1. 第七章 細胞如何釋放儲存的能量 前言

5. 細胞如何製造ATP
能量釋放途徑主要型式之比較
有氧呼吸的總覽

9. 醣解作用(Glycolysis):
能量釋放途徑的第 一階段

16. 有氧呼吸的第二階段

17. pyruvate + coenzyme A + NAD+
有氧呼吸的第二階段
前置步驟和Kreb循環
pyruvate + coenzyme A + NAD+
acetyl-CoA + NADH + CO2
One of the carbons from pyruvate is released in CO2
Two carbons are attached to coenzyme A and continue on to the Krebs cycle

18. What is Acetyl-CoA? A two-carbon acetyl group linked to coenzyme A
CH3
C=O
Coenzyme A
Acetyl group

22. Coenzyme Reductions During First Two Stages
Glycolysis 2 NADH
Preparatory
reactions NADH
Krebs cycle FADH NADH
Total FADH NADH

23. 有氧呼吸的第三階段

24. 電子傳遞磷酸化作用 (Electron Transport Phosphorylation)
Occurs in the mitochondria
Coenzymes deliver electrons to electron
transport systems
Electron transport sets up H+ ion gradients
Flow of H+ down gradients powers ATP
formation

25. Electron Transport
Electron transport systems are embedded in inner mitochondrial compartment
NADH and FADH2 give up electrons that they picked up in earlier stages to electron transport system
Electrons are transported through the system
The final electron acceptor is oxygen

26. Creating an H+ Gradient
OUTER COMPARTMENT
NADH
INNER COMPARTMENT

27. Making ATP: Chemiosmotic Model
INNER
COMPARTMENT
ADP + Pi

28. (per molecule of glucose)
能量報酬之摘要
(per molecule of glucose)
Glycolysis
2 ATP formed by substrate-level phosphorylation
Krebs cycle and preparatory reactions
Electron transport phosphorylation
32 ATP formed

29. Energy Harvest from Coenzyme Reductions
What are the sources of electrons used to generate the 32 ATP in the final stage?
4 ATP - generated using electrons released during glycolysis and carried by NADH
28 ATP - generated using electrons formed during second-stage reactions and carried by NADH and FADH2

30. Energy Harvest Varies
NADH formed in cytoplasm cannot enter mitochondrion
It delivers electrons to mitochondrial membrane
Membrane proteins shuttle electrons to NAD+ or FAD inside mitochondrion
Electrons given to FAD yield less ATP than those given to NAD+

31. Energy Harvest Varies Skeletal muscle and brain cells
Liver, kidney, heart cells
Electrons from first-stage reactions are delivered to NAD+ in mitochondria
Total energy harvest is 38 ATP
Skeletal muscle and brain cells
Electrons from first-stage reactions are delivered to FAD in mitochondria
Total energy harvest is 36 ATP

32. Efficiency of Aerobic Respiration
686 kcal of energy are released
7.5 kcal are conserved in each ATP
When 36 ATP form, 270 kcal (36 X 7.5) are captured in ATP
Efficiency is 270 / 686 X 100 = 39 percent
Most energy is lost as heat

34. ATP形成途徑
發酵作用途徑
乳酸發酵
酒精發酵
無氧電子傳遞

36. electrons, hydrogen from NADH
GLYCOLYSIS
C6H12O6 2
ATP
energy input
2 ADP
2 NAD+ 2
NADH 4
ATP
energy output
2 pyruvate
2 ATP net
ETHANOL FORMATION
2 H2O
2 CO2
2 acetaldehyde
electrons, hydrogen from NADH
Fig. 7.10, p. 119
2 ethanol

37. Carbohydrate Breakdown and Storage
Glucose is absorbed into blood
Pancreas releases insulin
Insulin stimulates glucose uptake by cells
Cells convert glucose to glucose-6-phosphate
This traps glucose in cytoplasm where it can be used for glycolysis

38. Energy Reserves
Glycogen makes up only about 1 percent of the body’s energy reserves
Proteins make up 21 percent of energy reserves
Fat makes up the bulk of reserves (78 percent)

39. Making Glycogen
If glucose intake is high, ATP-making machinery goes into high gear
When ATP levels rise high enough, glucose-6-phosphate is diverted into glycogen synthesis (mainly in liver and muscle)
Glycogen is the main storage polysaccharide in animals

40. Using Glycogen
When blood levels of glucose decline, pancreas releases glucagon
Glucagon stimulates liver cells to convert glycogen back to glucose and to release it to the blood
(Muscle cells do not release their stored glycogen)

41. Energy from Fats Most stored fats are triglycerides
Triglycerides are broken down to glycerol and fatty acids
Glycerol is converted to PGAL, an intermediate of glycolysis
Fatty acids are broken down and converted to acetyl-CoA, which enters Krebs cycle

42. Energy from Proteins Proteins are broken down to amino acids
Amino acids are broken apart
Amino group is removed, ammonia forms, is converted to urea and excreted
Carbon backbones can enter the Krebs cycle or its preparatory reactions

43. Processes Are Linked Aerobic Respiration Photosynthesis Reactants
Sugar
Oxygen
Products
Carbon dioxide
Water
Photosynthesis
Reactants
Carbon dioxide
Water
Products
Sugar
Oxygen