Chapter 24 Nutrition & Metabolism Lecture 12 Marieb’s Human Anatomy and Physiology Ninth Edition Marieb Hoehn.

Chapter 24Nutrition & Metabolism

Lecture 12

Marieb’s HumanAnatomy and

PhysiologyNinth Edition

Marieb Hoehn

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

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Overview of General Metabolic Pathways

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Lipolysis

Lipo-

genesis

Glycogenesis

Glycogenolysis

Overall goal of catabolism: generate a pool of 2- or 3-carbon molecules and ATP

Pyruvate is used to synthesize amino acids and Acetyl CoA

Pyruvate can also be used to synthesize glucose via gluconeogenesis.

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Carbohydrates

Sources• sugars (simple)• starches (complex) - usually from plant sources• glycogen (complex) in meats• cellulose (complex) is indigestible fiber

Recommended (Dietary) Daily Allowance (RDA) is 125-175g

Excesses lead to • obesity• dental caries• nutritional deficits

Deficiencies lead to • metabolic acidosis• weight loss

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Utilization of Carbohydrates

• oxidized for energy

• production of certain molecules (ribose, deoxyribose)

• stored in liver and muscles as glycogen

• converted to fats and stored in adipose tissue

Disaccharides – Sucrose, lactose, and maltose

Monosaccharides – Glucose, fructose, galactose

Glucose is the body’s CHO energy source

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Utilization of Carbohydrates

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LipidsSources

• meats• eggs• milk• lard• plant oils

RDA is 80-100g ( 30% of calories)( 10% saturated fat)

Excesses lead to • obesity• increased serum cholesterol• increased risk of heart disease

Deficiencies lead to • weight loss• skin lesions• hormonal imbalances

Fats generally take the longest to digest. Why?

9

Utilization of Lipids

How is fat absorbed from the digestive tract?

Know these terms (see table of these terms later in this lecture)

Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

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Beta-Oxidation of Fatty Acids

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 1.5-2.0 times the energy from a comparable amount of glucose

Mitochondrion

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Energy Values of Food

Carbohydrates4.1 Calories per gram

Lipids9.5 Calories per gram

Proteins4.1 Calories per gram

Calorie (kilocalorie, big calorie) – amount of heat needed to raise the temperature of 1 kg of water by 10 C

Diet is 2000 Calories. What is the maximum number of grams of fat that should be taken in daily?

How many grams of fat are there in a Whopper with cheese and a small order of french fries?

Know this - you can round these off to the 4, 4, and 9)

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Lipoprotein Traffic

Figure From: Martini, Anatomy & Physiology, Prentice Hall, 2001

Note the role of HDLs as scavengers of tissue/blood cholesterol.

TG-richCholesterol-rich

*Cholesterol can be manufactured from Acetyl-CoA

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Summary of LipoproteinsDesignation 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)

Liver Transports cholesterol from liver to cells in body

High Density Lipoprotein (HDL)

Liver Removes excess cholesterol from cells and transports to

liver

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Utilization of Lipids

The liver uses fatty acids to synthesize a variety of lipids

Triglyceride

Linoleic, linolenic (plant oils)

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Proteins

Sources• meats• cheeses• nuts• legumes

*RDA is 0.8g/kg body weight or 10% of diet(1 kg = 2.2 lbs)

Excesses can lead to obesity

Deficiencies lead to • extreme weight loss• muscle wasting• anemia• growth retardation

Essential amino acids (10; 8 in adult)– cannot be synthesized by the body (isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, and methionine; arginine, histidine)

Incomplete proteins – unable to maintain human tissues or support normal growth and development by themselves

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Utilization of Proteins

• build cell structures• enzymes• hormones• transport of oxygen

• regulation of water balance• control of pH• formation of antibodies

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Utilization of Proteins for EnergyAmmonia, 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

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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

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Nitrogen Balance

• 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

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.

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The “Fed” (Absorptive) State

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Know this

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The “Fasted” (Postabsorptive) State

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001Know this

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Metabolism

• 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)

-olysis breakdown of -neo new-genesis creation of

Hormones: Fed – Insulin Fasted – Glucagon, Corticosteroids, Epi/NE

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Energy RequirementsBasal 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

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

BMR is proportional to body weight

Body’s basal metabolic rate (BMR) falls 10% during sleep and about 40% during prolonged starvation

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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

* Source: World Health Organization

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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

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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

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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

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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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History of USDA’s Food Guidance

1940s

1950s-1960s

1970s

1992

2005

Food for Young

Children

1916

Slide from: http://www.mypyramid.gov/downloads/MyPyramid%20Peer%20to%20Peer.ppt

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New Food Pyramid (2005)

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Food Pyramid

From: http://www.mypyramid.gov/downloads/MyPyramid%20Peer%20to%20Peer.ppt

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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

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Starvation• person can survive 50-70 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

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Regulation of Appetite

Also see Table 18.2 in Hole

Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

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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.

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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

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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

39

Review

*Mineral *Symbol *Major/Trace Primary Distribution

*Major Function(s)

MajorSources

Conditions

*Calcium Ca Major Bones & Teeth Structure of bone/teeth;

nerve impulse conduction;

muscle contraction

milk; + kidney stones

- stunted growth

*Phosphorus P Major Bones & Teeth Structure of bone/teeth;

ATP;Nucleic acid &

proteins

meats;cheese;milk

+ none- stunted

growth

*Potassium K Major Intracellular Fluid maintenance of resting membrane potential (RMP)

avocados;bananas;potatoes

+ none- muscular &

cardiac problems

Sulfur S Major skin, hair, nails essential part of amino acids, thiamine, insulin, biotin, and MPS

meats;milk;eggs

+ none- none

*Sodium Na Major Extracellular Fluid maintenance of RMP, electrolyte, water, & pH balance

table salt;cured ham

+ hyperten-sion, edema

- cramps, convulsions

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Review

*Mineral *Symbol *Major/Trace Primary Distribution

*Major Function(s)

MajorSources

Conditions

*Chlorine Cl Major Extracellular Fluid

maintenance of RMP, electrolyte, water, & pH balance

table salt;cured ham

+ vomiting- muscle cramps

*Magnesium Mg Major 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 Trace liver, kidneys occurs in many enzymes

nuts + none- none

Copper Cu Trace liver, heart, brain essential in synthesis of hemoglobin, bone, melanin, myelin

liver;oysterscrabmeat

+ rare- rare

*Iodine I Trace thyroid essential in the synthesis of thyroid hormones

iodized table salt

+ thyroid hormone imbalance- goiter

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Review

*Mineral *Symbol *Major/Trace Primary Distribution

*Major Function(s)

MajorSources

Conditions

Cobalt Co Trace widely distributed component of cyanocobalamin (B12)

liver;lean meats

+ heart disease- pernicious anemia

*Zinc Zn Trace liver, kidneys, brain

wound healing; part of several enzymes

meats;cereals

+ slurred speech- decreasedimmunity

Fluorine F Trace bones & teeth tooth structure fluorida-ted water

+ mottled teeth- none

Selenium Se Trace liver & kidney occurs in enzymes lean meatscereals

+ vomiting, fatigue- none

Chromium Cr Trace widely distributed essential for use in carbohydrates

liver;lean meats

+ none- none