OCR Biology A - 5.2.2 - Respiration Part 2
The total theoretical ATP yield per pyruvate is 17 ATP. This includes ATP generated from 3 NADH (7.5 ATP), 1 FADH₂ (1.5 ATP), and 1 ATP (or GTP) from the Krebs cycle, plus additional ATP from NADH produced during glycolysis and pyruvate conversion. Since one glucose yields two pyruvates, the full yield per glucose is approximately 34 ATP.
Theoretical yield of ATP from 10 NADH
25
Key Terms
Theoretical yield of ATP from 10 NADH
25
Total theoretical yield of ATP per pyruvate
25 - NADH
2 - FADH2
1 - Krebs cycle
2 - glycolysis
= 30
Why is the yield of ATP not 100%
ATP has to be used for active transport of pyruvate and NADH
RQ
Vol. of CO2/ Vol. of O2 per unit time
RQ value for glucose
1
RQ value for AA
0.8/0.9
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| Term | Definition |
|---|---|
Theoretical yield of ATP from 10 NADH | 25 |
Total theoretical yield of ATP per pyruvate | 25 - NADH 2 - FADH2 1 - Krebs cycle 2 - glycolysis |
Why is the yield of ATP not 100% | ATP has to be used for active transport of pyruvate and NADH |
RQ | Vol. of CO2/ Vol. of O2 per unit time |
RQ value for glucose | 1 |
RQ value for AA | 0.8/0.9 |
RQ value for triglycerides | 0.7 |
Investigating respiration rates of yeast | Put a known vol. and conc. of a substrate sol. into a tt Add a known vol. of buffer soln. - keep pH constant Place tt in water bath (25 degrees) Add known mass of dry yeast After yeast has dissolved, place a bung on the tt which is attached to a gas syringe (should be set to 0) Start the stopwatch Record vol. of CO2 produced at regular intervals and calculate rate |
Using a respirometer to measure O2 consumption | Set up respirometer - one w/ glass beads and the other w/ woodlice of same vol. Add KOH to both - absorbs CO2 produced Use syringe to set fluid in manometer to known level Measure distance travelled by liquid in manometer - gives you vol. of O2 used up (pi r^2 h - need diameter of capillary tube) |
Why does the liquid move in the manometer | As the woodlice use up the O2, pressure decreases causing coloured liquid in manometer to move towards tt |
Limitation of using respirometer | Diff to accurately read the meniscus of the fluid in the manometer |
Substrate level phosphorylation | ATP is formed by the direct transfer of Pi to ADP | Only occurs in Glycolysis and Kreb's cycle |
Substrate level phosphorylation in glycolysis | 2 ATP per each glucose, when TP is converted to pyruvate | 4 - 2 = 2 |
Substrate level phsophorylation in Kreb's cycle | 1 per each turn | Occurs when 5C compound is converted to oxaloacetate |
NAD vs FAD | NAD used in all stages but FAD only in Kreb's NAD accepts 1 H, FAD accepts 2 H's NADH is oxidised at the start of the etc releasing e- and H+ while FADH2 is oxidised further along the chain NADH synthesises 3 ATP but FADH2 synthesises 2 ATP |
Oxidative phosphorylation | FADH2 and NADH deliver H to etc in cristae H dissociates into H+ and e- (used in synthesis of ATP through chemiosmosis) Energy is released as e- travel down etc, creates a proton gradient At end of etc, e- combines w/ H+ and O2 --> water Etc cannot operate w/out oxygen |
Obligate anaerobes | Cannot survive on the presence of oxygen at all |
Facultative anaerobes | Synthesie ATP by aerobic respiration if oxygen is present but can switrch to anerobic e.g. yeast |
Obligate aerobes | Can only synthesise ATP in the presence of oxygen e.g. mammals |
Fermentation | Produces ATP through substrate level phosphorylation only, no involvement of etc |
Alcoholic fermentation | Occurs in yeast and some root cells Glycolysis occurs and pyruvate is decarboxylated to ethanal Ethanal accepts H+ from NADH to produce ethanol and NAD (recycled) Produces ethanol and CO2 |
Lactate fermentation | Carried out in animal cells and produces lactate Glycolysis occurs as normal Lactate dehydrogenase causes pyruvate to accept H from NADH and is converted to lactate and NAD (recycled) Allows glycolysis to keep occurring |
Where is lactic acid converted back to glucose | Liver but requires oxygen --> oxygen debt after exercise |
Why can lactate fermentation not occur indefinitely | Reduced ATP isn't enough to sustain vital processes | Accumulation of lactic acid leads to fall in pH, proteins denature (respiratory enzy |