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Anatomy & Physiology
SIXTH EDITION
Chapter 25, part 3
Metabolism and Energetics
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
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Frederic H. Martini
Fundamentals of
SECTION 25-6
Metabolic Interactions
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Homeostasis
• No one cell of the human body can perform all
necessary homeostatic functions
• Metabolic activities must be coordinated
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Body has five metabolic components
• Liver
• The focal point for metabolic regulation and
control
• Adipose tissue
• Stores lipids primarily as triglycerides
• Skeletal muscle
• Substantial glycogen reserves
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Body has five metabolic components
• Neural tissue
• Must be supplied with a reliable supply of
glucose
• Other peripheral tissues
• Able to metabolize substrates under endocrine
control
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The absorptive state
• The period following a meal
• Nutrients enter the blood as intestinal
absorption proceeds
• Liver closely regulates glucose content of blood
• Lipemia commonly marks the absorptive state
• Adipocytes remove fatty acids and glycerol
from bloodstream
• Glucose molecule are catabolized and amino
acids are used to build proteins
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Figure 25.15 The Absorptive State
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Figure 25.15
The Postabsorptive state
• From the end of the absorptive state to the next
meal
• Body relies on reserves for energy
• Liver cells break down glycogen, releasing
glucose into blood
• Liver cells synthesize glucose
• Lipolysis increases and fatty acids released into
blood stream
• Fatty acids undergo beta oxidation and enter
TCA
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The Postabsorptive state
• Amino acids either converted to pyruvate or
acetyl-CoA
• Skeletal muscles metabolize ketone bodies and
fatty acids
• Skeletal muscle glycogen reserves broken down
to lactic acid
• Neural tissue continues to be supplied with
glucose
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Figure 25.16 Metabolic Reserves
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Figure 25.16a
Figure 25.17 The Postabsorptive State
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Figure 25.17
SECTION 25-7
Diet and Nutrition
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Diet and Nutrition
• Nutrition
• Absorption of nutrients from food
• Balanced diet
• Contains all the ingredients necessary to
maintain homeostasis
• Prevents malnutrition
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Food
• Food groups and food pyramids
• Used as guides to avoid malnutrition
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Food Groups
• Six basic food groups of a balance diet arranged
in a food pyramid
• Milk, yogurt and cheese
• Meat, poultry, fish, dry beans, eggs, and nuts
• Vegetables
• Fruits
• Bread, cereal, rice and pasta
• Base of pyramid
• Fats, oils and sweets
• Top of pyramid
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Figure 25.18 The Food Pyramid and Dietary
Recommendations
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Figure 25.18
Nitrogen balance
• N compounds contain nitrogen
• Amino acids, purines, pyrimidines, creatine,
porphyrins
• Body does not maintain large nitrogen reserves
• Dietary nitrogen is essential
• Nitrogen balance is an equalization of absorbed
and excreted nitrogen
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Minerals
• Act as co-factors in enzymatic reactions
• Contribute to osmotic concentrations of body
fluids
• Play a role in transmembrane potentials, action
potentials
• Aid in release of neurotransmitters and muscle
contraction
• Assist in skeletal construction and maintenance
• Important in gas transport and buffer systems
• Aid in fluid absorption and waste removal
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Vitamins
• Are needed in very small amounts for a variety of
vital body activities
• Fat soluble
• Vitamins A, D, E, K
• Taken in excess can lead to hypervitaminosis
• Water soluble
• Not stored in the body
• Lack of adequate dietary intake = avitaminosis
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SECTION 25-8
Bioenergetics
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Bioenergetics
• The study of acquisition and use of energy by
organisms
• Energy content of food expressed in Calories
per gram (C/g)
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Food and energy
• Catabolism of lipids yields 9.46 C/g
• Catabolism of proteins and carbohydrates yields
~4.7 C/g
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Metabolic rate
• Total of all anabolic and catabolic processes
underway
• Basal metabolic rate (BMR) is the rate of energy
used by a person at rest
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Thermoregulation
• Homeostatic regulation of body temperature
• Heat exchange with the environment involves
four processes:
• Radiation
• Conduction
• Convection
• Evaporation
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Figure 25.19 Routes of Heat Gain and Loss
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Figure 25.19
Regulation of heat gain and loss
• Preoptic area of hypothalamus acts as thermostat
• Heat-loss center
• Heat-gain center
• Mechanisms for increasing heat loss include:
• Peripheral vasodilation
• Increase perspiration
• Increase respiration
• Behavioral modifications
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Mechanisms promoting heat gain
• Decreased blood flow to the dermis
• Countercurrent heat exchange
• Shivering thermogenesis and nonshivering
thermogenesis
• Differs by individuals due to acclimatization
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Figure 25.20 Countercurrent Heat Exchange
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Figure 25.20
Thermoregulation
• Problems in infants
• Lose heat quickly due to their small size
• Do not shiver
• Use brown fat to accelerate lipolysis - energy
escapes as heat
• Variations in adults
• Use subcutaneous fat as an insulator
• Different hypothalamic thermostatic settings
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Pyrexia is elevated body temperature
• Fever is body temperature greater than 37.2oC
• Can result from a variety of situations including:
• Heat exhaustion or heat stroke
• Congestive heart failure
• Impaired sweat gland activity
• Resetting of the hypothalamic thermostat by
circulating pyrogens
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You should now be familiar with:
• Why cells need to synthesis new organic
components
• The basic steps in glycolysis, the TCA cycle, and
the electron transport chain
• The energy yield of glycolysis and cellular
respiration
• The pathways involved in lipid, protein and
nucleic acid metabolismBMR
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You should now be familiar with:
• The characteristics of the absorptive and
postabsorptive metabolic states
• What constitutes a balanced diet and why such a
diet is important
• Metabolic rate and the factors involved in
determining an individual’s BMR
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