5.2.2 Respiration Flashcards
What are the 3 stages of respiration?
- Glycolyisis (anaerobic)
- Kreb’s cycle (aerobic)
- Electron transport chain (aerobic)
Describe the glycolysis stage. (6)
Process occurs in the cytoplasm:
- Phosphorylation:
Two phosphate groups are added to glucose to form hexose bisphosphate. This process uses 2 molecules of ATP. - Lysis:
Hexose bisphosphate is unstable (like the 6 carbon ring in the Calvin cycle), so it splits into 2 triose phosphate molecules. - Phosphorylation 2:
Another phosphate group is added to each molecule of triose phosphate to form triose bisphosphate. - Dehydrogenation and formation of ATP:
Triose bisphosphate is oxidised which releases two phosphate groups. This causes substrate level phosphorylation to form 2 ATP molecules from ADP. A H+ ion is also released which reduces NAD.
Therefore 2 pyruvate molecules are the product of glycolysis.
Overall the net production of 2 ATP is produced as it requires 2 ATP for phosphorylation and releases 4 ATP at substrate level phosphorylation. 2 NADH is also released (one per triose bisphosphate).
Describe the link reaction between glycolysis and the Kreb’s cycle.
Oxidative decarboxylation: Occurs in the mitochondrial matrix
Pyruvate molecules are further oxidised which removes a carbon and releases CO2.
The two carbon Acetyl molecule reacts with Coenzyme A to form Acetyl Coenzyme A.
The process also releases H which reduces NAD to form NADH.
Describe the Kreb’s cycle.
Occurs in the mitochondrial matrix:
- CoA delivers the acetyl group to the cycle and is reused for the link reaction
- The acetyl group combines with a 4-C molecule Oxaloacetate to form a 6-C molecule, citric acid.
- Citric acid is decarboxylated and dehydrogenated when it reacts with O2. This reduces the 6-C molecule to a 5-C molecule. The carbon is released as CO2 and the H released reduces NAD to form NADH.
- Further decarboxylation and dehydrogenation for form a 4-C molecules, Oxaloacetate. This releases another CO2, reduces another NAD to form NADH.
- ATP is produced using substrate level phosphorylation.
FAD is reduced to FADH2. Another NAD is reduced to NADH.
At the end Oxaloacetate is recycled to be used at the start when it binds with the acetyl molecules.
Summarise the net production of how many: NADH FADH2 CO2 ATP
Are produced for one molecule of glucose.
6 NADH
2 FADH2
4 CO2
2 ATP
Substrate- level phosphorylation
The process where an enzyme transfers a phosphate group from one substrate to ADP to form ATP.
Oxidative phosphorylation
The aerobic process that relies on the supply of electrons from glycolysis and the Kreb’s Cycle through NADH and FADH2 for the electron transport chain.
Series of redox reactions provide the energy to form ATP.
Chemiososmosis
The process at which ATP is produces through the movement of protons down a proton gradient and the transport of electrons through the ETC.
Describe the electron transport chain in respiration.
This process occurs in the mitochondrial cristae.
NADH and FADH2 are transported to the electron transport chain
The co-enzymes dissociates to release H+ and electrons.
The electrons are passed down the ETC through electron carriers, until it reaches O2.
O2 acts as the final electron acceptor where it is then reduced to water.
These redox reactions in the ETC releases energy which allows a proton gradient to form.
The diffusion of H+ across ATP synthase then combines with ADP to form ATP. This process is oxidative phosphorylation as O2 REQUIRED.
NADH results in 3 ATP molecules being produced whereas FADH2 results in 2 ATP molecules.
What is the respiratory quotient (RQ)?
Ratio of CO2 produced compared to O2 consumed in a given time.
Glucose has the highest RQ, which equals 1, as equal amounts of CO2 and O2 is consumed.
Describe alcoholic fermentation. (4)
Occurs in yeast, where there is lack of oxygen supply, causing ethanol to be produced.
Glucose molecule undergoes glycolysis. Instead of link reaction, pyruvate molecule is decarboxylated by pyruvate decarboxylate, thus releasing CO2.
Ethanal is now an electron acceptor, which it receives when NADH is oxidised. This forms ethanol.
A yield 2 ATP molecules is still produced.
Describe anaerobic respiration in mammals. (3)
Occurs in muscle cells where the demand for oxygen exceeds the supply giving my red blood cells.
After glycolysis releases a yield of 2 ATP, pyruvate acts as an electron acceptor and is reduced when NADH is reoxidised.
This changes pyruvate molecules into lactic acid.
Explain the implication of lactic acid build up.
Lactic acid reduces the pH in the muscle tissue, which cause fatigue.
The low pH disrupts optimum conditions for enzymes involved in metabolic processes.
Why does anaerobic respiration produce less ATP than aerobic respiration? (4)
Glycolysis is responsible for the net production 2 ATP in anaerobic respiration.
Since there is no O2, link reaction cannot occur to decarboxylate pyruvate molecules and form acetyl molecule.
Acetyl CoA cannot be regenerate so Kreb’s cycle cannot occur to generate coenymes used in the E.T.C.
Therefore chemiosmosis cannot occur. Only 2 ATP produced in Glycolysis compared to 38 in aerobic.
What are the 2 main types of anaerobes?
Obligate- cannot survive with O2 present. Mainly prokaryotes
Facultative- Can adapt type of respiration depending on the availability of oxygen, eg fermentation in yeast, muscle cells in mammals.
