Cellular respiration is the process by which organisms convert glucose into energy in the form of ATP. It occurs in four main stages: glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain. Glycolysis breaks down glucose into pyruvate, producing a small amount of ATP. Pyruvate then enters the mitochondria where it is further oxidized, producing NADH and FADH2. These enter the Krebs cycle to produce more NADH and FADH2. Finally, the electron transport chain uses the energy from NADH and FADH2 to pump protons across a membrane, building an electrochemical gradient used to produce a large amount of ATP through oxidative

1. Cellular Respiration

2. Cellular Respiration Overview Transformation of chemical energy in food into chemical energy cells can use: ATP These reactions proceed the same way in plants and animals. Process is called cellular respiration Overall Reaction: C 6 H 12 O 6 + 6O 2 -> 6CO 2 + 6H 2 O

3. Cellular Respiration Terms Photoautotrophs – change light energy into chemical energy stored in bonds of glucose and polysaccharides (green plants, cyanobacteria) Heterotrophs – feed on other organisms for chemical energy Chemoautotrophs – microorganisms that can obtain energy from inorganic sources (Fe or S compounds in volcanoes, deep sea vents…)

4. Glucose – primary source of energy for most organisms Cellular respiration – process by which glucose is broken down and energy stored in bonds is released, can be aerobic or anaerobic Aerobic – oxygen used as an oxidizing agent (electron acceptor) Anaerobic – uses a molecule other than oxygen as an oxidizing agent

5. Cellular Respiration Overview Purpose of Cellular Respiration: Trap free energy in form of ATP Move H + electrons from glucose to oxygen creating 6 H 2 O Break bonds between 6C atoms in glucose creating 6 CO 2

6. Formation of ATP 2 Ways ATP is formed: Substrate-level Phosphorylation ATP formed directly in enzyme catalyzed reaction P containing compound transfers P gp to ADP making ATP 4 ATP created this way from 1 molecule glucose

7. 2.Oxidative Phosphorylation ATP formed indirectly in more complex process co-enzyme NAD + (nicotinamide adenine dinucleotide) removes 2 H + atoms and is reduced to NADH + + H + another co-enzyme, FAD (flavin adenine dinucleotide) also reduced by 2 H + to become FADH 2 these co-enzymes act as mobile energy carriers in cell, moving energy from one stage of cellular respiration to another where its used to create ATP

8. 4 Stages of Cellular Respiration multi-step process in mitochondrial membrane Electron Transport Chain Stage 4 8 step cycle in mitochondria Kreb’s Cycle Stage 3 1 step process in mitochondria Pyruvate Oxidation Stage 2 10 step process in cytoplasm Glycolysis Stage 1 Details Name

9. 1. Glycolysis Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate Process is an ancient one- all organisms from simple bacteria to humans perform it the same way Yields 2 ATP molecules for every one glucose molecule broken down (creates 4 ATP but uses 2) Yields 2 NADH per glucose molecule (used later to create more ATP) cellResp_main

10. 4 Parts to Glycolysis Glucose activation 2 molecules ATP transfer P to glucose results in 2 ADP and F1,6 BP (fructose 1,6 biphosphate)

11. Sugar Splitting F1,6 BP splits into 1 G3P (glyceraldehyde 3-phosphate) and 1 DHAP (dihydroxyacetone) DHAP is then immediately converted into G3P by enzyme isomearase (result is 2 G3P)

12. 3. Oxidation both G3P are oxidized by NAD resulting in 2 NADH. this releases energy and 2 ATP produced by substrate level phosphorylation. result is 2 molecules of 1,3 BPG (biphosphoglycerate)

13. 4. ATP Formation phosphate gps of BPG are transferred to 2 ADP creating 2 ATP by substrate level phosphorylation end result is 2 molecules pyruvate

14. Glucose + 2 ADP + 2 P i + 2 NAD + 2 pyruvate + 2 ATP + 2 NADH

15. Aerobic or Anaerobic Respiration? After glycolysis, life diverges into two forms and two pathways if O 2 is present, pyruvate from glycolysis moves from cytoplasm into mitochondria to start aerobic cellular respiration if no O 2 is present, pyruvate enters anaerobic cellular respiration (aka fermentation)

16. Aerobic Cellular Respiration Oxygen required=aerobic 3 more sets of reactions which occur in the mitochondria Pyruvate Oxidation Kreb’s Cycle Electron Transport Chain

17. 2. Pyruvate Oxidation 3 step reaction: carboxyl gp removed as CO 2 remaining 2 carbon group is oxidized by NAD + , forming NADH and becomes acetate co-enzyme A attaches to acetate, forming acetyl-coenzyme A

18. cellResp_main acetyl-co A formed by catabolism of carbs, proteins, and lipids in eukaryotes if ATP levels are high, acetyl-co A will be directed into synthesis of fatty acids for long term energy storage if ATP needed, acetyl-co A is directed to next part of cellular respiration: Kreb’s Cycle

19. Kreb’s Cycle (Citric Acid Cycle) Completes the breakdown of glucose Occurs in matrix of mitochandria 8 step process, each step catalyzed by a specific enzyme Product of 8 th reaction (oxaloacetate) is a reactant in the 1 st reaction (cycle) Takes the pyruvate (3-carbons) and breaks it down, all 6 carbon and oxygen atoms end up in CO 2 and H 2 O

20. Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce 6 NADH and 2 FADH 2 which are transported to the final step Production of only 2 more ATP (substrate level phosphorylation) cellResp_main

23. Electron Transport Chain NADH & FADH 2 loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase). made of 4 lg protein molecules and 2 smaller mobile protein carriers proteins are arranged in order of electronegativity, so each one will be reduced (gain 2e - ) then immediately oxidized (lose 2e - ) as electrons drop down stairs, energy released to form a total of 32 ATP oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water cellResp_main

24. Steps of ETC NADH gives 2e - to NADH dehydrogenase , first protein in ETC. Electrons (e - ) pass through the ETC, releasing energy. Energy is used to pump H + ions across membrane into intermembrane space. Build up of H + ions in the space creates an electrochemical gradient. H + ions want to diffuse back across membrane but are unable to and must use special protein channels called ATPase complex (facilitated diffusion). Pores in the protein channels contain an ATP-synthesizing enzyme called ATP synthase . So as the H + ions move through the channels, Pi (inorganic phosphate) is joined to ADP to create ATP.

25. Every e - NADH drops off will pump 3 H + ions across the membrane, therefore producing 3 ATP. FADH 2 skips the first protein and drops its e- off further down chain so only 2 H + ions are pumped across, therefore producing only 2 ATP. When e- from NADH and FADH2 reach last protein in chain called cytochrome oxidase, they have lost energy. Once cytochrome oxidase has 4e - , it gets oxidized by O 2 (high electronegativity). O 2 takes the e - and combines them with four H + ions from the matrix to produce 2 H 2 O molecules. VCAC: Cellular Processes: Electron Transport Chain: The Movie

27. Energy Tally 36 ATP for aerobic vs. 2 ATP for anaerobic Glycolysis 2 ATP Kreb’s 2 ATP Electron Transport 32 ATP 36 ATP Anaerobic organisms can’t be too energetic but are important for global recycling of carbon

31. Other Catabolic Pathways Carbohydrates broken into monosaccharide, then broken down for energy avg. yield of 16 kJ/g of energy Proteins broken down into amino acids to be used to produce cell’s proteins amino groups removed in deamination and converted into ammonia (wastes) rest of a.a. continue through glycolysis or Kreb’s cycle

32. Lipids triglycerides broken into glycerol and fatty acids glycerol broken down into glucose or G3P and goes through glycolysis fatty acids go into matrix of mitochandria and undergo oxidation – get converted in acetyl groups which combine with co-enzyme A to produce acteyl-coA (used in Kreb’s cycle) much more ATP formed than from carbs. ex lauric acid (12 C fatty acid) – produces 92 ATP avg yield is 38kJ/g of energy

33. Anaerobic Cellular Respiration Some organisms thrive in environments with little or no oxygen Marshes, bogs, gut of animals, sewage treatment ponds No oxygen used= ‘an’aerobic Results in no more ATP if no O 2 available to ETC it stops and NADH can’t drop off H + ions free NAD+ can’t return to pick up more electrons and hydrogens in glycolysis, causing it to stop

34. organisms have alternative methods to get energy ex. NADH can drop off H + ions to certain organic molecules instead of ETC (fermentation) End products such as ethanol and CO 2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

35. Photosynthesis

37. Photosynthesis Method of converting sun energy into chemical energy usable by cells done by autotrophs takes place in specialized structures inside plant cells called chloroplasts

38. Capturing light energy Using captured energy to make ATP and NADP + (energy carrying co-enzyme like NAD. It is reduced by 2 H atoms to NADPH + + H + ) Using ATP and energy from NADPH to synthesize molecules like glucose. first 2 steps require sunlight (light dependant) and occur in chlorophyll last step does not necessarily need sunlight (light independent) and takes place in stroma 3 Steps of Photosynthesis

40. Light-Dependent Phases occurs in thylakoid membrane light energy converted to chemical energy of ATP & NADPH (reduced NADP = NADPH) photosystems (highly organized light capturing complexes) are found in thylakoid membranes and made of 2 parts: antenna complex – system of chlorophyll molecules and pigments that transfers energy to reaction centre reaction centre – protein complex containing chlorophyll a that absorbs energy from antenna complex and raises it to high energy level to start photosynthesis

41. there are 2 kinds of photosytems (I and II) depending on which wavelength of light chlorophyll a absorbs

42. Steps in Light Dependent Reactions Photoexcitation: Sunlight hits leaf and some energy passes into stroma then absorbed by antenna complex of photosystem II and passed along to chlorophyll a . Electron Transport: An electon gets boosted to a higher level and passed along a ETC (like in cellular respiration) in thylakloid membrane. This energy boost also causes H 2 O to split which releases H + ions and O 2 which is vital to other living things.

43. e- passes through several carriers via redox reactions releasing energy as they pass through the proteins. H + ions are pumped from stroma into intermembrane space which creates electrochemical gradient. Chemiosmosis: H + ions move through ATPase complex back into stroma converting ADP to ATP a process called photophosphorylation . It takes 4 H + to make 1 ATP. At same time light of a different wavelength is also striking photosystem 1. e - from P1 pass through another ETC, then move to enzyme NADP reductase that reduces NADP to NADPH which moves to Light Independent Phase .

44. Reactants: H 2 O, sunlight Products: ½ O 2 , NADPH, ATP YouTube - Light (Dependant) Reactions of Photosynthesis Animation

47. 2. Light Independent Reactions (the Calvin Cycle) ATP and NADPH generated in light reactions used to fuel the reactions which take CO 2 and break it apart, then reassemble the carbons into glucose. called carbon fixation : taking carbon from an inorganic molecule (atmospheric CO 2 ) and making an organic molecule out of it (glucose) occur in stroma don’t require light also known as C 3 Cycle

49. Steps in Light Independent Phase: Carbon Fixation CO 2 molecule combines with 5C molecule called RuBisCO (ribulose biphosphate) to produce 2, 3C molecules called 3-PGA (3-phosphoglycerate). 2. Reduction Reactions 3-PGA phorphorylated by ATP then reduced by NADPH to produce G3P (glycerate 3-phosphate). 3. RuBisCO Regeneration G3P phosphorylated by ATP to re-create RuBisCO to restart the cycle. For every 2 G3P, 1 molecule glucose is removed from cycle, so need 6 CO 2 to create 1 glucose.

51. Other Methods of Carbon Fixation Succulents, cacti, orchids, pineapple… Water efficiency night CAM Corn, sugar cane, grasses… Faster photosynthesis day C 4 Most plants Uses fewer ATP day C 3 Examples Advantages Stomata open Type of carbon fixation