1. Chapter 20 Nutrition and Metabolism
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Nutrients
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.
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Healthy Eating
4 Cal/ gram for protein or carbohydrate
9 Cal/gram for lipids
Experted-suggested dietary calories:
50-60% Calories from carbohydrate
Should be <15% monosaccharides
<30% from fats (mostly triglycerides)
Should be < 10% from saturated fats
12-15% from protein
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4. Guidelines for Healthy Eating
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:
1 drink/day for women; 2 drinks/day for men
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My Pyramid
Introduced in 2005 by USDA
Web:
Personalized approach to healthy food choices
Based on gender, age, and activity
Food from each of 6 bands needed each day
Example: healthy, moderately active 18-year-old
Female requires about 2000 Calories/day
Male requires about 2800 Calories/day
Steps a reminder of daily activity needed
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My Pyramid
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7. Categories of Nutrients
Carbohydrates, proteins, lipids
Calories for energy + building materials.
Water
Minerals
Ca, P, K, S, Na, Cl, Fl, Mg, Fe, Cr, I, Mn, Co, Cu, Zn, Se. Table 21.1
Vitamins: essential or dietary provitamins
Lipid-soluble: A, D, E, K
Water-soluble: B vitamins and C
Functions: Table 20.2
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8. Categories of Nutrients: Six
Carbohydrates, proteins, lipids
Give calories for energy + building materials.
Minerals: inorganic (Table 20.1)
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)
Lipid soluble: A, D, E, K
Water soluble: B group, C
Many function as coenzymes
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Metabolism
Facilitated by enzymes and coenzymes
NAD+ from B vitamin niacin
FAD from riboflavin (B2)
Sequence of enzymatic steps is a pathway
Two categories
Anabolism: synthesis of more complex chemicals
Catabolism: breakdown with energy release
40%  cellular functions (ATP)
60%  heat
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Metabolism
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11. Metabolism Interactions Animation
Introduction to Metabolism
You must be connected to the internet to run this animation.
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Metabolism
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13. Carbohydrate Metabolism
Glucose: the body’s preferred source for ATP production
Possible uses of glucose
Used immediately for ATP production
Stored as glycogen in liver or skeletal muscle
Leftover: forms triglycerides in adipose tissue
Enters cells by facilitated diffusion
Insulin increases rate of transport
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Glucose Catabolism
Overall catabolism of glucose
Glucose + 6 O2  ATP + 6 CO2 + 6 H2O
Glycolysis (in cytosol)
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
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15. Glucose Anabolism and Regulation of Blood Glucose Levels
When blood glucose is high
Glucose + ATP  glycogen (in liver, muscle)
Effect: blood glucose level is lowered
When blood glucose is low
Hormones glucagon and epinephrine stimulate
Glycogen breakdown to  glucose
Hormones: glucagon and cortisol stimulate
Gluconeogenesis in liver cells by
Glycerol (from fat)  glucose
Some amino acids  glucose
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16. Glucose Anabolism and Regulation of Blood Glucose Levels
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Lipid Metabolism
Lipolysis (catabolism): triglycerides  glycerol + fatty acids
Glycerol  glycolysis or gluconeogenesis
Fatty acids  acetyl-CoA (2-carbon)  Krebs cyle  ATP
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)
Excess fats, carbohydrates, or proteins  fats
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Lipid Metabolism
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19. Lipid Transport in Blood
Lipids are not water soluble so need protein coating  lipoproteins
Types of lipoproteins
Chylomicrons: carry dietary fat to adipose
Very low-density lipoproteins (VLDL)
Made in liver; transport fat to adipose tissue
Converted to LDLs
Low-density lipoproteins (LDL): “bad”
Carry 75% of cholesterol to cells for use there
High-density lipoproteins (HDL): “good”
Remove excess cholesterol and transport to liver for disposal
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Protein Metabolism
Catabolism: protein breakdown
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
Essential amino acids (10): must come in diet
Nonessential amino acids (10): can be made in the body by modifications of essential amino acids
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21. Metabolism and Body Heat Gain
Heat is one form of energy
Measured in calories
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
Rate of production = metabolic rate
Basal metabolic rate (BMR) = heat produced from catabolism when resting and fasting
BMR for adult : Cal/day
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22. Metabolism and Body Heat
Metabolic rate is affected by the following
Exercise: rate can increase 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
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Body Heat Loss
Must be continuous as catabolism constantly produces heat
Routes of heat loss
Radiation: loss of body heat to air
Conduction: loss of body heat to surface, such as cold metal seat
Convection
Loss of body heat to air moving from a fan or from breeze outside shower curtain
Evaporation
Conversion of water to vapor as in sweating; helps prevent overheating with exercise
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24. Control of Body Temperature
Balance regulated by hypothalamus
Detects changes in temperature (“thermostat”)
Warming mechanisms
Sympathetic vasoconstriction   heat loss
Epinephrine   metabolism
Increased muscle tone  metabolism
Can lead to shivering   heat from muscles
 TSH  thyroid gland   thyroid hormone in blood   metabolism
Cooling mechanisms
The reverse + sympathetic-stimulated sweating
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End of Chapter 20
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