1. Higher Human Biology Unit 1 – Human Cells
Section 7 – Cellular Respiration

2. What can you remember? What is the equation for respiration?
Glucose + oxygen  water and carbon dioxide
What is the equation for respiration?
What two forms of respiration are there?
What is the energy currency molecule?
Describe the process of glycolysis
How many molecules of ATP are created overall from glycolysis?
What organelle is involved in aerobic respiration
What is produced from anaerobic respiration in plants and animals?
Aerobic and anaerobic
ATP 2
mitochondria
Animals – lactic acid
Plants – ethanol and carbon dioxide

3. a – Cellular Respiration
We will be learning to…
State that glycolysis is the breakdown of glucose to pyruvate
Describe the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis
State that this leads to the generation of more ATP during the energy pay-off stage which results in a net gain of ATP.
State that under aerobic conditions pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A
Describe how in the citric acid cycle the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.
State that the citric acid cycle if a series of enzyme-controlled steps.
State that citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.
State that the location of the citric acid cycle occurs in the matrix of the mitochondria.
Describe the role of dehydrogenase enzymes in both glycolysis and the citric acid cycle.
State the location of the electron transport chain
Describe how electrons and hydrogen ions from NADH are passed to the electron transfer chain.

4. What is a Cellular Respiration?
This is a series of metabolic pathways that bring about the release of energy from a foodstuff and the regeneration of the high-energy compound adenosine triphosphate (ATP).
Respiration is the process by which chemical energy is released from glucose by oxidation.
It takes place in every living cell, and involves the regeneration of ATP from ADP + Pi by a complex series of biochemical reactions.

5. Adenosine Triphosphate (ATP)
This is made up of three inorganic phosphate (Pi) and an adenosine molecule.
Molecule able to provide energy immediately.
adenosine Pi Pi Pi

6. ATP and Energy Transfer
ATP molecules are the energy currency of the cell
adenosine Pi Pi Pi
Adenosine diphosphate
The bond between the end phosphate must be broken by enzymes in order to release the energy.
Adenosine triphosphate

7. adenosine ADP + Pi ATP Pi Pi Pi Pi
The enzyme breaking the bond results in adenosine diphosphate (ADP) and inorganic phosphate (Pi)
Energy released
However, this reaction is reversible – where energy is required to regenerate ATP. This is called Phosphorylation.
breakdown releasing energy
ADP + Pi
ATP
building up requiring energy

8. Phosphorylation
This is the process, controlled by enzymes in which phosphate groups are added to a molecule e.g. ADP + Pi  ATP Phosphorylation can also occur when a phosphate and energy are transferred from ATP to the molecules in a metabolic pathway, making them more reactive Often this stage has to occur for the next reaction to take place. The reactant is now phosphorylated and energised which allows the pathway to proceed.
In respiration, some reactants must undergo phosphorylation in what is called the investment phase

9. The first step in the glycolysis pathway involves such a phosphorylation. The enzyme hexokinase transfers the phosphate group from ATP to the 6′ carbon of the glucose molecule. The effect of this is twofold. Firstly, it prepares the glucose for the next step in the chain of reactions. Secondly, it reduces the concentration of glucose in the cell and, at the same time, prevents its loss from the cell as glucose 6-phosphate is much less able to cross the cell membrane.

10. ATP acts as a link between catabolic, energy-releasing reactions, and anabolic, energy-consuming, reactions.

11. CO2 + water ATP Amino acids Protein Glucose + Oxygen ADP + Pi
ATP Transfer Diagram
CO2 + water
ATP
Amino acids
respiration
energy transfer
work
Protein
Glucose + Oxygen
ADP + Pi

12. ATP Production and Consumption
Some bacterial cells require 2 million molecules of ATP per second In fact, about 400g is produced and used per hour but only 50g is ever present within the body This is possible due to the rapid turnover of ATP molecules – where ATP is breaking down and being regenerated

13. Cellular Respiration
Process by which energy is released from foods by oxidation.
It involves the regeneration of ATP which is a high energy compound.
Consists of 3 stages
Glycolysis
Citric Acid Cycle
Electron Transport Chain

14. 1. Glycolysis Takes place in the cytoplasm of the cell.
It consists of a series of enzyme controlled reactions
Does not require oxygen (anaerobic).
Glucose (6-C) is broken down into two molecules of Pyruvate (3-C).
Net gain of 2 ATP.
Hydrogen released binds to a co-enzyme, NAD by reduction to form NADH (Nicotinamide Adenine Dinucleotide)

15. Energy Investment vs Energy Payoff
The reactions in the first half of the chain make up the energy investment phase where 2ATP are used up.
The reactions in the second half of the chain make up an energy payoff phase where 4ATP molecules are produced per molecule of glucose. H+ ions are also released from the substrate by the dehydrogenase enzyme. These are passed to NAD.
This gives a net gain of 2ATP

16. Glycolysis (in cytoplasm)
Glucose is the starting point of respiration and DOES NOT REQUIRE OXYGEN (anaerobic). It is broken down into two pyruvate molecules via a series of enzyme controlled steps.
GLUCOSE
Glycolysis literally means:
“Glucose splitting”
2ATP
2NAD
2ADP+Pi
2NADH
4ADP+Pi
4ATP (net gain of 2ATP!!!)
Used in stage 3
PYRUVATE
NAD is a molecule which is known as a hydrogen acceptor

17. GLUCOSE
2ATP
2NAD
These two ATP make up the energy investment phase
2ADP+Pi
4ADP+Pi
2NADH
4ATP (net gain of 2ATP!!!)
These two additional ATP make up the energy payoff phase
Used in stage 3
PYRUATE
The hydrogen ions are released in the payoff stage by the enzyme dehydrogenase

18. Glycolysis in More Detail
During this stage, two phosphorylation's take place. A molecule of ATP is converted to ADP; the phosphate group which is released is added to the substrate molecule. The first occurs when glucose is converted to glucose 6-phosphate. This step is irreversible, but the glucose 6-phosphate can be used in a variety of metabolic pathways:
it can enter the pentose phosphate pathway, generating the reducing agent NADPH, which supplies the hydrogen necessary for several reactions, such as fatty acid synthesis, and the precursor of nucleotides for DNA synthesis in the form of ribose phosphate;
it can be converted to glycogen for storage.

19. Structure of the Mitochondria
The mitochondrion is bounded by a double layer of membranes, each of which is itself composed of a phospholipid bilayer. The outer membrane surrounds the mitochondrion and acts as a boundary; although it is highly permeable to small molecules, the entry of larger molecules is strictly regulated. The inner membrane is folded, forming structures called cristae.
Citric Acid Cycle takes place in the matrix of the mitochondria.
Electron Transport Chain takes place on the cristae.

20. Mitochondria
When O2 is present, aerobic respiration occurs in the cell’s mitochondria.
The sausage shaped organelles are within the cytoplasm. The inner membrane is folded into many extensions (CRISTAE) which increases the surface area for ATP production.

21. 2. Citric Acid Cycle (Central Matrix)
Takes place in the matrix of the mitochondria and is a series of enzyme controlled steps.
Requires oxygen (aerobic).
3-C Pyruvate converted to CO2 and Acetyl CoA (2-C). H+ ions reduce the NAD to NADH for transfer to the electron transport chain
Acetyl CoA enters Krebs and combines with a 4-C (oxaloacetate) compound to form a 6-C compound (citrate).
The Coenzyme A returns to combine with more acetyl.

22. 2. Citric Acid Cycle (Central Matrix)
This Citrate (6-C) compound is converted back to a oxaloacetate (4-C) compound by a series of enzyme controlled reactions. This will again combine with acetyl coenzyme A to begin the cycle again.
During the cycle, carbon is released in the form of carbon dioxide and hydrogen H+ ions are released and become bound to NAD, forming NADH.

23. 2. Citric Acid Cycle (Central Matrix)
Pyruvate
anaerobic
2NAD
Pyruvate crosses the double membrane and enters the inner space of the mitochondrion, which is called the matrix. Here it is oxidised.
aerobic
2NADH
2CO2
Used in stage 3
Acetyl Coenzyme A
Coenzyme A
under aerobic conditions pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A

24. Citrate 6C Acetyl Coenzyme A 2C Oxaloacetate Citric Acid cycle 4C 3NAD
the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.
Acetyl Coenzyme A 2C
Citrate 6C
3NAD
3NADH
Oxaloacetate 4C
Citric Acid cycle
2CO2
Used in stage 3
citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.
Many enzyme controlled reactions
FADH2
ADP + Pi
FAD
ATP

25. Dehydrogenase Enzymes
Each step in the cycle is catalysed by a different enzyme which is specific to the substrate involved. the enzymes involved all belong to a class of enzyme called dehydrogenases. These enzymes transfer hydrogen ions and electrons to carrier molecules which then convey them to the electron transport system on the cristae. A similar reaction occurs later but to the coenzyme is FAD (flavine adenine dinucelotide) Also ATP is produced and carbon dioxide is released

27. 3.Electron Transport Chain (Cristae)
Also known as cytochrome system, electron transfer system or hydrogen transfer system.
It is aerobic
Takes place on the cristae of the mitochondria on groups of protein molecules.
The reduced co-enzymes (NADH and FADH2) from glycolysis and citric acid pathways transfer the hydrogen to a chain of carriers.
High energy electrons are also
released and pass to the electron
transport chains.
Produces the most ATP

28. 3.Electron Transport Chain (Cristae)
There are two parts to the system which are said to be coupled, meaning that one cannot occur without the other:
the electron transport chain, which comprises a series of enzyme-controlled electron donors and electron acceptors - each transfer of an electron provides the energy to pass a hydrogen ion (or proton) across the inner membrane into the space between the inner and outer membranes of the mitochondrion;
the ATP synthesis stage, which involves the enzyme ATP synthase - the protons are passed back from the intermembrane space into the matrix of the mitochondrion, releasing energy which is used to form ATP.

29. Electron Transport Chain
The reduced coenzyme NADH brings the positive hydrogen ions and electrons to the inner membrane of the mitochondrion. Here the hydrogen ions are released and the electrons are passed to a series of protein acceptors and donors which are arranged in three closely linked complexes.
When the electrons are passed from donor to acceptor, energy is released. This energy is used to pump the hydrogen ions across the inner membrane into the intermembrane space, building up a concentration there that can be up to ten times that of the matrix.
As the electrons pass along the chain, their energy level declines until eventually they reach their lowest energy level. At that point they are released to combine first with oxygen, and then with two hydrogen ions to from a water molecule (H2O).
The following illustration shows the stages in the electron transport chain. The electrons are shown passing from their coenzymes to carriers in the transport chain. The changing height of the carriers across the diagram indicates the relative energy level of the electrons.

30. Electron Transport Chain
As the electrons pass along the chain, their energy level declines until eventually they reach their lowest energy level. At that point they are released to combine first with oxygen, and then with two hydrogen ions to from a water molecule (H2O).

31. This transfer releases 3 ATP molecules.
Electron Transport Chain
The electrons begin in a high energy state and as they release their energy it is used to pump hydrogen ions across the membrane from the inner cavity (matrix) to the intermembrane space. This helps maintain a high H+ ion concentration.
The return journey of the H+ ions from the intermembrane to the matrix is via ATP synthase. This drives the synthesis of ATP from ADP and Pi.
This transfer releases 3 ATP molecules.

32. When the electrons come to the end of the chain, they combine with oxygen , the final acceptor.
Oxygen also combines with two hydrogen ions to form water.
36 molecules of ATP are produced from the electron transfer system.

34. Overview
In aerobic respiration 38 molecules of ATP are produced in total
2 from glycolysis and 36 from the electron transport chain

35. b – ATP Synthesis We will be learning to…
Describe the process of ATP synthesis
State this energy allows hydrogen ions to be pumped across the inner mitochondrial membrane
Describe how the flow of ions results in the production of ATP
State that oxygen is the final acceptor when hydrogen ions and electrons combine with oxygen.

36. Synthesis of ATP
When glucose is broken down it releases energy to synthesise ATP from ADP + Pi How? A flow of high energy electrons, from the respiratory pathway, transfer their energy to proteins in the membrane. This provides the energy used to pump hydrogen ions across the inner mitochondrial membrane, by active transport. It helps maintain a higher concentration of hydrogen ions on one side of the membrane

37. ATPsynthase
Molecules of the enzyme ATPsynthase are embedded in the mitochondrial membrane
The return flow of hydrogen ions from a region of higher concentration to a region of lower concentration makes the ATPsynthase molecules rotate and catalyse the synthesis of ATP from ADP and Pi

38. The return flow of hydrogen ions makes the ATPsynthase molecules rotate and catalyse the synthesis of ATP from ADP and Pi

39. c – Role of ATP in the Transfer of Energy
We will be learning to…
State the role of ATP in the transfer of energy

40. Use/Role of ATP
ATP is important because it acts as a link by which chemical energy is transferred from one type of reaction to another
ATP breakdown promotes the transfer of energy to new chemical bonds
e.g. peptide bonds joining amino acids together
ATP is necessary for muscle contraction, protein synthesis, and active transport

41. Oxidation is the removal of electrons (hydrogen) from a substance.
Reduction is the addition of electrons (hydrogen) to a substance.
OIL RIG!!!!!!

42. Now I can….. a – cellular Respiration
State that glycolysis is the breakdown of glucose to pyruvate
Describe the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis
State that this leads to the generation of more ATP during the energy pay-off stage which results in a net gain of ATP.
State that under aerobic conditions pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A
Describe how in the citric acid cycle the acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.
State that the citric acid cycle if a series of enzyme-controlled steps.
State that citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide.
State that the location of the citric acid cycle occurs in the matrix of the mitochondria.
Describe the role of dehydrogenase enzymes in both glycolysis and the citric acid cycle.
State the location of the electron transport chain
Describe how electrons and hydrogen ions from NADH are passed to the electron transfer chain.

43. Now I can….. b – ATP Synthesis Describe the process of ATP synthesis
State this energy allows hydrogen ions to be pumped across the inner mitochondrial membrane
Describe how the flow of ions results in the production of ATP
State that oxygen is the final acceptor when hydrogen ions and electrons combine with oxygen.
c – Role of ATP
State the role of ATP in the transfer of energy

44. Higher Human 2017 – A Q5 A

45. Higher Human 2017 – A Q6 B

46. Higher Human 2016 – A Q5 D

47. Higher Human 2016 – A Q6 C

48. Higher Human 2016 – A Q7 B

49. Word
Definition
Acetyl group
produced by breakdown of pyruvate; joins with oxaloacetate in the citric acid cycle
ADP
adenosine diphosphate;molecule that is phosphorylated to produce ATP
Alternative respiratory substrates
substrates for respiration other than glucose
ATP
adenosine triphoshate; molecule used for energy transfer in cells
ATP synthase
membrane-bound enzyme that synthesises ATP
Cellular respiration
release of energy from respiratory substrates
Citrate
citric acid; first substance produced in the citric acid cycle
Citric Acid Cycle
second stage of aerobic respiration occurring in the matrix of mitochondria
Coenzyme A
substance that carries acetyl groups into the citric acid cycle
Dehydrogenase
enzymes that remove hydrogen from their substrates;important in the citric acid cycle
Electron Transport Chain
group of proteins embedded in membranes of mitochondria and chloroplasts
FAD
hydrogen carrier important in the citric acid cycle

50. Word
Definition
Glucose
sugar that is the main respiratory substrate in cells
Glycolysis
first stage in cellular respiration – anaerobic, yields 2ATP overall, occurs in the cytoplasm
High-energy electrons
electrons that can yield energy as they pass through an electron transport chain
Intermediate
substance in a metabolic pathway between the original substrate and the end product
Matrix
central cavity of mitochondrion in which the citric acid cycle occurs
Mitochondrion
cell organelle in which the areobic stages of respiration occur (plural:mitochondria)
NAD
hydrogen carrier important in the citric acid cycle
Oxaloacetate
substance that combines with the acetyl groups in the citric acid cycle to form citrate
Phosphate
inorganic phosphate used to phosphorylate ADP
Phosphorylation
addition of a phosphate to a substance
Pyruvate
the end product of glycolysis
Oxidation
is the removal of electrons (hydrogen) from a substance.
Reduction
is the addition of electrons (hydrogen) to a substance.

51. ATP and Energy What is ATP? 1 What is ATP broken down to? 1
What is the first stage of respiration called? 1
Where does this take place in the cell? 1
What is glucose broken down into? 1
How many carbon atoms has this substance? 1

52. How many ATP molecules are needed to start the process of respiration
How many carbon atoms does Acetyl CoA have?
What is the second stage of respiration called?
Where does this stage take place?
How many carbons does citric acid have?
Apart from carbon dioxide what else is produced in the second stage of respiration?

53. What picks up the hydrogen that is produced? 1
Where is the hydrogen transported to? 1
Where does this stage take place?
What useful substance is formed?
What is the final hydrogen acceptor? 1
What other substrates could be used in respiration if carbohydrates were not available?

54. Suggested activities ?