Aerobic Respiration Flashcards
What are the 4 stages of aerobic respiration?
1) glycolysis
2) the link reaction
3) the kerbs cycle
4) oxidative phosphorylation
Where in the cell does each stage of the cycle take place
1) glycolysis in the cytoplasm
2) link reaction in mitochondrial matrix
3) kerbs cycle mitochondrial matrix
4) oxidative phosphorylation in crista
Explain the first stage of the process glycolysis
-glucose (6C) is converted into glucose-6-phosphate (6C), with a phosphorylation reaction occurring breaking ATP into ADP and Pi
-glucose-6-phosphate is converted into fructose 1,6 bisphosphate (hexose bisphosphate) (6C), with another phosphorylation reaction occurring breaking ATP into ADP and Pi
-hexose bisphosphate is converted into 2x Triose phosphate (TP) (3C), through a hydrolysis reaction
-finally 2xTP is converted into 2x Pyruvate (3C), whilst 4ADP + 4Pi is converted to 4ATP, and 2 x NAD is converted to 2x reduced NAD, releasing 2H
Why is phosphate added to the glucose?
To make it more reactive
What is the net gain of ATP produced from this stage? What is this process called
-2 ATP per glucose (4 made but 2 used up)
-substrate level phosphorylation as made directly with no electors transport carrier chains
Explain what type of reaction the 2x TP into 2x Pyruvate is
-dehydrogenation reaction, the TP is oxidised as it loses hydrogen
What is NAD?
-A co-enzyme
-A non protein organic molecule which helps the enzymes in the last part of glycolysis work
What are the 3 end products of glycolysis
1) Net gain of 2 ATP
2) 2 X Reduced NAD- will be used later on in oxidative phosphorylation to make lots of ATP
3) 2 X Pyruvate- actively passed into the mitochondrial matrix for link reaction
What kind of process takes place to move the 2 x ATP into the link reaction?
-active transport, requiring energy in the form of ATP to move against the concentration gradient from low to high
What is important to remember about this stage in the process of aerobic respiration?
For every glucose, 2 X Pyruvate is made, and each one feeds in to the link reaction, so it happens twice
Explain the steps in the link reaction process
-Pyruvate (3C) is converted into Acetyl/ acetate molecule (2C)
-Decarboxylation takes place (loss of Co2)
-Dehydrogenation also occurs, turning NAD into reduced NAD, releasing 2H atoms
-Acetyl is converted into acetyl co-enzyme A (2C) , in the presence of co-enzyme A
-this then splits into an acetyl group (2C) and co-enzyme A, which can be reused
Why must the link reaction take place?
-because Pyruvate can not directly enter the Krebs cycle
What is the Krebs cycle?
-a series of enzyme catalysed reactions, where the acetyl group from acetyl-co-A is accepted and converted into a series of other substances
What is important to remember about the Krebs cycle?
For every glucose molecule respired we get 2 X Pyruvate, therefore 2 X acetyl-Co-A, so we will get 2 turns of the Krebs cycle
Explain the steps of the Krebs cycle in aerobic respiration
-the acetyl group released combines with a 4C compound oxaloacetate, to form a 6C compound citrate
-citrate is decarboxylated and dehydrogenated, producing a 5C compound, 1 molecule of co2 and one molecule of reduced NAD
-this 5C compound is further decarboxylated and dehydrogenated, producing a 4C compound , one molecule of co2, and one molecule of reduced NAD
-this 4C compound combines temporarily with, and is then released by Co-enzyme A. At this stage substrate level phosphorylation takes place producing one molecule of ATP
-this 4C compound is dehydrogenated, producing a different 4C compound, and a molecule of reduced FAD
-rearrangement of the atoms in the 4C compound, followed by dehydrogenation to give a molecule of reduced NAD, regenerates a molecule of Oxaloacetate so the cycle can continue
Explain the steps in the final stage of aerobic respiration, oxidative phosphorylation
-reduced NAD and reduced FAD are reoxidised back to NAD/FAD when they release their hydrogen atoms next to the cristae
-these hydrogen atoms then split into protons (H+) and electrons (e-)
-the hydrogen ions are in solution in the mitochondrial matrix near the cristae
-the electrons pass along the chain of protein carriers on the cristae
-as electrons pass along the chain, energy is released. This is used to pump the hydrogen ions across the inner mitochondrial membrane into the Inter-membrane space
-as hydrogen ions accumulate in the Inter membrane space this creates a proton gradient across the membrane
-the inner membrane of the mitochondria is not freely permeable to hydrogen ions but they can diffuse back into the matrix via special protein channels associated with the enzyme ATP synthase
-the hydrogen ions flow through these protein channels (chemiosmosis) and it changes the shape of the ATP synthase enzyme activating it
-this allows ADP to join with Pi to make ATP
-the final electron acceptor is oxygen, and hydrogen ions and electrons rejoin with oxygen to form water
