生化報告 13組 0993B004 朱珮萱 0993B017 曾馨卉.

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1 生化報告 13組 0993B004 朱珮萱 0993B017 曾馨卉

2 心智圖 起始反應 allosterically inhibited Hexokinase by G-6-P G-6-P to F-6-P
Part 1 心智圖 起始反應 allosterically inhibited by G-6-P Hexokinase G-6-P to F-6-P Phosphogluco isomerase ATP inhibits, AMP reverses inhibition committed step Phosphofructokinase First phase glucose to two G-3-P 步驟 C6 to 2 C3s (DHAP, Gly-3-P) inhibit by borohydride) Aldolase Glycolysis 特色 Triose Phosphate Isomerase DHAP to G-3-P Second phase Ethanol + CO2 pyruvates Acetyl-CoA Coupled Reactions ATP hydrolysis Lactate

3 Essential Features of Glycolysis
2.每個細胞所進行的糖解作用都有十個步驟，但用的Enzyme不一定相同 3.這十個步驟可以分為兩個Phase： (1)第一個phase(前五個步驟)：Glucose進G3P出 (2)第二個phase(後五個步驟)：G3P進Pyruvate出 4.Glycolysis的產物為Pyruvate、ATP、NADH 5.Pyruvate可分為3個可能的fates

4 The First Phase of Glycolysis
• Starting material: 1 X Glucose(加入一個葡萄糖) • Ending material: 2 X Glyceraldehyde-3-phosphate (G-3-P) (放出兩個G-3-P)

5 Phosphorylation of glucose
STEP.1 Phosphorylation of glucose 在Cytoplasm(細胞質)中反應 Glucose + ATP → glucose-6-phosphate + ADP 為nonequilibrium (非平衡) reaction & exogenic (放能) reaction 有兩種作用的酵素：Hexokinase (in muscle) & Glucokinase (in liver) 反應一個Glucose 消耗 一個ATP glucose-6-phosphate會抑制Hexokinase的活性

6 STEP.2 Isomerization of G-6-P
葡萄糖→果糖（醛糖→酮糖） Glucose-6-phosphate→Fructose-6-phosphate 作用酵素： Phosphoglucoisomerase Why? 1.為了讓下個步驟更容易進行(因為primary –OH比較容易被ATP上的磷酸phosphorylation，而在C1上的 hemiacetal -OH 比較難) 2.果糖較容易進行aldolase reaction，使六碳糖被切割 中間產物： Ene-diol

7 Phosphorylation of F-6-P
　STEP.3　 Phosphorylation of F-6-P Fructose-6-phosphate + ATP → Fructose-1,6-bisphosphate + ADP 作用酵素：Phosphofructokinase (PFK) 為自發向右放熱反應(不可逆)，反應後只能繼續glycolysis 反應一個F-6-P 消耗 一個 ATP (second priming reaction) ATP為抑制劑，AMP為反抑制劑 Mg2+可穩定ATP磷酸根之電荷 PFK：能量低時活性高，能量高時活性低

8 Cleavage of fructose-1,6-bisphosphate
STEP.4 Cleavage of fructose-1,6-bisphosphate Fructose-1,6-bisphosphate → Glyceraldehyde-3-phosphate(G3P)+DHAP 作用酵素：Aldolase

9 STEP.5 Isomerization of DHAP
Dihydroxyacetone phospate(DHAP) → G3P 作用酵素：triose phosphate isomerase 中間產物：enediol (烯二醇)

10 習題: How does Glucose-6-P to Fructose-6-P reaction occur??
Ans: (1)Phosphorylation at C-1 would be tough for hemiacetal –OH (2)Isomerization activates C-3 for cleavage in aldolase reaction 2. What are the 3 fates of pyruvate? Ans: (1) Ethanol + CO In fermentation to ethanol in yeast (2) Acetyl-CoA 檸檬酸循環 CO2+H2O-- In animal,plant… … (3) Lactate In vigorously contracting muscle, in some other cells,and in some microorganisms.