Respiration Flashcards
Where does glycolysis occur
In the cytosol of the cytoplasm
This stage occurs before the aerobic and anaerobic pathway.
The stages of glycolysis
Glucose is phosphorylated (an ATP is broken down to ADP and a phosphate group; the phosphate group is added to the glucose structure). This forms glucose-6-P.
This is then converted to its isomer, Fructose-6-P.
This is phosphorylated again to form Hexose-1,6-bisphosphate. This is broken to two Triose phosphate (3C) molecules.
Next, substrate level phosphorylation (2ATPs produced) and dehydrogenation occurs, producing intermediate compounds. From here, substrate level phosphorylation occurs again producing 2ATPs and pyruvates.
Why is important to phosphorylate glucose in the initial stages of glycolysis.
Keeps the glucose in the cell
Hence, maintains the glucose concentration gradient. Plus, phosphorylated glucose is easier to split.
What is substrate level phosphorylation
When ADP molecules react with phosphate groups to form ATP.
What is dehydrogenation
When two hydrogen atoms are donated by a compound. In other words, the compound is oxidised whereas the coenzyme NAD and FAD are reduced. This is a redox reaction. These hydrogens may be accepted by the coenzymes, NAD or FAD.
When NAD accepts hydrogen atoms, it becomes redNAD (reduced NAD); it can also be called NADH+H
The same applies for FAD
What is the net gain of ATP in glycolysis
2ATPs
2ATPs are used up to first convert glucose to glucose-6-P and then to convert fructose-6-P to Hexose-1,6-bisphosphate
2ATPs are made while converting Triose phosphate to Intermediate Compounds and two more when intermediate compounds are being converted to Pyruvates.
Therefore, a net gain of 2ATPs.
What is the Links reaction
The two pyruvate molecules go through decarboxylation and produce two more redNAD- ultimately forming Acetyl CoA.
The CoA is another coenzyme that binds to the acetate immediately formed. Next, this CoA breaks off and then joins another acetate forming acetyl CoA. This acetate moves onto the Krebs Cycle.
What is decarboxylation
When a carboxyl group is removed from a compound. This carbon then binds with the oxygen that is breathed in, thus forming carbon dioxide. Since, oxygen is required from this point, this is considered as an aerobic pathway.
Where does the Link’s reaction occur
The pyruvate is actively transported from the cytosol to the matrix of the mitochondria.
What is CoA made from
Pantothenic acid (B group vitamin), adenosine (ribose + adenine), 3 phosphate groups and cysteine.
What is the Kreb’s cycle
The acetate (2C) formed at the end of the links reaction reacts with oxaloacetate (4C) from the end of the Kreb’s cycle to form citrate (6C). Here, decarboxylation (CO2 is formed) and dehydrogenation occurs- two hydrogens are given off to form one redNAD. The citrate then is turned into a 5C compound. Next, an isomer of this compound forms. This 5C compound goes through decarboxylation and dehydrogenation again forming CO2 and one redNAD.
This causes it to be converted to a 4C compound. While, an isomer of this is being formed, substrate level phosphorylation occurs (ATP is produced). From this new 4C compound, another isomer forms. In this process, dehydrogenation occurs, thus forming one redFAD.
The final 4C compound is converted to oxaloacetate. During this process, dehydrogenation occurs and one redNAD.
Why does the Kreb’s cycle run twice
In glycolysis, the hexose-1,6-bisphosphate is broken to 2 triose phosphate groups which go through rest of glycolysis and links reaction to ultimately produce 2 acetates.EACH acetate goes through the Kreb cycle producing two redNAD at citrate; two redNAD at the second 5C compound; two redFAD at the 3rd 4C compound and another two redNAD at the oxaloacetate stage.
Due to the cycle running twice, two of CO2 and ATP are also made.
Where does Kreb’s cycle occur
In the matrix of the mitochondrion
What is NAD
Organic, non-protein coenzyme
Made of 2 linked nucleotides.
Made from nicotinamide (Vitamin B3), 2 ribose, adenine and 2 phosphate groups.
The nicotinamide ring accepts hydrogen atoms.
Overall, how many redFAD, redNAD and CO2 molecules are produced in glycolysis, Link’s reaction and Kreb’s cycle
Glycolysis: 2 redNAD; 0 CO2 and 0 redFAD
Link’s reaction: 2 redNAD; 2 CO2 and 0 redFAD
Krebs cycle: 6 redNAD; 2 redFAD; 4 CO2
Where does the redNAD go to
The redNAD transports the hydrogen to the inner mitochondrial membrane where the electron carriers are embedded in protein complexes. Once it has dropped off the hydrogen in the mitochondrion the NAD is in its oxidised form again and free to accept more hydrogen.
How is the inner mitochondrial membrane adapted to imporve the rate or respiration
It has cristae (folds) in its structure that provides more surface area for more embedded protein electron carriers to be present.
It is made of phospholipids which causes it to be impermeable to small charged particles. This is essential so the electrochemical gradient is maintained.
It also has stalked particles with ATPsynthase.
What is electron transport chain (ETC)
It is a series of coupled redox reactions catalysed by oxidoreductase enzymes, and requires oxygen as the final electron acceptor for the process to work.
The first stage of ETC
RedNAD delivers 2 hydrogen atoms to Complex I. These atoms split into 2H+ ions and 2e-. The electrons are passed on to Complex II (through redox reactions) and this process releases enough energy to pump the H+ ions against their concentration gradient from the matrix into the intermembrane space of the mitochondrion.
