Flashcards
Aerobic/ anaerobic respiration
Cards in this deck (54)
- 1Aerobic RespirationThe release of large amounts of energy made available as ATP- produced from breakdown of molecules, w/ oxygen as terminal electron acceptor
- 2Anaerobic Respirationbreakdown of molecules in the absence of oxygen , releasing relatively little energy, making a small amount of ATP by substrate- level phosphorylation.
There’s obligate aerobes, facultative anaerobes and obligate anaerobes - 3Anaerobic respirationbreakdown of molecules in the absence of oxygen , releasing relatively little energy, making a small amount of ATP by substrate- level phosphorylation.
There’s obligate aerobes, facultative anaerobes and obligate anaerobes - 4DehydrogenationThe removal of one or more hydrogen atoms from a molecule
- 5DecarboxylationThe removal of a carboxyl group from a molecule, releasing CO2.
- 6MetabolismRespiration is a catabolic process involving a series of enzyme-catalysed reactions in cells, where energy-rich respiratory substrates, e.g. glucose and fatty acids, are broken down to release energy: some is trapped as chemical energy in ATP and some is released as heat energy.
- 7Metabolism pt 2During respiration, high energy C-C, C-H and C-OH bonds are broken, lower energy bonds are formed and the difference is released and used to attach iP to ADP to make ATP- ATP does not ‘produce’ energy- but when hydrolysed releases energy. Energy= available to use by cell or is lost as heat.
- 8Oxidative phosphorylationoccurs on inner membranes of mitochondria in aerobic respiration- energy for making ATP comes from oxidation- reduction reactions- released in the transfer of electrons- along a chain of electron carrier molecules.
- 9PhotophosphorylationPhotophosphorylation- occurs in thylakoid membranes of the chloroplasts in the light- dependent stage of photosynthesis- energy for making ATP comes from light- is released in transfer of electrons along a chain of electron carrier molecules- photophosphorylation does not occur in respiration.
- 10Substrate level phosphorylationSubstrate level phosphorylation- occurs when phosphate groups are transferred from donor molecules e.g. glycerate 3- phosphate to ADP to make ATP in glycolysis or when enough energy is released from a reaction to bind ADP to inorganic phosphate eg in krebs.
- 11More on respiration- processes/ aerobic formulaProcesses that require energy- active transport, movement, formation of complex molecules eg proteins- comes from respiration
Formula for aerobic respiration of glucose
C6H1206 +6CO2—> 6CO2 +6H2O+ energy (ATP)
Glucose + oxygen—> carbon dioxide + water
But can also use lipids and proteins in respiration - 12ATPCritical molecule in energy transfer- Ribose and adenine part of molecule together is called adenosine
Energy carrying molecule- if we react ATP with water the end phosphate can leave-this reaction releases energy- energy can then be used for processes in the cell - 13ATP- moreReacting ATP with water is an example of a hydrolysis reaction catalysed with with ATP hydrolase also called ATPase
ATP + water —> ADP + Pi + energy
At end of the reaction made adenosine diphosphate (ADP) and released phosphate ion
Given symbol Pi- i tells us it’s inorganic- not bonded to a carbon containing molecule
-2 processes in respiration that can reform ATP- substrate level phosphorylation and oxidative phosphorylation- oxidative phosphorylation produces the vast majority of ATP during respiration - 14ATP formationOnce ATP is hydrolyzed has to be reformed to be used again
ATP is formed in respiration in the energy stored in glucose- when ATP is reformed- energy from glucose is used is used to add a phosphate ion back on to ADP- process is called phosphorylation - 15ATP formation- moreCells use energy in glucose to produce ATP in respiration- during respiration a large no. chemical reactions gradually break down the glucose molecule- during some of these reactions a hydrogen ion is released - dehydrogenation or oxidation reaction- hydrogen ion has 2 electrons- hydrogen ions are rich in energy- can be used to form large quantities of ATP- takes place during oxidative phosphorylation- when H= is released it’s added to a molecule called a hydrogen carrier- good example- coenzyme NAD- by adding hydrogen with its 2 electrons to NAD - carry out a reduction reaction
NAD + H —> NADH (reduced NAD) - 16Glycolysis overviewAt different stages, energy contained within glucose can be transferred to other molecules
Energy transfer can take place in 2 different ways- in some reactions the energy transferred can be used to produce a molecule of ATP directly releasing energy- energy is used to form a molecule of ATP from ADP and Pi (substrate level phosphorylation) -
Or hydrogen and 2 electrons can be removed from a molecule- (dehydrogenation/ oxidation - hydrogen and 2 electrons are transferred to a hydrogen carrier such as coenzyme NAD, forming reduced NAD- reduced NAD is then used used later to produce ATP in process called oxidative phosphorylation. - 17Where does glycolysis take place + whyGlycolysis takes place in the cytoplasm and does not require oxygen
Glycolysis consists of 10 different reactions but we learn a simplified version
Initial stage of both aerobic and anaerobic respiration- occurs in cytoplasm as glucose can’t pass through mitochondrial membrane- but even if it could- enzymes for breakdown= not present in mitochondria- so glucose could not be metabolised - 18Glycolysis- steps pt 1glucose molecule is phosphorylated by addition of 2 phosphate groups using 2 molecules of ATP- ATP molecules each transfer 1 phosphate onto the glucose molecule- makes hexose diphosphate
As a result- phosphorylated molecule= more reactive- less AE required for enzyme controlled reactions- also more polar than glucose= less likely to diffuse out of cell
Hexose diphosphate converted to 2 molecules of triose phosphate- a 3 carbon sugar, glyceraldehyde-3- phosphate - 19Glycolysis pt 2Hydrogen is removed from the triose phosphate molecules- a dehydrogenation/ oxidation reaction- triose molecules oxidised to form pyruvate- this hydrogen is added onto NAD forming reduced NAD (hydrogen carrier molecule). - Also each phosphate group on triose phosphate is added to ADP, converting these molecules to ATP- so for each triose phosphate molecule 2 molecules of ATP is produced-4 ATP molecules produced overall- this is an example of substrate level phosphorylation- happens without redox reactions along electron transport chain- produces pyruvate
- 20Overall products of glycolysisAt start used 2 ATP molecules but produced 4 ATP molecules at end- net yield- 2 ATP
Produced 2 reduced molecules of reduced NAD- will be used in a later stage of respiration called oxidative phosphorylation- if O2 available each has potential for synthesis of an additional 3 molecules of ATP- making 6 altogether from electron transport chain
Released 2 molecules of Pyruvate
Doesn’t seem to have released too much energy- because pyruvate still contains a great deal of energy- gradually released during later stages of respiration in krebs cycle- if O2 is available - 21Link reaction- overviewWhat happens after glycolysis depends on amount of oxygen present- in absence of oxygen anaerobic respiration takes place in the cytoplasm
If oxygen is present then cell carries out aerobic respiration- takes place in mitochondria- has a double membrane- internal region of a mitochondria= mitochondrial matrix - 22Link reaction overview pt2Pyruvate molecules produced by glycolysis are actively transported from cytoplasm into mitochondrial matrix- at this point the pyruvate molecules take part in the link reaction
Link reaction formula
Pyruvate + coenzyme A —> acetyl coenzyme A + carbon dioxide
(at same time) NAD —> reduced NAD - 23Link reaction- steps pt1Pyruvate contains 3 C atoms - pyruvate now reacts with enzyme called coenzyme A- pyruvate molecule splits- A 2 C group is added to coenzyme A, forms acetyl coenzyme A- the remaining one carbon part of the pyruvate leaves as a molecule of CO2
At same time an oxidation reaction takes place- forms reduced NAD
At end of a link reaction- got 3 products- one molecule of acetyl coenzyme A, one molecule of CO2, one molecule of reduced NAD - 24Link- REMEMBERREMEMBER- glycolysis produces 2 pyruvate molecules for each molecule of glucose- so the link reaction takes place twice for each molecule of glucose entering respiration- so produces 2x of each product
- 25Link- pt 3Also- during link reaction a CO2 molecule is released from the pyruvate- when CO2 is removed from a molecule- called decarboxylation reaction
Because we have oxidation alongside decarboxylation during link reaction- called oxidative decarboxylation
Link reaction doesn’t require O2 - 26Krebs pt 1The function of the Krebs cycle is a means of liberating energy from carbon bonds via reduced intermediates to provide ATP and reduced NAD (and reduced FAD), with the release of carbon dioxide
Glucose has 6C atoms - during link reaction- 2 of those atoms have left as 2 CO2 molecules - remaining 4C atoms are now in 2 molecules of remaining acetyl coenzyme A
Acetyl coenzyme A now enters next stage of respiration - Krebs cycle- takes place in the mitochondrial matrix
Can divide krebs cycle into 2 main stages
In 1st stage acetyl coenzyme A reacts with a 4 carbon molecule - the 2 carbon part of acetyl coenzyme A moves onto this molecule, creating a 6C molecule- at same time the coenzyme A and goes back to take part in the link reaction-
2nd stage- a whole series of chemical reactions takes place: - 27Krebs pt 2For 6C molecule- First a decarboxylation reaction releases 1 CO2 molecule and a dehydrogenation reaction produces a molecule of reduced NAD- now have 5C molecule
Another dehydrogenation reaction takes place- produces 1 molecule of reduced NAD/ another decarboxylation reaction- produces 1 CO2 molecule- 1 molecule of ATP also produced during krebs cycle- produced through substrate level phosphorylation
Finally 2 more dehydrogenation reactions- produces 1 molecule of reduced FAD and 1 molecule of reduced NAD- coenzyme FAD is a hydrogen carrier similar to NAD - 28Krebs pt 3NOTE- during these reactions we regenerate our starting molecule (the 4 C molecule) via 6C and 5C intermediates.- allows krebs cycle to continue again
When Kreb’s cycle operates once we make 1 molecule of ATP, 3 molecules of reduced NAD, 1 molecule of reduced FAD, also release 2 CO2 molecules.
REMEMBER- 1 glucose molecule forms 2 pyruvate molecules in glycolysis
So- per glucose- link reaction produces 2 molecules of acetyl coenzyme A- krebs cycle operates x2
the acetate fragment which entered the Krebs cycle from the glucose molecule is completely broken down to CO2 and water Note that H2O is fed in at three reactions.
Krebs cycle does not require oxygen - 29Coming up to oxidative phosphorylation- what's happened so farSo far in respiration created several molecules of reduced hydrogen carriers
Next stage of respiration the reduced hydrogen carriers used to produce ATP- called oxidative phosphorylation
Whole purpose of respiration is to generate ATP, However in reactions we’ve seen so far- only made net yield of 4 ATP molecules- per glucose- we produced a yield of 2 ATP molecules in glycolysis and 2 ATP molecules in 2 turns of Krebs cycle- These ATP molecules are formed by substrate level phosphorylation
Also produced 12 molecules of reduced hydrogen carriers:
2 reduced NAD- glycolysis
2 reduced NAD link
6 reduced NAD, 2 reduced FAD- krebs - 30Oxidative phosphorylation- startWhen hydrogen carrier is reduced it gains a hydrogen ion and 2 electrons- 2 e’s contain a great deal of energy- used to create ATP in oxidative phosphorylation
Inner mitochondrial membrane is folded into cristae- increases SA- inbetween 2 membranes we have inter membrane space
On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase - 31Oxidative phosphorylation- steps pt 1On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase
reduced NAD and reduced FAD deliver their pairs of hydrogen atoms to the electron transport system chain in the inner mitochondrial membrane- first protein is reduced
2 electrons then pass to 2nd protein- 1st protein now oxidised- 2nd reduced
KEY NOTE- as electrons move down the electrons transport chain, the electrons lose energy- used by electron transport chain proteins to pump protons (hydrogen ions) from matrix into intermembrane space - 32Oxidative phosphorylation- steps pt 2Because inner membrane is impermeable to protons- protons build up in intermembrane space
Electrons continue making way down chain in series of oxidation and reduction reactions- at each stage protons are pumped into the intermembrane space - 33Oxidative phosphorylation- steps- pt 3At the end the 2 electrons have transferred all of their energy
These 2 electrons now combine with oxygen and 2 hydrogen ions (protons) to make a molecule of water
equation= 2 e- + ½ O2 + 2H+ —> H2O - 34Oxidative phosphorylation- steps pt4Reduced FAD operates in the same way as reduced NAD- However, the electrons from reduced FAD enter the transport chain in the middle rather than the start
As we said molecule of glucose generates 10 reduced NAD molecules and 2 reduced FAD molecules- so as a result of the electron transport chain, the concentration of protons is much greater in the intermembrane space than the matrix- proton gradient is now used to generate ATP - 35Reaches ATP synthetase pt 1Enzyme ATP synthase is found on inner mitochondrial membrane- contains an ion channel through centre
Protons now diffuse down the gradient through the ion channel into the matrix- this movement of protons is used by ATP synthase to generate ATP from ADP and Pi- process is called chemiosmosis - ADP+Pi→ ATP+ H2O
At end protons combine with electrons and oxygen to form water- O2 from blood- taken to cells - 36Reaches ATP synthetase pt 2Oxygen is described as the final (terminal) electron acceptor-essential as it removes protons and electrons- oxygen reduced by addition of hydrogen atoms and electrons to make water
Cyanide is a non competitive inhibitor of the final carrier of the electron transport chain- in its presence electrons and protons can’t be transferred to water- accumulate and so electron transport chain no longer functions- proton gradient not maintained- ATP synthetase can’t produce ATP- cell dies quickly - 37Oxidative phosphorylation - ATP products: 38 ATPs per glucose molecule formed as follows:
• net 2 ATPs in glycolysis (substrate-level
phosphorylation)
• 2 ATPs in the Krebs cycle (substrate-level
phosphorylation)
• 34 ATPs from oxidative phosphorylation (using chemiosmosis) from 10 reduced NAD (2 from glycolysis, two from the link reaction, six from the Krebs cycle) and 2 reduced FAD (Krebs cycle). - 38Oxidative phosphorylation general productsATP is the major product of oxidative phosphorylation, as it is the premier energy molecule of the cell. Oxidative phosphorylation also produces NAD+, FAD, and water.
- 39Anaerobic respirationno oxygen to remove atoms from reduced NAD and make water- electron transport chain cannot function- no oxidative phosphorylation- no ATP formed- no O2- no reduced NAD can be reoxidised - no NAD regenerated to pick up more hydrogen consequently- link and Krebs can't take place- only glycolysis is possible
- 40Anaerobic respiration- how does glycolysis continueFor glycolysis to continue- pyruvate and hydrogen must be constantly removed and NAD must be regenerated
Done how? Pyruvate accepts hydrogen from reduced NAD - 2 different anaerobic pathways to remove hydrogen from reduced NAD- both in cytoplasm - 412 anaerobic pathways- path1In animals- muscle cells may not get sufficient O2 during vigorous exercise-when deprived of O2 pyruvate= hydrogen acceptor- converted to lactate- regenerating NAD- lactate can build in muscle cells or be transported to liver- converted back to glucose or stored as glycogen- if O2 later becomes available- lactate can be respired to CO2 and water- releasing energy it contains
- 422 anaerobic pathways- path2In various microorganisms eg yeast and in plant cells under certain conditions eg roots in waterlogged soils- pyruvate is converted o CO2 and to ethanal, a hydrogen acceptor- converted by decarboxylase- Ethanal is reduced to ethanol and NAD is regenerated in alcoholic fermentation ( a process in which some sugars (as glucose) are converted into alcohol and carbon dioxide by the action of various yeasts, molds, or bacteria or carbohydrate materials) pathway= irreversible- even if O2 becomes available again ethanol is not broken down- accumulates in cells- can rise to toxic concentrations
- 43Energy budget aerobic respirationp 47- table shos how many H+ atoms and ATP molecules produced from 1 molecule of glucose- gives 2 turns of krebs cycle
- 44How many ATP molecules overall respired38 overall per glucose molecule- theoretical total- cell is generally not this efficient as-
- ATP used to move pyruvate, ADP, reduced NAD and reduced FAD across mitochondrial membrane
-Proton gradient may become compromised by proton leakage across the inner mitochondrial membrane, rather than passing through ATP synthetase
Molecules may also leak through membranes
on average 30-32 ATP molecules tend to be produced - 45MathsIf a mole of glucose is combusted in oxygen- produces 2880 kJ energy required to make ATP= 30.6 kJ/mol-1- if theoretical max is considered- a mole of glucose makes 38 moles of ATP- equivalent to 30.6x38= 1162.8 kJ
therefore efficiency of ATP production=
energy made through ATP/ energy released in combustion= 1162.8/2880x 100= 40.4% - 46Anaerobic respiration- brief overviewWithout ATP synthetase associated with the electron transport system- the only ATP formed is in glycolysis makes 2 molecules of ATP per molecule of glucose by substrate level phosphorylation- small compared to 38 molecules of ATP produced during aerobic-
- 47anaerobic more pt2in anaerobic pyruvate not transferred to the mitochondria but is converted in the cytoplasm- to ethanol in plants or lactate in mammals-2H released in conversion of glucose to pyruvate reduces NAD - given up again in formation of ethanol in plant cells or lactate in animal cell- many different metabolic pathways have been identified in bacteria or archaea- many organic acids and alcohols produced by their fermentation
- 48anaerobic respiration- mathsEfficiency of ATP production= energy made available through ATP/ energy released in combustion x100=
30.6x2/2880x100=2.1%
much less efficient - 49Alternative respiratory pathwaysKreb's cycle- sometimes called metabolic hub as the Metabolic pathways of carbohydrates, lipids and proteins can feed into it and in some situations fats and proteins can be used as respiratory substrates - Acetyl Coenzyme A is a most significant molecule as it links the metabolism of the three types of macromolecule
- 50Lipid pathwaysTriglyceride molecule has 2 parts-3 carbon glycerol part and on right - 3 fatty acids- fatty acids and glycerol= joined by 3 ester bonds- when triglycerides are digested - ester bonds= hydrolysed- release glycerol and fatty acid molecules- 3 carbon glycerol is converted to triose phosphate, an intermediate of glycolysis- converted to pyruvate - enters link reaction and krebs cycle as previously seen
- 51Lipids pt 2 electric boogaloofatty acid molecules broken down into 2 carbon units eg
O H H H
|| | | |
C C- C - C
| | | |
H H H H
Start of a fatty acid chain- 2 units here (2C acetate fragments) - fed into the Krebs
cycle as acetyl co-enzyme A; - 52Lipids pt 3Acetyl coenzyme A now enters the krebs cycle- fatty acids contain great amount of carbon to hydrogen bonds- forms very large number of acetyl coenzyme A molecules- so triglycerides contains great amount of energy- more than glucose
- 53Protein- aerobic respiration pathwayFirst protein must be hydrolysed to its individual amino acids during digestion- all proteins have an amino group- in first stage- amino group is removed- called deamination- carbon part of amino acid is then processed (entirety that isn't N-H-H)-
- 54Protein- aerobic respiration pathway- pt 2proteins are hydrolysed into their constituent amino acids, which are deaminated in the liver, forming a keto acid and ammonia;
• Some keto acids are fed into glycolysis (e.g. pyruvate) and some others are fed into the Krebs cycle.energy value of proteins is approx same as carbs