Respiration Flashcards
What is respiration?
series of metabolic reactions where respiratory substrate molecules are metabolised to produce ATP molecules which can then be hydrolysed to release energy for energy requiring processes in cells
What is a respiratory substrate?
any molecule that can be metabolised to produce ATP
Why is glucose not very useful (why does it need to be respired)?
1 glucose molecule has a lot of chemical potential energy but not very useful because energy in 1 big package
Why is ATP more useful than glucose?
- around 32 ATP molecules produced by resp
- high energy molecules but much more useful bc energy is in small packages
respiration does not produce…
ENERGY, produces ATP
ATP requiring processes e.g.?
- AT
- muscle contraction
- protein synthesis
- cilia movement
- bulk transport
- DNA rep
Stages?
- Glycolysis
- link reaction
- Krebs cycle
- Oxidative Phosphorylation
Glycolysis?
- splitting of glucose
- occurs in aerobic and anaerobic
Size of ribosomes in mitochondria?
70s, needed for translation of mitochondrial proteins
Why are there stalked particles in mitochondria?
- all along IMM
- ATP synthase molecules 1-2micrometer long
- H+ move through ATP synthase molecules by FD allowing synthesis of ATP
why does mitochondria have DNA?
• contains genes for mitochondrial proteins e.g. ATP synthase
cristae in mitochondria?
- folds
- inc SA
- for e- carrier proteins - OP
membrane of mitochondria?
- inner membrane
- intermembranal space
- outer membrane
envelope
inner mitochondrial membrane?
- folds to inc SA
- separates intermembranal space from matrix
- contains membrane proteins involved in OP
- H+ ion move thru ATP synthase
intermembranal space?
provides a space for the build up of a H+ proton gradient
outer mitochondrial membrane?
compartmentalises the link reaction, krebs cycke, and OP from cytoplasm of the cell
glycolysis doesn’t occur in?
mitochondria, actually occurs in cytoplasm
Steps in glycolysis?
Glucose
⬇ (ATP ➡ ADP + Pi)
hexose phosphate
⬇ (ATP ➡ ADP + Pi)
hexose bisphosphate
⬇
2 TP
⬇ (4ADP ➡ 4ATP), (2redNAD produced)
2PyruvateGlucose to hexose bisphosphate is
phosphorylation
triose phosphate to pyruvate is ?
oxidation, (2redNAD produced)
how many ATP needed to start resp
2
NAD?
- coenzyme
- H carrier
- takes part in reactions catalysed by dehydrogenases (takes H)
- when it gets reduced, gains 2 H atoms (2H+ + 2e-)
reduction of NAD equation?
NAD + 2H+ + 2 e- ➡ NADH + H+
The link reaction?
- happens in matrix
* links glycolysis and krebs cycle
Steps of link reaction?
2 Pyruvate (3C)
⬇ (2CO2 removed, decarboxylation reaction)
(H lost, dehydrogenation)
2 Acetate (2C)
⬇ ⬅ coenzyme A
2 Acetyl coenzyme A
⬇
2 Acetatewhat happens to acetate?
combines with the coenzyme A (upwards arrow), fed into KC
How many acetates from 1 pyruvate?`
1
H that are lost are used to
reduce NAD
KC a.k.a
citric acid cycle or TCA
What enters the krebs cycle?
- acetyl coA combines with oxolacetate (4C)
- forming citrate (6C)
- goes off to collect more acetate
- Citrate then decarboxylated and dehydrogenated (oxidised)
- H combine with NAD to form redNAD and FAD to form redFAD
KC summary - per 1 turn ?
- 3 redNAD
- 2 CO2 produced
- 1 ATP
- redFAD
ATP produced from glycolysis and KC is
substrate level phosphorylation, OP contrasts
⭐ 2 TURNS OF KC PER
1 GLUCOSE
OP?
- ETC
- located within mitochondrial membrane, happens in IMM, IMS and matrix
- where the most energy required
OP?
- redNAD and redFAD give up their H to the ETC where the H are split into H+ + e- using energy from e- movement
- H+ are pumped (not AT) into IMS
- more H+ in IMS = diffusion gradient
- H+ move into matrix through ATP synthase, producing ATP
- -chemisosmosis
- O2 accepts e- from ETC - final electron acceptor
- O- + 2H+ -> H2O
OP is not?
substrate level phosphorylation
OP - if O is not available?
- If O2 not avbl to collect e-, e- is stuck
- traffic jam queue of NAD and FAD waiting to drop off H+
- causes shortage for krebs cycle
- prevents other stages
why do we not achieve the potential yield of ATP molecules?
- only get potentials if enough ADP + Pi in mitochondria
* 25% of ATP made is used to transport ADP into mitochondria and ATP out into cell
how many ATPs produced in OP?
• 28, 32 in total from resp - 2 gained in KC and 2 in Gly
How many turns of KC for every glucose ?
- 2
- Glycolysis: 2 molecules of pyruvate formed
- make 2 molecules of acetyl coA
- so, for each molecule of glucose, 2 turns of krebs cycle
Other reasons why max theoretical yield of glucose of not achieved ?
- 38
- pyruvate has to be AT from cytoplasm into matrix
- ADP and Pi have to be AT from cytoplasm into matrix
- some H+ leak across IMM back into matrix
H+ ion movement thru ATP synthase is?
facilitated diffusion
Evid for chemisosmosis?
- pH gradient, high in matrix - chemiosmosis
- dinitrophenol causes IMM to be very leaky to H+. Mit treated with DNP produce less ATP - H+ can bypass ATP synthase so less ATP made
- isolated thylakoids can be made to produce ATP
When there’s no O2?
- O cannot accept electron
- so ETC stops
- redNAD can’t be reoxidised so
- Krebs cycle stops
- pyruvate not made so acetyl coA not made
Why should glycolysis no longer continue?
• redNAD made can no longer release H and be recycled
2 pathways of anaerobic resp?
- ethanol pathway (yeast and some bacteria)
* lactate pathway
Ethanol pathway?
- 2 pyruvate produced in pyruvate
- 2Pyruvate decarboxylated into 2 Ethanal by pyruvate decarboxylase
- Ethanal reduced from ethanal into 2 ethanol by ethanol dehydrogenase
- redNAD to oxNAD - oxNAD regen so glycolysis can continue
ethanol pathway - ATP yield & plants?
- low ATP yield
* occurs in waterlogged plants bc they’re O2 deprived
lactate pathway?
- all mammals
- only 2 mols of ATP produced
- glycolysis continues
- but pyruvate is reduced to lactate generating oxNAD so glycolysis can continue
what happens to pyruvate in lactate pathway?
Pyruvate ➡ lactate by lactate dehydrogenase
oxNAD made
in both anaerobic systems ?
- there is a toxic build up
* if toxic levels of ethanol, reaction can be reversed
how do we deal w lactate?
- travels in blood to liver
- where it’s combined with O2 (the oxygen debt!) to form CO2 and H2O - 20% oxidised
- lactate to pyruvate in liver
- if there’s a lot: pyruvate ➡ glucose➡glycogen
which reactions happen to keep glycolysis going?
- mammals: lactate pathway
* yeast: ethanol pathway
what are the disadvantages of anR comp to AR?
- lactate and ethanol r toxic
- lactate causes pain, can’t happen for long
- ethanol kills yeast cells if closed envir
- 2 ATP produced in lactate
what happens to the lactate when ATP demand returns to a level where it can be met by AR?
- lactate ➡ pyruvate in the liver
- pyruvate enters link reaction
- pyruvate can b converted to glycogen for storage
Removal of lactate also needs?
- to become oxidised back to pyruvate, lactate also needs oxNAD to be reduced
- oxNAD supplied by OP when AR restarts
What is a resp substrate?
substance used to produce ATP in a cell by respiration
How can triglycerides be respired?
- hydrolysed to FA
- which enters KC via acetyl coA
- and glycerol which ➡ pyruvate
lipids & resp?
lipids store and release about 2x as much energy as carbs
how can proteins be respired?
- proteins are hydrolysed to AA
- AA have to be deaminated at hepatocytes - ornithine cycle
- requires ATP, reducing net ATP production
how is RQ measured?
using a respirometer
Where does each RS enter resp?
- glycerol in TP (gly)
- FA in acetyl coA
- lactate at pyruvate
- AA from proteins at pyruvate or KC
energy content in decreasing order?
lipids > alcohol > carbs/ proteins
oxidation involves ?
dehydrogenation - loss of H atoms
why do different RS have diff energy densities?
- ATP is obtained from RS thru oxidation forminh redNAD
- involves dehydrogenation
- if a molecule has proportionally more H atoms, then more redNAD molecules are formed and more ATP molecules can be synthesised in OP
- also means more O2 needed to accept e-s at the end of ETC - so lipids have RQ of >1
What can the RQ value show?
- what is being respired
* whether or not anR is occuring
RQ equation?
vol of CO2 out (in a set time)/ vol of O2 in (in a set time)
RQ values ?
carbs: 1
protein: 0.8-0.9
lipids: 0.7
RQ general?
- can be volume, n, molecules
* if RQ values are high, more CO2 is being produced than O2 is being used, indicating high levels of anR
if RQ is over 2 ?
- ethanol pathway
* some O2 in the yeast may be taken up
RQ for lactate pathway?
• can’t calc
Why is the RQ for complete anR of glucose in yeast infinite?
2CO2 produced but none used -2/0 = infintity
why can the RQ for anR of glucose in humans can’t be calc?
no O2 used and no CO2 produced
Respirometer: bubble movement?
- when O2 taken in, would move ⬅ towards the thing
* when CO2 exhaled (more than taken in) moves ➡
when something is respiring (taking in O2) as much as it is exhaling CO2?
• bubble would move the same amount in each direction so no overall movement: RQ is 1
respirometer: why does the exp need to be done 2x?
- with KOH/ sodalime - absorb CO2
- more movement towards organism
- record movement - will tell us the O2 consumption
- repeat w/o absorber - to get CO2 production along (minus the values)
if RQ is >1?
could be respiring anR, producing more CO2 than O2 consumption
Glycolysis is?
substrate level phosphorylation
Why is ATP needed in glyolysis?
- addition of phosphate group to glucose destabilises glucose bc P = polar which makes it more likely to undergo the following reactions
- glucose = stable so ATP needed
what is the point of the KC?
To make red coenzymes
KC products?
- 3redNAD, 1red FAD for acetyl
* 6 redNAD, 1 redFAD, 1 ATP per glucose
if ETC stops, how are other stages affected?
- NADH and FADH build up
- this is bc they can’t give up e- bc the 1st e- carrier is already occupied w e-
- means no oxNAD and oxFAD regen
- so KC will stop ^ are needed there
- link reaction stops - needs NAD and coA
- glycolysis continues
when the coenzymes are reoxidised in OP?
can go back to KC and accept more H+.
Respirometer: why is a gauze platform used?
• stops organisms from falling into the liquid
Respirometer: why is a screw clip used?
seal apparatus
Respirometer: why is a syringe used?
to reset position of liquid in capillary tube
Respirometer: 3 way tap?
• to top up O2 to inc volume
Respirometer: why are glass beads used in the control tube?
to ensure exactly the same V as respiring organisms
Respirometer: why is a capillary U tube used?
to measure CO2 production and O2 consumption
Respirometer: why is a control tube used?
- Cancels out the effect of temp in respirometer
- same V of air in each tube because same vol of organisms and beads
- so if T inc, air inside both tubes expands so the liquid is pushed up and down by the same degree - doesn’t move
effect of T on respirometer?
- causes gas to expand
- which causes the movement of fluid
- but fluid should only move due to O2/ CO2
