1. Cellular Respiration
Pp 69 – 73 &

2. 3.7 Cell respiration (Core)
Define cell respiration.
State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.
Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.
Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

3. 8.1 Cell respiration (AHL)
State that oxidation involves the loss of electrons from an element, whereas reduction involves a gain of electrons; and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen.
Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation.
Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs.
Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen.
Explain oxidative phosphorylation in terms of chemiosmosis.
Explain the relationship between the structure of the mitochondrion and its function.

4. Define cell respiration
Cell respiration is the controlled release of energy from organic compounds in cells to form ATP
Glucose is the major substrate for respiration
Adenosine triphosphates (ATP) is the molecule which directly fuels the majority of biological reactions.

5. Why cell respiration?
Cells require a constant source of energy to perform various tasks e.g.
Movement
Transport
Division

6. Types of Respiration (i) Anaerobic Respiration
(ii) Aerobic Respiration
Occurs in the absence of Oxygen
Occurs in presence of Oxygen
Occurs in the cells’ cytoplasm
Occurs in the cells’ mitochondria
Yields small amount of ATP (2 molecules) per molecule of glucose
Yields large amount of ATP (38 molecules) per molecule of glucose
Involves fermentation of pyruvate to lactate in muscles/CO2 & ethanol in plant & yeast
Does not involve fermentation

7. Adenosine triphosphate (ATP):
ATP is the chemical molecule which directly fuels the majority of biological reactions
About 1025 ATP molecules are hydrolysed to ADP and inorganic phosphate (Pi) daily
ADP is reduced back to ATP using the free energy from the oxidation of organic molecules

8. ATP Cycle

9. Glycolysis and Cell Respiration
all types of cell respiration starts with glycolysis
glycolysis occurs in the cytoplasm of the cell
1 glucose molecules is broken down into 2 pyruvate molecules
there is a net production of 2 ATP molecules
glycolysis does not require oxygen
the fate of pyruvate depends on presence or absence of oxygen

10. Anaerobic Cell Respiration
anaerobic cell respiration occurs in the absence of oxygen
during glycolysis glucose is broken breakdown in the cytoplasm
leading to the production of pyruvate,
production of small amount of energy (2 ATP molecules per molecule of glucose)
in muscles, pyruvate is converted into lactic acid during lactic acid fermentation
anaerobic respiration occurs in animals during intense muscular activity
in yeast & plant cells, pyruvate is converted into alcohol (ethanol) & CO2 during alcoholic fermentation
no additional APT is produced during fermentation

11. Outline the process of aerobic respiration
during glycolysis glucose is partially oxidized in the cytoplasm
small amount ATP produced during glycolysis
two pyruvate molecules are formed by glycolysis
pyruvate absorbed into mitochondrion
pyruvate is broken down in the mitochondrion in the presence of oxygen
to produce carbon dioxide & water
large amount of energy in form of ATP is produced per glucose molecule

12. Forms of oxidation and reduction
cellular respiration involves oxidation & reduction (redox) reactions
oxidation involves the loss of electrons from an element, gaining oxygen or losing hydrogen by a substance
reduction involves a gain of electrons, losing oxygen or gaining hydrogen by a substance

13. Summary of oxidation and reduction

14. Animation: How the NAD+ Works

15. Process of glycolysis
glycolysis occurs in cytoplasm of the cell & does not require oxygen
hexose sugar (glucose) is phosphorylated using ATP
hexose biphosphate is split (lysis) into two triose phosphates
triose phosphates are oxidised by removal of hydrogen by NAD+
NAD+ is concerted to NADH + H+
there is net gain of 2 ATP molecules (2 ATP are used & 4 ATP produced)
2 pyruvate molecules are produced per glucose molecule undergoing glycolysis

16. Animation: How Glycolysis Works

17. Structure of a mitochondrion
the electron micrograph on the left shows the structure of a mitochondrion as seen under the electron microscope
draw a labelled diagram to show the structure of a mitochondrion
explain the relationship between the structure of the mitochondrion and its function

18. electron micrograph
interpretive drawing

19. Structural adaptation of mitochondrion to its function
large inner surface area of cristae for respiratory complexes such as electron transport chains
matrix contains DNA and ribosomes for protein (enzyme) synthesis
it also contains Krebs cycle enzymes
double membrane(s) isolates metabolic processes from the rest of the cytoplasm
small intermembrane space between inner and outer membranes allows accumulation of protons for chemiosmosis

20. Aerobic respiration

21. Stages of aerobic respiration
aerobic respiration includes the following:
glycolysis; basis of aerobic cell respiration, produces ATP, reduced coenzymes & pyruvate
link reaction; pyruvate is transported into the matrix of the mitochondria
Krebs Cycle; decarboxylation of carbon fragments to yield ATP and reduced coenzymes
electron transport chain; reduced coenzymes are used to generate more ATP

22. Key players in aerobic respiration
Glucose: substrate, source of fuel
NAD+/FAD+: electron carriers
Enzymes: mediate entire process
Mitochondria: site of aerobic respiration
ATP: principal end product
Protons/Electrons: sources of potential energy
Oxygen: final electron acceptor

23. Link reaction
Link reaction forms the link between glycolysis & Krebs cycle
pyruvate from glycolysis enters a mitochondrion
enzymes in the matrix of the mitochondria remove one carbon dioxide and hydrogen from the pyruvate
hydrogen is accepted by NAD+ to forms NADH + H+
removal of hydrogen is oxidation
removal of carbon dioxide is decarboxylation
the whole process in link reaction is oxidative decarboxylation
the product is an acetyl group which reacts with coenzyme A (CoA) to form acetyl CoA which enters Krebs cycle

24. Krebs Cycle
During Krebs Cycle, also called citric acid cycle, oxidative decarboxylation of the C2 Acetyl group (CH3CO) occurs yielding ATP, reduced coenzymes & CO2 is produced as a by-product
Acetyl CoA joins with the C4 acceptor group - oxaloacetate
CoA is released to transport more pyruvate into the matrix
A C6 fragment, citrate is formed
C6 Citrate is oxidatively decarboxylated
A C5 group is formed
The Carbon is given off as CO2
NAD+ is reduced to NADH + H+
The C5 fragment is oxidised and decarboxylated further to a C4 compound
Again the carbon removed forms CO2
NAD+ is further reduced to NADH + H+
The final stage in the cycle has the C4 acceptor regenerated
There is a reduction of NAD+ to NADH + H+
FAD (Coenzyme)is reduced to FADH2
ADP is reduced to ATP

25. Animation: How the Krebs Cycle Works

26. Oxidative phosphorylation in terms of chemiosmosis

27. Oxidative phosphorylation
oxidative phosphorylation occurs during the electron transport chain
electrons are passed between electron carriers
this occurs in cristae of mitochondria
releasing energy
the energy released is used to move protons against their concentration gradient
into the intermembrane space between the two membranes
finally, the protons join with oxygen to produce water
protons flow back to the matrix through the enzyme, ATP synthase
this movement of protons (hydrogen ions ) down the concentration gradient is called chemiosmosis
energy is released from chemiosmosis which produces more ATP (i.e. combines ADP and Pi)

28. Chemiosmosis
There is high concentration of H+ in the intermembrane space & lower concentration in the matrix
ATP synthetase is an enzyme embedded in the cristae membrane
H+create an electrochemical gradient (chemical potential energy)
The H+ passes through a channel in the enzyme driving the motor
The motor spins generating energy which bringing together ADP and Pi to produce ATP

29. Animation: Electron Transport System and ATP Synthesis

30. Animation: Electron Transport System and Formation of ATP

31. Control of Cellular Respiration
The important switch in the control of respiration is the enzyme phosphofructokinase
This enzyme catalyzes step 3 of glycolysis
Phosphofructokinase is inhibited by ATP and stimulated by ADP or AMP.
An example of end-product inhibition in control of metabolic pathway
It is also inhibited by citric acid. This synchronizes the rates of glycolysis and the Krebs Cycle

32. "Cell Respiration" - Cellular Respiration Song

33. Self Assessment Questions (SAQs)
Define the term cell respiration [2]
Outline the process of anaerobic cell respiration in yeast [6]
Outline the process of aerobic cell respiration [6]
Outline the process of glycolysis [5]
Draw labelled diagram of a mitochondrion as seen in an electron micrograph [5]
Explain the relationship between the structure of the mitochondrion and its function [5]
Explain oxidative phosphorylation in terms of chemiosmosis [9]