Cellular Respiration PDF

Cellular Respiration Monday, September 11, 2023 9:23 AM CELLULAR METABOLISM: RESPIRATION Glycolysis → A chemical process involving 10 sequential reactions that break down of 1 glucose (6 carbon molecule) into two pyruvate (3 carbon molecule) → Some energy from the broken chemical bond...

Cellular Respiration Monday, September 11, 2023 9:23 AM CELLULAR METABOLISM: RESPIRATION Glycolysis → A chemical process involving 10 sequential reactions that break down of 1 glucose (6 carbon molecule) into two pyruvate (3 carbon molecule) → Some energy from the broken chemical bonds of glucose is used directly to convert ADP into ATP (2 ATP) Picture description: ○ During the process of glycolysis: - 2 NAD+ are turned into 2 NADH - 2 ATP molecules are made Additional Notes on Glycolysis: ◊ Numerous metabolic diseases affect glycolysis ◊ McArdle disease: the absence of the enzyme involved in the first step of converting glycogen to glucose ○ Glycogen stores excess glucose Pyruvate Decarboxylation → Pyruvate enters the mitochondrial matrix and is catalyzed into Acetyl CoA ( a 2 carbon molecule ). THIS STEP REQUIRES OXYGEN Picture description: ○ Pyruvate is turned inro Acetyl CoA (coenzyme A) AS IT ENTERS THE MITOCHONDRIAL MATRIX - CO2 is released from the pyruvate molecule - CoA is added to make Acetyl coA - 1 pyruvate generates 1 CO2 and 1 NADH - At the end of this process 2 NADH's are made Citric Acid Cycle (Tricarboxylic Acid Cycle) → An 8 separate reaction directed by enzymes from the mitochondrial matrix → Two carbon (2C) are sequentially removed from the 6C citrate molecule -> converted back to the 4C oxaloacetate, ready to accept a new Acetyl-CoA → These 2C are converted into 2 molecules of CO2 as well as the one produced during the pyruvate decarboxylation, pass out of the cell -> blood Picture description: ○ The starting enzyme is oxaloacetate ○ oxaloacetate plus Acetyl CoA will make citrate ○ Citrate goes through a 8 series process twice, at the end of the process we get: - 6 NADH and 2 FADH2 - Lose 2 carbons, one each cycle (occurs at the 3-4 step) § The carbons are lost to the NADH's and the FADH2 ○ Only 2 ATP molecules are produced, 1 per cycle ○ This process occurs in the mitochondrial matrix Continuation of slide notes: → The O2 used to form these CO2 molecules is coming from these molecules involved in the cycle, not from the free O2 supplied from breathing → Hydrogen atoms are removed and will be used in the ETC (Electron Transport Chain) → Hydrogen carrier molecules: - Nicotinamide Adenine Dinucleotide (NAD+) -> NADH - Flavine Adenine Dinucleotide (FAD) -> FADH2 → The processing of ACoA releases energy -> linkage of inorganic phosphate to Guanosine diphosphate (GDP -> GTP) Oxidative Phosphorylation: Electron Transport Chain (ETC) → Most of the energy is still stored in H (they contain electrons at high energy levels) → Series of electron carrier molecules on inner membrane of the mitochondria → Electrons extracted from NADH and FADH2 → Most energy produced (ATP) Picture descriptions: ○ This process changes from the matrix (yellow part) to the inner mitochondrial membrane (red part). This includes the intermembrane space ( the space b/w the outer and inner membrane Slide notes: → Ultimately elections are passed to O2. This process is called oxidative phosphorylation b/c of the usage of oxygen to make ATP → NADH and FADH2 are converted back into NAD+ and FAD ○ When its converted back it can now pick up new Hydrogen molecules ○ They represent the link b/w the TCA and ETC → 1 NADH = 2-3 ATP (2.5 ATP average) → 1 FAD = 1-2 ATP (1.5 ATP average) Slide notes: → The high-energy electrons fall to successively lower energy levels as they are transferred from carrier to carrier through the ETC → As electrons move through the electron transport system, they release free energy. Part of the released energy is harnessed to transport H+ from matrix into the intermembrane space at Complexes I, II, III, and IV → As a result, H+ ions are more heavily concentrated in the intermembrane space than in the matrix. This H+ gradient supplies the energy that drives ATP synthesis by ATP synthase Picture description: ○ The green blobs are called complexes bc it's made up of multiple proteins ○ NADH and FADH2 give their H to complex 1 and 2 ○ The H molecules come into the intermembrane space and travel against their will into the ATP synthase and results in ATP - H+ powers the ATP synthase ○ When there are too many electrons in the chain, oxygen takes the last one for the process to continue - Oxygen becomes water at some point ○ ATP is the currency paid by hydrogen ions in order for them to return to the mitochondrion matrix CELLULAR METABOLISM → Cellular respiration under AEROBIC conditions Picture Description: → The total amount of ATP generated from 1 glucose molecule is 32 ○ 2 from glycolysis ○ 2 from the TCA cycle / citric acid cycle ○ 3 from FADH2 § 2 FADH from the entire process, multiplies by 1.5 = 3 ○ 25 from NADH - 2 NADH from glycolysis - 2 NADH from pyruvate decarboxylation - 6 NADH from TAC - In total that's 10 x 2.5 = 25 → 32 is an average number, you can result in less or more → Cellular respiration under ANAEROBIC conditions → if oxygen is limited or unavailable, pyruvate is not converted unto Acetyl CoA but into Lactate instead → Degradation of glucose does not proceed beyond glycolysis → But much more energy produced by aerobic pathways → Fatty acids and protein (if necessary) can also be a source of ATP production ○ Enters at the Acetyl CoA step Picture Description: ○ Regenerated NADH that was made can't go to the ETC b/c that isn’t an option due to the absence of oxygen ○ Glycolysis requires NAD+ to become into NADH ○ The reaction for pyruvate to become lactic acid needs NADH - You spend 1 NADH per reaction - The NADH made in glycolysis is reused to turn pyruvate into lactic acid ○ The anaerobic condition generates 2 ATP Additional notes: ◊ When you run a lot and don't have enough oxygen, they start generating ATP which causes a build up of lactic acid ◊ The issue with too much lactic acid is: ○ The muscle is trying to get rid of it but isn't doing it fast enough so the build up of the lactic acid causes the muscle to stop working b/c it can't function anymore, it's toxic