1. 25 Metabolism and Energetics C h a p t e r
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings

2. Metabolism
Metabolism is all the chemical reactions that occur in an organism
Cellular metabolism
Cells break down excess carbohydrates first, then lipids
Cells conserve amino acids
40% of the energy released in catabolism is captured in ATP
Rest is released as heat

3. Figure 23.1 An Introduction to Cellular Metabolism

4. Anabolism Performance of structural maintenance and repairs
Support of growth
Production of secretions
Building of nutrient reserves

5. Figure 23.2 Metabolic Turnover and Cellular ATP Production

6. Cells and Mitochondria
Cells provide small organic molecules for their mitochondria
Mitochondria produce ATP used to perform cellular functions

7. Figure 23.3 Nutrient Use in Cellular Metabolism

8. Most cells generate ATP through the breakdown of carbohydrates
Glycolysis
One molecule of glucose = two pyruvate ions, two ATP, two NADH
Aerobic metabolism (cellular respiration)
Two pyruvates = 34 ATP
The chemical formula for this process is C6H12O6 + 6 O2  6 CO H2O

9. Glycolysis The breakdown of glucose to pyruvic acid
This process requires:
Glucose molecules
Cytoplasmic enzymes
ATP and ADP
Inorganic phosphate
NAD (nicotinamide adenine dinucleotide)
The overall reaction is: Glucose + 2 NAD + 2 ADP + 2Pi  Pyruvic acid + 2 NADH + 2 ATP

10. Figure Glycolysis
Figure 23.4

11. Mitochondrial ATP Production (cellular respiration)
Pyruvic acid molecules enter mitochondria
Broken down completely in TCA cycle
Decarboxylation
Hydrogen atoms passed to coenzymes
Oxidative phosphorylation

12. Figure The TCA Cycle
PLAY
Animation: TCA cycle
Figure 23.5a

13. Figure The TCA Cycle
Figure 23.5b

14. Oxidative phosphorylation and the ETS
Requires coenzymes and consumes oxygen
Key reactions take place in the electron transport system (ETS)
Cytochromes of the ETS pass electrons to oxygen, forming water
The basic chemical reaction is: H2 + O2  2 H2O

15. Figure 23.6 Oxidative Phosphorylation
PLAY
Animation: Chemiosmosis
Figure 23.6a

16. Figure 23.6 Oxidative Phosphorylation
Figure 23.6b

17. Energy yield of glycolysis and cellular respiration
Per molecule of glucose entering these pathways
Glycolysis – has a net yield of 2 ATP
Electron transport system – yields approximately 28 molecules of ATP
TCA cycle – yields 2 molecules of ATP

18. Figure 23.7 A Summary of the Energy Yield of Aerobic Metabolism

19. Synthesis of glucose and glycogen
Gluconeogenesis
Synthesis of glucose from noncarbohydrate precursors
Lactic acid, glycerol, amino acids
Liver cells synthesis glucose when carbohydrates are depleted
Glycogenesis
Formation of glycogen
Glucose stored in liver and skeletal muscle as glycogen
Important energy reserve

20. Figure 23.8 Carbohydrate Breakdown and Synthesis

21. Lipid catabolism Lipolysis
Lipids broken down into pieces that can be converted into pyruvate
Triglycerides are split into glycerol and fatty acids
Glycerol enters glycolytic pathways
Fatty acids enter the mitochondrion

22. Lipid catabolism Beta-oxidation
Breakdown of fatty acid molecules into 2-carbon fragments
Enter the TCA
Irreversible
Lipids and energy production
Cannot provide large amounts in ATP in a short amount of time
Used when glucose reserves are limited

23. Figure Beta Oxidation
Figure 23.9

24. Lipid synthesis (lipogenesis)
Almost any organic molecule can be used to form glycerol
Essential fatty acids cannot be synthesized and must be included in diet
Linoleic and linolenic acid

25. Figure 23.10 Lipid Synthesis

26. Lipid transport and distribution
5 types of lipoprotein
Lipid-protein complex that contains large glycerides and cholesterol
Chylomicrons
Largest lipoproteins composed primarily of triglycerides
Very low-density lipoproteins (VLDLs)
Contain triglycerides, phospholipids and cholesterol

27. Lipid transport and distribution
5 types of lipoprotein (continued)
Intermediate-density lipoproteins (IDLs)
Contain smaller amounts of triglycerides
Low-density lipoproteins (LDLs)
Contain mostly cholesterol
High-density lipoproteins (HDLs)
Equal amounts of lipid and protein

28. Lipoprotein lipase Enzyme that breaks down complex lipids
Found in capillary walls of liver, adipose tissue, skeletal and cardiac muscle
Releases fatty acids and monglycerides

29. Figure 23.11 Lipid Transport and Utilization
Figure 23.11a

30. Figure 23.11 Lipid Transport and Utilization
Figure 23.11b

31. Amino acid catabolism
If other sources inadequate, mitochondria can break down amino acids
TCA cycle
Removal of the amino group (-NH2)
Transamination – attaches removed amino group to a keto acid
Deamination – removes amino group generating NH4+
Proteins are an impractical source of ATP production

32. Figure 23.12 Amino Acid Catabolism

33. Protein synthesis Essential amino acids
Cannot be synthesized by the body in adequate supply
Nonessential amino acids
Can be synthesized by the body via amination
Addition of the amino group to a carbon framework

34. Figure Amination
Figure 23.13

35. Figure 23.14 A Summary of the Pathways of Catabolism and Anabolism

36. Nucleic acid metabolism
Nuclear DNA is never catabolized for energy
RNA catabolism
RNA molecules are routinely broken down and replaced
Generally recycled as nucleic acids
Can be catabolized to simple sugars and nitrogenous bases
Do not contribute significantly to energy reserves

37. Nucleic acid synthesis
Most cells synthesis RNA
DNA synthesized only when preparing for division

38. Homeostasis
No one cell of the human body can perform all necessary homeostatic functions
Metabolic activities must be coordinated

39. Body has five metabolic components
Liver
The focal point for metabolic regulation and control
Adipose tissue
Stores lipids primarily as triglycerides
Skeletal muscle
Substantial glycogen reserves

40. Body has five metabolic components
Neural tissue
Must be supplied with a reliable supply of glucose
Other peripheral tissues
Able to metabolize substrates under endocrine control

41. The absorptive state The period following a meal
Nutrients enter the blood as intestinal absorption proceeds
Liver closely regulates glucose content of blood
Lipemia commonly marks the absorptive state
Adipocytes remove fatty acids and glycerol from bloodstream
Glucose molecule are catabolized and amino acids are used to build proteins

42. Figure 23.15 The Absorptive State

43. The Postabsorptive State
From the end of the absorptive state to the next meal
Body relies on reserves for energy
Liver cells break down glycogen, releasing glucose into blood
Liver cells synthesize glucose
Lipolysis increases and fatty acids released into blood stream
Fatty acids undergo beta oxidation and enter TCA

44. The Postabsorptive State
Amino acids either converted to pyruvate or acetyl-CoA
Skeletal muscles metabolize ketone bodies and fatty acids
Skeletal muscle glycogen reserves broken down to lactic acid
Neural tissue continues to be supplied with glucose

45. Figure 23.16 The Postabsorptive State

46. Diet and Nutrition Nutrition Absorption of nutrients from food
Balanced diet
Contains all the ingredients necessary to maintain homeostasis
Prevents malnutrition

47. Food Food groups and food pyramids
Used as guides to avoid malnutrition

48. Food Groups
Six basic food groups of a balance diet arranged in a food pyramid
Milk, yogurt and cheese
Meat, poultry, fish, dry beans, eggs, and nuts
Vegetables
Fruits
Bread, cereal, rice and pasta
Base of pyramid
Fats, oils and sweets
Top of pyramid

49. Figure 23.17 The Food Pyramid and Dietary Recommendations

50. Nitrogen balance N compounds contain nitrogen
Amino acids, purines, pyrimidines, creatine, porphyrins
Body does not maintain large nitrogen reserves
Dietary nitrogen is essential
Nitrogen balance is an equalization of absorbed and excreted nitrogen

51. Minerals Act as co-factors in enzymatic reactions
Contribute to osmotic concentrations of body fluids
Play a role in transmembrane potentials, action potentials
Aid in release of neurotransmitters and muscle contraction
Assist in skeletal construction and maintenance
Important in gas transport and buffer systems
Aid in fluid absorption and waste removal

52. Vitamins
Are needed in very small amounts for a variety of vital body activities
Fat soluble
Vitamins A, D, E, K
Taken in excess can lead to hypervitaminosis
Water soluble
Not stored in the body
Lack of adequate dietary intake = avitaminosis

53. You should now be familiar with:
Why cells need to synthesis new organic components
The basic steps in glycolysis, the TCA cycle, and the electron transport chain
The energy yield of glycolysis and cellular respiration
The pathways involved in lipid, protein and nucleic acid metabolismBMR

54. You should now be familiar with:
The characteristics of the absorptive and postabsorptive metabolic states
What constitutes a balanced diet and why such a diet is important