glycolysis Flashcards
what process is every cell able to generate ATP
glycolysis even in anaerobic conditions
where does glycolysis occur
in the cytoplasm, cytosol
what is the first step of glycolysis and which enzyme is involved
- phosphorylation of glucose to glucose 6 - phosphate
- enzyme hexokinase
what is the second step - after formation of glucose 6 -phosphate
- each glucose 6 phosphate is oxidised by a series of reactions to two pyruvate molecules
- generating two molecules of NADH and two molecules of ATP
- the ATP is generated by direct transfer of the phosphate groups (substrate level phosphorylation)
in aerobic conditions what happens to the pyruvate after being formed from glucose 6 phosphate
- the pyruvate is oxidised to produce CO2 - maintains ph balance and ATP via the TCA cycle and oxidative phosphorylation
what happens in anaerobic conditions and what enzyme is involved
- cells have to resort to anaerobic glycolysis
- this is important to regenerate the NAD so glycolysis can occur
- involves reducing pyruvate to lactate
- enzyme lactate dehydrogenase
what happens when a lot of lactate is produced
- when enough lactate is produced it can use lactate acidaemia (making muscles burn)
what is the first step in the TCA cycle in the presence of oxygen - what happens to the pyruvate and by what enzyme
- pyruvate is converted into acetyl co - a
- enzyme pyruvate dehydrogenase (PDH)
- it is a complex of three enzymes
how does the TCA cycle contribute to generating majority of ATP
- by oxidising acetyl co - A to the electron donors NADH and FADH2 which enter the electron transport chain
why does ATP drive most processes
- due to its high energy phosphoanhydride bonds between the phosphate groups
- phosphate groups are negatively charged and repel each other - meaning lots of energy is required to keep them together and energy is released when one of the phosphate groups is released
- the release of a phosphate group converts ATP to ADP
what is oxidative phosphorylation (how is ADP converted back into ATP)
- ADP converted to ATP using the enzyme ATP synthase
- using reduced co enzymes formed during glycolysis and the TCA cycle in the ETC
= oxidative phosphorylation
what is most of the energy generated in the TCA in the form of what
- reduced enzymes NADH and FADH2
in oxidative phosphorylation was does the electron transport chain do to NADH and FADH2
- NADH and FADH2 is oxidised and donates the electron to O2 which is reduced to H20
the energy which is generated from the reduction of O2 to H20 what is it used for
- used to phosphorylate ADP
how is ATP generated from ADP via the electron transport chain
- the etc contains proteins which span the inner membrane of the mitochondria (protein complexes 1, 3, 4)
- electrons pass through these proteins - oxidation - reduction reactions whilst at the same time pumping protons (H+ ions) across the inner mitochondrial membrane (from matrix towards outside)
- this creates an electrochemical gradient, which protons return to the matrix, passing through a pore in ATP synthase
- shape change of ATP synthase as protons pass through - synthesising and releasing ATP
what is uncoupling of proton movement from atp generation
- allowing protons to move back across the inner mitochondrial membrane into the matrix - generating heat but no ATP is produced
- occurs in brown fat cells of young babies
what is the enzyme phosphofructokinase - 1
- regulatory enzyme
- allosteric regulation either speeding up its activity or slowing it down
- regulated according to the availability of substrate or product
what do yeast and plants form and what enzymes are involved
- ethanol produced
- pyruvate - acetaldehyde
enzyme pyruvate decarboxylate - acetaldehyde - ethanol
enzyme alcohol dehydrogenase
where is lactate converted back to glucose
- lactate is toxic and forms lactic acid - changing blood pH
- lactate goes to liver and converted back to glucose
which two bacterias form lactic acid in mouth - anaerobic fermentation of sugar
- lactobacillus
- streptococcus mutans
a lowered ph promotes demineralisation leading to decay
where does oxidative phosphorylation occur
- inner membrane of mitochondria
what is NAD+
- electron accepting co - enzyme
- not bound to an enzyme - once its reduced it leaves enzyme and can inhibit others
what is FAD
- electron accepting co enzyme
- only accepts single electrons
- tightly bound to enzymes
what is purpose of atp synthase
- generates ATP
- multi subunit enzyme
- spans inner mitochondrial enzyme
- F1 unit contains 3 catalytic sites
- F0 unit forms a rotor
- influx of protons turns rotor, changing conformation of active site in F1 unit release an ATP molecule
what is electron flow dependent on in the electron transport chain
- proton pumping
; electron movement requires proton pumping
; needs proton to return to matrix - uncoupling means protons return back to the matrix without passing through the ATP synthase
what are the 3 types of couplers
- chemical
- physiological
- proton leak
chemical uncouplers
- chemicals which transport protons across inner membrane
- destroy proton gradient
- no ATP
physiological couplers
- uncoupling proteins form channels through inner membrane
- protons pass through these
- thermogenin
proton leak
- low level leaks across inner membrane
- more than 20% metabolic energy needed to overcome this and maintain proton gradient
inhibitors
- inhibition of complexes blocks passage of electrons and proton pumping
- cyanide blocks cytochrome oxidase and stops electron flow therefore blocks proton pumping and atp synthesis
OXPHOS disease
- mitochondrial DNA encodes some of this protein in the complexes of oxidative phosphorylation
- mitochondrial dna has no repair mechanisms
- mutations are therefore permanent
- resulting in faulty complexes
- leads to a number of diseases affecting tissue with high energy demand = OXPHOS disease
