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what are the three pathways through which energy is released in cellular respiration?
- - Aerobic celluar respiration
- - Anerobic cellular respiration
- - Fermentation
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what is cellular respiration?
- - A process that uses cells to release the energy needed for all kinds of work such as muscle contraction. ( air to cells )
- - two type of cellular resp = aerobic- that uses oxygen and anaerobic = no oxygen
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Aerobic cellular resp
- - occurs in the presence of O2 and involves complete oxidation of glucose.
- - Involves 4 stage
- 1 ) glycolysis
- 2) pyruvate oxidation
- 3) Kreb's cycle
- 4 ) electron transport chain and chemosmosis
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Anaerobic cell resp in detail
- - occurs in the presence without O2 and the glucose is not fully oxidized
- -2 types of anaerobic resp that both occur in the cytoplasm of cells .
- - Type 1 produces ethanol, which is found in plants and has co2 as a product.
- - type 2 is found in animals, and produces lactic acid, no carbon dioxide and atp as a product
- stage 1 = glycolysis
- stage 2 = fermentation
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glycolysis in detail ( stage 1 ) ( technically an anaerobic process but occurs in both forms of resp)
- - Converts a 6-carbon molecule ( glucose ) into 2 pyruvates with 2 - 3 carbon molecules.
- - This process requires 2 ATP molecules as the reactants and then produces 4 atp molecules and 2 Nadh+ are produced
- - occurs in both aerobic and anaerobic ( 1st stage for both) However, aerobic produces more atp molecules (36) vs anaerobic only produces 2 atp molecules
- - occurs in the cytoplasm.
- - 10 reactions, which are all catalyzed by an enzyme.
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reactants and products for glycolysis
- reactants = glucose, 2 nad+, 2 Atp , 4 adp
- products = 2 pyruvate,2 nadh ions, 4 atp and 2 adp
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why is glycolysis not efficient?
- -This is because it only transfers 2.2% of the available energy in glucose to atp
- -most energy remains in the 2 pyruvate and 2 NADH
- some unicellular organisms use glycolysis for energy
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where does aerobic resp take place?
- - it occurs in the mitochondria. Specifically eukaryotic cells in that space specialize in ATP production.
- - consists of 2 membranes, the semipermeable outer and the highly folded inner membrane, where the cellular resp takes place.
- - end products = co2 , water , atp
- - Furthermore, the inner membrane creates 2 components within the mitochondria. The mitochondrial matrix, which is a protein rich liquid that feels the innermost space of the mitochondria.
- - As well as the " Fluid", that fills the intermembrane space
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stage 2 ( pyruvate oxidation)( summary)
- -connects glycolysis in the cytoplasm to the Krebs cycle in the mitochondrial matrix.
- -2 pyruvate molecules are transported through to outer mitochondrial membrane into the matrix.
- 3 steps summary
- 1 carbon is removed from the pyruvate molecules, then acetic acid forms, then co enzyme a attaches to acetic acid-forming acetyl co a
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pyruvate oxidation in detail
- - an enzyme known as pyruvate decarboxylase is used to remove 1 carbon from each pyruvate and is released/ breathed out as co2.
- - step 2 = The remaining 2 carbon portions are oxidized by NAD+➡️ then each gaining 2 hydrogen from the pyruvate. ( 2 electrons and 2 protons) ( these 2 NADH move to stage 4 of aerobic resp)
- - step 3 = The remaining 2 pyruvates become acetic acid ( because they are only 2 carbons left on each). Then the the Coenyme A attaches to each of the acetic acid becoming Acetyl Co-A
- - then is transported to the next stage of aerobic cell resp
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the Krebs cycle
- - also known as the Citric acid cycle as well as happens in the mitochondrial matrix.
- - occurs 2 times for every acetyl co-A
- - it is a cyclic reaction because one of the products comes back as the reactant
- - Basically 1 acetyl co-A attaches to oxaloacetate (4-carbon molecule ) to form a 6-carbon molecule known as citric acid.
- - Then basically at the e beginning of the cycle , 2 nad+ gain electrons from the citric acid. And in the process two carbon molecules are breathed out as carbon dioxide. However, we are now left with a 4 carbon complex that transfers its elections to adp to make atp, fad to fadh2 and 1 more nad+ to make nadh
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products of the Krebs cycle
- - 3 NAD+ are reduced to from 3 NADH
- - 1 adp + p is reduced to form 1 atp molecule
- - 1 FAD is reduced to form 1 FADH2
- - 2 carbons are released as carbon - dioxide
- - happens twice for each acetyl co- a molecule
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stage 4 electron transportation chain and chemosmosis
- - 1 NADH gives up 2 electrons at the beginning of the etc to turn on the pumps to allow for the hydrogen molecules in the matrix to move to the intermembrane space as they pass through the protein complexes to create a higher concentration of hydrogens in the intermembrane space.
- - As well as FADH2 gives its electrons to the second protein complex ( or any other complex but not the first) to allow the hydrogens to move from the matrix to the intermembrane space.
- - As the electrons reach the last protein in the etc, they are accepted by oxygen( final electron acceptor ) and then form water which we breathe out.
- - Then with the high amount of hydrogen in the intermembrane space ( more positive), an electrochemical gradient is made. So, the hydrogens in the intermembrane space go through to the atp synthase complex and help in the construction of atp and p, to make ATP in the matrix. ( through diffusion because we are moving from a higher concentration to a lower concentration)
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difference between NADH and FADH2
- - NADH gives up 2 electrons at the beginning of the etc and pumps enough hydrogen ions to make 1-3 ATP
- - FADH2 gives up its electrons later in the etc so pumping less hydrogen ions and ends up generating 1-2 ATPS
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review of the etc
- etc is followed by chemiosmosis and the last stage of oxidative phosphorylation
- -begins with the reduction of fad and nad+ atoms from glucose
- -dependent on hydrogen reservoir and continuous movement throughout the etc
- - dependant on oxygen availability as the final electron acceptor.
- - atp is transported through both mitochondrial membranes into the cytoplasm
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energy tally ( most important)
- step 1 glycolysis: 2 NADH , 0 FADH2 , 2 ATP ARE PRODUCED
- step 2 pyruvate oxditaion; 2 NADH , 0 FADH2 , 0 ATP IS MADE
- step 3 : Krebs cycle ; 6 NADH, 2 FADH2 , 2 ATP IS MADE
- step 4 ; ETC/ CHEMI ; 0 NADH, 0 FAHD, 32 ATP IS MADE
- in conclusion, we have at least we have 36 atp being made on average
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theoretical and actual yield for ATP
- - theo = 36 ATP per glucose cell
- - actual = 30 ATP per glucose cell because glycolysis is 2.2 % efficient but aerobic respiration is 32% efficient which is till good
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Anaerobic cell resp
- glycolysis is step 1 , as well as the conversion of NAD+ to NADH is crucial otherwise glycolysis will stop
- - anaerobic organisms transfer H atoms to organic molecules instead of the ETC which is used by aerobic resp
- - fermentation
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fermentation
- 2 types = alcohol fermentations occurs in plants , lactic acid fermentation that occurs in animals
- similarities
- - both occur in 2 stages
- both occur in the cytoplasm
- both require glycolysis as its first step
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alcohol fermentation
- - so basically when glycolysis takes place, it creates NADHS that pass these hydrogen atoms to 2 acetaldehyde ( electron acceptor) which is formed when 2 co2 are removed from the 2 pyruvate. With the help of the enzyme known as pyruvate decarboxylase and then forms 2 ethanol ( alcohol)
- - carried out by yeast cells, breads cuz rise cuz of the release of c02 .
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lactic acid fermentation
- - NADH produced during glycolysis transfers the hydrogen atoms to pyruvate in the cytoplasm allowing for the NAD+ to be regenerated to create lactic acid.
- glucose + 2 ADP + 2 Pi ➡️ lactic acid and 2 ATP
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intermediate products of cell resp
- NADH, fahd2, ATP
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