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.
How are the electrons transferred between complexes
As the complex passes on the 2e-, it becomes oxidised whereas the complex it is passed onto is reduced as it gains 2e-. This redox reaction occurs a number of times between complexes.
The second stage of ETC
The electrons from NAD continues from Complex II to Complex III. The energy released at this stage is NOT enough to pump H+ ions from the matrix into the intermembrane space.
The third stage of ETC
redFAD from the Krebs cycle drops off 2H atoms directly to Complex II (bypassing Complex I). Again, these hydrogen split into 2H+ and 2e-. The electrons are passed onto Complex III but the H+ ions remain in the matrix due to lack of energy for pumping at this stage.
The fourth stage of ETC
The four electrons (the 2 from the NAD and the 2 from the FAD) pass from Complex III to Complex IV. The energy released is enough to pump H+ ions from the matrix to the intermembrane space.
What is the fifth stage of ETC
The 4 electrons move from Complex IV into the matrix where they combine with 4H+ ions and O2 to form H2O. The energy released at this stage IS enough to pump H+ ions into the intermembrane space.
So overall, how many Complexes (electron carriers) are needed to carry out ETC
5 complexes
Complex I- NADH Coenzyme Q (oxidoreductase)
Complex II- Succinate Coenzyme Q (oxidoreductase)
Complex III- Coenzyme Q Cytochrome C (oxidoreductase)
Complex IV- Cytochrome C (oxidase)
Complex V- ATP synthase
Complex IV only transfers electrons to the Complex V where the electron bonds to the 2H+ and oxygen. Therefore, only oxidation occurs- there is no reduction. This is why it is an oxidase rather than oxidoreductase.
What is chemiosmosis
The pumping of H+ ions into the intermembrane space generates a electrochemical gradient and a proton (low pH) gradient. This generates a proton motive force that should lead to the diffusion of H+ ions back into the matrix.
However, the membrane is relatively impermeable to H+ ions, and the only way they can return to the matrix is through the ATPsynthase enzyme complex.
This enzyme catalyses oxidative phosphorylation.
What is proton motive force
This is the force that promotes the movement of H+ ions through the channel in the stalk particle; down the electrochemical potential. This energy is coupled by the enzyme, ATPsynthase to carry out oxidative phosphorylation.
What is oxidative phosphorylation
As the H+ moves through the complex V, the ATPsynthase catalyses the formation of ATP from ADP and Pi.
You are phosphorylating ADP to ATP by using oxygen as the final electron acceptor of the electron transport chain.
How many ATPs are formed in glycolysis, Link’s reaction and Kreb’s Cycle through substrate level phosphorylation
Glycolysis- net production of 2ATPs
Link’s reaction- none
Kreb’s cycle- 2ATPs
Difference between redNAD and redFAD
redNAD produces more ATP and also provides more energy for H+ to be pumped to the intermembrane space as the electrons are transferred between complexes.
Theoretically redNAD produces 3 ATPs whereas redFAD produces 2ATPs.
This is because redNAD release its 2 hydrogen atoms much further away from Complex V (the stalk particle). So, the 2e- given off by the hydrogen atoms are transferred along more complexes thus providing more energy to maintain a steeper electrochemical gradient. Therefore, create a stronger proton motive force.
Theoretically, how many ATPs is produced by oxidative phosphorylation.
First, we need to see how many redNAD and redFAD are created, from glycolysis to Kreb’s cycle.
Glycolysis- 2redNAD
Links- 2 redNAD
Krebs- 6redNAD and 2redFAD
Since, theoretically each redNAD produces 3ATP, 10 x 3= 30
Theoretically each redFAD produces 2ATP, 2 x 2= 4
There is also 4 ATPs that are produced through substrate level phosphorylation.
Therefore 30 + 4 + 4= 38
In reality, why aren’t 38 ATP molecules produced?
In reality, only 32 ATP molecules are produced per glucose molecule. This is because each redNAD produces 2.5ATP per glucose molecule whereas each redFAD produces 1.5ATP per glucose molecule
This is because some ATP gets used up in the process of respiration.
What are some uses of ATP in respiration
ATP is used to actively transport pyruvate from the cytosol of the cytoplasm to the matrix of the mitochondrion.
Some ATP is used to bring redNAD from glycolysis in the cytoplasm into the mitochondrion
Some energy is used to transport ADP from the cytoplasm into the mitochondrion.
Some H+ ions leaks back across the mitochondrial membrane reducing the proton motive force that generates ATP. This occurs when the membrane is too fluid.
Definition of respiration
A process in which energy stored in complex organic molecules are used to make ATP in living cells.
Uses of ATP
Cytoskeleton- intercellular movement Endo/exocytosis Motor proteins Protein synthesis DNA replication Activation of chemicals (phosphorylation)
Structure of an ATP
Adenine (purine; two rings- a six carbon ring bonded to a 5 carbon one)
This is bonded to ribose sugar
And the ribose is bonded to three phosphate groups
Structure of a mitochondria
Double membraned- inner membrane is folded (has cristae)
There is an inter membrane space between both the outer membrane and the inner mitochondrial membrane.
There is mDNA- a loop of DNA inside the mitochondrion
There are glycogen granules (storage for sugar)
There are 70s ribosomes
There are embedded proteins (electron carriers plus stalk particle with ATPsynthase) the enzyme is also a protein
Anaerobic respiration in animal cells
Pyruvate is converted to lactate once the pyruvate accepts hydrogen atoms from redNAD. Lactate dehydrogenase catalyses this reaction.
The NAD gets oxidised and can be reused during glycolysis.
Anaerobic respiration in yeast fungi cells (FERMENTATION)
Pyruvate goes through decarboxylation (a carboxyl group is removed, releasing carbon dioxide); forming ethanal. Pyruvate decarboxylase catalyses this reaction.
The ethanal accepts 2 hydrogen atoms from redNAD to form ethanol. The enzyme ethanol dehydrogenase catalyses this reaction. NAD is in its oxidised state again and can be reused in glycolysis.
Yeast is a facultative anaerobe. What does this mean?
It can respire aerobically and anaerobically.
Yeast grows faster under aerobic conditions. So, in the brewing industry, it is first grown in oxygen, and then grown under anaerobic conditions for alcoholic fermentation to take place.
What happens to the lactate produced in anaerobic respiration in animal cells
It is carried away in the blood to the liver
When more oxygen is available the lactate is converted back to pyruvate to enter the kreb cycle or it is recycled back to glucose or glycogen.
What is muscle fatigue caused by
NOT by a build up of lactic acid rather it is due to the reduction in pH that reduces the enzyme activity in the muscle cells.
What type of substrate generates more ATP
The more hydrogen atoms in a molecule of respiratory substrate, the more ATP it can generate. This is because more H+ ions will be pumped to the inter membrane space, maintaining a steep electrochemical gradient. There will be a higher proton motive force.
However, a substrate with more hydrogen atoms, the more oxygen it will need.
This is why lipids release way more energy than carbohydrates or proteins.
EXAM: why do triglycerides produce a lot of energy
Triglycerides are made of glycerol and three fatty acids.
Fatty acids are long hydrocarbon chains. So, they have many hydrogen atoms. These maintain a steep electrochemical gradient and thus form a strong proton motive force.
What is respiratory quotients
RQ= CO2 evolved/ oxygen used
Carbohydrates have a RQ of 1
Proteins have a RQ of 0.9
Lipids have a RQ of 0.7
Practical of respiration
Sodaline is placed much below the living sample in the respirometer. This is used to absorb carbon dioxide. This ensures the carbon dioxide doesn’t impact the volume of air.
Set the fluid by using the syringe. Leave the apparatus for 20 minutes.
Measure the distance moved by the fluid.
Exam question
Some individuals can large quantities of fatty and carbohydrate-rich food without putting on weight. One possible hypothesis that could explain this is related to the mitochondrial inner membrane.
Scientists have suggested that some individuals may have a larger number of proton pores in their inner mitochondrial membrane than normal.
Explain how having a larger number of proton in the inner mitochondrial membrane would result in a person being less likely to gain weight.
The membrane is impermeable to H+ ions therefore H+ ions cannot go back to the matrix once they are pumped to IMS (inter membrane space) by the electron carriers. The only way they are able to go to the matrix is through the stalk particles- which have ATP
synthase at the end. This is responsible for coupling the energy from the proton motive force to form ATP. However, when there are hydrogen pores in a membrane, H+ ions can easily enter the matrix through facilitated diffusion. This is because these hydrogen pores are channel proteins. As a result, the electrochemical gradient decreases and fewer ATP are made.
To fulfil the metabolic demand, more glucose is required to form ATP. The metabolic demand is the amount of ATP required by one.
Definition of ATP
This is the energy-currency by which most metabolic reactions occur
