1. Chapter 24 Nutrition & Metabolism Lecture 12
Marieb’s Human
Anatomy and Physiology
Ninth Edition
Marieb w Hoehn
Chapter 24
Nutrition & Metabolism
Lecture 12
Slides 1-15; 80 min (with review of syllabus and Web sites) [Lecture 1]
Slides 16 – 38; 50 min [Lecture 2]
118 min (38 slides plus review of course Web sites and syllabus)

2. Lecture Overview Nutrition, nutrients, and metabolism Macronutrients
Energy and energy requirements
Vitamins
Minerals
Nutritional abnormalities
Life-span changes

3. Nutrients
Nutrients – chemical substances supplied by the environment required for survival (used for growth, repair, or maintenance of the body)
Macronutrients
carbohydrates
proteins
fats
Micronutrients
vitamins
minerals
Essential Nutrients
human cells cannot synthesize
include certain fatty acids, amino acids, vitamins

4. Overview of General Metabolic Pathways
Overall goal of catabolism: generate a pool of 2- or 3-carbon molecules and ATP
 Lipo-genesis
Glycogenolysis 
 Glycogenesis
Lipolysis 
Pyruvate is used to synthesize amino acids and Acetyl CoA
Pyruvate can also be used to synthesize glucose via gluconeogenesis.
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

5. Carbohydrates Sources Excesses lead to sugars (simple) obesity
starches (complex) - usually from plant sources
glycogen (complex) in meats
cellulose (complex) is indigestible fiber
Excesses lead to
obesity
dental caries
nutritional deficits
Deficiencies lead to
metabolic acidosis
weight loss
In body: about 325 g. muscle glycogen, g of liver glycogen, and g of blood glucose.
Avg American eats about 100 lbs of sugar per year (60 lbs sucrose, 40 lbs corn syrup) compared with 4 lbs per year about a century ago.
RDA - The RDA, the estimated amount of a nutrient (or calories) per day considered necessary for the maintenance of good health by the Food and Nutrition Board of the National Research Council/ National Academy of Sciences. The RDA is updated periodically to reflect new knowledge. It is popularly called the Recommended Daily Allowance.
Recommended (Dietary) Daily Allowance (RDA) is g

6. Utilization of Carbohydrates
Disaccharides – Sucrose, lactose, and maltose
Monosaccharides – Glucose, fructose, galactose
Glucose is the body’s CHO energy source
oxidized for energy
production of certain molecules (ribose, deoxyribose)
stored in liver and muscles as glycogen
converted to fats and stored in adipose tissue

7. Utilization of Carbohydrates

8. Lipids Sources meats eggs milk lard plant oils Excesses lead to
obesity
increased serum cholesterol
increased risk of heart disease
Deficiencies lead to
weight loss
skin lesions
hormonal imbalances
RDA is g ( 30% of calories)
( 10% saturated fat)
Fats generally take the longest to digest. Why?

9. Utilization of Lipids How is fat absorbed from the digestive tract?
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
How is fat absorbed from the digestive tract?
In the absence of sufficient CHO, oxaloacetic acid (the ‘pickup’ molecule for Acetyl CoA in the TCA cycle) is converted to glucose and is no longer available to bind with Acetyl CoA. This causes acetyl CoA to be converted into ketone bodies resulting in ketoacidosis.
Know these terms (see table of these terms later in this lecture)

10. Beta-Oxidation of Fatty Acids
Mitochondrion
Long chain fatty acids (FA) require carnitine for transport into mitochondria
FA are broken down in a step-wise manner, 2 carbons at a time in beta-oxidation
Oxidation of FA yields about times the energy from a comparable amount of glucose

11. Energy Values of Food
Calorie (kilocalorie, big calorie) – amount of heat needed to raise the temperature of 1 kg of water by 10 C
Carbohydrates
4.1 Calories per gram
Diet is 2000 Calories. What is the maximum number of grams of fat that should be taken in daily?
Proteins
4.1 Calories per gram
How many grams of fat are there in a Whopper with cheese and a small order of french fries?
Lipids
9.5 Calories per gram
Know this - you can round these off to the 4, 4, and 9)

12. Lipoprotein Traffic TG-rich Cholesterol-rich
Figure From: Martini, Anatomy & Physiology, Prentice Hall, 2001
TG-rich
Cholesterol-rich
*Cholesterol can be manufactured from Acetyl-CoA
Note the role of HDLs as scavengers of tissue/blood cholesterol.

13. Summary of Lipoproteins
Designation
Origin
Action
Chylomicron
GI tract
Transports dietary fats (mainly triglycerides) to liver for processing
Very Low Density Lipoprotein (VLDL)
Liver
Transports triglycerides from liver to adipose cells
Low Density Lipoprotein (LDL)
Transports cholesterol from liver to cells in body
High Density Lipoprotein (HDL)
Removes excess cholesterol from cells and transports to liver

14. Utilization of Lipids
The liver uses fatty acids to synthesize a variety of lipids
Triglyceride
Essential fatty acids are used for: 1) synthesis of membrane components 2) synthesis of eicosanoids
Linoleic, linolenic (plant oils)

15. Proteins Sources Excesses can lead to obesity 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)
Cereals are low in lysine; grains are low in isoleucine and lysine; legumes are low in methionine, tryptophan, and cysteine.
Net protein utilization of animal proteins is about 70-90%; in vegetable proteins about 40-70%.
Legumes - A member of the plant family Leguminosae, and the name for the fruit produced by members of that family, as idealized in a bean or pea pod. The legume and grass families are by far the world's most important sources of food. Legumes, which include beans, soybeans, peas, and alfalfa, supply protein and fats. Through their root nodules, which are inhabited by Rhizobium bacteria, the legumes also preserve the nitrogen balance in the soil.
Essential amino acids (10; 8 in adult)– cannot be synthesized by the body (isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine; arginine, histidine)

16. Utilization of Proteins
regulation of water balance
control of pH
formation of antibodies
build cell structures
enzymes
hormones
transport of oxygen

17. 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

18. Transamination Clinically important transaminases:
- Alanine Transaminase (ALT) (also: Alanine Aminotransferase, Glutamic-Pyruvic Transaminase (SGPT)) – primarily for detecting liver disease
- Aspartate Transaminase (AST) (also: Asparatate Aminotransferase, Glutamic-Oxaloacetic Transaminase (SGOT) – detect cell death in tissues with high metabolic activity

19. 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

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

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

22. Metabolism Glycolysis – metabolism of glucose to pyruvate (Fed)
Hormones: Fed – Insulin Fasted – 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) – (Fed)
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)

23. 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
For every liter of oxygen consumed, approx. 4.8 kcal of energy is released from organic nutrients (although the exact figure depends upon the types of nutrients being oxidized).
BMR is profoundly affected by circulating thyroid hormone levels

24. 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)
Thin
< 18.5
Healthy or Normal
18.5 – 24.9
Overweight
25.0 – 29.9
Obese
30.0 – 39.9
Morbidly Obese
 40.0
BMI = [Wt (lbs) x 714] / [Height (in)]2
* Source: World Health Organization

25. 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 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

26. 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
The function of vitamin D has been expanded beyond regulating plasma calcium and phosphorus levels, and hence healing the diseases of rickets and osteomalacia. It is now known that the vitamin D hormone controls parathyroid gland growth and production of the parathyroid hormone. It is an immunomodulator. Vitamin D hormone also appears to play a role in the regulation of insulin production or secretion. Finally, it is required for female reproduction. These new sites of action of vitamin D are under intense investigation.
Vit E - the major function of vitamin E is to serve as a chain-breaking antioxidant, protecting cell membranes against free-radical damage. Major symptoms of deficiency are in the nervous system: Ataxia (lack of muscular coordination) and other neurologic symptoms result in severe incoordination and subsequent musculoskeletal changes.

27. Deficiency/Excess of Fat-soluble Vitamins
Deficiency (avitaminosis)
Rarely occurs in developed countries
Stored in adipose tissues
Deficiencies from other causes more common
Insufficient absorption
Inadequate storage
Excess (hypervitaminosis)
Excessive intake
Inability to excrete
Vitamin toxicity

28. 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
About 2-3 years of reserve B12 in body; about 15 days reserve of vit C.

29. History of USDA’s Food Guidance
Slide from:
Food for Young Children
1992
1916
1940s
1970s
2005
1950s-1960s

30. New Food Pyramid (2005)

31. Food Pyramid
From:

32. Malnutrition poor nutrition
undernutrition – deficiency of essential nutrients
overnutrition – excess of nutrient intake
primary malnutrition – malnutrition from diet alone
secondary malnutrition – diet is sufficient but nutrients cannot be absorbed, e.g., insufficient bile

33. Starvation
person can survive days without food (but vitamin deficiencies and their effects begin to appear after a week or two)
symptoms include metabolic acidosis, low blood pressure, slow pulse, chills, dry skin, hair loss, and poor immunity
Marasmus – lack of all nutrients
Kwashiorkor – protein starvation
Anorexia nervosa – eating disorder; self-starvation
Bulimia – eating disorder; bingeing and purging
Body will adapt to starvation by using CHO first, then fats, and finally protein

34. Regulation of Appetite
Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007
Also see Table 18.2 in Hole
Ghrelin (parietal cells of stomach, esp when empty) – sensation of hunger.
Peptide YY (PYY) – secreted by ileum and colon; signals satiety and terminates eating. Also acts to keep stomach from emptying too fast (ileal brake).
CCK – enteroendocrine cells of duodenum and jejunum – appetite suppressing effect.
Letpin (long-term regulator) – secreted by adipocytes throughout body. Level proportional to fat stores (let’s brain know how much body fat we have). Also inhibits the secretion of endocannabinoids (appetite stimulators named for their resemblance to THC of marijuana).
Insulin has a similar, but weaker effect, than leptin in the brain.
Norepinephrine stimulates the appetite for CHO, galanin for fatty foods, and endorphins for proteins.
There are currently two known types of cannabinoid receptors, termed CB1 and CB2.
CB1 receptors are found primarily in the brain, specifically in the basal ganglia and in the limbic system, including the hippocampus. They are also found in the cerebellum and in both male and female reproductive systems. CB1 receptors are essentially absent in the medulla oblongata, the part of the brain stem that is responsible for respiratory and cardiovascular functions. Thus, there is not a risk of respiratory or cardiovascular failure as there is with many other drugs. CB1 receptors appear to be responsible for the euphoric and anticonvulsive effects of cannabis.
CB2 receptors are almost exclusively found in the immune system, with the greatest density in the spleen. CB2 receptors appear to be responsible for the anti-inflammatory and possibly other therapeutic effects of cannabis.

35. I didn’t want to say anything, Dear, but…
A mutation in the leptin gene in the ob/ob mouse (Right) leads to morbid obesity and provides an excellent experimental model.

36. Life-Span Changes
BMR rises in early childhood and peaks in adolescence
BMR declines in adulthood
change in nutrition often reflects effects of medical conditions and social and economic circumstances

37. Metabolism and fate of macronutrients
Review
Metabolism and fate of macronutrients
Carbohydrate
Broken down into monosaccharides
Metabolism, glycogen, fat, pentose sugars
Lipids
Saturated vs. unsaturated fats
Broken down into glycerol and fatty acids
Used for energy (or storage of energy)
Proteins
Complete vs. incomplete proteins
Broken down into amino acids
Structural components or energy

38. Review Fat-soluble vitamins Water-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

39. Review *Mineral *Symbol *Major/Trace Primary Distribution
*Major Function(s)
Major
Sources
Conditions
*Calcium Ca
Bones & Teeth
Structure of bone/teeth;
nerve impulse conduction;
muscle contraction
milk;
+ kidney stones
- stunted growth
*Phosphorus P
ATP;
Nucleic acid & proteins
meats;
cheese;
milk
+ none
*Potassium K
Intracellular Fluid
maintenance of resting membrane potential (RMP)
avocados;
bananas;
potatoes
- muscular & cardiac problems
Sulfur S
skin, hair, nails
essential part of amino acids, thiamine, insulin, biotin, and MPS
eggs
- none
*Sodium Na
Extracellular Fluid
maintenance of RMP, electrolyte, water, & pH balance
table salt;
cured ham
+ hyperten-sion, edema
- cramps, convulsions

40. Review *Mineral *Symbol *Major/Trace Primary Distribution
*Major Function(s)
Major
Sources
Conditions
*Chlorine Cl
Extracellular Fluid
maintenance of RMP, electrolyte, water, & pH balance
table salt;
cured ham
+ vomiting
- muscle cramps
*Magnesium Mg
Bones
needed in mitochondria for cellular respiration;
ATP/ADP conversion
milk;
dairy;
legumes
+ diarrhea
- neuro-muscular problems
*Iron Fe
Trace
Blood
part of hemoglobin
liver
+ liver damage
- anemia
Manganese Mn
liver, kidneys
occurs in many enzymes
nuts
+ none
- none
Copper Cu
liver, heart, brain
essential in synthesis of hemoglobin, bone, melanin, myelin
liver;
oysters
crabmeat
+ rare
- rare
*Iodine I
thyroid
essential in the synthesis of thyroid hormones
iodized table salt
+ thyroid hormone imbalance
- goiter

41. Review *Mineral *Symbol *Major/Trace Primary Distribution
*Major Function(s)
Major
Sources
Conditions
Cobalt Co
Trace
widely distributed
component of cyanocobalamin (B12)
liver;
lean meats
+ heart disease
- pernicious anemia
*Zinc Zn
liver, kidneys, brain
wound healing; part of several enzymes
meats;
cereals
+ slurred speech
- decreased
immunity
Fluorine F
bones & teeth
tooth structure
fluorida-ted water
+ mottled teeth
- none
Selenium Se
liver & kidney
occurs in enzymes
+ vomiting, fatigue
Chromium Cr
essential for use in carbohydrates
+ none