The document summarizes key aspects of nutrition and metabolism. It describes six major types of nutrients - carbohydrates, lipids, proteins, minerals, vitamins, and water. Guidelines are provided for healthy eating, including recommendations for calorie intake from carbohydrates, fats, and proteins. The roles of the major categories of nutrients in metabolism are explained. Carbohydrate, lipid, and protein metabolism are summarized, along with how the body regulates blood glucose levels and body temperature.

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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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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: http://www.mypyramid.gov/
 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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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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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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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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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  36-38 ATP + 6 CO2 + 6 H2O
1. 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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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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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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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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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 1o
C
 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 :1200-1800 Cal/day

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Metabolism and Body Heat
 Metabolic rate is affected by the following
 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

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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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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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