Respiration 5.7 Flashcards
What are the three stages of glycolysis?
1) phosphorylation
2) Splitting of hexose bisphosphate
3) Oxidation
What are the net products of glycolysis?
NADH: 2
ATP: 2
Pyruvate: 2
What enzyme aids the oxidation of NAD?
Dehydrogenase enzymes
Where does glycolysis occur?
Cytoplasm
How do the products of glycolysis get from the cytoplasm to the krebs cycle?
1) active transport to the mitochondria
2) link reaction to get inside
What is the name of the folds of the mitochondrial membrane?
Cristae
What is the name of the mitochondrial cytoplasm?
Matrix
What do organisms need energy for?
- active transport
- endo/exocytosis
- synthesis
- replication
- cell division
What happens during the link reaction?
Pyruvate gets decarboxylated and dehydrogenised to produce the acetyl group, which combines with CoA to form acetyl CoA.
What is Decarboxylation?
The removal of a carboxyl group from a substrate molecule.
What is Dehydrogenation?
The removal of hydrogen atoms from a molecule.
How is a pyruvate made into an acetyl group?
Its decarboxylated (producing CO2) and dehydrogenised (converting NAD to NADH)
What are the products of the link reaction? (2 pyruvate)
NADH: 2
CO2: 2
acetyl CoA: 2
Where does acetyl CoA fit into the Krebs cycle?
CoA leaves the compound and acetyl (2C) combines with oxaloacetate to form citrate (6C).
Why is the Krebs cycle an important part of respiration?
It produces NADH and FADH required for the enzyme transport train, while also producing some ATP.
What are the important changes occurring in the Krebs cycle?
Oxaloacetate (4C) -> Citrate (6C) -> 5C compound -> 4C compound (3 different ones) -> Oxaloacetate
What happens to convert citrate into a 5C compound?
It is Decarboxylated and dehydrogenated.
What happens to convert the 5C compound into a 4C compound?
It is Decarboxylated and dehydrogenated.
What happens to the 4C compounds before they are returned to being Oxaloacetate?
1) ADP –> ATP
2) FAD –> FADH
3) NAD –> NADH
What are the products of the Krebs cycle from one molecule of glucose?
NADH: 6
FADH: 2
CO2: 4
ATP: 2
How can amino acids be used in the Krebs cycle?
They are deaminated (amino group NH2 removed) and the rest of the molecule can enter the krebs cycle directly, or be converted to pyruvate.
What substrates beside glucose can be respired aerobically?
- fatty acids
- glycerol
- amino acids
What is oxidation phosphorylation?
The formation of ATP by passing electrons down the electron transport chain. The last stage in respiration.
Where does Oxidative phosphorylation occur?
In the mitochondria, across the cristae.
Outline the electron transport chain.
1) NADH and FADH are reoxidised when they deliver their hydrogen atoms to the start of the chain
2) The hydrogen atoms split into protons and electrons
3) The protons go into solution in the mitochondrial matrix
4) The electrons move between the electron carrier protein
5) As each electron moves between the proteins, energy is produced, which is used to pump protons across the membrane into the inter membrane space
6) Protons build up in the inter membrane space.
How do the electrons move down the electron transport chain?
Each electron carrier protein has an iron ion at its core, which can gain the electron.
This causes it to become reduced Fe 2+ so it can then donate the electron to the next electron carrier in the chain.
How Is ATP produced after the electron transport chain?
The build up of protons in the inter membrane space creates a proton gradient, where the protons move back across the membrane via a channel protein called ATP synthase. The movement of proteins down the channel protein causes conformational change and allows ADP and a phosphate to combine, producing ATP.
What is chemiosmosis?
The flow of proteins down their concentration gradient across a membrane.
What happens to the electrons coming from the end of electron transport chain?
Oxygen is used as the electron acceptor. It combines with the electrons and protons to form water.
How many ATP molecules can NADH and FADH produce?
NADH: 2.5
FADH: 1.5
How many NADH and molecules are made during respiration and are therefore supplied to the electron transport chain?
NADH: 10
FADH: 2
What is the theoretical yield of ATP from oxidative phosphorylation and how many ATP molecules are made in total?
Oxidation Phosphorylation
NADH produced ATP: 10 x 2.5 =25
FADH produced ATP: 2 x 1.5 = 3
ATP from krebs and glycolysis = 4
In total
28 + 4 = 32
Why can normal respiration not occur without oxygen?
- Oxygen cannot be used as the final electron acceptor
- Protons build up in the matrix and reduces the proton gradient across the inner mitochondrial matrix
- Oxidative phosphorylation stops
- NADH and FADH cant unload their hydrogen atoms and cannot be reoxidised so the krebs cycle and link reaction stop.
What different types of anaerobic respiration?
Yeast and plants use the ethanol fermentation pathway
Mammals use the lactate fermentation pathway
How does the fermentation pathway allow for reoxidation of NAD without oxidative phosphorylation?
1) The pyruvate is decarboxylated and converted to ethanal.
2) The ethanal can then accept hydrogen atoms from the NADH, returning it to NAD,
3) The ethanal is turned into ethanol by accepting the H+ ions
4) This allows Glycolysis to continue, through accepting H+ ions from the triose phosphate.
How does the lactate fermentation pathway enable glycolysis to occur anaerobically?
- The pyruvate accepts H+ ions from the NADH
- The NADH is reoxidised into NAD
- The pyruvate is converted into lactate
The reoxidised NAD can then accept more hydrogen atoms from triose phosphate during glycolysis and glycolysis can continue to produce enough ATP for a short period.
What happens to the lactate, and what would happen if it were not removed?
The lactate is moved to the live where it is either converted back to pyruvate when oxygen become available, or recycled into glucose and glycogen.
If it lactate wasn’t removed, the pH would be lowered and inhibit the action of many of the enzymes involved in glycolysis and muscle contraction.
What are disadvantages of anaerobic respiration?
Only glycolysis can occur, so much less ATP is produced
However, as glucose is only partly broken down, many more molecules can undergo glycolysis per minute.
What enzyme is involved in ethanol fermentation?
Pyruvate decarboxylase
Catalyses the decarboxylation of pyruvate into ethanal
Pyruvate dehydrogenase
Catalyses the dehydrogenation of ethanal into ethanol
What enzyme is involved in the lactate fermentation pathway?
Lactate dehydrogenase
What anaerobic pathway does yeast use?
Ethanol pathway
What other substances can be used as respiratory substrates?
- Carbohydrates
- Lipids
- Proteins
How are lipids used in respiration?
Triglycerides are hydrolysed in to glycerol and fatty acids.
Glycerol can be converted into triose phosphate
Fatty acids are converted into acetyl groups.
How can proteins be used in respiration?
The amino acids are deaminated to form keto acid, which enters the pathway as pyruvate, acetyl CoA or a krebs cycle acid.
How is the respiratory quotient of a substrate calculated?
CO2 produced / 02 Consumed
What does an RQ greater than 1 show?
Anaerobic respiration has taken place
Why does aerobic respiration yield fewer molecules of ATP than the theoretical maximum?
1 some ATP used to actively transport pyruvate into the mitochondrion
2 some ATP used to actively transport H+ from NADH , formed in glycolysis / into the mitochondrion
3 some energy released in ETC , is not used to transport H+ (across inner membrane) / is released as heat
4 not all the H+ movement (back across membrane) , is used to generate ATP / is through ATP synthase
5 not all the NADH , is used to feed into the ETC
Explain why the anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed
In animals, pyruvate is converted to lactate, which can be reversed as no atoms are lost, and lactate dehydrogenase is available to reverse.
In yeast, pyruvate is converted to ethanol and CO2, so cant be reversed as CO2 is lost
