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What can respiration be defined as?
A chemical reaction that oxidises glucose to carbon dioxide and water
Where does respiration take place?
What is the initial source of power for respiration?
The breakdown of chemical bonds in glucose releases high energy electrons
What happens to the high energy electrons released by the lysis of glucose?
They are stored as ATP to be used by the cell
What is glucose split into during glycolysis?
2 molecules of 3 carbon pyruvate
How is the glucose made more reactive?
- 2 ATP molecules are used to add two phosphate groups
- This is called phosphorylation
What is the net gain of ATP molecules in glycolysis?
What happens to high energy electrons released due to the addition of chemical bonds in glycolysis?
- Added (along with hydrogen ions) to a molecule of NAD
- This reduces NAD to NADH
Describe the first stage of Oxidative decarboxylation
Pryruvate reacts with coenzyme A
What is formed from the reaction of coenzyme A and Pyruvate during the link reaction
- Acetyl coenzyme A- a 2 carbon molecule
- CO2 is also released
What happens to a number of high energy electrons released when the chemical bonds are broken during the link reaction?
They are added to a molecule of NAD, reducing it to NADH
What happens to Acetyl coenzyme A during the Krebs cycle?
The carbon atoms are removed through a series of reactions, converting them to CO2
What happens to all of the high energy electrons released during the Krebs cycle?
- They are used to reduce NAD to NADH
- Also reduce FAD to FADH
Other than CO2 what is also produced during the Krebs cycle, and what is the name for this reaction?
- Substrate level Phosphorylation
What happens to the high energy electrons stored in NADH during the electron transfer chain?
It is released from NADH when electrons are and hydrogen ions are passed along a series of electron carriers
What happens to the NADH molecules during the electron transfer chain?
They are oxidised back to NAD
What ensures that electrons are released during the transfer chain?
Each carrier has a lower energy level than the last
What ensures that electrons do not move back along the transfer chain?
Each carrier has a higher affinity for electrons than the last
What happens to the carriers when they interact with electrons?
- They are reduced when they gain an electron and are oxidised when they pass it on
- This is known as a redox reaction
What acts as the final electron acceptor and what happens to it?
- Reduced to become water
Write a word equation for the reduction of water
O2 + 4H+ + 4e- = 2H2O
What is the energy that is released during the electron transfer chain used for?
- Used to pump hydrogen ions across an inner membrane of the cristae into the intermembranal space
- Creates a concentration gradient
What happens to the Hydrogen ions that have been pumped into the intermembranal space following the electron transfer chain?
They diffuse back into the matrix through protein channels
What does the movement of hydrogen ions into the matrix following the electron transfer achieve?
The flow of hydrogen ions provides the energy required to produce ATP
What is ATP synthesised from and by which enzyme is this reaction controlled
- Adenosine diphosphate and inorganic phosphate
- ATP synthase
In which region of the mitochondrion does glycolysis occur?
How is Pyruvate made available for the krebs cycle?
It passes through the double membrane of the mitochondrion into the fluid matrix
Where does the electron transfer chain take place?
What do mitochondrians possess in the way of genetic material
- Circular loop of DNA
- Ribosomes for the synthesis of proteins
Why does anaerobic respiration stop in the absence of oxygen?
There is no final electron acceptor
What effects does the lack of oxygen have on the electron transfer chain and NADH
- The electron carriers remain reduced
- NADH cannot be oxidised and so builds up
What knock on effects does the lack of oxygen have on NADH due to the inability for it to be oxidised?
There is a lack of NAD to accept electrons from the Krebs cycle and link reaction
How can glycolysis occur in some cells when oxygen is not present?
The pyruvate is reduced to either lactate or ethanol using hydrogen ions and electrons from NAD
Write the word equation for the anaerobic reduction of pyruvate in animals
Pyruvate + NADH = Lactate + NAD
Write the word equation for the anaerobic reduction of pyruvate in plants
Pyruvate + NADH = Ethanol + Carbon dioxide + NAD
Give two problems with anaerobic respiration
- Much less energy is released due to incomplete oxidation of glucose (2 fewer ATP molecules)
- The waste products are toxic (in animals the lactate can be oxidised back into pyruvate in the liver when oxygen is available)
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