Transcript Human Anatomy & Physiology II

Chapter 20
Nutrition and
Metabolism
Copyright 2010, John Wiley & Sons, Inc.
Nutrients
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Nutrients are chemicals the body uses for
growth, maintenance, and repair
Essential nutrients: ones needed in the diet
because the body cannot make sufficient
amounts to meet body needs.
There are six major types of nutrients:
carbohydrates, lipids, proteins, minerals,
vitamins, and water.
Copyright 2010, John Wiley & Sons, Inc.
Healthy Eating
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4 Cal/ gram for protein or carbohydrate
9 Cal/gram for lipids
Experted-suggested dietary calories:
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50-60% Calories from carbohydrate
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<30% from fats (mostly triglycerides)
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Should be <15% monosaccharides
Should be < 10% from saturated fats
12-15% from protein
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Guidelines for Healthy Eating
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Eat a variety of foods
Maintain a healthy weight
Choose foods low in fat, saturated fat, and
cholesterol
Eat plenty of fruits, vegetables, and grains
Use sugars in moderation
Use sodium in moderation: < 2.3 grams/day
Use alcoholic beverages in moderation only:
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1 drink/day for women; 2 drinks/day for men
Copyright 2010, John Wiley & Sons, Inc.
My Pyramid
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Introduced in 2005 by USDA
Web: http://www.mypyramid.gov/
Personalized approach to healthy food
choices
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Based on gender, age, and activity
Food from each of 6 bands needed each day
Example: healthy, moderately active 18-year-old
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Female requires about 2000 Calories/day
Male requires about 2800 Calories/day
Steps a reminder of daily activity needed
Copyright 2010, John Wiley & Sons, Inc.
My Pyramid
Copyright 2010, John Wiley & Sons, Inc.
Categories of Nutrients
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Carbohydrates, proteins, lipids
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Water
Minerals
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Calories for energy + building materials.
Ca, P, K, S, Na, Cl, Fl, Mg, Fe, Cr, I, Mn, Co, Cu,
Zn, Se. Table 21.1
Vitamins: essential or dietary provitamins
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Lipid-soluble: A, D, E, K
Water-soluble: B vitamins and C
Functions: Table 20.2
Copyright 2010, John Wiley & Sons, Inc.
Categories of Nutrients: Six
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Carbohydrates, proteins, lipids
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Minerals: inorganic (Table 20.1)
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Give calories for energy + building materials.
Ca, P, K, S, Na, Cl, Fl, Mg, Fe, I, Mn, Co, Cu, Zn,
Se, Cr
Electrolytes, components of skeleton, enzymes
Vitamins: organic (Table 20.2)
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Lipid soluble: A, D, E, K
Water soluble: B group, C
Many function as coenzymes
Copyright 2010, John Wiley & Sons, Inc.
Metabolism
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Facilitated by enzymes and coenzymes
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NAD+ from B vitamin niacin
FAD from riboflavin (B2)
Sequence of enzymatic steps is a pathway
Two categories
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Anabolism: synthesis of more complex chemicals
Catabolism: breakdown with energy release
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40%  cellular functions (ATP)
60%  heat
Copyright 2010, John Wiley & Sons, Inc.
Metabolism
Copyright 2010, John Wiley & Sons, Inc.
Metabolism
Interactions Animation
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Introduction to Metabolism
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Metabolism
Copyright 2010, John Wiley & Sons, Inc.
Carbohydrate Metabolism
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Glucose: the body’s preferred source for ATP
production
Possible uses of glucose
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Used immediately for ATP production
Stored as glycogen in liver or skeletal muscle
Leftover: forms triglycerides in adipose tissue
Enters cells by facilitated diffusion
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Insulin increases rate of transport
Copyright 2010, John Wiley & Sons, Inc.
Glucose Catabolism
Overall catabolism of glucose
Glucose + 6 O2  36-38 ATP + 6 CO2 + 6 H2O
1. Glycolysis (in cytosol)
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 Glucose  pyruvate + ATP + NADH + H
 Anaerobic cellular respiration
2. Transition step (in mitochondria):
Pyruvate  acetyl CoA + CO2 + NADH + H+
3. Krebs cycle (in mitochondria): aerobic
CO2 + ATP + NADH + H+ + FADH2
4. Electron transport chain (in mitochondria): aerobic
 NADH + H+ + FADH2 + O2  ATP + H2O
Copyright 2010, John Wiley & Sons, Inc.
Glucose Anabolism and Regulation of
Blood Glucose Levels
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When blood glucose is high
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Glucose + ATP  glycogen (in liver, muscle)
Effect: blood glucose level is lowered
When blood glucose is low
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Hormones glucagon and epinephrine stimulate
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Glycogen breakdown to  glucose
Hormones: glucagon and cortisol stimulate
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Gluconeogenesis in liver cells by
Glycerol (from fat)  glucose
 Some amino acids  glucose
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Glucose Anabolism and Regulation of
Blood Glucose Levels
Copyright 2010, John Wiley & Sons, Inc.
Lipid Metabolism
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Lipolysis (catabolism): triglycerides 
glycerol + fatty acids
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Glycerol  glycolysis or gluconeogenesis
Fatty acids  acetyl-CoA (2-carbon)  Krebs
cyle  ATP
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Liver converts some acetyl-CoA  ketone bodies
Diabetics can form excessive ketone bodies  acetone
(causes sweet breath) + acidosis (with possible coma
and death)
Lipogenesis (anabolism)
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Excess fats, carbohydrates, or proteins  fats
Copyright 2010, John Wiley & Sons, Inc.
Lipid Metabolism
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Lipid Transport in Blood
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Lipids are not water soluble so need
protein coating  lipoproteins
Types of lipoproteins
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Chylomicrons: carry dietary fat to adipose
Very low-density lipoproteins (VLDL)
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Low-density lipoproteins (LDL): “bad”
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Made in liver; transport fat to adipose tissue
Converted to LDLs
Carry 75% of cholesterol to cells for use there
High-density lipoproteins (HDL): “good”
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Remove excess cholesterol and transport to liver for
disposal
Copyright 2010, John Wiley & Sons, Inc.
Protein Metabolism
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Catabolism: protein breakdown
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Deamination in liver to remove NH2  NH3
Liver converts toxic NH3  urea  urine
Rest of amino acid  Krebs cycle  ATP
Anabolism: protein synthesis to form many
different proteins in the body
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Essential amino acids (10): must come in diet
Nonessential amino acids (10): can be made in
the body by modifications of essential amino
acids
Copyright 2010, John Wiley & Sons, Inc.
Metabolism and Body Heat Gain
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Heat is one form of energy
Measured in calories
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1 calorie (cal) = energy needed to raise 1 g of
water 1oC
For foods use kilocalories (1000 cal) = Calorie
Heat is produced (gained) from catabolism
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Rate of production = metabolic rate
Basal metabolic rate (BMR) = heat produced from
catabolism when resting and fasting
BMR for adult :1200-1800 Cal/day
Copyright 2010, John Wiley & Sons, Inc.
Metabolism and Body Heat
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Metabolic rate is affected by the following
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Exercise: rate can increase 15-20 times
Hormones: thyroid is primary
Nervous System: ANS can increase
Body temperature: warming increases
Ingestion of food: gives 10-20% increase
Age: metabolic rate of child higher than adult’s
Gender, pregnancy, climate, sleep, malnutrition
Copyright 2010, John Wiley & Sons, Inc.
Body Heat Loss
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Must be continuous as catabolism constantly
produces heat
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Routes of heat loss
 Radiation: loss of body heat to air
 Conduction: loss of body heat to surface, such as
cold metal seat
 Convection
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Loss of body heat to air moving from a fan or from
breeze outside shower curtain
Evaporation
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Conversion of water to vapor as in sweating; helps
prevent overheating with exercise
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Control of Body Temperature
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Balance regulated by hypothalamus
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Detects changes in temperature (“thermostat”)
Warming mechanisms
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Sympathetic vasoconstriction   heat loss
Epinephrine   metabolism
Increased muscle tone  metabolism
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Can lead to shivering   heat from muscles
 TSH  thyroid gland   thyroid hormone in
blood   metabolism
Cooling mechanisms
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The reverse + sympathetic-stimulated sweating
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End of Chapter 20
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