T12 Processes and Key Points

Question 1

ATP Adaptation for Universal Energy Currency

Answer 1

-Readily hydrolysed to release energy
-Immediete source of energy
-Small and water soluble
-Has a high turnover rate
-Links anabolic (energy requiring) and catabolic (energy yielding reactions
-Produced from a variety of reactions

Question 2

Glycolysis

Answer 2

1. Phosphorylating glucose using 2 ATP, this is done to provide activation energy for the reaction
2. Glucose is first converted to glucose phosphate using ATP, then to its isomer fructose phosphate without the use of ATP, and finally to fructose bisphosphate using another ATP.
3. 2 molecules of triose phosphate (3C) are formed
4. Pyruvate, still contains large amount of chemical potential energy therefore if oxygen is available, then Krebs cycle and oxidative phosphorylation is continued to make use of this energy.
5. Overall 2 ATP is used, 4 ATP and 2 reduced NAD are gained. Net gain: 2 ATP and 2 reduced NAD

Question 3

Link reaction

Answer 3

1. Occurs in the matrix of mitochondrion therefore must require pyruvate to actively be transported into matrix
2. Decarboxylation occurs; which is the removal of CO2
3. Dehydrogenation also occurs: removal of H2
4. Coenzyme A acts as a carrier for acetyl groups (CH3-CO) to the Krebs cycle.
5. Net gain: 2 CO2 and 2 reduced NAD

Question 4

Krebs Cycle

Answer 4

1. Occurs in the matrix
2. Although reaction is part of aerobic respiration, the reactions make use no oxygen as it is only necessary for oxidative phosphorylation
3. Acetyl (2C) CoA combines with Oxaloacetate (4C) to produce Citrate (6c)
4. Citrate is decarboxylated to product CO2, and dehydrogenated to reduce NAD and FAD
5. Oxaloacete is regenerated to continue the cycle

Question 5

Oxidative Phosphorylation and the Electron Transport Chain (ETC)

Answer 5

1.Reduced NAD and FAD are passed to the electron transport chain
2.Reduced NADs and FADs release hdyrogen atoms which then split up into h+ and 1e-
3. Electrons move down an energy graident across the ETC to release energy
4.This energy is utilised to pump H+ ions from the matrix to the itnermembrane space producing a proton graident
5. H+ then move down conc. gradient thorugh ATP synthase back into the matris via faicliateed difufsion
6.ADP +Pi ATP, also occurs hwile the protons pass through ATP synthase. This happends by utilising the protons electircal protnetial energy for chemiosmsosis
7.Oxygen acts as the final e- acceptor to form water. 1/2O2 +2H+ + 2e- H2O

Question 6

Respiration with Oxygen

Answer 6

-In the absence of oxygen, the final e- is not accepted and hydrogen can’t be disposed of in the ETC. Thus, reduced NAD is not oxidised and the chain stops.
-This produces a small yield of ATP as only glycolysiss occurs

Question 7

Alcohol Fermentation in Plants

Answer 7

-Glycolysis takes place nromally
-Pyruvate is decarboxylated to ethanal
-Ehtnanal is reduced to ethanol by accepting hydrogen drom reduced NAD, with the help of enzyme alcohol dehydrogenase ( this enzyme helps wiht the removel of H from NADH)
-Reactio cannot be reversed, and remaining chemical protnetial energy in ethanol is wasted

Question 8

Lactate Fermentation in Animals

Answer 8

-Pyruvate is reduced to lactate by the enzyme alctate dehydrogenase
-Reaction is reverseible by transproing lactate to the liver, convertiing it back to pyruvate
-Oxygen debt: the post oexercise uptake of extra oxygen pay of oxgyen deficiency which is needed for :
-Conversioln of lactate to glycogen in the liver
-Oxidation of lactate to CO 2 and H2O
-Reoxygenation of haemoglobin in the blood
-A high metbolic rate, as many organs are operating above resting level

Question 9

Respiratory Subtrate

Answer 9

-The more hydogens per moelcule a substance has, the more energy value per unit mass, thus greater energy density
-This is because most of the energy liberated in respiration comes from oxidation of hydrogen to water
-To calculate the enrgy vlaue of substance, burn a known mass with oxygen in a calorimeter
-The energy is determined by the rise in temp of the water

Question 10

Respiratory Quotient (RQ)

Answer 10

-The ratio of oxygen taken in to carbon dioxide given out
-It is used to show what substrate is being used in respriation, and whether or not anaerobic respriation is occurring
-When values are close to infinity of higher than 1.0, anaerobic respiration is occurinr, values below 1 shows aerobic respiration
-No RQ value for muscle cells in anaerboci respiration as only lactate is produced with no CO2 beign produced