This topic looks at the details of glycolysis, the link reaction and the krebs cycle. The structure of mitochondria is related to its function and the amazing process of chemiosmosis is outlined leading to the production of water and ATP
Key concepts
Learn and test your biological vocabulary using these 8.2 Cell respirationflashcards.
Essentials
These slides summarise the essential understanding and skills in this topic. They contain short explanations in text and images - great revision.
Read the slides and look up any words or details you find difficult to understand.
Summary
Summary list for 8.2 Respiration
Introduction to reactions in respiration
Cell respiration involves:
the oxidation and reduction of electron carriers.
the phosphorylation of molecules which makes them less stable.
decarboxylation removes a carbon atom from a molecule.
Glycolysis & the Krebs cycle
Glycolysis is the conversion of glucose to pyruvate in the cytoplasm giving a small net gain of ATP (without the use of oxygen).
Aerobic cell respiration converts the pyruvate by decarboxylation and oxidation, into an acetyl compound.
In the link reaction acetyl is attached to coenzyme A to form acetyl coenzyme A.
In the Krebs cycle;
the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
reduced NAD and FAD (NADH+H+ and FADH+) carry energy released by oxidation reactions to the cristae of the mitochondria.
The electron transport chain & Mitochondrion structure.
the electron transport chain in the membrane of the cristae is coupled to proton pumping.
oxygen is the final electron acceptor.
In chemiosmosis protons diffuse through ATP synthase to generate ATP.
Oxygen binds with the free protons to maintain the hydrogen gradient and resulting in the formation of water.
The structure of the mitochondrion is adapted its function. Annotate a diagram of a mitochondrion to show these adaptations.
Skills
Active mitochondria have been studies using electron tomography - images.
students will be able to identify where decarboxylation and oxidation reactions occur in diagrams of the pathways of aerobic respiration.
Guidance: The names of the intermediate compounds in glycolysis and the Krebs cycle are not required.
Mindmaps
This diagram summaries the main sections of topic 8.2. Test if you can draw something like these concept maps from memory.
Exam style questions
Exam style question about cell respiration.
Explaining the link reaction is an important skill from this topic.
Answer the question below, on a piece of paper, then check your answer against the model answer below.
Compare and contrast the link reaction and the krebs cycle . [2]
The link reaction produces acetyl-CoA the Krebs cycle uses acetyl-CoA.
The acetyl group reacts with CoA in the link reaction but it reacts with a with 4 carbon compound in the Krebs cycle.
Both link reaction and the Krebs cycle occur in the mitochondria matrix.
Model answer
The link reaction produces acetyl-CoA the Krebs cycle uses acetyl-CoA.
The acetyl group reacts with CoA in the link reaction but it reacts with a with 4 carbon compound in the Krebs cycle.
Both link reaction and the Krebs cycle occur in the mitochondria matrix.
Extra exam style question on mitochondria. Click to open.
Exam style question about mitochondria and respiration.
The relationship between the structure and function of the mitochondrion is an important aspect of aerobic respiration.
Outline six ways in which the structure of a mitochondrion is related to its function. (6 marks)
Examiner's hint: In an 'Outline' question give the most important points with an explanation or detail for each.
Where there are six ways asked for it's best to try to outline seven, in case one point is incorrect. Avoid any points which contradicts another. Try to put the structural feature with the function.
Click the + icon to see a model answer
Model answer
Outline 6 ways in which the structure of a mitochondrion is related to its function. (6 marks)
The outer membrane of the mitochondrion is permeable to oxygen and carbon dioxide which allows the exchange of these gases.
The outer membrane has a transfer protein for pyruvate which brings pyruvate into the mitochondrion.
The inner membrane contains the electron carriers for the electron transfer chain.
The inner membrane is folded into cristae to give a larger surface area for the electron transport chain.
The double membrane creates an intermembrane space for hydrogen ions to accumulate.
The electron carriers of the inner membrane pump hydrogen ions into the intermembrane space.
The hydrogen pump creates a high hydrogen ion concentration/electrical potential gradient in the intermembrane space.
The inner membrane is impermeable to hydrogen ions (except at ATP synthase).
ATP synthase embedded in the inner membrane allows the protons to flow back through the inner membrane into the matrix.
Proton flow through ATP synthase provides energy for ATP formation (by chemiosmosis).
The matrix contains the enzymes of the Krebs cycle.
The matrix contains microbial DNA (and ribosomes) to manufacture the enzymes of the Krebs cycle.
Model answer
Outline 6 ways in which the structure of a mitochondrion is related to its function. (6 marks)
The outer membrane of the mitochondrion is permeable to oxygen and carbon dioxide which allows the exchange of these gases.
The outer membrane has a transfer protein for pyruvate which brings pyruvate into the mitochondrion.
The inner membrane contains the electron carriers for the electron transfer chain.
The inner membrane is folded into cristae to give a larger surface area for the electron transport chain.
The double membrane creates an intermembrane space for hydrogen ions to accumulate.
The electron carriers of the inner membrane pump hydrogen ions into the intermembrane space.
The hydrogen pump creates a high hydrogen ion concentration/electrical potential gradient in the intermembrane space.
The inner membrane is impermeable to hydrogen ions (except at ATP synthase).
ATP synthase embedded in the inner membrane allows the protons to flow back through the inner membrane into the matrix.
Proton flow through ATP synthase provides energy for ATP formation (by chemiosmosis).
The matrix contains the enzymes of the Krebs cycle.
The matrix contains microbial DNA (and ribosomes) to manufacture the enzymes of the Krebs cycle.
Extra exam question on the role of oxygen in aerobic respiration Click to open.
The role of oxygen in aerobic respiration is an important concept in this topic.
Answer the question below, on a piece of paper, then check your answer against the model answer below.
Describe the role of oxygen in the production of ATP aerobic respiration (4 marks).
Hint: Your response must link the use of oxygen to the production of ATP.
Click on the "+" icon to see a model answer.
Model answer
Describe the role of oxygen in the production of ATP by aerobic respiration (4 marks).
Aerobic respiration produces ATP using a proton gradient and chemiosmosis.
Creating the proton gradient requires a flow of electrons through the electron transport chain.
Oxygen is the final electron acceptor.
Allowing the maintenance of the proton gradient (flow of electrons) for the production of ATP.
When the protons pass through ATP synthase pores, they bind to oxygen.
The protons, electrons and oxygen form water.
Model answer
Describe the role of oxygen in the production of ATP by aerobic respiration (4 marks).
Aerobic respiration produces ATP using a proton gradient and chemiosmosis.
Creating the proton gradient requires a flow of electrons through the electron transport chain.
Oxygen is the final electron acceptor.
Allowing the maintenance of the proton gradient (flow of electrons) for the production of ATP.
When the protons pass through ATP synthase pores, they bind to oxygen.
The protons, electrons and oxygen form water.
Test yourself
This is a self marking quiz containing questions covering the topic outlined above. Try the questions to check your understanding.
Reduced and FAD produced in the cycle donate to the electron transport chain (ETC) in the mitochondrial membrane. These electrons are passed down the ETC in the membrane causing to accumulate in the intermembrane space.
The accumulated protons pass through an ATP pore in the membrane into the stroma (chemiosmosis), losing electrical energy which is used to drive the formation of ATP by . The electrons and protons then combine with to form water.
The ETC cannot function in the absence of oxygen as it is the final electron at the end of the ETC.
Explanation: The ETC creates the proton gradient for ATP formation. The role of oxygen is to act as tyhe final electron acceptor for the ETC.
Just for fun
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