TOPIC 9 Nutrition, Metabolism & Body Temperature Regulation

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TOPIC 9 Nutrition, Metabolism Body
Temperature Regulation
Biology 221 Anatomy Physiology II

• Chapter 25
• pp. 949-997

E. Lathrop-Davis / E. Gorski / S. Kabrhel
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Definitions

• Calorie (kilocalorie) amount of heat energy
  needed to raise the temperature of 1 kilogram of
  water 1 oC
• Nutrient substance that is used to promote
  normal growth, body maintenance and tissue repair
• major nutrients needed in large amounts
• minor nutrients needed in small amounts

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Nutrients

• Major nutrients
• include protein amino acids, carbohydrate,
  lipid
• water is also a major nutrient
• ingested water comes in food and drink
• metabolic water is made during respiration
• Minor nutrients
• vitamins are organic (Vit. B, Vit. C, Vit. D,
  etc.)
• minerals are inorganic (e.g, iron, calcium,
  iodine)

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Major Food Groups

• Grains
• Fruits
• Vegetables
• Protein
• Dairy
• Fats, oils, sweets

Fig. 25.1, p. 949
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Carbohydrates Sources Uses

• Dietary sources mostly from plants (lactose
  comes from milk)
• Uses in the body
• energy source
• glucose (six-carbon sugar or hexose) is the
  primary sugar used to make ATP
• fructose and galactose (also hexose sugars) can
  be converted to glucose
• structure backbone of nucleic acids (ribose and
  deoxribose)
• cell recognition joined to proteins to form
  glycoproteins

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Carbohydrates Miscellaneous

• Stored as
• glycogen in liver, and skeletal and cardiac
  muscle (medium-term storage)
• excess is converted to fat in adipose cells
  (long-term storage)
• Cellulose (a polymer of glucose) is not
  digested but provides bulk to feces

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Hormonal Control of Blood Glucose

• see AP I Unit 11 Endocrine System
• hypoglycemic hormones decrease blood sugar
  insulin
• hyperglycemic hormones increase blood sugar
• glucagon
• glucocorticoids (cortisol)
• epinephrine
• growth hormones

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Lipids Sources

• most are neutral fats (triglycerides - fats
  oils)
• saturated fats fatty acid chains contain no
  double bonds
• found in animal products and a few plant products
  (e.g., coconut)
• generally solid at room temperature

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Lipids Sources

• unsaturated fats come mainly from plants liquid
  at room temp.
• monounsaturated fats (fatty acid chains have one
  double bond)
• polyunsaturated fats (fatty acid chains have more
  than one double bond)
• cholesterol comes from animal products

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Lipids Sources Essential Fatty Acids

• must be in diet because liver lacks enzymes to
  synthesize them found in plants
• linoleic acid fatty acid component of lecithen,
  a membrane lipid
• linolenic acid may be essential, research not
  clear

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Lipids Uses in the Body

• Component of adipose
• long-term energy storage
• cushions organs
• insulates (keeps body heat in)
• Components of plasma membranes (phospholipids
  cholesterol)
• unsaturated fats and cholesterol help prevent
  cell membrane from crystallizing at low
  temperatures

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Lipids Uses in the Body

• Regulatory molecules
• steroid hormones gonads adrenal cortex
• prostaglandins paracrines (locally acting)
• Pain, sensitize blood vessels to inflammatory
  compounds (See Topic 6)

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Proteins Dietary Sources

• All-or-none rule all amino acids needed must be
  present for a protein to be synthesized (if any
  are lacking, the protein will not be made)
• Complete proteins
• contain all essential amino acids
• from animal products (eggs, milk, meat)
• Soybeans only plants with complete protein

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Proteins Dietary Sources

• Incomplete proteins
• low amounts or lacking certain amino acids
• plant proteins
• need to be mixed to get all essential amino acids
  at the same time
• mix grains (like rice or corn) with legumes (peas
  or beans)

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Proteins Essential Amino Acids

• Cannot be made by the body (liver lacks the
  proper enzymes) therefore, must be in diet
• Vegetarians can get all by combining grains
  (e.g., corn, rice) with legumes (beans, peas)
• tryptophan
• Methionine (cysteine)
• valine
• threonine
• phenylalanine (tyrosine)
• leucine
• histadine (needed by infants)

Fig. 25.2, p. 952
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Proteins Uses in the Body

• Structure
• important components of plasma membranes
• collagen and elastin fibers of CTs
• cytoskeleton
• cell junctions
• Catalysts - enzymes (increase reaction rates)

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Proteins Uses in the Body

• Transport storage
• intracellular transport
• membrane transport proteins (channels, pumps,
  facilitated transport carriers)
• hemoglobin (O2 transport), transferrin (Fe
  transport)
• storage proteins hemosiderin (Fe), ferritin
  (Fe), myoglobin (O2 in red-twitch skeletal and
  cardiac muscle), thyroglobulin (thyroxine)

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Proteins Uses in the Body

• Contraction myosin, actin, tropomyosin,
  troponin
• Regulation
• hormones
• control body functions
• e.g., insulin, ADH, glucagon, and other hormones
  except from adrenal cortex and gonads
• calmodulin intracellular regulation
• Defense immunoglobulins (antibodies) provide
  specific resistance to disease by attacking
  antigens

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Proteins Miscellaneous

• Adequacy of caloric intake diet must include
  sufficient carbohydrates or fat for ATP
  production so that amino acids are used for
  protein synthesis
• Nitrogen balance of the body
• balance occurs when intake (through diet) equals
  loss through urine and feces
• transamination adds amino (NH3) group from one
  molecule to another to make nonessential amino
  acid
• deamination removes amino group from amino acid
  so that carbon skeleton can be used for energy
  (amino is converted to urea)

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Proteins Hormonal Control of Protein Synthesis

• Anabolic hormones (e.g., testosterone, GH)
  promote protein synthesis
• Catabolic hormones (e.g., glucocorticoids)
  promote degradation

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Water-soluble Vitamins

• Vit. C, B-complex vit. absorbed along with
  water in the small intestine
• Absorption of Vit. B12 requires presence of
  intrinsic factor produced by stomach
• pernicious anemia anemia caused by inadequate
  intake of vit. B12 due to lack of intrinsic
  factor
• Some B vitamins produced by gut bacteria
• Excesses usually eliminated in urine

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Fat-soluble Vitamins

• Vit. A, D, E and K
• Vit. K produced by gut bacteria
• Vit. D made by body
• Absorption aided by micelles in small intestine
• Excesses of Vit. A, D, and E stored in fat
  (megadoses may cause problems)

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Functions of Vitamins

• Coenzymes molecules that help enzymes perform
  their functions
• riboflavin and niacin form part of electron
  carriers (FAD and NAD, respectively) that carry
  electrons during catabolism of glucose
• Antioxidants (Vit. A, C and E) interact with
  free radicals in cell to prevent damage to cell
• Vit. A is precursor to visual pigments in retina

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Minerals Miscellaneous Sources

• Dietary sources vegetables, legumes, milk, some
  meats
• Some minerals required in large amounts
• calcium, potassium, phosphorus, sulfur, sodium,
  chloride, magnesium
• Others required in small amounts trace minerals
• include iron, zinc and iodine

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Minerals Uses in Body

• Structure (especially Ca2 and Mg2 / PO4 salts
  in bones and teeth)
• Enzyme cofactors form part of active sites of
  enzymes (Mg2)
• Oxygen transport by hemoglobin and storage by
  myoglobin (Fe)
• Ionic and osmotic balances (especially Na, Cl-,
  and K)
• affect blood pressure as a result of water
  retention (especially Na)

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Minerals Uses in Body

• Essential to action potentials and impulses (Na,
  K, Ca2)
• Essential to contraction (Na, K, Ca2)
• Thyroid hormones (I-)
• Essential to clotting (Ca2 clotting factor IV)
• Energy transfers (PO4)

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Metabolism Definitions

• Metabolism sum of all the chemical processes
  occurring in the body
• Anabolism reactions in which larger molecules
  manufactured from smaller ones
• require energy (ATP) input
• e.g., amino acids --gt peptides (proteins)

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Metabolism Definitions

• Catabolism reactions in which larger molecules
  are broken into smaller ones
• includes breakdown of food in GI tract
• cellular respiration releases energy, some of
  which is used to make ATP
• e.g., glucose oxidation

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Metabolism Phosphorylation

• Substrate-level phosphorylation
• phosphate group passed from phosphorylated
  (energized) molecule to ADP to make ATP
• occurs during glycolysis and Krebs cycle
• also transfer from phosphocreatine to ADP (in
  skeletal muscle)

Fig. 25.4 p. 964
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Metabolism Phosphorylation

• Oxidative phosphorlyation
• under aerobic conditions
• occurs in mitochondria
• ATP synthesized by addition of phosphate to ADP
  using energy of H gradient
• used to make most of cells ATP

Fig. 25.4 p. 964
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Glucose Oxidation Overview

• Three main stages
• Glycolysis
• Krebs cycle
• Electron transport chain with oxidative
  phosphorylation

See also animations of aerobic and anaerobic
metabolism - Metabolism Review
Fig. 25.5 p. 965
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Glucose Oxidation Glycolysis

• Produces pyruvate (3-carbon) as glucose
  (6-carbon) is cleaved
• Net of 2 ATP are made by substrate-level
  phosphorylation
• Occurs in cytoplasm
• Anaerobic (does not require oxygen)

Fig. 25.6, p. 966
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Glucose Oxidation Krebs cycle

• Produces 2 ATP
• Occurs in mitochondria
• Aerobic (requires oxygen)
• Requires intermediate step involving acetyl-CoA
• Produces
• reduced energy carriers (NADHH FADH2)
• CO2

Fig. 25.7, p. 968
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Glucose Oxidation Electron Transport and
Oxidative Phosphorlyation

• Most ATP is made by oxidative phosphorylation
• Occurs in mitochondria
• Reduced electron carriers (FADH2 and NADH H)
  pass electrons to membrane proteins
• Energy associated with transfer of electrons used
  to pump H into intermembrane space

Fig. 25.8, p. 969
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Glucose Oxidation Electron Transport and
Oxidative Phosphorlyation

• Energy of H gradient used by ATP synthase to
  make ATP
• Aerobic (requires oxygen as final electron
  acceptor ?produces metabolic water)

Fig. 25.8, p. 969
Fig. 25.9, p. 971
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Summary of ATP Production

• Glycolysis produces a net of 2 ATP
• Krebs cycle produces a net of 2 ATP
• Oxidative phosphorylation produces 32 (most
  cells) or 34 (liver) ATP
• Total net ATP produced 36 or 38 ATP

Fig. 25.10, p. 965
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Role of the Liver in Metabolism

• Fat metabolism
• Packages fatty acids into forms that can be
  stored or transported
• Stores fat
• Synthesizes cholesterol (from which it can
  synthesize bile salts)
• Forms lipoproteins for transport of fats, fatty
  acids and cholesterol to and from other tissues

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Role of the Liver Lipoproteins

• VLDLs carry triglycerides from liver to
  peripheral tissues (mostly adipose)
• LDLs cholesterol-rich lipoproteins transporting
  cholesterol from adipose to peripheral tissues
  for incorporation into plasma membrane
• HDLs
• transport cholesterol from peripheral tissues to
  liver for removal
• pick up cholesterol from tissues and from
  arterial walls
• transport cholesterol to gonads and adrenal cortex

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Role of the Liver in Metabolism

• Protein metabolism
• Synthesizes plasma proteins
• including clotting proteins
• albumins (osmotic balance)
• Synthesizes nonessential amino acids by
  transamination (transferring amino group (NH2)
  from one molecule to another)
• Converts ammonia formed by deamination of amino
  acids into urea
• urea is less toxic than ammonia
• carbon skeleton burned as fuel

See Fig. 25.14, p. 976
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Role of the Liver in Metabolism

• Carbohydrate metabolism
• Stores glucose as glycogen
• Glycogenesis
• stimulated by insulin
• Releases glucose when blood sugar is low
• stimulated by hyperglycemic hormones (glucagon)
  or under stress (GH, epinephrine, cortisol)
• gluconeogenesis formation of glucose from
  noncarbohydrate sources (e.g., fats or amino
  acids)
• glycogenolysis break down of glycogen

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Role of the Liver in Metabolism

• Miscellaneous
• Stores vitamins A, D, B12
• Stores iron from worn-out red blood cells
• Degrades hormones
• Detoxifies toxic substances (e.g., drugs,
  alcohol)
• prolonged substance abuse or exposure to
  toxins/toxics damages liver

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Body Temperature

• Normal body temperature 96-100 oF (35.6-37.8
  oC)
• varies with activity and time of day
• averages around 98.2 oF (36.6 oC)
• represents a balance between heat production and
  heat loss
• Core temperature
• temperature of organs within skull, thoracic and
  abdominal cavities (ventral body cavity)
• more critical than shell temp.
• Shell temperature temperature of skin and
  appendages
• Increased temperature chemical reaction rates

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Heat Exchange Mechanisms

• Radiation loss or gain of heat in the form of
  infrared radiation
• Conduction transfer of heat from one object to
  another (e.g., touching a warm radiator or a cold
  cement bench)
• Convection loss to air moving over body surface
• Evaporation loss of body heat to water as it
  evaporates from body surface

See Fig. 25.25
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Heat Producing Mechanisms

• Basal metabolism (amount of energy needed to
  maintain body at rest without activity from
  digestion)
• most heat is generated by activity in the brain,
  liver, endocrine organs, and heart
• inactive skeletal muscle accounts for 20-30
• Muscular activity
• uses more ATP so increases metabolism
• includes shivering
• Thyroxine and epinephrine stimulate metabolic
  rates in cells

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Role of the Hypothalamus

• Thermoreceptors respond to changes in temperature
• Thermoregulatory centers
• heat-loss center
• activated when core temperature rises above
  normal range
• promotes heat loss
• heat-promoting center
• activated when core temperature falls below
  normal range
• promotes production of heat

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Keeping the Body Warm Fast-acting Mechanisms

• Vasocontriction of cutaneous blood vessels
• keeps warm blood closer to core (away from
  surface where heat is lost)
• Increased metabolic rate
• non-shivering thermogenesis increased metabolic
  rate in response to norepinephrine secreted by
  sympathetic nervous system
• shivering (brain alternately stimulates small
  contractions in antagonistic muscles)
• Behavioral modifications

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Keeping the Body WarmSlow-acting mechanism

• Not very important in adult, but does work in
  children
• Decreased body temperature in response to
  seasonal cooling
• Hypothalamus releases more thyrotropin releasing
  hormone (TRH)
• Adenohypophysis responds by releaseing more
  thyroid-stimulating hormone (TSH)
• Thyroid responds with enhanced thyroxine release
• increases basal metabolic rate
• increases heat production

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Cooling the Body When Core Becomes Too Hot

• Vasodilation of cutaneous blood vessels
• Enhanced sweating --gt evaporative cooling
• Behavioral changes
• decreased activity
• removing insulating layers of clothing

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Imbalances of Thermoregulation

• Hyperthermia excessive body heat
• Heat exhaustion elevated body temperature and
  mental confusion or fainting due to dehydration
• Heat stroke loss of ability to regulate body
  heat due to increased body temperature (a rather
  nasty form of positive feedback)
• Fever controlled hyperthermia in response to
  infection and release of pyrogens (see Topic 6)
• may also be caused by cancer, allergic reactions,
  CNS injuries
• promotes function of white blood cells

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Imbalances of Thermoregulation

• Hypothermia decreased body temperature due to
  excessive loss of body heat
• Core temperature may drop so low that CNS
  function stops (chemical reaction rates decrease
  to level that does not support life)
• Lowers oxygen requirement (improves chances of
  survival during drowning)