respiration Flashcards
(12 cards)
what is the first stage of aerobic respiration and its overall products?
glycolysis: (cytoplasm, oxygen isn’t required, substrate=glucose) glucose is activated and broken by ATP into 2 3C pyruvate. each pyruvate reduces NAD to NADH with dehydrogenase, phosphorylation of ADP to ATP, oxygen is not required
- 4 ATP (2 net), 2 NADH, 2 pyruvate
what is cellular respiration?
- a series of redox reactions taking place within living cells
- results in the release of energy from organic compounds such as glucose
- molecules used in respiration are called respiratory substrates since they can be broken down
- most living organisms respire aerobically (with oxygen) but some respire anaerobically (without oxygen)
what is the overview of respiration?
- glycolysis, occurs in the cytoplasm
- the Krebs cycle, takes place in the matrix of the mitochondria
- oxidative phosphorylation via the electron transport chain (ETC), carried out on the inner mitochondrial membrane of the mitochondria
what happens in the first stage, glycolysis?
- 6-carbon sugar (glucose) is broken down into two molecules of a 3-carbon molecule, pyruvate, through activation of ATP
- the change is accompanied by a net gain of 2 ATP molecules and 2 reduced NAD (NADH) molecules
*does not require oxygen
what is the link reaction?
- not classed as a main stage as it only links glycolysis to the Krebs cycle
- takes place in mitochondrial matrix
- pyruvate is decarboxylated and dehydrogenated to acetate (2C) with the production of CO2 and NADH2
- acetate combines with coenzyme A (CoA) to make acetyl CoA which contains 2 carbons
what is the Krebs cycle?
takes place in mitochondrial matric as it contains lots of dissolved enzymes to catalyse reactions
- the 2 carbon acetyl CoA adds acetate to the cycle and is accepted by a 4 carbon molecule called oxaloacetate, which makes a 6 carbon compound called citrate (CoA is recycled)
- citrate is decarboxylated into a 5 carbon compound, releasing CO2 and is dehydrogenated forming an NADH molecule
- the 5 carbon compound is converted to a 4 carbon compound by decarboxylation (CO2 removed) and dehydrogenation (H removed) occurs again and NADH is made as well as a molecule of ATP made by substrate level phosphorylation
- the 4 carbon compound undergoes dehydrogenation, the hydrogen carrier FAD is reduced making one FADH2
- isomerisation occurs to make a different shaped 4 compound molecule, which is dehydrogenated to the starting molecule, oxaloacetate, creating another NADH
one glucose means TWO of these cycles take place so the total output of the Krebs cycle per glucose is 2 ATP, 4 CO2, 6 NADH and 2 FADH2
what is the electron transfer chain and oxidative phosphorylation?
takes place on the inner-mitochondrial membrane because it has a large surface area due the presence of cristae so there is more room for ATP synthase molecules to make ATP
- the glucose molecule has been completely oxidised by the beginning of the ETC, however much of the energy is in the form of hydrogen atoms attached to NADH and FADH2
- the NADH and FADH2 all carry their protons and electrons to the ETC (only in the presence of oxygen)
- due to the chemiosmotic theory, ATP is generated by oxidative phosphorylation
- for every NADH molecule, 3 ATP are made by OP
- for every FADH2 molecule, 2 ATP are made by OP
- the electrons are passed along a series of electron carriers powering proton pumps
- finally the electrons combine with the hydrogen ions to form hydrogen atoms and are passed on to oxygen to form water
OXYGEN IS THE FINAL ELECTRON ACCEPTOR
34 ATPS PER GLUCOSE
what is the energy budget of one glucose?
glycolysis:
- 2 ATP net by substrate level phosphorylation
- 2 NADH = 6 ATP by oxidative phosphorylation
link reaction:
- 2 NADH = 6 ATP by oxidative phosphorylation
Krebs cycle:
- 2 ATP by substrate level phosphorylation
- 6 NADH = 18 ATP by oxidative phosphorylation
- 2 FADH2 = 4 ATP by oxidative phosphorylation
TOTAL OF 38 ATP MOLECULES
what is anaerobic respiration?
- occurs in animal muscle tissue, some microorganisms (e.g. yeast) and plants
- it is respiration in the absence of oxygen
- process only involves glycolysis
- for every glucose molecule, only 2 ATP are made, much less than aerobic respiration
- does also produce 2 NADH but they are useless as they are only available to be used in stages that require oxygen
what is the process of anaerobic respiration?
- in the absence of oxygen glycolysis continues as long as NAD is available for reduction
- however levels of NADH rise as the electron transport chain has stopped as there is no oxygen as the final electron acceptor
- in order for glycolysis to continue, NAD must be recycled
- therefore NADH donates its protons and electrons to pyruvate/ethenal reducing it to lactate/ethanol (animals/plants), regenerating NAD so glycolysis can continue
what is the result of anaerobic respiration in animals?
- the energy can be released, later changing lactate back to pyruvate which is then oxidised in the usual way
- this happens in the liver
- it requires oxygen and if none is available the lactate must be excreted
- the build up of lactate in muscle causes fatigue and cramp
- when O2 become available again, the lactate is broken down
- oxygen debt is repaid by continuous deep and rapid breathing
what is the result of anaerobic respiration in plants?
- pyruvate is not directly converted into ethanol
- pyruvate is decarboxylated to ethanal, ethanal is reduced to ethanol (fermentation)
- ethanol becomes toxic if it accumulates and cannot be broken down to yield any additional energy
