Carbohydrates 6: Terminal respiration Flashcards
what is substrate level phosphorylation?
The direct transfer of a phosphoryl group to form ATP or GTP.
- occurs in glycolysis
- little ATP made
what is oxidative phosphorylation?
- The formation of ATP through the complex processes of oxidation coupled to the movement of electrons and production of proton gradients, most of which occurs in the mitochondrial matrix.
- process requires oxygen to act as an electron acceptor coupled to the formation of a proton gradient that drives the formation of ATP through the action of ATPase enzyme.
how many electropositive H atoms are being stripped from food molecules at a time?
2 at a time
to which two electron carriers are electrons passed to from CAC?
- NAD+
- FAD
the now reduced co-reactants, NADH and FADH2 can now be used in abaolism and what other reaction?
terminal respiration (through a series of carrier proteins)
what 2 products are produced when glucose (hexose) is split into pyruvate? (during glycolysis/ substrate level phosphorylation)
- NADH + H+
2. ATP
what product is produced when pyruvate is converted to acetyl CoA?
NADH + H+
what 3 products are produced when acetyl CoA is made into CO2 during CAC?
- 3NADH + 3H+
- 1 FADH2
- 1 GTP
what is the mitochondria the site of?
CAC and terminal respiration (oxidative phosphorylation)
what does the mitochondria utilise to produce ATP?
proton gradients
what part of the mitochondria is the matrix?
liquid part
what part of the mitochondria is the cristae?
the folded/ convoluted part (for max. SA)
where is the proton gradient formed?
in the matrix
where is majority of NADH and FADH2 formed?
in CAC and B oxidatation of fatty acids
where is some NADH also formed?
in cytoplasm (during glycolysis)
can cytoplasmic NADH cross the mitochondrial membrane?
no
what does NADH combine with to create G-3-P which can pass its electrons to FADH2?
dihydroxy acetone phosphate
G-3-P combines with FAD to create which molecule?
FADH2 (which travels to electron transport chain)
what is the name of the shuttle which transports cytoplasmic NADH in the form of FADH2 for terminal respiration?
Glycerol phosphate shuttle
what produces less ATP in the electron transport chain, oxidation of FADH2 or oxidation of NADH?
oxidation of FADH2 (energy price of the glycerol phosphate shuttle)
what enzyme does the complex 1 in the e transport chain use?
NADH-Q oxidoreductase
what enzyme does the complex 2 in the e transport chain use?
Succinate- Q reductase
what enzyme does the complex 3 in the e transport chain use?
Q-cytochrome C Oxidoreductase
what enzyme does the complex 4 in the e transport chain use?
Cytochrome C oxidase
what happens at complex 1?
- NADH is oxidised
- high energy electrons passed to ubiquinone to give ubiquinol (QH2)
- utilises Fe-S centres and FMN (flavin mononucleotide)
- pumps H+ into intermembrane space
as 2 electorns travel through complex 1, what do they form?
QH2 (ubiquinol)
what 3 substances inhibit e flow from Fe-S centres in the proteins to ubiquinone, therefore blocking the transport chain?
- amytal (barbiturate)
- piercidin A (antibiotic)
- rotenone (insecticide)
what happens at complex 2?
- FADH2 is oxidised
- high energy electrons passed to ubiquinone to give ubiquinol (QH2)
- utilises Fe-S centres to channel electrons
where else is succinate- Q reductase enzyme used?
in CAC under the guise of sucicnate dehydrogenase
what is the function of the heme group (Fe) in the protein?
- blocks stray electrons
- if electrons leak from system, they can form free radicals of O2 (superoxide) leading to cancer.
- point mutations near heme groups can give rise to paraganglioma
what is another name for ubiquinone?
Coenzyme Q10
what else can ubiquinone act as?
antioxidant (dietary supplement believed to reduce free radicals)
what happens at complex 3? (2)
- electrons taken from ubiquinol (QH2) and passed to cytochrome C
- protons pumped to intrermembrane space
how many ubiquinols (QH2) are oxidised to produce how many reduced cytochrome Cs?
1 QH2 is oxidised to yiled 2 reduced cytochrome C
what happens at complex 4? (3)
- electrons taken from cytochrome C and passed on to molecular O2
- electrons channeled through Fe-CU centre
- protons pumped into intermembrane space
What is oxidised at complex 1?
NADH
what is oxidised at complex 2?
FADH2
what is formed at complex 3?
Cytochrome C from ubiquinol (from complexes 1 and 2)
what are electrons passed to at complex 4?
electrons from cytochrome C passed onto O2 molecule
where is the NADH used in terminal respiration from? (3)
- glycolysis
- CAC
- B oxidation
where is the FADH2 used in terminal respiration from? (2)
- B oxidation
- NADH via glycogen phosphate shuttle
what is set up across the inner mitochondria membrane?
proton gradient
what is chemiosmosis?
as electrons pass through the complexes of the transport chain, protons move from the matrix to the outside of the inner mitochondrial membrane
what is the movement of protons with particular spatial directionality called?
vectoral movement (energy transformation)
what do protons on the outside of the membrane act as?
store of potential energy
what is proton motive force?
when electrons are allowed to flow back down their gradient, they release energy to work
what is ATP synthase? (ATPase for short?)
large multi-unit protein complex on the mitochondrial membrane where protons flow down their concentration gradient back into mitochondrial matrix
what does ATPase allow?
Protons to pass through it
What are the 2 parts which make up ATPase and what do they do?
F0 part: membrane bound proton conducting unit (10 subunits)
F1 part: protrudes into the mitochondrial and acts as a catalyst for ATP synthesis (produces lots of ATP form proton motive force energy collected by F0)
Which part of the ATPase does “all the work”?
F1 part (produces the ATP)
in which subunits of the F1 is ATP produced from?
Beta subunits
as proton enter F0, rotation of F0 cylinder and gamma shaft causes what to Beta-subunits of F1?
conformational change
In what way (positive/negative) do protons move from?
From positive to negative side of the membrane
where is the higher concentration of H ions, outside or inside the mitochondrial membrane
Outside
what are the steps for generating energy at the ATPase complex?
- 1 proton enters the ATPase complex from intermembrane space
- upper part of the ATPase complex rotates every time a new proton enters
- once 3 protons entered the matrix space, there is enough energy in ATPase to generate 1 ATP.
what happens once the gradient has disapperared when there is no more protons in intermembrane space?
no more energy available to make ATP which is why in biological system this gradient ALWAYS exists
As electrons pass through complexes 1,2,3 and 4, how many protons from the matrix move outside of the membrane?
8 protons
ATPase can produce how many ATPs for every 3 protons which move back into the matrix?
1 ATP
what would happen if the inner mitochondrial membrane became permeable to protons?
proton gradient could not be generated and neither could ATP
what does it mean when a process is coupled?
electron transport is said to be coupled to ATP synthesis
what does it mean when a process is uncoupled?
no ATP is made since proton gradient is not established, energy is released as heat
what disease is caused by “leaky” mitochondrial membranes that uncouple electron transport and ATP synthase?
Malignant hypothermia
what are people with malignant hypothermia exposed to which makes their mitochondrial membranes leaky?
halothane
what is an example of intentional uncoupling?
brown fat formation in newborn infants
what is the name of the channel which sits inside a protein on inner mitochondrial membrane of brown fat cells?
thermogenin
what causes brown fat to be a brown colour?
haem group in proteins
what are examples in plants which generate intentional uncoupling?
- arum lily to attract insects
-skunk cabbage to melt snow
(generate heat by uncoupling oxidative phosphorylation)
