 Respiration

35 of 58

Step 3 - The five carbon compound undergoes decarboxylation (CO₂ is removed) and oxidation (hydrogen is removed) again to form a 4 carbon compound. The hydrogen is accepted by NAD+ and forms NADH + H⁺.

2.8 Respiration

36 of 58

Step 4 - The four carbon compound then undergoes substrate-level phosphorylation and during this reaction it produces ATP. Oxidation also occurs to the compound (2 hydrogens are removed). The one hydrogen is accepted by NAD+ and forms NADH + H⁺. The other is accepted by FAD and forms FADH₂. The four carbon compound is then ready to accept a new acetyl group and the cycle is repeated.

2.8 Respiration

37 of 58

2.8 Respiration

Hydrogen carriers donate high energy electrons

8.2U8Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.

8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.

When the electrons move through the chain they lose energy, which is transferred to the electron carriers within the chain

Electron carriers use this energy to pump hydrogen ions from the matrix and into the intermembrane space

The accumulation of H⁺ ions in the intermembrane space creates an electrochemical gradient

Electrochemical Gradient

Chemiosmosis

ATP Synthase

Oxidative (Oxidation)

Phosphorylation

Electron Transport Chain

Final Acceptor

H⁺ ions return to the matrix via the transmembrane enzyme ATP synthase (this diffusion of ions is called chemiosmosis)

As the ions pass through ATP synthase they trigger a phosphorylation reaction which produces ATP (from ADP + Pi)

Oxygen removes the electrons and also binds matrix protons to form water

38 of 58

NADH

NAD+

H+

O₂

4H⁺ + 4e^- + O₂🡪 2H₂O

H+

ADP

ATP

H+

FADH₂

FAD

NADH is oxidised = 2 e^- and 1 H⁺

FADH₂ is oxidised = 2 e^- + 2 H⁺

Electrons are carried by mobile electron carriers down the electron transport chain

The energy from the electrons moves 1 x H+ into the intermembrane space

Oxygen is the final electron acceptor and forms water

8 x H⁺ + 4 x e^- and O₂🡪 2H₂O + 4H⁺ move into intermembrane space

As H⁺ ions have been pumped into the intermembrane space, an electrochemical gradient has been formed.

The H⁺ ions move through ATP synthase by the process of chemiosmosis down the gradient.

ADP + Pi are synthesised to make ATP

H⁺ ions are reused to maintain the electrochemical gradient

Matrix

Intermembrane Space

Outer Membrane

39 of 58

8.2 Respiration

How many ATP are produced?

8.2 U8. Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.

Glycolysis Score Card:

4 ATP

2 NADH

2 H₂O

Link’s Score Card:

0 ATP

2 NADH

2 CO₂

Krebs Cycle Score Card:

2 ATP

6 NADH

4 CO₂

2 FADH

NADH produces 3 molecules of ATP

FADH₂ produces 2 molecules of ATP

ETC Score Card:

10 NADH x 3 = 30 ATP

2 FADH x 2 = 4 ATP

Total Score Card:

38 ATP

6 CO₂

6 H₂O

40 of 58

	a membrane protein called ATP synthase.
	which form an electron transport chain.
	H⁺ are pumped by membrane proteins into the inner membrane space.
	Reduced NAD+ and FAD are oxidised releasing electrons and H⁺ ions.
	embedded in this membrane are proteins
	These H⁺ ions accumulate and their concentration increases.
	The inner membrane is folded into cristae and
	When they diffuse back to the matrix they pass through
	drives an enzyme reaction which converts ADP + Pi to ATP.
	The electrons are passed along the chain while the
	The flow of protons through ATP synthase

41 of 58

Hydrogen carriers donate high energy electrons to the electron transport chain (located on the cristae)
As the electrons move through the chain they lose energy, which is transferred to the electron carriers within the chain
The electron carriers use this energy to pump hydrogen ions from the matrix and into the intermembrane space
The accumulation of H⁺ ions in the intermembrane space creates an electrochemical gradient (or a proton motive force)
H⁺ ions return to the matrix via the transmembrane enzyme ATP synthase (this diffusion of ions is called chemiosmosis)
As the ions pass through ATP synthase they trigger a phosphorylation reaction which produces ATP (from ADP + Pi)
The de-energised electrons are removed from the chain by oxygen, allowing new high energy electrons to enter the chain
Oxygen also binds matrix protons to form water – this maintains the hydrogen gradient by removing H⁺ ions from the matrix

2.8 Respiration

8.2U8Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping.

8.2.U9 In chemiosmosis protons diffuse through ATP synthase to generate ATP.

42 of 58

A respirometer is used to calculate the rate of respiration by measuring the consumption of oxygen.

2.8 Respiration

Can you describe how a respirometer works?

2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.

43 of 58

CO₂ + KOH 🡪 K₂CO_{3 (s)}
Soda lime is a mixture of NaOH & CaO chemicals
NaOH 🡪 NaCO₃₊H₂O

Filter paper wicks

Increase the efficiency of carbon dioxide absorption

2.8 Respiration

Can you describe how a respirometer works?

2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.

44 of 58

The apparatus consists of two tubes, one containing the living organisms and the other with glass beads (same mass) to act as a control

The movement of the coloured liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration

The reduction of volume in the tube increases pressure causing the coloured liquid to move

The distance moved by the liquid in a given time is measured will provide the volume of oxygen taken in by the insect per minute

2.8 Respiration

Can you describe how a respirometer works?

2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.

45 of 58

https://www.biologycorner.com//worksheets/cellular_respiration_AP_Lab5_virtual.html

2.8 Respiration

Respiring organism: If using invertebrates rather than seeds what are the ethical questions that need answering?

Nature of Science: assessing the ethics of scientific research - the use of invertebrates in respirometer experiments has ethical implications. (4.5)

Is it acceptable to remove animals from their natural habitat for use in an experiment?
Can the animals be safely returned to their habitat?
Will the animals suffer pain or any other harm during the experiment?
Can the risk of accidents that cause pain or suffering to the animals be minimized during the experiment? In particular, can contact with the alkali be prevented?
Is the use of animals in the experiment essential or is there an alternative method that avoids using animals?

46 of 58

http://www.nuffieldfoundation.org/sites/default/files/PB_measuring-rate-of-metabolism-respirometer2-500.jpg

https://www.youtube.com/watch?v=R_Hdx8wxwEY

You should aim to carry out your own investigation

In the absence of equipment you can use the worksheet (Q1-10) with the virtual lab:

http://biologycorner.com/worksheets/cellular_respiration_AP_Lab5_virtual.html

2.8 Respiration

Complete the experiment

2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.

47 of 58

What is respiratory quotient?

Respiratory quotient (RQ) is the ratio of the volume of carbon dioxide produced to the volume of oxygen used in the same period of time.

RQ =

volume of CO₂ given out

volume of O₂ taken in

RQ gives an indication of the respiratory substrate being respired and whether respiration is aerobic or anaerobic.

anaerobic

> 1

aerobic

carbohydrate

1.0

protein

approx. 0.9

lipid

approx. 0.7

glucose

Substrate

Type of respiration

49 of 58

2.8 Respiration

What types of respiration are there?

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + 36 ATP

In anaerobic respiration, glucose is converted (in the absence of oxygen) to either lactate or ethanol. The ATP yield is low.

C₆H₁₂O₆ → 2 C₃H₆O₃ + 2 ATP

lactate

C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂ + 2 ATP

ethanol

50 of 58

2.8 Respiration

Let’s start baking!

2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.

Ethanol is also produced by anaerobic cell respiration, but it evaporates during baking.

http://commons.wikimedia.org/wiki/File:Frenchbread3000ppx.jpg

Bread is made by adding water to flour, kneading the mixture to make dough and then baking it. Usually an ingredient is added to the dough to create bubbles of gas, so that the baked bread has a lighter texture (e.g. yeast).

After kneading (mixing) the dough is kept warm to encourage the yeast to respire.

Yeast can respire aerobically or anaerobically, but oxygen in the dough is soon used up so the yeast is forced to respire anaerobically.

The carbon dioxide produced by anaerobic cell respiration cannot escape from the dough and forms bubbles causing the dough to swell and rise.

51 of 58

2.8 Respiration

Let’s get sprinting

2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.

Certain human activities require anaerobic respiration such as weightlifting and sprinting.

Rapid generation of ATP enables us to maximise the power of muscle contractions.

Aerobic respiration generates a much greater yield of ATP, but anaerobic respiration can supply ATP very rapidly, as oxygen is not required.

Anaerobic cell respiration produces lactate. There is a limit to the concentration that the body can tolerate and this limits how much or how long anaerobic respiration can be done for.

Afterwards lactate must be broken down. This involves the use of oxygen. It can take several minutes for enough oxygen to be absorbed for all lactate to be broken down. The demand for oxygen that builds up during a period of anaerobic respiration is called the oxygen debt.

52 of 58

2.8 Respiration

2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.

http://en.wikipedia.org/wiki/File:Ethanol_plant.jpg

http://en.wikipedia.org/wiki/File:Saab_9-3_SportCombi_1.8t_BioPower_Facelift_rear.JPG

http://commons.wikimedia.org/wiki/File:Cornfield_in_South_Africa2.jpg

Bioethanol (ethanol produced by organisms) is a renewable energy source.

Most bioethanol is produced from sugar cane and maize, using yeast.

Fermenters are used to keep the yeast in optimum conditions.

When yeast carry out anaerobic respiration the sugars in the plant material are converted to ethanol and carbon dioxide.

Starch and cellulose in the plant material are broken down by enzymes into sugars.

The ethanol produced by the yeasts is purified by distillation and water is removed to improve combustion.

1 of 58

2 of 58

3 of 58

4 of 58

5 of 58

6 of 58

7 of 58

8 of 58

9 of 58

10 of 58

11 of 58

12 of 58

13 of 58

14 of 58

15 of 58

16 of 58

17 of 58

18 of 58

19 of 58

20 of 58

21 of 58

22 of 58

23 of 58

24 of 58

25 of 58

26 of 58

27 of 58

28 of 58

29 of 58

30 of 58

31 of 58

32 of 58

33 of 58

34 of 58

35 of 58

36 of 58

37 of 58

38 of 58

39 of 58

40 of 58

41 of 58

42 of 58

43 of 58

44 of 58

45 of 58

46 of 58

47 of 58

48 of 58

49 of 58

50 of 58

51 of 58

52 of 58

53 of 58

54 of 58

55 of 58

56 of 58

57 of 58

58 of 58