Chapter 24 Nutrition & Metabolism Lecture 12

1. Marieb’s Human Anatomy and Physiology Ninth Edition Marieb w Hoehn Chapter 24 Nutrition & Metabolism Lecture 12 Part 2: Proteins, Metabolic States, Vitamins & Minerals

2. Proteins • Sources • meats • cheeses • nuts • legumes Excesses can lead to obesity • Deficiencies lead to • extreme weight loss • muscle wasting • anemia • growth retardation Incomplete proteins – unable to maintain human tissues or support normal growth and development by themselves *RDA is 0.8g/kg body weight or 10% of diet (1 kg = 2.2 lbs) Essential amino acids (10; 8 in adult)– cannot be synthesized by the body (isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine; arginine, histidine)

3. Utilization of Proteins Figure from: Hole’s Human A&P, 12th edition, 2010 • regulation of water balance • control of pH • formation of antibodies • build cell structures • enzymes • hormones • transport of oxygen

4. Utilization of Proteins for Energy Ammonia, NH3, or ammonium, NH4+ Highly toxic, even in small amounts Liver converts these to urea, a harmless water-soluble compound that can be excreted in the urine * Figure from: Hole’s Human A&P, 12th edition, 2010

5. Nitrogen Balance Variety of compounds in the body contain nitrogen (N): amino acids, purines, pyrimidines, creatine, porphyrins. The body neither stores nor maintains reserves of N. There’s only about 1 kg of N in body at any one time. During starvation, N-containing compounds, like skeletal muscle, are conserved; CHO and fats are metabolized first (protein-sparing effect). Order of usage: CHO, fat, protein. • nitrogen balance - amount of nitrogen taken in is equal to amount excreted • negative nitrogen balance develops from starvation • positive nitrogen balance develops in growing children, pregnant women, or an athlete in training

6. The “Fed” (Absorptive) State Know this Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

7. The “Fasted” (Postabsorptive) State Know this Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

8. Pyruvate is a Key Junction in Metabolism Pyruvate is used to synthesize amino acids and Acetyl CoA Pyruvate can also be used to synthesize glucoseviagluconeogenesis. Glycogenolysis Glycogenesis Lipo-genesis Lipolysis Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

9. Metabolism Hormones:Fed – InsulinFasted – Glucagon, Corticosteroids, Epi/NE -olysis  breakdown of -neo  new-genesis  creation of • Glycolysis – metabolism of glucose to pyruvate (Fed) • Gluconeogenesis – metabolism of pyruvate to glucose (CHO from non-CHO source) – (Fasted) • Glycogenesis – metabolism of glucose to glycogen (Fed) • Glycogenolysis – metabolism of glycogen to glucose (Fasted) • Lipolysis – breakdown of triglyceride into glycerol and fatty acids (Fasted) • Lipogenesis – creation of new triglyceride (fat) – (Fed)

10. Energy Requirements • Basal metabolic rate (BMR) • rate at which body expends energy at rest (kcal/hr) • primarily reflects energy needed to support activities of organs • varies with gender, body size, body temperature, and endocrine function BMR is proportional to body weight Body’s basal metabolic rate (BMR) falls 10% during sleep and about 40% during prolonged starvation • Energy needed • to maintain BMR • to support resting muscular activity • to maintain body temperature • for growth in children and pregnant women BMR is profoundly affected by circulating thyroid hormone levels

11. Energy Balance • occurs when caloric intake in the form of food equals caloric output from BMR and muscular activities • positive energy balance leads to weight gain • negative energy balance leads to weight loss Body Mass Index (BMI)* = Wt (kg) / Height2 (m) * Source: World Health Organization

12. Overview of Vitamins • Organic substances required in small amounts that are not synthesized in adequate amounts to meet the body’s needs • Divided into two groups by solubility • Water-soluble – vitamins B (group) and C • Not generally stored • Excesses are excreted, e.g., in urine • Fat-soluble – vitamins A, D, E, and K • Stored in liver, adipose, other tissues • Excesses accumulate in tissues

13. The Fat-soluble Vitamins • Absorbed with fats in digestive tract • Function/Other sources • Vitamin A; structural component of retinal • Vitamin D • increases absorption of calcium and phosphorus from intestine • skin and UV light • Vitamin E • stabilizes internal cellular membranes • antioxidant • Vitamin K • Clotting (‘K’lotting) • bacteria in intestine and green, leafy vegetables *

14. Water-soluble Vitamins • Rapidly exchanged between fluid compartments of digestive tract and circulating blood • Excesses excreted in urine • Vitamins B12 and C are stored in larger quantities than other water-soluble vitamins • B vitamins [know these functions] • as a group, are coenzymes used to harvest energy • Vitamin B12 is important in hematopoiesis and maintenance of myelin sheath and epithelial cells • Vitamin C (ascorbic acid) [know these functions] • collagen production • Antioxidant / immune system booster •  absorption of iron

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18. Review • Fat-soluble vitamins • Excesses are stored in tissues (liver, adipose) and not excreted; may become toxic • Includes vitamins A, D, E, and K • For exam see Table 18.8 on p. 708 and know the functions of the fat-soluble vitamins • Water-soluble vitamins • Excesses are excreted, e.g., urine • Vitamins B and C • For exam see Table 18.9 on p. 713 • B vitamins – know name/designation and know that the B vitamins are coenzymes that function in energy metabolism • Vitamin C – know its name and functions