1. Nutrition, Metabolism, and Body Temperature Regulation

2. Nutrition
Nutrient – a substance that promotes normal growth, maintenance, and repair
Major nutrients – carbohydrates, lipids, and proteins
Other nutrients – vitamins and minerals (and technically speaking, water)

3. Carbohydrates
Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes
Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream
Glucose is the molecule ultimately used by body cells to make ATP
Neurons and RBCs rely almost entirely upon glucose to supply their energy needs
Excess glucose is converted to glycogen or fat and stored

4. Lipids
The most abundant dietary lipids, triglycerides, are found in both animal and plant foods
Essential fatty acids – linoleic and linolenic acid, found in most vegetables, must be ingested
Dietary fats:
Help the body to absorb vitamins
Are a major energy fuel of hepatocytes and skeletal muscle
Are a component of myelin sheaths and all cell membranes

5. Proteins Proteins supply:
Essential amino acids, the building blocks for nonessential amino acids
Nitrogen for nonprotein nitrogen-containing substances
Daily intake should be approximately 0.8g/kg of body weight

6. Vitamins Organic (carbon) compounds needed for growth and good health
They are crucial in helping the body use nutrients and often function as coenzymes
Only vitamins D, K, and B are synthesized in the body; all others must be ingested
Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract
B12 additionally requires gastric intrinsic factor to be absorbed

7. Minerals Seven minerals are required in moderate amounts
Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium
Dozens are required in trace amounts
Minerals work with nutrients to ensure proper body functioning
Calcium, phosphorus, and magnesium salts harden bone

8. Minerals
Sodium and chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function
Uptake and excretion must be balanced to prevent toxic overload

10. Metabolism
Metabolism – all chemical reactions necessary to maintain life
Cellular respiration – food fuels are broken down within cells and some of the energy is captured to produce ATP
Anabolic reactions – synthesis of larger molecules from smaller ones
Catabolic reactions – hydrolysis of complex structures into simpler ones

11. Metabolism
Enzymes shift the high-energy phosphate groups of ATP to other molecules
These phosphorylated molecules are activated to perform cellular functions

12. Stages of Metabolism
Energy-containing nutrients are processed in three major stages
Digestion – breakdown of food; nutrients are transported to tissues
Anabolism and formation of catabolic intermediates where nutrients are:
Built into lipids, proteins, and glycogen
Broken down by catabolic pathways to pyruvic acid and acetyl CoA
Oxidative breakdown – nutrients are catabolized to carbon dioxide, water, and ATP

13. Stages of Metabolism

14. Carbohydrate Metabolism
Since all carbohydrates are transformed into glucose, it is essentially glucose metabolism
Oxidation of glucose is shown by the overall reaction:
C6H12O6 + 6O2  6H2O + 6CO ATP + heat
Glucose is catabolized in three pathways
Glycolysis
Krebs cycle
The electron transport chain and oxidative phosphorylation

15. Carbohydrate Catabolism

16. Glycolysis A three-phase pathway in which: Pyruvic acid:
Glucose is oxidized into pyruvic acid
NAD+ is reduced to NADH + H+
ATP is synthesized by substrate-level phosphorylation
Pyruvic acid:
Moves on to the Krebs cycle in an aerobic pathway (with O2)
Is reduced to lactic acid in an anaerobic environment (if no O2)

17. 3 Outcomes of Glycolysis
3. ATP is synthesized by substrate-level phosphorylation
2. NAD+ is reduced to NADH + H+
Glucose is oxidized into pyruvic acid

18. Glycolysis: Phase 1 and 2 Phase 1: Sugar activation
Two ATP molecules activate glucose into fructose-1,6-diphosphate
Phase 2: Sugar cleavage
Fructose-1,6-bisphosphate is cleaved into two 3-carbon isomers
Bishydroxyacetone phosphate
Glyceraldehyde 3-phosphate

19. Glycolysis: Phase 3 Phase 3: Oxidation and ATP formation
The 3-carbon sugars are oxidized (reducing NAD+)
Inorganic phosphate groups (Pi) are attached to each oxidized fragment
The terminal phosphates are cleaved and captured by ADP to form four ATP molecules

20. Glycolysis: Phase 3 The final products are: Two pyruvic acid molecules
Two NADH + H+ molecules (reduced NAD+)
A net gain of two ATP molecules

21. Krebs Cycle: Preparatory Step
Occurs in the mitochondrial matrix and is fueled by pyruvic acid and fatty acids

22. Krebs Cycle: Preparatory Step
Pyruvic acid is converted to acetyl CoA in three main steps:
Decarboxylation
Carbon is removed
Carbon dioxide is released
Oxidation
Hydrogen atoms are removed from pyruvic acid
NAD+ is reduced to NADH + H+
Formation of acetyl CoA – the resulting acetic acid is combined with coenzyme A, a sulfur-containing coenzyme, to form acetyl CoA

23. Krebs Cycle
An eight-step cycle in which each acetic acid is decarboxylated and oxidized, generating:
Three molecules of NADH + H+
One molecule of FADH2
Two molecules of CO2
One molecule of ATP
For each molecule of glucose entering glycolysis, two molecules of acetyl CoA enter the Krebs cycle

24. Krebs Cycle

25. Electron Transport Chain
Food (glucose) is oxidized and the released hydrogens:
Are transported by coenzymes NADH and FADH2
Enter a chain of proteins bound to metal atoms (cofactors)
Combine with molecular oxygen to form water
Release energy
The energy released is harnessed to attach inorganic phosphate groups (Pi) to ADP, making ATP by oxidative phosphorylation

26. Mechanism of Oxidative Phosphorylation
The hydrogens delivered to the chain are split into protons (H+) and electrons
The protons are pumped across the inner mitochondrial membrane by:
NADH dehydrogenase (FMN, Fe-S)
Cytochrome b-c1
Cytochrome oxidase (a-a3)
The electrons are shuttled from one acceptor to the next

27. Mechanism of Oxidative Phosphorylation
Electrons are delivered to oxygen, forming oxygen ions
Oxygen ions attract H+ to form water
H+ pumped to the intermembrane space:
Diffuses back to the matrix via ATP synthase
Releases energy to make ATP

28. Mechanism of Oxidative Phosphorylation
1. Hydrogens are split into protons and electrons

29. Mechanism of Oxidative Phosphorylation
2. Protons are shuttled across membrane

30. Mechanism of Oxidative Phosphorylation
3. Electrons cross membrane as well but fall back sooner

31. Mechanism of Oxidative Phosphorylation
When electrons fall back, you have 2 gradients, a pH gradient and a strong charge gradient

32. Mechanism of Oxidative Phosphorylation
5. When H comes back, it can give off energy that is used to make ATP

33. Summary of ATP Production

34. Lipid Metabolism
Most products of fat metabolism are transported in lymph as chylomicrons
Lipids in chylomicrons are hydrolyzed by plasma enzymes and absorbed by cells
Catabolism of fats involves two separate pathways
Glycerol pathway
Fatty acids pathway
Glycerol
Fatty Acids

35. Lipid Metabolism

36. Lipogenesis and Lipolysis
Excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides
Glucose is easily converted into fat since acetyl CoA is:
An intermediate in glucose catabolism
The starting molecule for the synthesis of fatty acids

37. Lipogenesis and Lipolysis
Lipolysis, the breakdown of stored fat, is essentially lipogenesis in reverse
Oxaloacetic acid is necessary for the complete oxidation of fat
Without it, acetyl CoA is converted into ketones (ketogenesis)

38. Lipogenesis and Lipolysis
Define glycerol, fattyacids
The main point here is that lipids and sugars are interconvertible

39. Protein Metabolism
Excess dietary protein results in amino acids being:
Oxidized for energy
Converted into fat for storage
Amino acids must be deaminated prior to oxidation for energy

40. Protein Metabolism

41. Synthesis of Proteins
Amino acids are the most important anabolic nutrients, and they form:
All protein structures
The bulk of the body’s functional molecules

42. State of the Body
The body exists in a dynamic catabolic-anabolic state
Organic molecules (except DNA) are continuously broken down and rebuilt
The body’s total supply of nutrients constitutes its nutrient pool

43. Absoprtive and Postabsorptive States
Metabolic controls equalize blood concentrations of nutrients between two states
Absorptive
The time during and shortly after nutrient intake
Postabsorptive
The time when the GI tract is empty
Energy sources are supplied by the breakdown of body reserves

44. Absorptive State (Full Stomach)
The major metabolic thrust is anabolism and energy storage
Amino acids become proteins
Glycerol and fatty acids are converted to triglycerides
Glucose is stored as glycogen
Dietary glucose is the major energy fuel
Excess amino acids are deaminated and used for energy or stored as fat in the liver

45. Absorptive State

46. Principal Pathways of the Absorptive State
In muscle:
Amino acids become protein
Glucose is converted to glycogen
In the liver:
Amino acids become protein or are deaminated to keto acids
Glucose is stored as glycogen or converted to fat

47. Principal Pathways of the Absorptive State
In adipose tissue:
Glucose and fats are converted and stored as fat
All tissues use glucose to synthesize ATP

48. Principal Pathways of the Absorptive State

49. Insulin Effects on Metabolism
Insulin controls the absorptive state and its secretion is stimulated by:
Increased blood glucose
Elevated amino acid levels in the blood
Gastrin, CCK, and secretin
Insulin enhances:
Active transport of amino acids into tissue cells
Facilitated diffusion of glucose into tissue

50. Insulin Effects on Metabolism

51. Diabetes Mellitus
A consequence of inadequate insulin production (Type I) or abnormal insulin receptors (Type II)
Glucose becomes unavailable to most body cells
Metabolic acidosis, protein wasting, and weight loss result as fats and tissue proteins are used for energy

52. Postabsorptive State
The major metabolic thrust is catabolism and replacement of fuels in the blood
Proteins are broken down to amino acids
Triglycerides are turned into glycerol and fatty acids
Glycogen becomes glucose
Glucose is provided by glycogenolysis and gluconeogenesis
Fatty acids and ketones are the major energy fuels
Amino acids are converted to glucose in the liver

53. Postabsorptive State

54. Principle Pathways in the Postabsorptive State
In muscle:
Protein is broken down to amino acids
Glycogen is converted to ATP and pyruvic acid (lactic acid in anaerobic states)

55. Principle Pathways in the Postabsorptive State
In the liver:
Amino acids, pyruvic acid, stored glycogen, and fat are converted into glucose
Fat is converted into keto acids that are used to make ATP
Fatty acids (from adipose tissue) and ketone bodies (from the liver) are used in most tissue to make ATP
Glucose from the liver is used by the nervous system to generate ATP

56. Principle Pathways in the Postabsorptive State

57. Hormonal and Neural Controls of the Postabsorptive State
Decreased plasma glucose concentration and rising amino acid levels stimulate alpha cells of the pancreas to secrete glucagon (the antagonist of insulin)
Glucagon stimulates:
Glycogenolysis and gluconeogenesis
Fat breakdown in adipose tissue
Glucose sparing

58. Hormonal and Neural Controls of the Postabsorptive State
In response to low plasma glucose, the sympathetic nervous system releases epinephrine, which acts on the liver, skeletal muscle, and adipose tissue to mobilize fat and promote glycogenolysis

59. Cholesterol
Is the structural basis of bile salts, steroid hormones, and vitamin D
Makes up part of the hedgehog molecule that directs embryonic development
Is transported to and from tissues via lipoproteins

60. Cholesterol Lipoproteins are classified as:
HDLs – high-density lipoproteins have more protein content
LDLs – low-density lipoproteins have a considerable cholesterol component
VLDLs – very low density lipoproteins are mostly triglycerides

61. Lipoproteins
High levels of HDL are thought to protect against heart attack
High levels of LDL, especially lipoprotein (a), increase the risk of heart attack

62. Metabolic Rate
Rate of energy output (expressed per hour) equal to the total heat produced by:
All the chemical reactions in the body
The mechanical work of the body
Measured directly with a calorimeter or indirectly with a respirometer

63. Metabolic Rate Basal metabolic rate (BMR) Total metabolic rate (TMR)
Reflects the energy the body needs to perform its most essential activities
Total metabolic rate (TMR)
Total rate of kilocalorie consumption to fuel all ongoing activities

64. Factors that Influence BMR
Surface area, age, gender, stress, and hormones
As the ratio of surface area to volume increases, BMR increases
Males have a disproportionately high BMR
Stress increases BMR
Thyroxine increases oxygen consumption, cellular respiration, and BMR