Module 5.7 Flashcards
Respiration
Why is cellular respiration needed
active transport
endo/exocytosis
DNA replication
cell division
activation of chemicals
movement e.g. flagella
components of the mitochondria
inner membrane
outer membrane
cristae
matrix
mitochondrial DNA
role of the matrix
where the link reaction and krebs cycle take place
contains enzymes for these reactions
contains the mitochondrial DNA to code for enzymes and other proteins
mitochondrial ribosomes assemble these proteins
role of the outer membrane
contains proteins which form channels or carriers for the passage of molecules e.g. pyruvate
role of the inner membrane
folded into cristae for increased surface area for oxidative phosphorylation
less permeable to small ions like hydrogen
has proteins embedded in it e.g. electron carriers and ATP synthase
role of the intermembrane space
involved in oxidative phosphorylation
inner membrane is in close contact with the matrix so reduced NAD and FAD can easily deliver hydrogens to the electron transport chain
where does glycolysis occur
cytoplasm
what are the 3 stages of glycolysis
phosphorylation of glucose
splitting of hexose bisphosphate
oxidations of triose phosphate
what is phosphorylation of glucose - glycolysis
ATP is hydrolysed and 2 phosphoryl groups are added to the glucose to for hexose bisphosphate
the energy from the hydrolysed ATP molecules activates the hexose sugar and prevents it from being transported out of the cell
what is splitting of hexose bisphosphate - glycolysis
each molecule of hexose bisphosphate is split into 2 3C molecules of triose phosphate
what is oxidation of triose phosphate - glycolysis
dehydrogenase enzymes aided by coenzyme NAD remove hydrogens from triose phosphate
2 molecules of NAD accept the hydrogens and become reduced
4 molecules of ATP are made for every 2 triose phosphate molecules undergoing oxidation
pyruvate is produced
products of glycolysis
for every molecule of glucose
2 molecule of ATP
2 molecules of reduced NAD
2 molecules of pyruvate
where does the link reaction occur
matrix
how is the acetyl group produced in the link reaction
pyruvate is decarboxylated (produces carbon dioxide) and dehydrogenated (reduces NAD)
to produce the acetyl group
how is reduced NAD produced in the link reaction
the hydrogen removed from pyruvate combines with NAD to produce reduced NAD
how is acetyl coenzyme A produced int he link reaction
coenzyme A combines with the acetyl group to become acetyl coenzyme A
products of the link reaction
glycolysis produces 2 pyruvate molecules so
2 reduced NAD
2 acetyl coenzyme A
2 carbon dioxide
where does the krebs cycle occur
matrix
how does acetyl co enzyme A enter the krebs cycle
co enzyme a is removed from acetyl coenzyme A and the acetyl group enters the krebs cycle
how is citrate formed in the krebs cycle
the acetyl group (2C) from acetyl coenzyme A combines with oxaloacetate (4C) to produce citrate (6C)
how is citrate converted to a 4C compound
citrate is decarboxylated and dehydrogenated to a 5C compound then dehydrogenated and decarboxylate again to a 4C compound
the decarboxylation produced CO2 and the dehydrogenation produces hydrogen to reduce NAD
how is ATP produced in the krebs cycle
the 4C compound temporarily combines with and is then released from coenzyme A
at this stage substrate level phosphorylation occurs producing one molecule of ATP
how is the 4C compound converted to oxaloacetate in the krebs cycle
the 4C compound is dehydrogenated to a different 4C compound and reduced FAD is produced
further dehydrogenation produces oxaloacetate and reduced NAD
products of the krebs cycle
for every molecule of glucose there are two turns of the krebs cycle
6 reduced NAD
2 reduced FAD
4 carbon dioxide
2 ATP
where does oxidative phosphorylation occur
the cristae/ inner membrane and the intermembrane space
what happens to reduced NAD and FAD in oxidative phosphorylation
they are reoxidised when they deliver their hydrogen atom to the electron transport chain
what happens to the hydrogen atoms delivered from reduced NAD and FAD
the hydrogen atoms split into protons and electrons
the protons go into solution in the matrix and the electrons go to the electron transport chain
how does the electron transport chain work
electron carriers are proteins embedded in the cristae
each electron has an iron ion at its core
the iron ions can gain electrons becoming reduced and then become reoxidised donating the electron to the iron ion in the next electron carrier
role of the electron transport chain
as electrons pass along the chain some of their energy is used to pump protons across the inner mitochondrial membrane into the intermembrane space to create a proton gradient
role of the proton gradient and chemiosmosis
the proton gradient generate a chemiosmotic potential that is a source of potential energy
the protons diffuse through protein channels associated with ATP synthase the flow of protons causes a conformational change in the enzyme which allows ADP and Pi to combine to form ATP
role of oxygen in oxidative phosphorylation
oxygen is the final electron acceptor
it combines with the electrons coming off the electron transport chain and with protons diffusing through the ATP synthase channel forming water
products of oxidative phosphorylation
theoretically 28 molecules of ATP per molecule of glucose
what is the total theoretical yield of ATP during aerobic respiration
32
why is the theoretical yield of aerobic respiration rarely achieved
some ATP is used to actively transport pyruvate into the mitochondria
some ATP is used to transport reduced NAD from glycolysis into the mitochondria
some protons may leak out through the outer mitochondrial membrane
respiration in the absence of oxygen
oxygen cant act as the final electron acceptor combining electron and protons with oxygen to form water
proton gradient reduced so oxidative phosphorylation stops
reduced NAD and FAD cannot unload their hydrogen atoms and become reoxidised
krebs cycle and link reaction stop
glycolysis can take place but the reduced NAD had to be reoxidised for glycolysis to continue
what are the two pathways used to reoxidise the reduced NAD in anaerobic respiration
ethanol fermentation (fungi and plants)
lactate fermentation (mammals)
how is reduced NAD reoxidised in the ethanol fermentation pathway
each molecule of pyruvate produced in glycolysis is decarboxylate by pyruvate decarboxylase producing ethanal
ethanal accepts hydrogen atoms from reduced NAD becoming ethanol catalysed by ethanol dehydrogenase
this reoxidises the NAD so it can accept more hydrogen atoms from triose phosphate for glycolysis to continue
how is reduced NAD reoxidised in the lactate fermentation pathways
pyruvate from glycolysis accepts hydrogen atoms from the reduced NAD producing lactate catalysed by lactate dehydrogenase and reoxidising the NAD
benefits of anaerobic respiration
faster than aerobic respiration
provides energy when oxygen supply is insufficient e.g. intense exercise
glucose is only partly broken down so more molecule can undergo glycolysis per minute making overall yield of ATP quite large
why does anaerobic respiration produce a lower ATP yield than aerobic respiration
allows glycolysis to continue so the net gain of 2 ATP molecules is still obtained
for each molecule of glucose only 2 ATP molecules are produced compared to the 32 in aerobic respiration
how can yeast cells be used to investigate respiration
if oxygen is available yeast respires aerobically
if oxygen is lacking the yeast respires anaerobically
to divide by mitosis yeast requires ATP and rate of reproduction depends o amount of ATP available - faster reproduction under aerobic condition
yeast can also oxidise ethanol under aerobic conditions so alcohol content will decrease in aerobic conditions or increase in anaerobic conditions
energy value of carbohydrates
15.8
energy value of lipids
39.4
energy value of protein
17
how is respiratory quotient calculated
CO2 produced divided by O2 consumed
RQ value of glucose
1
RQ value of fatty acids
0.7
RQ value of amino acids
0.8-0.9
what does and RQ value greater than 1 mean
some anaerobic respiration is taking place as more carbon dioxide is being produced than oxygen is being consumed
