Glycolysis. Goal: use 6 carbon compounds to produce

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1 Goal: use 6 carbon compounds to produce Remember 1 st law of thermodynamics: Matter (energy) can be Energy in C-C bonds of glucose is transferred Specifically: The break down of into Glycolysis Energy Production: - ATP - ATP - ATP Oxidative process accompanied by the reduction of NAD separate enzymatic reactions to produce pyruvate from glucose - we will study each reaction in detail. - you must know: - each enzyme, name & order - order and structure of each metabolite What is fate of Pyruvate? 1

2 Fate of pyruvate: Aerobic (presence of O 2 ) - citric acid cycle breaks down pyruvate - reduces - next lecture series Anaerobic (lack of O 2 ) 1. Fermentation: loss of CO 2 and 2. Anaerobic glycolysis: reduction of pyruvate to lactate - this lecture series 2

3 History Louis Pasteur French Scientist - Inventor of pasteurization: heating of liquids to kill harmful organisms - sponsored by French wine industry to study fermentation - determined in 1860 that glucose supplied more energy in presence of O 2 3

4 History a.k.a.: Embden - Meyerhof Pathway Otto Fritz Meyerhof German born biochemist - University of Kiel - between 1912 and 1918 determined the intermediates of glycolysis - awarded Nobel prize in physiology or medicine, 1922 Gustav Georg Embden German born biochemist - Worked out precise steps involved in the breakdown of glucose - Not included on Nobel prize 4

5 Two phases or parts to glycolysis (10 steps between both phases) Phase 1: - 2 phosphorylating glucose twice. of - forms fructose 1,6,-bisphosphate - split into two molecules of glyceraldehyde-3-phosphate - Phase 2: - conversion of glyceraldehyde-3-phosphate to - coupled formation - 5

6 Structure of Sugars, Chapter 16 a.k.a. carbohydrates, saccharides, sugars: simple organic compounds that are - Can range in carbon number from 3 (simplest) to 4, 5, 6, and 7 (most complex) Simplest 3 carbon sugars - Exist as an aldehyde or ketone 6

7 Structure of Sugars, Chapter 16 Sugars have used in glycolysis 7

8 Structure of Sugars, Chapter 16 Numbering of carbons in sugars is based on. - the most oxidized In ketone sugars the 8

9 Structure of Sugars, Chapter 16 5 or 6 carbon sugars normally exist The free electrons on OH of C-5 bond with forming cyclic structure Cyclic structure is similar to pyran: a six member ring with 5 carbons and one oxygen Can produce α and β forms called anomers 9

10 Structure of Sugars, Chapter 16 Different representations of sugar structures Fischer projections - stereochemistry of 3-D molecule Haworth projections - a perspective representation of the Fischer linear cyclized 10

11 Structure of Sugars, Chapter 16 Hermann Emil Fischer Walter Haworth German organic chemist - worked at University of Berlin - determined the structure and stereochemistry of sugars between 1884 and Nobel Prize in Chemistry, British organic chemist - worked at St. Andrews University - worked on structure of polysaccharides starting in Nobel Prize in Chemistry,

12 Phase 1 Step 1 - phosphorylation of glucose producing - reaction carried out by the enzyme - requires - phosphorylation of glucose with out ATP has ΔG = - coupled to ATP hydrolysis to give reaction ΔG = 12

13 Phase 1 Step 1 - Glucose-6-phosphate (G6P) formation Hexokinase Remember : kinase is an enzyme that transfers a phosphate from ATP to substrate Hexokinase undergoes large Glucose becomes almost Glucose not bound Glucose bound This is an example of what kind of enzymesubstrate interaction? 13

14 Phase 1 Step 2 - G6P is isomerized to - reaction carried out by the enzyme - ring structure is broken producing aldehyde at C-1 which is then - C-2 OH is oxidized to give ketone, ring is closed connecting - no net oxidation or reduction 14

15 Phase 1 Step 3 - Fructose-6-phosphate (F6P) is phosphorylated to give - reaction carried out by the enzyme - requires - phosphorylation of F6P with out ATP has ΔG > 0 - coupled to ATP hydrolysis to give reaction ΔG = -3.4 kcal/mole 15

16 Phase 1 Step 3 - Fructose-1,6-bisphosphate formation Phosphofructokinase (PFK) - Both G6P and F6P can be utilized by. Do not have to - Once PFK produces fructose-1,6-bisphosphate it is. It must go - reaction carried out by PFK is not reversible - PFK is key regulatory enzyme in glycolysis pathway 16

17 Phase 1 Step 3 - Fructose-1,6-bisphosphate formation Phosphofructokinase (PFK) ATP is an allosteric regulator of PFK In the presence of low [ATP] In the presence of high [ATP] Reasoning? High cellular [ATP] - no need for - PFK inactivated, Low cellular [ATP] - requirement for - PFK activated, 17

18 Phase 1 Step 4 - Fructose-1,6-bisphosphate is split into two 3-carbon molecules: and - reaction carried out by the enzyme - intermediates no - DHAP and GA3P 18

19 Phase 1 Step 5 - DHAP is converted to - reaction carried out by the enzyme - reaction produces a second - now 6 carbon glucose has been 19

20 Phase 2 - two molecules of each intermediate take part in each reaction Step 6 - GA3P is oxidized to - reaction carried out by the enzyme - involves oxidation of GA3P, NAD + as e - acceptor, and phosphorylation at C-1 - Phosphate comes not from ATP but from inorganic phosphate: 20

21 Phase 2 Step 6 - GA3P is oxidized to 1,3-bisphosphoglycerate Takes place in a two step reaction 1. GA3P is oxidized to 3-phosphoglycerate - aldehyde is oxidized 21

22 Phase 2 Step 6 - GA3P is oxidized to 1,3-bisphosphoglycerate Takes place in a two step reaction 2. 3-phosphoglycerate is phosphorylated by P i This reaction has ΔG, but overall ΔG 22

23 - substrate level phosphorylation- ATP production by the direct transfer of phosphate from intermediate 23 Glycolysis Phase 2 Step 7-1,3-bisphosphoglycerate is dephosphorylated to produce ATP - reaction carried out by the enzyme - two ATP are produced per - thus two ATP used in Phase 1

24 Phase 2 Step 8-3-phosphoglycerate is converted to - reaction carried out by the enzyme - this reaction takes place to set up next reaction 24

25 Phase 2 Step 9-2-phosphoglycerate loses H 2 O to produce - reaction carried out by the enzyme - e - transfer is not involved - requires Mg 2+ which binds H 2 O for elimination 25

26 Phase 2 Step 10 - phosphoenolpyruvate is dephosphorylated to form ATP from ADP, producing - reaction carried out by the enzyme - two ATP are produced per glucose molecule, substrate level phosphor. - pyruvate kinase is allosterically regulated by - inhibited by high levels 26

27 Regulation points of glycolysis 1. Glucose-6-phosphate production 2. Fructose 1,6-bisphosphate production inhibited by ATP 3. pyruvate produced inhibited by ATP 27

28 What is the energy production of glycolysis? 2 ATP used in phase ATP produce in phase Overall ATP production: 28

29 What is the fate of pyruvate? Depends on the conditions: - pyruvate enters citric acid cycle (TCA cycle), to generate reducing agents for ATP production (next lecture series) conditions: 1. Anaerobic glycolysis, the production of. Occurs in muscles 2. Alcohol fermentation, production of ethanol from pyruvate 29

30 Anaerobic Glycolysis - Pyruvate is reduced to lactate - occurs in - only form of glycolysis - catalyzed by enzyme - oxidizes NADH to NAD + reduction 30

31 Anaerobic Glycolysis Why carry out anaerobic glycolysis? - citric acid cycle (TCA cycle) requires. - but during anaerobic conditions - lactate dehydrogenase produces - this NAD + can then be used by - only place in glycolysis NAD + required, thus glycolysis can continue and produce 31

32 Alcoholic Fermentation 2 steps in the production of ethanol from pyruvate 1. The enzyme removes CO 2 from pyruvate to produce acetaldehyde 32

33 Alcoholic Fermentation 2 steps in the production of ethanol from pyruvate 2. The enzyme reduces acetaldehyde to ethanol Produces NAD + that can then be used by glyeraldehyde-3-phosphate dehydrogenase 2H + + 2e - reduction NAD + NADH 33

34 Glycolysis Alcoholic Fermentation Beer making Extract sugars from malted barley in water yeast Aerobic glycolysis Anaerobic fermentation CO2 CO2 Place in air tight bottle, yeast produced CO2 carbonates beer Use of O2 EtOH EtOH EtOH EtOH EtOH Air tight container with exhaust for gas 34