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Chapter 17
Nutrition and Metabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Topics
Introduction
Cellular Metabolism
Diet and Nutrition
Bioenergetics
Aging and Nutritional Requirements
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Cells require oxygen and nutrients to
carry out energy-generating processes
– Nutrients obtained from diet
Absorbed at the digestive tract
Distributed by the cardiovascular system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
ATP energy supports:
–
–
–
–
–
Growth
Cell division
Contraction
Secretion
All other special functions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Nutrient requirements
– Vary between any 2 tissues
– Changes as metabolic needs change
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Different organs and tissues store
excess nutrients
– Example: Lipids in adipose tissue
Endocrine system controls the storage
and release of nutrients
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Nutrition
– Absorption of nutrients from food
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Metabolism
– Refers to all chemical reactions in the
body
Cellular metabolism
– Chemical reactions within cells
– Provides energy to maintain homeostasis
and perform essential functions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nutrient pool
– Includes all nutrients in the cytoplasm
– Includes amino acids, lipids, and simple
sugars
– Utilized for all the cell’s metabolic
operations
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Catabolism
– Breakdown of
organic molecules
– Releases energy
Used to synthesize
ATP and other
high-energy
compounds
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Steps in catabolism
– Initial steps occur in cytosol
Enzymes break down large organic
molecules
Form smaller fragments
Example: Carbohydrates broken down into short
carbon chains
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Steps in catabolism
– Initial steps
Produce very little ATP
Products can be absorbed and processed by
mitochondria
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Steps in
catabolism
– Mitochondrial steps
Release significant
amounts of energy
Mitochondrial
enzymes break
covalent bonds
Capture roughly
40% of energy
released
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Steps in
catabolism
– Mitochondrial steps
Captured energy
Converts ADP to
ATP
Escapes as heat
that warms the
interior of the
cell and
surrounding
tissue
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Anabolism
– Synthesis of new
organic molecules
Involves the
formation of new
chemical bonds
Uses the energy
produced by
mitochondrial
processes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Mitochondrial processes
– Energy supports anabolism and other
functions
Ciliary or cell movement
Contraction
Active transport
Cell division
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
4 reasons for synthesis of new organic
components
– To perform structural maintenance and
repairs
– To support growth
– To produce secretions
– To build nutrient reserves
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
To perform structural maintenance and
repairs
– Metabolic turnover
Continuous removal and replacement of cell
structures
Most cell structures are temporary
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
To support growth
– Enlarge and synthesize extra proteins
and organelles
– Necessary as cells prepare to divide
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
To produce secretions
– Secretory cells synthesize their products
– Deliver them to interstitial fluid
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
To build nutrient reserves
– Utilized during periods of extreme activity
– Utilized when nutrient supply in
bloodstream is inadequate
– Nutrients mobilized as needed
– Example: Glucose stored as glycogen
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nutrient pool
– Source of organic molecules
– Used for anabolism and catabolism
– Conserve materials to build new
compounds
– Break down remaining compounds
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nutrient pool
– Anabolic activities
Require more amino acids than lipids and
carbohydrates
– Catabolic activities
Process organic molecules in reverse order
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Mitochondria
– Requires specific
organic molecules for
processing and energy
production
Chemical reactions
occur in cytoplasm
Break organic nutrients
in the pool into smaller
carbon chains
Mitochondria use the
small carbon chains
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Mitochondria
– Chemical reactions continue to break
down fragments
– Generate carbon dioxide, water, and ATP
Involves 2 pathways
TCA cycle
Electron transport system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate metabolism
– Important sources of energy
Sugars and starches
Break down to generate ATP and other
high-energy compounds
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate metabolism
– Chemical reaction
C6H12O6 + 6 O2 ↔ 6 CO2 + 6 H2O
Glucose + oxygen ↔ carbon dioxide + water
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate metabolism
– Occurs in a series of small steps
– Releases enough energy to support
conversion between ADP and ATP
– Completes conversion creates 36 ATP
molecules
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate metabolism
– First steps occur in cytosol
Reactions called glycolysis
Anaerobic
– Most ATP production occurs in the
mitochondria
Consume oxygen
Called aerobic or cellular metabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Glycolysis
– Breakdown of glucose to pyruvic acid
– C6H12O6 breaks into 2 C3H4O3 (CH3-COCOOH)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Glycolysis requirements
–
–
–
–
Glucose molecules
Appropriate cytoplasmic enzymes
ATP and ADP
NAD (nicotinamide adenine dinucleotide)
Coenzyme that removes hydrogen atoms
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Glycolysis
– Reaction gains 2 ATP for each glucose
molecule converted to 2 pyruvic acid
molecules
Only energy production used by red blood
cells
Most cells cannot survive on ATP from
glycolysis alone
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Glycolysis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy production within mitochondria
– Additional energy stored in pyruvic acid
bonds
– Requires oxygen to liberate energy
Mitochondria absorb pyruvic acid
Completely break down molecule
Hydrogen removed with coenzymes
Source of energy gain
Carbon and oxygen removed as carbon dioxide
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy production within mitochondria
– Mitochondria have 2 membranes
Outer membrane permeable to pyruvic acid
Inner membrane utilizes a carrier protein
Transports pyruvic acid into matrix
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy production within mitochondria
– Pyruvic acid participates in reaction
– Leads to a series of enzymatic reactions
Tricarboxylic acid (TCA) cycle
Removes hydrogen from organic molecules
Transfers hydrogen to coenzymes in electron
transport system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Involves
Pyruvic acid
NAD
Coenzyme A (CoA)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Yields:
1 molecule of carbon dioxide
1 molecule of NADH
1 molecule of acetyl-CoA
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Acetyl CoA
2-carbon acetyl group
CH3CO
Bound to coenzyme A
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Acetyl group transferred from CoA to a
4-carbon molecule
– Forms a 6-carbon molecule
Citric acid
Reaction referred to as the citric acid cycle
Also referred to as the Krebs cycle
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Citric acid produced
– CoA released intact to bind again
– Removes 2 added carbon atoms
Regenerates the 4-carbon chain
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– 2 carbon atoms
Generates 2 carbon dioxide molecules
Metabolic waste product
Hydrogen atoms of acetyl group
Removed by coenzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Benefit of 1 revolution
Forms a single molecule of guanosine
triphosphate (GTP)
High-energy compound
Readily converted to ATP
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Hydrogen atoms
Removed by coenzymes
NAD
FAD
Flavine adenine dinucleotide
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– Coenzymes form:
NADH
FADH2
– Transfers atoms to the electron transport
system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The Electron Transport System (ETS)
– Embedded in the inner mitochondrial
membrane
– Consists of an electron transport chain
Made up of cytochromes
Series of protein-pigment complexes
– Does not produce ATP directly
Creates conditions necessary for ATP
production
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
– Hydrogen atoms do not enter ETS intact
Only electrons enter ETS
Protons released into mitochondrial matrix
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
– Electron transport from NADH
Involves the coenzyme FMN
– Electron transport FADH2
Moves directly to coenzyme Q
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
–
–
–
–
Electrons passed from coenzyme Q
Move to the first cytochrome
Continue to pass between cytochromes
Lose energy in a series of small steps
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
– Energy used to drive hydrogen ion pumps
Move hydrogen ions from mitochondrial matrix
Move into the intermembrane space
Located between the 2 mitochondrial membranes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
– Creates a large concentration gradient across
inner membrane
– Hydrogen ions diffuse into the matrix
Requires membrane enzyme
ATP synthase
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The ETS
– Hydrogen ions create kinetic energy
Used to attached phosphate group to ADP
Forms ATP
Process called chemiosmosis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
End of the ETS
Oxygen atom accepts the electrons
Combines with 2 hydrogen ions
Forms water molecule
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
The TCA cycle
– ETS
Most important mechanism for ATP
generation
Provides 95% of ATP needed by cells
Cells die if ETS stopped by lack of oxygen in
mitochondria
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy yield of glycolysis and cellular
respiration
– Chemical reactions begin with glucose
End with carbon dioxide and water
Main method of generating ATP
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy yield of glycolysis and cellular
respiration
– ATP gains
During glycolysis in cytoplasm
2 ATP for each glucose molecule converted to pyruvic
acid
Inside mitochondria
Pyruvic acid fully broken down in TCA cycle
Each revolution of TCA cycle yields 1 ATP
2 ATP gained
Electron transport chain
32 ATP generated for each glucose molecule broken
down
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Energy yield of glycolysis and cellular
respiration
– Total ATP gain
1 glucose molecule processed
36 ATP produced
34 ATP produced inside mitochondria
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Alternate catabolic pathways
– Aerobic metabolism
Cells require adequate oxygen and glucose
supplies
Without oxygen
Cells survive for brief periods
Without glucose
Cells break down other nutrients
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Alternate catabolic
pathways
– Nutrient sources
Cells can switch as the
need arises
Move from glucose to
lipids
Cells at rest rely on
fatty acids
Active cells use
glucose
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Alternate catabolic
pathways
– Protein use
Only when lipids
and carbohydrates
not available
Enzymes and
organelles needed
for cell survival
Composed of
proteins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Alternate catabolic pathways
– Nucleic acids
Present only in small quantities
Seldom catabolized for energy
Even when cells die from acute starvation
DNA in nucleus determines cells
characteristics
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate synthesis
– Glycolysis steps not reversible
– Glucose cannot be produced using same
enzymes
Requires different enzymes
Independently regulated
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate
synthesis
– Glucose synthesis
Uses pyruvic acid or
other three-carbon
molecules
Can be completed
from noncarbohydrate
precursors
Lactic acid, glycerol,
or amino acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate synthesis
– Acetyl-CoA
Cannot be used
Reaction between pyruvic acid and
acetyl-CoA not reversible
Removes carbon dioxide
Called decarboxylation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate
synthesis
– Gluconeogenesis
Synthesis of glucose
from
noncarbohydrate
precursors
Cannot use fatty
acids and many
amino acids
Breakdown
produces acetylCoA
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate
synthesis
– Glucose
molecules used
to manufacture
molecules
Simple sugars
Complex
carbohydrates
Nucleic acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Carbohydrate synthesis
– Glucose molecules
Stored as glycogen in the liver
Energy reserve
Broken down when cells cannot obtain glucose
from interstitial fluid
Form compact, insoluble granules
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid metabolism
– Contain carbon,
hydrogen, and
oxygen
Different
proportions than
carbohydrates
– Triglycerides
Most abundant
lipid in the body
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Referred to as
lipolysis
– Lipids broken down
Converted to
pyruvic acid
Can be channeled
directly into TCA
cycle
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Triglycerides
Split into component parts by hydrolysis
Yields:
1molecule of glycerol
3 fatty acid molecules
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Glycerol
Converted to pyruvic acid by cytoplasmic enzymes
Enters the TCA cycle
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Fatty acid catabolism
Referred to as beta-oxidation
Reaction with different enzymes
Broken down into two-carbon fragments
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Two-carbon fragments
Enter TCA cycle
Combine to form ketone bodies
Short carbon chains
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– Beta-oxidation
Occurs inside the mitochondria
Two-carbon fragments enter TCA cycle
immediately
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid catabolism
– ATP generation
Break down 118-carbon fatty acid molecule
Generates 144 ATP molecules
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipids and energy production
– Important energy reserves
– Breakdown provides large quantities of
ATP
– Insoluble in water
Stored in compact droplets in cytosol
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipids and energy production
– Large droplets
Difficult access for water-soluble enzymes
Reserves more difficult to access then
carbohydrates
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipids and energy production
– Processed in mitochondria
Activity limited by oxygen availability
Cannot provide large amounts of ATP
quickly
Used when glucose supplies are limited
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid synthesis
– Referred to as
lipogenesis
– Glycerol
Synthesized from
three-carbon product
of glycolysis
– Most other lipids
Synthesis begins with
acetyl-CoA
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid synthesis
– Can use almost any organic molecule
Can be converted to acetyl-CoA
Cannot synthesize everything they can
break down
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid synthesis
– Essential fatty
acids
Not synthesized by
the body
Must be included
in diet
Used to synthesize
prostaglandins and
phospholipids
Used in the cell
membrane
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Lipids needed to maintain cell
membranes
– Steroid hormones must reach target cells
in different tissues
– Lipids not soluble in water
– Require special mechanisms for
transport
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Lipoproteins
Lipids circulating in the bloodstream
Lipid-protein complexes
Contain triglycerides and cholesterol
Outer coating of phospholipids and proteins
Make complex soluble
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Exposed proteins
Bind to specific membrane receptors
Determine which cells absorb associated
lipids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Classification of lipids
Size
Relative proportions of lipids and proteins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Chylomicrons
Form in the intestinal tract
Largest lipoproteins
95% of weight consists of triglycerides
Transport to the bloodstream
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Other major groups of lipoproteins
Formed in the liver
Contain few triglycerides
Low-density lipoproteins (LDLs)
High-density lipoproteins (HDLs)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– LDLs
Deliver cholesterol to peripheral tissues
May end up in arterial plaques
Often called “bad cholesterol”
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– HDLs
Transport excess cholesterol from peripheral
tissues
Transported to the liver
Stored
Excreted in the bile
Does not cause circulatory problems
Called “good cholesterol”
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Free fatty acids (FFA)
Lipids that easily diffuse across the cell
membranes
Major source is breakdown of fat stored in
adipose tissue
Released into the blood
Bind to albumin
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Lipid transport and distribution
– Free fatty acids
Important energy source during starvation
Can be metabolized by:
Liver cells
Cardiac muscle cells
Skeletal muscle fibers
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Protein metabolism
– Body synthesizes over 400,000 proteins
Varied forms, functions, and structures
Composed of combinations of 20 amino
acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Protein metabolism
– Normal conditions
Continuous recycling of cellular proteins
Occurs in the cytoplasm
Peptide bonds are broken
Free amino acids used to manufacture new
proteins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Protein metabolism
– Inadequate energy sources
Mitochondria break down amino acids in
TCA cycle
Generate ATP
Benefits vary
Yield comparable to carbohydrate catabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– First step
Removal of the amino
group
Requires coenzyme
Derived from vitamin
B6
Pyridoxine
Removed by
transamination or
deamination
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Transamination
Attaches amino group to another carbon
chain
Creates a new amino acid
Enables the cell to synthesize many amino
acids for protein synthesis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Transamination
Locations
Liver
Skeletal muscles
Heart
Lung
Kidney
Brain
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Deamination
Prepares amino acid for breakdown in TCA
cycle
Removes the amino group
Generates an ammonia molecule (NH3)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Deamination
Ammonia
Highly toxic in low concentrations
Production occurs in the liver
Enzymes combine ammonia with carbon dioxide
Produces urea
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Deamination
Carbon chain remains
Can be converted to pyruvic acid
Used in gluconeogenesis
Can be converted to acetyl-CoA
Broken down in TCA cycle
Can be converted to ketone bodies
Organic acid like acetone
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Ketone bodies
Diffuse into general circulation
Not metabolized by the liver
Reconverted into acetyl-CoA
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acid catabolism
– Ketosis
High concentration of ketone bodies in body
fluids
Increased production of ketone bodies
Occurs during protein and lipid catabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Protein catabolism
– Impractical source of quick energy
More difficult to break apart than complex
carbohydrates or lipids
Ammonia is toxic to the cells
Extensive catabolism threatens homeostasis
at cellular and systems levels
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acids and protein synthesis
– 10 essential amino acids
8 cannot be synthesized
Isoleucine
Leucine
Lysine
Threonine
Tryptophan
Phenylalanine
Valine
Methionine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acids and protein synthesis
– 2 essential amino acids can be
synthesized
Amounts are insubstantial for growing
children
Arginine
Histidine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acids and protein synthesis
– Nonessential amino acids
Can be synthesized on demand
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acids and protein synthesis
– Protein deficiency diseases
Develop with inadequate consumption of
essential amino acids
All amino acids must be present for protein
synthesis to occur
Transfer RNA molecule must appear at the
proper time
If it does not, process is halted
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Amino acids and protein synthesis
– Inherited metabolic disorders
Result from an inability to produce specific
enzymes
Involved in amino acid metabolism
Phenylketonuria (PKU)
Cannot convert specific amino acid due to an
enzyme defect
Essential in the synthesis of NE, E, and melanin
CNS development inhibited resulting in severe
brain damage
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nucleic acid metabolism
– Living cells contain both DNA and RNA
– DNA essential in long-term cell survival
Never catabolized for energy, even when
dying of starvation
– RNA involved in protein synthesis
Broken down and replaced regularly
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
RNA catabolism
– Molecule disassembled into individual
nucleotides
Most recycled into new nucleic acids
Can be broken down to simple sugars and
nitrogen bases
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
RNA catabolism
– Generation of ATP
Only cytosine and uracil can enter TCA cycle
Adenine and guanine cannot be catabolized
Undergo deamination
Excreted as uric acid
Nitrogenous waste
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
RNA catabolism
– Hyperuricemia
Elevated level of uric acid
Saturates body fluids
Symptoms do not appear immediately
May begin to form crystals
Develops into gout
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nucleic acid synthesis
– RNA synthesis
Occurs in most cells
– DNA synthesis
Occurs only in cells preparing for mitosis or
meiosis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nucleic acid synthesis
– RNA polymerase
Enzyme that transcribes different forms of
RNA
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nucleic acid synthesis
– Messenger RNA
Manufactured as needed
When specific genes are activated
Has a life span measured in minutes to
hours
– Ribosomal RNA
Lasts just over 5 days
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Cellular Metabolism
Nucleic acid synthesis
– Typical cell
100,000 ribosomes
Many times more tRNA molecules
Replacement involves great deal of synthetic
activity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Maintenance of homeostasis
– Continues indefinitely
Digestive tract absorption must keep pace
with cellular demands
Nutrition is the absorption of essential
nutrients form food
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Nutrient requirements
– Varies from day to day
Person to person
– Nutritionists
Analyze diet’s ability to prevent and treat
illnesses
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Balanced diet
– Contains all nutrients needed to maintain
homeostasis
Adequate substrates for generating energy
Essential amino acids
Fatty acids, minerals, and vitamins
Water
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and the food pyramid
– 5 basic food groups
Grains
Vegetables
Fruits
Milk
Meat and beans
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and the food pyramid
– Food groups
Vary in protein, carbohydrate, and lipid
content
Vary in amounts and types of vitamins and
minerals
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and
the food pyramid
– Food pyramid
6 groups
5 basic food
groups
Fats, sugars,
and salt
category
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and the
food pyramid
– Food pyramid
6 bands
Different colors and
widths
Width is a guide to
daily recommended
consumption
Stairs on the side
Stress daily physical
activity and weight
control
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and the food pyramid
– Proper nutrition
Sufficient quantity
Adequate quality
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Food groups and the food pyramid
– Complete proteins
Animal proteins
Contain all essential amino acids in sufficient
quantities
– Incomplete proteins
Plants
Contain adequate amounts of proteins
Deficient in one or more essential amino
acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals, vitamins, and water
– Essential components of the diet
– Body cannot synthesize minerals
– Cells generate only small quantities of
water and very few vitamins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals
– Inorganic ions
– Released through the dissociation of
electrolytes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals
– Ions such as sodium and chloride
determine the osmotic concentration of
body fluids
Potassium important in maintaining osmotic
concentration inside cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals
– Ions in various combinations play major
roles in important physiological
processes
Maintenance of membrane potentials
Construction and maintenance of the
skeleton
Action potential generation
Neurotransmitter release
Transport of gasses
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals
– Ions are essential cofactors in a variety
of enzymatic reactions
Example: Enzyme responsible for
breakdown of ATP in contracting skeletal
muscles
Requires calcium and magnesium ions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Minerals
– Reserves
Significant for several important minerals
Reduce effects of dietary variations
Chronic deficiencies lead to clinical problems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Vitamins
– Essential organic nutrients
– Related to lipids and carbohydrates
– 2 groups
Fat-soluble
Water-soluble
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Fat-soluble vitamins
– A, D, E, and K
– Absorbed primarily from the digestive
tract
With the lipid contents of micelles
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Fat-soluble vitamins
– Vitamin D
A group of steroid-like molecules
Includes vitamin D3 or cholecalciferol
Can be synthesized in adequate amounts
Requires exposure of skin to sunlight
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Fat-soluble vitamins
– Dissolve in lipids
Allows diffusion into cell membranes
Body can contain significant reserves
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Fat-soluble vitamins
– Avitaminosis
Vitamin deficiency disease
Rarely results from dietary insufficiency
Caused by inability to absorb vitamins,
inadequate storage, or excessive demand
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Fat-soluble vitamins
– Hypervitaminosis
Dietary intake exceeds ability to store,
utilize, or excrete
Usually involves fat-soluble vitamins as they
are stored in body lipids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water-soluble vitamins
– Most are components of coenzymes
Example: NAD derived from niacin, CoA
from vitamin B3
– Rapidly exchanged between the
digestive tract and circulating blood
– Excesses are readily excreted in the
urine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water-soluble vitamins
– Intestinal bacteria
Help prevent deficiency diseases
Produce 5 of the 9 water-soluble vitamins
Also produce vitamin K
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water-soluble vitamins
– Intestinal epithelium
Readily absorb all water-soluble vitamins
Except vitamin B12
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water-soluble vitamins
– Vitamin B12
Large molecule
Must bind to intrinsic factor before
absorption
Secreted by the gastric mucosa
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water
– Daily requirement
Roughly 2500 ml or 40 ml/kg
Varies with environment and metabolic
activities
Example: 1°C fever increases water loss by
200 ml
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Water
– Daily requirements
Most obtained through eating and drinking
Small amount produced in mitochondria
Electron transport system
Called metabolic water
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Diet and Nutrition
Diet and disease
– Long-term problems
Caused by elevated calorie intake
Elevated proportion of lipids
Increases the incidence of obesity, heart
disease, HTN, DM
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
How organisms acquire and use
energy
– Chemical bonds are broken
– Energy is released
Some energy is captured as ATP
Most lost as heat
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Calorie (cal)
– Unit of energy measurement
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Kilocalorie (kcal)
– Calorie (Cal)
– Amount of energy required to raise the
temperature of 1 kg of water 1ºC
– Designation used in calorie-counting
guides
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
The energy content of food
– Organic molecules combine with oxygen
– Broken down to carbon dioxide and
water
– Oxygen also consumed when something
burns
Combustion can be observed and measured
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
The energy content of food
– Measurement
Known amount of food is placed into a
container
Calorimeter
Filled with oxygen and surrounded by a
known amount of water
Chamber is sealed
Contents ignited electrically
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
The energy content of food
– Measurement
Food completely burned
Only ash remains
Compare water temperature before and after
Determines calories released
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
The energy content of food
– Catabolism of foods
Lipids
9.46 cal/g
Carbohydrates
4.18 cal/g
Proteins
4.32 cal/g
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Metabolic rate
– Sum of all various anabolic and catabolic
processes occurring in the body
– Varies with activity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Basal metabolic rate (BMR)
– Standardized testing conditions
– Reflects minimum resting energy
expenditures of an awake, alert person
– Average is 70 cal/hr or 1680 cal/day
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Basal metabolic rate
– Influential factors
Age
Sex
Physical condition
Body weight
Genetic differences
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Metabolic rate
– If intake exceeds energy demand
Excess stored, primarily as triglycerides in
adipose tissue
– If expenditures exceed intake
Energy reserves reduced, resulting in weight
loss
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Thermoregulation
– BMR
Estimate of the rate of energy use
Body cells capture only a part of that energy
Remaining is lost as heat
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Thermoregulation
– Homeostatic process
– Anatomical and physiological
mechanisms control body temperature
Regardless of environmental conditions
– Temperature control necessary as
enzymes require a narrow temperature
range to function
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Mechanisms of heat transfer
– 4 basic processes
Radiation
Conduction
Convection
Evaporation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Mechanisms of heat transfer
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Radiation
– Warm objects lose heat as infrared heat
energy
– Accounts for more than half of the heat
lost
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Conduction
– Direct transfer of energy through physical
contact
– Not an effective method of gaining or
losing heat
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Convection
– Result of conductive heat loss to air that
overlies the surface of an object
– Warm air rises, moving away from the
skin
– Cool air replaces it, again warming
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Evaporation
– Water changes from a liquid to a vapor
– Process absorbs energy
580 calories per gram of water
– Cools any surface on which it occurs
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Evaporation
– Insensible perspiration
Evaporation from the alveolar surfaces of
the lungs and skin surface
20–25 ml/hr
– Sensible perspiration
Sweat glands
Can range from nothing up to 2–4 l/hr
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Mechanisms of heat transfer
– Maintaining homeostasis
Heat loss must equal heat gain
Coordinated by the hypothalamus
Heat-loss center
Heat-gain center
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Mechanisms of heat transfer
– Heat-loss center
Makes adjustments through
parasympathetic division of ANS
– Heat-gain center
Makes adjustments through sympathetic
division of ANS
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat loss
– Temperature at heat-loss center exceeds
set point
Triggers 3 responses
Peripheral blood vessels dilate
Sweat glands stimulated
Respiratory centers stimulated
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat loss
– Dilation of peripheral vessels
Sends warm blood to the surface of the body
Skin becomes red
Skin temperature rises
Heat loss through radiation and convection
increases
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat loss
– Stimulation of sweat glands
Perspiration flows across the skin
Accelerates heat loss through evaporation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat loss
– Stimulation of respiratory centers
Depth of respiration increases
Enhances heat loss through evaporation
from the lungs
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat loss
– Heat loss by evaporation
Efficiency varies with environmental
conditions
Increased humidity decreases effectiveness of
evaporation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat gain: heat
conservation and generation
– Heat-gain center of the brain
Prevents hypothermia
Activation promotes heat conservation and
generation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat gain: heat
conservation and generation
– Heat conservation
Decreased blood flow to the skin
Reduces heat loss through radiation, convection,
and conduction
Skin may become bluish or pale
Blood is shunted to deep veins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Promoting heat gain: heat
conservation and generation
– 2 mechanisms for heat generation
Shivering thermogenesis
Nonshivering thermogenesis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Shivering thermogenesis
– Muscle tone gradually increased
– Stretch receptors stimulate brief,
oscillatory contractions of antagonistic
skeletal muscles
– Shivering stimulates energy consumption
by skeletal muscles
– Generated heat warms deep vessels
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Nonshivering thermogenesis
– Hormones released
Increase metabolic activity of cells in all
tissues
Epinephrine
Increases breakdown of glycogen and glycolysis
Increases metabolic rate
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Bioenergetics
Nonshivering thermogenesis
– Heat-gain center stimulates release of
thyroxine
Accelerates carbohydrate use
Accelerates the breakdown of all other
nutrients
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional
Requirements
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Nutritional requirements do not
change drastically with age
Other changes directly affect nutrition
and health
– Lifestyle changes
– Eating habits
– Income
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Caloric requirements change with
aging
– Proportions of calories by different food
groups do not
– Caloric requirement reduces 10% for
each decade over 50
Associated with reductions in metabolic
rates, body mass, activity, and exercise
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Increased need for calcium
– Osteoporosis is a normal consequence
of aging
Sedentary lifestyle increases the problem
– Rate of bone loss decreases if calcium
levels remain elevated
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Require supplemental vitamin D3 for
calcium absorption
– Remaining indoors eliminates production
by the skin
– Vitamin converted to calcitrol
Stimulates calcium absorption in the small
intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Olfactory and gustatory receptor
sensitivity decreases with age
– Food becomes less appetizing
– Less food is eaten
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and Nutritional Requirements
Digestion and absorption
– Mucosal lining of digestive tract
Becomes thinner
Nutrient absorption is less efficient
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Summary
Describe and understand the
components of glycolysis, the TCA
cycle, and ETS
Describe how materials are
metabolized
Describe the types and functions of
nutrients
Understand how temperature is
regulated
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.
© 2008 by Pearson Education, Inc. Upper Saddle River, NJ