Respiration, types, glycolysis, kreb cycle

Respiration, types aerobic, anaerobic, glycolysis, citric acid cycle

1. RESPIRATION It is an intracellular oxidation process in which complex organic substances are broken down into simpler substances with stepwise release of energy. Oxidative, energy - releasing, universal in life Respiration, with its associated carbon metabolism, releases the energy stored in carbon compounds in a controlled manner for cellular use. Respiration Aerobic respiration Anaerobic respiration

2. Overview of respiration. Substrates for respiration are generated by other cellular processes and enter the respiratory pathways.

3. Respiratory Substrate  – carbohydrate, fats, proteins

4.                                                            Aerobic Respiration                                                      Anaerobic Respiration It takes place in the presence of oxygen It takes place in the absence of oxygen Aerobic respiration require oxygen and takes place in cytoplasm and mitochondria Anaerobic respiration does not require oxygen and takes place in cytoplasm only Substrate is completely oxidized Substrate is incompletely oxidized The oxidation of one molecules of glucose produce 38 ATP molecule The number of ATP produced is only 2 The end product are CO2 and H2O The end product are lactic acid or alcohol and CO2 Found in all plant and Higher animals Usually found in Microorganism Non toxic to plants. Toxic to higher plants

5. In Prokaryotes In Eukaryotes Glycolysis Cytosol Cytosol Citric acid cycle Cytosol Mitochondrial Matrix Oxidative Phosphorylation PM (Mesosome ) Inner mitochondrial membrane Aerobic Respiration

6. Respiratory Quotient Respiratory quotient is the measure of moles CO 2  evolved to moles O 2  absorbed in plant cells The  respiratory quotient   (RQ) is often used to estimate metabolic  stoichiometry . R atio of CO2 release to O2 consumption, which is called the respiratory quotient, or RQ, varies with the substrate oxidized respiratory quotient   (RQ) = volume of CO2 released/ volume of O2 consumed Lipids, sugars, and organic acids represent a series of rising RQ because lipids contain little oxygen per carbon, and organic acids Alcoholic fermentation releases CO2 without consuming O2, so a high RQ is also a marker for fermentation

7. " A molecule of glucose (respiratory substrate) is degraded in a series of enzyme catalyzed reactions to yield two molecules of the three-carbon compound pyruvate" Glycolysis : " glykys " ( sweet) + "lysis" (splitting) GLYCOLYSIS Glycolysis occurs in all living organisms (prokaryotes and eukaryotes). The principal reactions associated with the classic glycolytic pathway in plants are almost identical to those in animal cells Embden- Meyerhof- Parnas pathway Fundamental energy generating pathway; Universal, oxidative pathway ; Involve partial oxidation Occur in both presence or absence of Oxygen It involves both reversible and irreversible steps Glycolysis is a ten step enzyme catalyzed reactions ; Site: Cytosol (PK/EK)

8. Major pathway of glucose utilization Although not the only possible fates for glucose, these four pathways are the most significant in terms of the amount of glucose that flows through them in most cells

9. Involves oxidation at one step Involves substrate level phosphorylation – 2 step ( direct ATP production ) No – decarboxylation 2 moles of ATP is consumed 2 moles of ATP is produced Involves synthesis of 2 mol of NADH Pay off phase  – 5 step;  Glyceraldehyde 3- P                Pyruvate           Preparatory phase  -  5 step;  Glucose               Glyceraldehyde 3- P GLYCOLYSIS

10. Preparatory Phase First priming reaction Second priming reaction Cleavage of 6-carbon sugar phosphate to two 3- carbon sugar phosphates Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Glyceraldehyde 3-phosphate Dihydroxyacetone phosphate Hexokinase Phosphohexose isomerase Phosphofructokinase -1 Aldolase Triose phosphate isomerase ATP ATP ADP ADP 1 2 3 4 5

11. (2) Glyceraldehyde 3-phosphate (2) 1,3-Bisphosphoglycerate (2) 3-Phosphoglycerate (2) 2-Phosphoglycerate (2) Phosphoenolpyruvate Glyceraldehyde 3-Phosphate dehydrogenase Phosphoglycerate Kinase Phosphoglycerate mutase Enolase (2)ATP (2)ADP 6 7 8 9 (2) Pyruvate 10 (2)ADP (2)ATP Pyruvate kinase (2)  H 2 O (2)NADH (2) NAD + Payoff Phase Oxidation and phosphorylation Substrate level phosphorylation Substrate level phosphorylation

12. Citric Acid Cycle Citric acid cycle—also called the tricarboxylic acid cycle or Krebs cycle . This cycle constitutes the second stage in respiration and takes place in the mitochondrial matrix Pyruvate generated in the cytosol during glycolysis be transported through the impermeable inner mitochondrial membrane via a specific transport protein Once inside the mitochondrial matrix, pyruvate is decarboxylated in an oxidation reaction catalyzed by pyruvate dehydrogenase Pyruvate dehydrogenase, a large complex consisting of several enzymes The products are NADH, CO2, and acetyl-CoA, in which the acetyl group derived from pyruvate is linked by a thioester bond to a cofactor, coenzyme A (CoA)

13. Pyruvate Dehydrogenase (E1) – Decarboxylation & Oxidation of Pyruvate Dihydrolipoyl Transacetylase (E2) – Catalyzes transfer of acetyl group to Co A Dihydrolipoyl Dehydrogenase (E3)- Reoxidize Dihydroliopamide Pyruvate Dehydrogenase Complex- Multienzyme Oxidation of Pyruvate to Acetyl CoA – Thiamine Pyrophosphate(TPP), Lipoic acid, CoA , FAD, NAD+

14. Factors affecting Respiration OXYGEN – Oxygen can affect plant respiration because of its role as a substrate in the overall respiratory process . Respiration rates decrease if the atmospheric oxygen concentration is below 5% for whole organs or below 2 to 3% for tissue slices. These findings show that oxygen supply can impose a limitation on plant respiration. environmental factors can alter the operation of metabolic pathways and change respiratory rates. TEMPERATURE – Respiration operates over a wide temperature range. It typically increases with temperatures between 0 and 30°C and reaches a plateau at 40 to 50°C. At higher temperatures, it again decreases because of inactivation of the respiratory machinery. The increase in respiration rate for every 10°C increase in temperature is commonly called the temperature coefficient, Q10 . This coefficient describes how respiration responds to short-term temperature changes, and it varies with plant development and external factors Potatoes are best stored at 7 to 9°C, which prevents the breakdown of starch while minimizing respiration and germination

15. Factors affecting Respiration CARBON DIOXIDE – Carbon dioxide has a limited direct inhibitory effect on respiration at the artificially high concentration of 3 to 5%. It is common practice in commercial storage of fruits to take advantage of the effects of oxygen concentration and temperature on respiration by storing fruits at low temperatures under 2 to 3% O2 and 3 to 5% CO2 concentrations.

16. Fermentation Oxidative phosphorylation does not function in the absence of oxygen . Glycolysis then cannot continue because the cell’s supply of NAD+ is limited and once the NAD+ becomes tied up in the reduced state (NADH), the glyceraldehyde-3-phosphate dehydrogenase comes to a halt. To overcome this limitation, plants and other organisms can further metabolize pyruvate by carrying out one or more forms of fermentation Alcoholic fermentation lactic acid fermentation Pyruvate decarboxylase and alcohol dehydrogenase , act on pyruvate, ultimately producing ethanol and CO2 and oxidizing NADH in the process. Common in plants, although more widely known from brewer’s yeast, The enzyme lactate dehydrogenase uses NADH to reduce pyruvate to lactate, thus regenerating NAD+ Common in mammalian muscle, but also found in plants,

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