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Transcript of Cellular Respiration
By Nick Bingle
Where does our energy come from?
Our main source of energy are lipids (fats) however all lipids are burnt in a carbohydrate "flame". Our bodies store carbohydrate in the form of glycogen this in turn is constructed from long chains of glucose which produce ATP when hydrolised.
The first stage of respiration is glycolosis. This can occur both aerobically and anaerobically.
The Link Reaction
Krebs cycle is the process by which acetate is oxidised into carbon dioxide. NAD and FAD are reduced and 1 ATP molecule is produced. The Importance of the process is to provide hydrogen atoms to the electron transport chain.
Why Do We Respire?
The body requires energy to perform all metabolic functions.
Energy is described as the capacity of a physical system to perform work.
Glycolosis is the only part of respiration that can occur without oxygen. If this happens an "oxygen debt" is built up and lactic acid is created.
In Aerobic conditions respiration can continue onto the next stage known as the link reaction. This reaction takes place inside the mitochondria.
The net result of this reaction is 2 ATP and 2 NADH
What is ATP?
Adenosine triphosphate consists of an adenine base, a five carbon sugar (ribose) and 3 phosphate groups. (Blamire, 2001)
The removal of the 3rd phosphate group creates energy and changes ATP in to adenosine diphospate ADP
The purpose of the link reaction is to convert pyruvate into acetate in a process called Decarboxylation.
• Carbon dioxide is removed from pyruvate by pyruvate decarboxylase
• Hydrogen atoms are removed by pyruvate dehydrogenase and transferred to NAD reducing it to NADH
• At the end of the reaction the 3 carbon pyruvate is turned into a 2 carbon acetyl group
No ATP are produced at this stage
The powerhouse of the cell
Has an inner and outer membrane folded into cristae for a large surface area
The link reaction and Krebs cycle occur in the mitochondrial matrix
Krebs cycle turns twice for each molecule of glucose.
Acetate is passed from co enzyme A to a 4 carbon compound called oxaloacetate creating the 6 carbon compound Citrate.
Citrate is decarboxylated (loses CO2) and then dehydrogenised (loses 2 hydrogen atoms) leaving a 5 carbon compound (ketogluterate).
NAD is reduced during this process
Step 2 happens again and a 4 carbon compound (succinate) is left. This process yields 1 ATP molecule and another reduced NAD.
FAD is reduced and Succinate becomes Malate another 4 cabon compund.
A final NAD is reduced and Malate is converted back to Oxaloacetate ready to start the whole process again.
Electron Transport Chain
The electron transport chain is where the majority of ATP is produced.
The reduced NAD and FAD from Krebs Cycle transport [H+] ions to a series of protein carriers
The electrons are transported down the chain and the hydrogen passes through the cell membrane into the extracellular space
this is an example of active transport as it takes place against a concentration gradient
The final protein in the chain transfers the electrons out which enable hydrogen and oxygen atoms to combine creating water.
The enzyme ATP synthase allows [H] to pass back into the intracellular space
the energy provided by the chain allows hydrogen and a phosphate group to bond with ADP to create ATP
around 34 ATP molecules are formed per glucose molecule
Electron transport Chain
By the end of cellular respiration 38 ATP have been created.
2x ATP from Glycolosis
2x ATP from Krebs Cycle
34x ATP from the Electron Transport Chain
For each molecule of Glucose Krebs cycle produces