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Cell respiration (2)
Bio 2 Lecture 9
| Question | Answer |
|---|---|
| Recall what are the end-products of glycolysis | 2 NADH, 2 ATP and 2 molecules of pyruvate for EACH GLUCOSE |
| Cellular respiration produces ATP from glucose using 5 stages (pathways :), what are they? | 1)Glycolysis 2)Pyruvate oxidation 3)Krebs cycle 4)Electron transport chain 5)Chemiosmosis |
| Where does pathway 2 occur? How does it occur? | Pathway 2 is pyruvate oxidation and it happens in mitochondrial matrix. In the presence of oxygen, pyruvate enters the mitochondrion to be oxidized |
| Identify on a mitochondria image the location of the pyruvate oxidation pathway | slide 5, in the matrix (inner compartiment) |
| What happens in pyruvate oxidation? | 3C pyruvate becomes 2C acetyal CoA. |
| In pyruvate oxidation, what is produced? | For every pyruvate produced, here's what is made: 1 NADH, 1 CO2 and 1 Acetyl CoA. Recall 2 pyruvates are produced from glycolysis, so 2 NADH, 2 CO2 and 2 acetyl CoA are producer per one glucose |
| What is the first carbon atom to be released from the OG glucose? | The carbon from CO2 in pyruvate oxidation |
| What happens to each product from ONE pyruvate oxidation? | The 1 CO2 is given off as wate, the 1 NADH donates electrons to ETC and the 1 acetyl CoA will be oxidized by Krebs cycle to make more NADH and FADH2. |
| What links glycolysis and the reactions of the citric acid cycle? | Acetyl-CoA is the molecules that links them |
| How many pyruvates are oxidized? | We know glycolysis produces 2 pyruvates, so pyruvate oxidation happens 2 times, which means the products are doubled. SOO there's 2 pyruvate oxidations PER glucose :D Bc glycolysis initial has 1 glucose, 2 pyruvates produced... Logic |
| Where does pathway 3 occurs? What happens? | The krebs cycle happens in matrix of mitochondria. The acetyl will be completely oxidized resulting in the production of 2 CO2. |
| Where does the krebs cycle harvest energy from? | harvest energy as NADH and FADH2 |
| Where dod acetyl carbons originate from? | from glucose |
| How many Avetyl-CoA are made per glucose? | 2 CoA per glucose |
| What are the 3 steps (segments) of the krebs cycle? | 1)Reduction 2)Oxidation 3)Regeneration |
| What happens in the reduction segment of the krebs cycle? | The Acetyl-CoA (2 carbons enter cycle) binds to OXALOACETATE (4 carbon) to join the cycle in a reduction step releasing CoA. |
| What happens in the oxidation segment of the krebs cycle? | The 6 carbon intermediate is oxidized to a 4 C molecule, releasing 2-CO2 and moving the captured energy to 2 NADH and 1 ATP. |
| What happens in the regeneration segment of the krebs cycle? | Regeneration of the 4 C molecule to oxaloacetate produces 1 FADH2 and 1 NADH |
| What does the citric acid cycle release? | Per Acetyl-CoA, here's what's released: CoA recycled back to pyruvate ocidation, 3 NADH go to ETC, 1 FADH2 go to ETC, 1 ATP used by cell and 2 CO2 released to environment. Recall 2 acetyl-CoA made per glucose |
| By the end of the Krebs cycle, how many CO2 has been given off as waste? | Glucose has been completely oxidized to 6 CO2 (given off as waste) |
| By the end of the Krebs cycle, what energy has been harvested? | 4 ATP net , 10 NADH and 2 FADH2 |
| Where does the NADH and FADH2 produced by krebs go? | The 10 NADH and the 2 FADH2 go to electron transport chain to make more ATP. |
| Explain where the 4 ATP, 10 NADH and 2 FADH2 come from | 1)4 ATP: 2 glycolysis, 2 from two turns of krebs cycle 2)10 NADH: 2 glycolysis, 2 from 2 pyruvate oxidations, 6 from 2 krebs cycles 3)2 FADH2: 2 from krebs cycle which turns once per acetyl-CoA or twice per glucose. |
| Where does the pathway 4 happen? | Electron Transport Chain (ETC) occurs in cristae membrane |
| What is the electron transport chain (ETC)? | It's a series of membrane-bound electron carriers in the cristae membrane. |
| What does the electron transport chain accepts, needs and contains? | Accepts electrons from NADH and FADH2 (recall from krebs). Needs O2 as the final electron acceptor. Contains H-ion pumps (moves ions to inner membrane space) |
| Recall what is the proton motor force (PMF) | PMF is the proton motor force generated by the electrical gradient resulting from high protons (H+) in the intermembrane space. |
| What are the steps in the electron transport chain? | 1)Electrons donated to ETC from electron carriers (N and F) 2)H-ions are pumped into intermembrane space for chemiosmosis 3)Electrons fall down energy staircase, releasing energy at each step and reducing O2 to H2O 4)O2 captures electrons and forms H2O |
| As the electrons are transferred between carriers, what is the released energy used for? | As the electrons are transferred between carriers, released energy is used to pump protons (H + ) across the membrane from the matrix to the intermembrane space |
| Explain what is the 5th pathway *seen in previous SS* | Chemiosmosis; The accumulation of protons in the intermembrane space creates a gradient that drives protons through ATP-synthase into the matrix via diffusion. ATP-synthase generates ATP |
| What is the term when pathway 4 and 5 are considered as one pathway? | Electron transport chain and chemiosmosis together is oxidative phosphorylation :D |
| What is the final electron acceptor in ETC? | It's oxygen (O2) (it removes electrons) |
| How are most protons diffuse into the matrix? | Through ATP synthase |
| Why not all H+ is used to make ATP?! | Bc the inner membrane is inneficient: it's a leaky membrane :_( |
| Is cristae disappointing and leaky as well? | yeah. Cristae contains other protein pores which allows some H+ to leak |
| What is the theoretical energy yields per glucose for bacteria and eukaryotes? | 38 ATP per glucose for bacteria and 36 ATP per glucose for eukaryotes |
| What is the actual energy yields per glucose for eukaryotes? | 30 ATP per glucose for eukaryotes |
| Why is the actual energy yield lower than the theoretical for eukaryotes? | 1)Bc of the leaky inner membrane and use of the proton gradient for purposes other than ATP synthesis 2)Energy is needed to transport pyruvate into organelle |
| In summary, where does glycolysis, pyruvate oxidation happen, krebs, ETC and chemiosmosis happen? | 1)Glycolysis: cytoplasm 2)Pyruvate oxidation: mitochondrial matrix 3)Krebs: matrix 4)ETC: within matrix 5)Chemiosmosis: in cristae |
| In summary, what happens in glycolysis and pyruvate oxidation? | Glycolysis: Glucose (6C)--» 2 pyruvates (3C) Pyruvate oxidation: Pyruvate--»Acetyl-CoA + CO2 getting ready to join the krebs cycle (3C cut to 2C in the mitochondrial matrix) |
| In summary, what happens in krebs cycle? | (Oxaloacetate+ Acetyl-CoA) + NAD+ + FAD ==» oxaloacetate+ ATP + NADH +FADH2 +CO2. Oxaloacetate is recycled by krebs |
| In summary, what happens in ETC? | NADH +FADH2 + O2 ==» NAD+ + FAD + H2O + H+. Generates hydrogen ion gradient in mitochondrion Oxidized coenzymes are recycled here (keeps glycolysis going) |
| In summary, what happens in chemiosmosis? | ADP + H+ + Pi ==(ATP synthase)==» H+ + ATP |
| How is respiration regulated? | By feedback inhibition |
| What inhibits glycolysis? | Glycolysis is allosterically inhibited by high ATP and by high citrate at phospho-fructokinase in glycolysis |
| What inhibits pyruvate oxidation? | High NADH (from Krebs) inhibits pyruvate oxidation at pyruvate dehydrogenase. |
| Different organic molecules can enter in the metabolic pathways of respiration to make ATP; what other energy source can be used for cellular respiration? | 1)Various carbohydrates 2)Beta-oxidation of neutral fats 3)Deamination of amino acids (last resort) |
| How does the catabolism of protein work? | 1)Amino acid is deaminatedto remove the amino group 2) Remainder is converted to a molecule that enters pyruvate oxidation or the Krebs cycle |
| Give examples of catabolism of protein | 1) Alanine to pyruvate 2) Aspartate to oxaloacetate |
| How does the catabolism of fat work? | 1) Fats are broken down to fatty acids and glycerol 2)Fatty acids are converted to acetyl groups by beta-oxidation entering at Krebs; glycerol can be converted to G3P and enter glycolysis |
| What's the yield of the respiration of a 6-carbon fatty acid compared to glucose in energy? | The respiration of a 6-carbon fatty acid yields 20% more energy than glucose. |
Created by:
Malayka
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