Metabolism

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Metabolism

• Chapter 25 - pages 962-987

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Linking anabolism catabolism
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Topics in Chapter 25

• In AP I glucose catabolism ? ATP was discussed
• This semester in Ch 25 focus on
• Glucose anabolism
• Lipid metabolism
• Protein metabolism
• Metabolism during absorptive and post absorptive
  states
• Heat and energy balance
• Nutrition

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Glucose

• Most glucose catabolized to make ATP
• Some used in anabolic rxns
• To produce glycogen
• To produce more glucose from lipid and protein
  components

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Do not confuse these terms!

• Glucose
• Glycogen
• Glucagon
• Glycolysis
• Glycogenolysis
• Glycogenesis
• Gluconeogenesis

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Glycogenesis fig 25.11

• Glucose storage
• Occurs when glucose not immediately needed for
  ATP synthesis
• _____________- stimulates hepatocytes skeletal
  muscle cells to carry out
• From pancreatic beta cells
• ______________ - polysaccharide, polymer of
  glucose and only stored carb in our body
• 75 stored in skeletal muscle
• 25 in hepatocytes

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Glycogenolysis fig 25.11

• Glucose release
• Body activities require ATP ? glycogen stores in
  hepatocytes break down
• Glucose ? blood ? cells for catabolism
• Glucose ? ATP
• Lactic acid (in muscle) ? glucose (in liver)
• Phosphorylase activated by ____________ (from
  pancreatic alpha cells) ___________ (adrenal
  medulla)
• Reversal of steps in glycogenesis

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Glycogenesis glycogenolysis
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Insulin pg 646-649

• Released in response to ? blood glucose
• Ach released from vagus nerve ? _________________
• Certain amino acids in blood (after protein meal)
• ________ s.i. hormone released due to glucose
  in gi tract
• Accelerates facilitated diffusion of glucose
• ? glycogenesis (glucose ? glycogen)
• ? a.a uptake for ? protein synthesis
• ? f.a. synthesis
• Slows glycogenolysis
• Slows gluconeogenesis

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Fig 18.18
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Figure 18.19
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Glucagon

• Stimulates ________________ in liver cells
• Stimulates ________________
• Glucose released into blood
• Secretion stimulated by
• Low blood glucose
• ? activity of sympathetic NS (as w/exercise)
• ? a.a in blood if blood glucose is low (after
  high protein meal)

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Gluconeogenesis

• Newly formed glucose
• Non carbohydrate sources
• Lactic acid
• Glycerol
• Amino acids about 60 of a.a. in body can be
  used for this
• Stimulated by
• _______________(glucocorticoid)
• _______________

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Gluconeogenesis fig 25.12
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Glucose tolerance

• Test bodys ability to process glucose
• Diagnostic for hypoglycemia, __________
  __________, or malabsorption syndrome
• Dependent upon ability of
• Pancreas to produce release insulin
• Cell response to insulin (membrane sensitivity)
• Small intestine to absorb glucose
• Liver to take up store glucose

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Glucose tolerance (2)

• ________ mg/100 mL blood normal, fasting
• Load ? glucose ? within 1 hour
• Normal followed by gradual decline
• Abnormal glucose levels remain elevated
• Insulin response major factor
• See lab manual, exercise 3 for more info

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Diabetes mellitus

• Endocrine disorder, inability to produce (type 1)
  or use (type 2) insulin
• 4th leading cause of death by disease in US
• Type 1 insulin-dependent diabetes mellitus
• ____________________ destroys pancreatic beta
  cells
• Insulin injections required to prevent death
• Type 2- non-insulin dependent
• More common than type 1 ? gt90 of cases
• Often obese gt35 yr, but, type 2 obese children
  teens ?
• Target cells ____________ to insulin, downreg of
  receptors

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Lipoproteins are transporters

• __________________- lipid protein combination
• Outer- proteins, phospholipids, cholesterol
• Proteins help solubilize lipids in body fluids
• Inner core- triglycerides and other lipids
• Categorized by _________ (lipids low, proteins
  high density)
• Chylomicrons- s.i., many dietary lipids ? adipose
  
• VLDLs- very low density lipoproteins, form in
  hepatocytes, lipids? adipocytes for storage or
  muscle
• LDLs- carry 75 of total cholesterol in blood
  which goes to
• Cell membranes for repair, synthesis of steroid
  hormones, bile salts
• When in excess deposit in smooth muscle of
  arteries ? fatty plaque
• HDLs- remove excess cholesterol from cells? liver
  (elimination)

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Lipoprotein figure 25.13
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Pathways of lipid metabolism
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Metabolic regulation depend on

• Chemical environment in cell
• ATP level
• Oxygen
• Nervous system
• Endocrine system
• Some functions of metabolism depend on- time
  since last meal

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Absorptive state figure 25.17

• Ingested ______________________ necessary for 2
  main events of this state
• Oxidation of glucose for ATP production
• Storage of excess food molecules occurring (for
  later use between meals)
• Hepatocytes, adipocytes, skeletal muscle
• ? 4 hours for complete absorption
• _____________ dominates during this state

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Reactions (absorptive state) figure 25.17

• 50 glucose absorbed from meal ? _________
• Most glu that enters liver (10) ? ___________
• Some f.a. triglycerides syn in liver
• Some stay in liver
• Most ? VLDLs to carry lipids to adipose
• Adipocytes uptake glu (40)? _____________
• Most dietary lipids ? adipose tissue
• Chylomicrons, VLDLs, or synthesized
• Many a.a.? liver? Krebs- ATP, or syn glu fa
• Some a.a. ? hepatocytes synthesize proteins
• a.a not taken up in hepatocytes ? body cells
• synthesis of proteins, hormones, or enzymes

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Absorptive state
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Regulation of metabolism- absorptive

• GIP ? blood glu ( some aa)?______________
• Insulin (see table 25.3)
• ? enzymes of anabolism syn to storage molecules
• ? enzymes of catabolism
• Promotes glucose a.a ? ____________________
• Stim. phosphoyrlation of glu - hepatocytes?G6P
• Stim. G6P ? glycogen in liver muscle
• Enhances _____________________(liver adipose)
• Stim. protein syn throughout body

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Postabsorptive state figure 25.18

• ________ of nutrients from GI tract ________
• Bodily energy needs being met by fuel already
  created
• If no snacks, times ? 4 hours spent in
  postabsorptive state (late morning, late
  afternoon, most night)
• __________________ involved in regulation
• Glucose production glucose conservation

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Postabsorptive glucose production

• ATP dominant fuel in ______ (fa cant cross bbb)
• RBC get ATP from glycolysis - lack mitochondria
• Rxns that _____________________ in this state
• Breakdown of liver glycogen
• Lipolysis
• Gluconeogenesis using lactic acid
• Gluconeogenesis using amino acids

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Postabsorptive glucose conservation

• Reactions to _______________ in this state
• Oxidation of fatty acids
• Oxidation of lactic acids (in cardiac muscle)
• Oxidation of amino acids (in hepatocytes)
• Oxidation of ketone bodies
• Can be used by heart, kidneys, other tissue ?
  ATP
• breakdown of muscle glycogen
• Glycogen ? G6P (glycolysis) ? ATP

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Postabsorptive state
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Regulation of metabolism postabsorb

• Hormones
• ______________ hormones
• Glucagon- ? gluconeogenesis glycogenolysis
• See table 25.4 for summary
• Sympathetic NS
• Glucose sensitive neurons activate release of NT
  norepinephrine
• Adrenal medulla releases
• Epinephrine stimulates glycogen breakdown
• Norepinephrine both NE E stimulate lipolysis

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Metabolism- fasting starvation

• ___________- w/out food several hours few days
• Glycogen stores depleted within hours
• Protein catabolism gt anabolism, aa? gluconeo
• _______________- weeks or months of food
  deprivation or inadequate intake
• Triglyceride proteins stores- last several
  weeks
• Amt of adipose tissue determines survival time
• During both
• Nervous tissue RBC use glucose ? ATP
• ? ketone bodies in hepatocytes ? plasma ? bbb
• ? glu needed for ATP syn, ? need for gluconeo, ?
  catabolism of muscle proteins

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Heat and energy

• Heat- form of energy
• Measured by temperature
• Expressed in units- calories
• calorie (cal) amt of heat to ? temp of 1g of
  water 1C
• cal is small ? use kilocalories (kcal) or Calorie
  (Cal)
• Core body temp 37C, shell 1-6C less
• Too high ? denatures body proteins
• Too low ? cause cardiac arrhythmias (? death)

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Heat production

• ________________
• Hormonesthyroid, testosterone, insulin, hGH
• _________________ NE E
• Body temp - ? body temp ? ? biochem rxns
• Ingestion of food energy cost of digestion
• ________ child gt elderly (? during growing)
• Others gender (males gt females, exception-
  pregnancy ?), climate, sleep, malnutrition

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Metabolic Rate

• Overall rate at which metabolic rxns use energy
• _________________- body quiet, resting fasting
• BMR- measure amt of oxygen used per kilocalorie
  of food metabolized
• 1L ____________ to oxidize mix of carbs, proteins
  fats ? 4.8 Cal of energy released
• BMR 1200-1800 Cal/day in adults
• Added calories needed 500 small relatively
  inactive person ? 3000 for a person training for
  the Olympics
• Accounts for 60 of energy expenditure

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Thyroid hormones metabolism

• TRH (hypothalamus) ? TSH (pituitary)? release
  thyroid hormones
• ___________________ in skin hypothalamus sense
  temp ? ? TRH release
• Thyroid hormones released in bloodstream
• Slowly ? _____________ by stimulating cell resp.
• Cells use more O2 ? body temp ?
• 1C rise in core temp ? biochemical rxns by 10
• Part of negative feedback loop (fig 25.19)

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Vitaminsfat vs. water soluble, table 25.6

• Vitamins organic nutrients- small amt to
  maintain growth metab
• Do not provide energy, function as coenzymes
• Most must be ingested, cannot be synthesized
• _______________ vitamins- absorbed w/dietary
  lipids in chylomicrons, need lipids to be
  absorbed adequate quantities
• Can be stored in cells (esp. hepatocytes)
• Vitamins A, D, E, K -- see table for functions
• Water soluble vitamins- dissolved in bodily
  fluids
• Excess quantities excreted in urine
• Several B vitamins, vitamin C see table
• C, E and beta-carotene-________________________

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Vitamin Source Function
A, fat soluble Carotene (veg), liver, milk General health of epi cells, antiox.
B complex, fat Whole grain, egg, pork, nuts, liver yeast metabolism, Ach synthesis, steroid hormones
C, water Citrus, tomatoes, green vegetables Protein syn, Ab, collagen form, antioxidant
D, fat Fish-liver oil, egg yolk, fortified milk Absorb Ca P, works w/PTH
K, fat Intes bacteria, spinach, cauli, cabbage, liver Synthesis of several clotting factors by liver
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Importance of minerals table 25.5

• Minerals inorganic elements occur naturally in
  earths crust
• 4 of total body mass, heavily conc in
  _____________
• Body generally uses ion form
• Na distribution of water, bicarbonate buffer,
  AP
• K generation conduction of AP
• Ca form bones teeth, clotting, nerve muscle
  activity, endo exocytosis, cell chromosome
  motility, glycogen metab, rel NT hormones
• Fe component of Hb cytochromes in ETC
• P form bones teeth, blood buffer system,
  nerve muscle activity, energy transfer (ATP),
  part of DNA, RNA
• I req by thyroid to make hormones, reg
  metabolic rate

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Nutrition figure 25.20

• Nutrients- chemical substances in food body cells
  use (growth, maintenance, repair)
• Water, carbs, lipids, proteins, minerals,
  vitamins
• Dietary Reference Intake (DRI)- or Recommended
  Daily Allowance (RDA)
• http//fnic.nal.usda.gov/nal_display/index.php?inf
  o_center4tax_level2tax_subject256topic_id13
  42placement_default0
• Proteins listed as macronutrients on website

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Amino acids

• Building blocks for structural functional cmpds
  in the body (enzymes, membrane carriers,
  hormones)
• _______________amino acid or ________________amino
  acid that which cannot be synthesized by the
  body and must be acquired through dietary intake
• Histidine, isoleucine, leucine, lysine,
  methionine, phenylalanine, theronine, tryptophan
  valine
• Nonessential amino acid can be made by human
  body

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Protein types and sources

• _____________ proteins the 9 indispensible a.a.
  are found in animal sources meat, fish,
  poultry, eggs, milk, cheese and yogurt
• Incomplete proteins- sources that lack 1 of the 9
  indispensible a.a., are found in plants, legumes,
  seeds, grains, nuts, vegetables
• Complementary protein combinations- those that
  give all the indispensible a.a. by combining
  incomplete with complete protein sources

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DRI establishment see www.nap.edu

• Are developed from recommended daily allowance
  adequate intake
• Increases from infancy thru childhood to
  adulthood- RDA for males females up to the
  age of 13 34 g/day
• RDA levels off
• age 19-30 males 56g/d
• Age 14-18 females 46g/d
• Males have higher RDA than females
• Pregnancy double amt of 9-13 yr old girl
  (71g/d)
• Lactation same as pregnancy

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