1. Metabolism
Chapter 25

2. An Introduction to Cellular Metabolism
Figure 25–1

3. Essential Nutrients 45 – 50 molecules must be ingested.
This includes representatives from the 4 major organic molecule groups, plus a number of inorganic substances such as including water, vitamins and minerals (Na, Fe, etc.)
The USDA has made major revision in its nutritional recommendations.

4. It was never based on solid science

5. Nutrient – A substance in food used by the body for growth, maintenance, energy and repair.
USDA IOM for young adult female
Carbohydrates: 271g (55%) g ( %)
Lipid: total 65g (17%) – 25%
saturated 17g (7.8%)
Protein: g (18%) g (10 – 35%)
Water: 1500 ml (average) per day.

6. Uses of nutrients
Carbohydrate: Primary energy molecule. Also found on cell membranes and as part of structure of connective tissue matrix molecules
Lipid: Energy storage, plasma membrane structure, cushioning, steroid hormones.
Proteins: Enzymes, receptors, hormones, structures of all kinds. Must be “complete” or “complimentary” in order to supply essential amino acids.

7. Nutrient Use in Cellular Metabolism

8. Essential amino acids

9. 10 Essential Amino Acids 8 not synthesized:
isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine
2 insufficiently synthesized:
arginine and histidine

10. 4 Types of Nitrogen Compounds
Amino acids:
framework of all proteins, glycoproteins, and lipoproteins
Purines and pyrimidines:
nitrogenous bases of RNA and DNA

11. 4 Types of Nitrogen Compounds
Creatine:
energy storage in muscle (creatine phosphate)
Porphyrins:
bind metal ions
essential to hemoglobin, myoglobin, and cytochromes

12. Energy Metabolism Metabolism = catabolism + anabolism
Cellular respiration is a series of catabolic reactions that provide energy for the production of
This energy is used to generate ATP from phosphorylation of ADP.
It is a series of Redox reactions.
ATP

13. Energy Metabolism: Generation of ATP

14. Overview of aerobic respiration

15. Summary of steps of energy metabolism

16. Generation of ATP by “substrate-level phosphorylation”

17. Oxidative phosphorylation

18. Overview of cellular respiration

19. Carbohydrate Metabolism
Oxidation of Glucose
C6H12O6 + 6 O2 6 CO H2O + 36 ATP + Heat

20. Glycolysis
It is the first stage in cellular respiration

21. Steps of glycolysis

22. Aerobic vs anaerobic pathways

23. Overview of TCA (Krebs cycle)

24. TCA (Krebs) Cycle

25. Summary: The TCA Cycle
CH3CO — CoA + 3NAD + FAD + GDP + Pi + 2 H2O  CoA + 2 CO2 + 3NADH + FADH2 + 2 H+ + GTP

26. The ETS creates an chemiosmotic gradient

27. The Electron Transport System

28. The ETS

29. Summary of ATP synthesis Gains & losses

30. Visual summary of cellular respiration

31. Carbohydrate Breakdown and Synthesis
Figure 25–7

32. Glycogenesis/ Glycogenolysis

33. Gluconeogenesis
Is the synthesis of glucose from noncarbohydrate precursors:
lactic acid
glycerol
amino acids
Stores glucose as glycogen in liver and skeletal muscle

34. Summary of metabolic pathways

35. Lipid metabolism: oxidation

36. 3 Energy Benefits of Beta-Oxidation
For each 2-carbon fragment removed from fatty acid, cell gains:
12 ATP from acetyl-CoA in TCA cycle
5 ATP from NADH
Cell can gain 144 ATP molecules from breakdown of one 18-carbon fatty acid molecule
Fatty acid breakdown yields about 1.5 times the energy of glucose breakdown

37. Lipid Transport and Utilization
Figure 25–9

38. 5 Classes of Lipoproteins
Chylomicrons
Very low-density lipoproteins (VLDLs)
Intermediate-density lipoproteins (IDLs)
Low-density lipoproteins (LDLs)
High-density lipoproteins (HDLs)

39. Chylomicrons Are produced in intestinal tract
Are too large to diffuse across capillary wall
Enter lymphatic capillaries
Travel through thoracic duct:
to venous circulation and systemic arteries

40. Distribution of Other Lipoproteins: Step 1
Liver cells synthesize VLDLs:
for discharge into bloodstream

41. Distribution of Other Lipoproteins: Step 2
Lipoprotein lipase removes many triglycerides from VLDLs:
leaving IDLs
Triglycerides are broken down:
into fatty acids and monoglycerides

42. Distribution of Other Lipoproteins: Step 3
When IDLs reach liver:
additional triglycerides are removed
protein content of lipoprotein is altered
LDLs are created
LDLs are transported to peripheral tissues to deliver cholesterol

43. Distribution of Other Lipoproteins: Step 4
LDLs leave bloodstream through capillary pores:
or cross endothelium by vesicular transport

44. Distribution of Other Lipoproteins: Step 5
In peripheral tissues:
LDLs are absorbed through receptor-mediated endocytosis
Amino acids and cholesterol enter the cytoplasm

45. Distribution of Other Lipoproteins: Step 6 & 7
Cholesterol not used by the cell:
diffuses out of cell
Cholesterol reenters bloodstream:
is absorbed by HDLs and returned to liver

46. Distribution of Other Lipoproteins: Step 8
In the liver:
HDLs are absorbed
cholesterol is extracted
Recovered cholesterol is used:
in synthesis of LDLs
in excreted in bile salts

47. Distribution of Other Lipoproteins: Step 9
Free HDLs are released into bloodstream:
travel into peripheral tissues
absorb additional cholesterol

48. Composition of Lipoproteins

49. Proteins The body synthesizes 100,000 to 140,000 proteins:
each with different form, function, and structure
All proteins are built from the 20 amino acids

50. Amino Acid Catabolism
Figure 25–10 (Navigator)

51. Amination
Figure 25–11

52. Amino acid use in TCA cycle

53. Protein metabolism in the Liver

54. Summary: Pathways of Catabolism and Anabolism
Figure 25–12

55. 5 Metabolic Tissues Each tissue has its own requirements
Liver
Adipose tissue
Skeletal muscle
Neural tissue
Other peripheral tissues

56. Other Peripheral Tissues
Do not maintain large metabolic reserves
Can metabolize glucose, fatty acids, and other substrates
Preferred energy source varies:
according to instructions from endocrine system

57. Metabolic Interactions
Relationships among 5 components change over 24-hour period
Body has 2 patterns of daily metabolic activity:
absorptive state
postabsorptive state

58. Regulatory Hormones: Effects on Peripheral Metabolism
Table 25–1

59. Pathways of the Absorptive state

60. The effects of insulin on metabolism

61. The Postabsorptive state

62. Influences of Glucagon on blood glucose levels

63. Lipid and Amino Acid Catabolism
Generates acetyl-CoA
Increased concentration of acetyl-CoA:
causes ketone bodies to form

64. Ketone Bodies
Acetoacetate
Acetone
Betahydroxybutyrate

65. Ketone Bodies Liver cells do not catabolize ketone bodies:
compounds diffuse into general circulation
peripheral cells absorb ketone bodies
Cells reconvert ketone bodies to acetyl-CoA for TCA cycle

66. Ketone Bodies Are acids that dissociate in solution
Fasting produces ketosis:
a high concentration of ketone bodies in body fluids

67. Ketonemia Is the appearance of ketone bodies in bloodstream
Lowers plasma pH, which must be controlled by buffers

68. Ketoacidosis Is a dangerous drop in blood pH:
caused by high ketone levels
exceeding buffering capacities

69. Severe Ketoacidosis
Circulating concentration of ketone bodies can reach 200 mg dl:
pH may fall below 7.05
may cause coma, cardiac arrhythmias, death

70. Minerals and Vitamins Are essential components of the diet
The body does not synthesize minerals
Cells synthesize only small quantities of few vitamins

71. Minerals and Mineral Reserves
Table 25–3

72. Minerals
Are inorganic ions released through dissociation of electrolytes

73. Importance of Minerals
Ions such as sodium, chloride and potassium determine osmotic concentrations of body fluids
Ions are essential:
cofactors in many enzymatic reactions
in many important physiological processes

74. Metals Each component of ETS requires an iron atom
Final cytochrome of ETS requires a copper ion

75. Mineral Reserves The body contains significant mineral reserves:
that help reduce effects of variations in diet

76. The Fat-Soluble Vitamins
Table 25–4

77. Fat-Soluble Vitamins Vitamins A, D, E, and K:
are absorbed primarily from the digestive tract along with lipids of micelles
normally diffuse into cell membranes and lipids in liver and adipose tissue

78. Vitamin A Vitamin D Vitamin E
A structural component of visual pigment retinal
Vitamin D
Is converted to calcitriol:
which increases rate of intestinal calcium and phosphorus absorption
Vitamin E
Stabilizes intracellular membranes

79. Vitamin K Helps synthesize several proteins:
including 3 clotting factors

80. Vitamin Reserves
The body contains significant reserves of fat-soluble vitamins
Normal metabolism can continue several months without dietary sources

81. The Water-Soluble Vitamins
Table 25–5

82. Metabolic Rate If daily energy intake exceeds energy demands:
body stores excess energy as triglycerides in adipose tissue
If daily caloric expenditures exceeds dietary supply:
body uses energy reserves, loses weight

83. Cholecystokinin (CCK): Adrenocorticotropic hormone (ACTH): Leptin:
Hormonal Effects
Thyroxine:
controls overall metabolism
T4 assay measures thyroxine in blood
Cholecystokinin (CCK):
suppresses appetite
Adrenocorticotropic hormone (ACTH):
Leptin:
released by adipose tissues during absorptive state
binds to CNS neurons that suppress appetite

84. Heat Balance

85. Regulatory pathways for homeostatic control of body temperature

86. Temperature regulation mechanisms

87. Maynard or Hans?