SALADIN C. 26

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SALADIN C. 26

• Nutrition Metabolism,

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Body Weight Energy Balance

• 30 50 of variation in human body weight is
  heredity, rest is environmental factors eating
  exercise habits.

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Appetite

• Many peptide hormones regulatory pathways are
  involved in short long term appetite control
• Short term regulators
• Ghrelin from stomach sensation of hunger
  stimulates hypothalamus to release
• GHRH

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Appetite

• Peptide YY PYY from ileum colon secreted
  with feeding proportional to calories consumed
  stop eating signal.
• CCK from SI stimulates secretion of bile
  pancreatic enzymes. Also causes appetite
  suppressing effect on vagus a stop eating
  signal

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Appetite

• Long term regulators
• Leptin from adipocytes proportional to levels
  of body fat most human obesity related to
  leptin is due to receptor defect, not hormone
  defect
• Insulin from pancreas receptors in brain
  functions like leptin - weaker

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Appetite

• Brain center arcuate nucleus of hypothalamus
  2 groups of neurons
• 1 secretes neuropeptide Y stimulates
  appetite
• 2 secretes melanocortin inhibits
• eating
• Gastric peristalsis also stimulates hunger

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Control of Feeding Satiety
Figure 24.23
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Appetite

• Neurotransmitters influence types of food
  consumed
• Norepinephrine CBH
• Galanin fat
• Endorphins - protein

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Appetite

• Obesity more than 20 above norm for
  demographic. In US 30 are obese and an
  additional
• 35 are overweight.
• Predisposition to obesity is increased by
  over-feeding in infancy and early childhood.

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Heat kinetic energy

• Heat kinetic energy
• calorie-amount of heat required to raise one gram
  of H2O 1oC

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Energy Yields

• Carbohydrates - 4Kcal/g
• Lipid- 9 Kcal/g
• Protein 4 Kcal/g

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Nutrients

• Nutrient a substance that promotes normal
  growth, maintenance, and repair.
• Major nutrients carbohydrates, lipids, and
  proteins.
• Other nutrients vitamins and minerals (and
  technically speaking, water).

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Nutrition see www.mypyramid.gov for details
Figure 24.1
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CBH

• Fates of CBHs
• ATP production aerobic respiration, anaerobic
  fermentation
• Glycogen adipose storage
• Amino Acid synthesis
• Structural component of nucleotides,
  glycoproteins, glycolipids

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CBH

• Excretion spill over onto urine
• Neurons erythrocytes depend almost entirely on
  CBH
• Review Insulin/glucagon homeostasis Ch 17 CBH
  in API notes

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• Requirements higher than other nutrients
• Sources plants
• Fiber resist digestion plant animal

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CBH

• Promotes intestinal function. Water soluble
  forms reduce blood cholesterol LDLs.
• Blood sugar levels 70 -110 mg/dL normal

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Lipids

• Fatty acids, glycerol, cholesterol
• Meet 80 90 of resting energy needs
• Required for absorption of fat soluble vitamins
• Membrane hormone structural components.

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Lipids

• Needs no more than 30 of diet most should be
  unsaturated
• Must get linoleic acid from diet rest appear to
  be able to be made.

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Lipids

• Cholesterol Metabolism
• Structural unit of bile salts, steroids, Vitamin
  D and cell membranes.
• 15 of blood cholesterol is from diet
• 85 is made by the body

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Lipids

• Cholesterol Lipoproteins - transported as
  spheres
• The spheres are lipoproteins hydrophobic
  triglycerides cholesterol esters are in
  interior, hydrophilic phospholipid heads,
  cholesterol proteins are on exterior

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Lipids

• Classes
• Chylomicrons 2 protein, 90 triglyceride, 3
  phospholipid, 5 cholesterol
• VLDL 8 protein, 55 triglycerides, 17
  phospholipid, 20 cholesterol

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Lipids

• LDL (bad cholesterol gets deposited in blood
  vessels) 20 protein, 6 triglyceride, 21
  phospholipid, 53 cholesterol gets deposited in
  vessel walls from adipose.
• HDL 50 protein, 5 triglyceride, 25
  phospholipid, 20 cholesterol (good cholesterol)
  cleared by liver no vascular buildup.
  transport TO liver

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Lipids

• Desirable levels
• Total cholesterol - lt 200mg/dL
• LDL lt 130mg/dL
• HDL gt 40mg/dL 60 or higher gives some protection
  against heart disease
• Total lt200mg/dL
• Ratio of total/HDL lt4 desired

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Lipids

• Bad
• LDL gt 159 mg/dL
• Total gt 239 mg/dL

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Lipids

• Factors regulating plasma cholesterol
• Increased dietary cholesterol decreases liver
  production, BUT doesnt stop it.
• Saturated fatty acids increase liver synthesis
  and decrease excretion
• Unsaturated fatty acids increase excretion
• Hydrogenated fats increase LDLs and decrease HDL
  worst effect of all

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Proteins

• Proteins ? amino acids
• 8 essential amino acids - we don't or can't make
  enough
• 12 non-essential - synthesized by the body by
  transamination.
• Not stored must be present from ingestion.
• Nitrogen balance in out positive with
  growth, negative with insufficiency.

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Vitamins Mnerals

• Vitamins review table 26.3
• Fat soluble - A, D, E, K
• Water soluble - B1, B2, niacin, B6, B12, Folic
  acid, C
• Minerals review table 26.2 - Ca, P, Fe, I, Cu,
  Na, K, Cl, Mg, S, Zn, F, Mn

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Metabolism

• Metabolism all chemical reactions necessary to
  maintain life.
• Anabolic reactions synthesis of larger
  molecules from smaller ones.
• Catabolic reactions hydrolysis of complex
  structures into simpler ones.

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CBH Metabolism

• All oxidative CBH consumption is essentially
  glucose catabolism
• C6H12O6 6O2 ? 6H2O 6CO2 ATP heat
• Glucose catabolism glycolysis, anaerobic
  fermentation, aerobic respiration

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Oxidation-Reduction (Redox) Reactions

• Oxidation removes electrons.
• Reduction adds electrons.
• Coenzymes act as hydrogen (or electron pair)
  acceptors.
• Two important coenzymes are nicotinamide adenine
  dinucleotide (NAD) and flavin adenine
  dinucleotide (FAD).

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Carbohydrate Metabolism

• Glucose is catabolized in three pathways
• Glycolysis anaerobic fermentation
• Krebs cycle
• The electron transport chain oxidative
  phosphorylation

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Carbohydrate Catabolism
Figure 24.5
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Glycolysis

• A three-phase pathway in which
• Glucose is oxidized into pyruvic acid.
• NAD is reduced to NADH H.
• ATP is synthesized by substrate-level
  phosphorylation.

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Glycolysis

• Glycolysis occurs in cytoplasm converts
  glucose to pyruvate
• Immediately upon entry into the cell, glucose is
  converted to glucose-6-phosphate
• 10 steps SEE HANDOUT and Figure 26.3
• Ends for 1 glucose 2 pyruvates, 2 net ATP and
  2NADH 2H

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Glycolysis

• Anaerobic fermentation
• Glucose Metabolism in the Absence of O2
• Lactic acid fermentation in muscle cells
• Starts with pyruvate and NADH
• Produces lactic acid and NAD. Lactic acid can
  be used in liver for glucose synthesis.
• Renews NAD in cytoplasm for continued ATP
  production.

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Matrix Reactions

• Starts with pyruvate, NAD and Coenzyme A CoA
  --gt AcetylCoA CO2 NADH H
• Runs twice per original glucose ? 2 Acetyl CoAs

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Matrix Reactions

• Krebs Cycle in matrix of mitochondrion
• 8 steps SEE Handout
• Starts with Acetyl CoA, oxaloacetic acid, NAD,
  FAD
• Runs twice per original glucose molecule
• Ends - with 2 pyruvates 6CO2 2 ATP 8 NADH
  8H 2FADH2

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Figure 24.7
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Membrane Reactions

• Membrane reactions - oxidize NADH FADH2 to move
  electrons, regenerate NAD FAD
• Electron Transport System on inner
  mitochondrial membrane cristae - pumps H ions
  for Chemiosmosis.

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Membrane Reactions

• Need electron carriers pass electrons from one
  carrier to another by paired redox reactions.
• Carriers Flavin Mononucleotide FMN,
  cytochromes, Fe-S centers, Cu, Coenzyme Q.

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Electronic Energy Gradient
Figure 24.9
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Membrane Reactions

• 3 pumps present
• 1 NADH dehydrogenase complex FMN 5 Fe-S
  centers start NADH H is oxidized to NAD
  and FMN is reduced to FMNH2. Ends with Coenzyme Q
  a mobile carrier that transports the electrons
  it receives to the next pump.

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Membrane Reactions

• 2 Cytochrome b-c1 complex electrons passed
  from Q to cyt b --- to cyt c gt passes electrons
  to next pump
• 3 cytochrome oxidase complex receives
  electrons from cyt c passes them o Cu then to
  cyt a, cyt a3 then to O. The negative O picks
  up 2 H ? H2O only place in respiration where O
  is consumed!!!

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Chemiosmosis

• Energy from step-wise release powers pumping H
  into intermembrane space by chemiosmosis
• The concentration of H outside gt than that
  inside this produces an electrostatic gradient
  and a net voltage.
• Since it is positive charges it is called
  proton motive force instead of electromotive
  force (from electron distribution).

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Chemiosmosis

• Facilitated diffusion channels containing enzymes
  for ATP formation ATP synthase allow the H to
  move back across the membrane driven by this
  force.
• The energy from the force is used for the ATP
  production.
•  

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Figure 24.8
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Energy Yield of Cellular Respiration

• Step Product Energy (O) Energy (no O)
• Glycolsis 2 ATP 2ATP 2ATP
• 2 NADH 4-6ATP
• Transition 2NADH 6ATP
• Krebs 2ATP 2ATP
• 6NADH 18ATP
• 2FADH2 4ATP
• Totals 36-38ATP 2ATP

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Glycogen Metabolism

• Gluconeogenesis
• Forms glucose from non-CBH molecules.
• In the liver.
• Protects the body, especially the brain, from the
  damaging effects of hypoglycemia by ensuring ATP
  synthesis can continue.
• Stimulated by insulin

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Glycogen Metabolism

• Glycogenolysis breakdown of glycogen in
  response to low blood glucose
• Stimulated by glucagon

Figure 24.12
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Glycogen Metabolism
Glycogenesis Glucose is converted to Glucose 6
P Glucose 6 P is converted to glucose -1-P
which is converted to glycogen
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Liver Disorders

• Liver disorders
• Hepatitis - inflammation - viral usually - 5
  strains
• A most common - transmitted in large restricted
  groups by foods
• B C are sexually transmitted by blood and
  fluids.
• Symptoms - Fatigue, malaise, nausea, weight loss

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Hepatitis C
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Lipid Metabolism

• Lipid transport
• Most non-polar lipids complex with protein to
  produce water soluble spheres

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Lipogenesis

• Excess glycerol fatty acids undergo lipogenesis
  to form triglycerides in the liver.
• Glucose or amino acids converted into lipids
  Glucose ? glyceraldehyde ? glyceraldehyde-3-phosph
  ate ? glycerol or to acetyl CoA which can go on
  to form fatty acids
• Amino acids ? Acetyl CoA ? fatty acids, etc.
• Stimulated by Insulin

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Lipid Catabolism

• Lipolysis
• Lipids are split into glycerol fatty acids.
• Fatty acids undergo beta oxidation which produces
  2-carbon acetic acid fragments, that can enter
  the Krebs cycle, or form ketone bodies

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Lipid Metabolism
Figure 24.13
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Protein Metabolism

• Excess protein results in amino acids being used
  to make other proteins, glucose, triglycerides or
  ATP.
• Proteins are not stored.

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Protein Catabolism

• Use as fuel
• Deaminated amino acids can be converted into
  pyruvic acid into one of the keto acid
  intermediates of the Krebs cycle.

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Proteins

• Transamination, ammonia urea
• Amino group ? ammonia ? urea
• Amino group is transferred to citric acid --gt --gt
  glutamic acid --gt liver --gt removal of NH2 --gt
  ammonia --gt urea
• Protein synthesis - occurs on ribosomes, directed
  by DNA and RNA
• Stimulated by GH, Insulin, T3, T4, estrogen and
  testosterone

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Summary Carbohydrate Metabolic Reactions
Table 24.2.1
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Summary Lipid and Protein Metabolic Reactions
Table 24.2.2
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Absorptive and Postabsorptive States

• Metabolic controls balance blood concentrations
  of nutrients between two states
• Absorptive
• The time during shortly after nutrient intake

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Absorptive and Postabsorptive States

• Postabsorptive
• The time when the GI tract is empty.
• Energy sources are supplied by the breakdown of
  body reserves.

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Absorptive State

• Ingested nutrients enter blood and lymphatic
  system --gt hepatic portal system to liver
• Lasts about 4 hours after completing a meal

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Absorptive State

• Events
• Glucose
• Glucose uptake by liver ? converted to
  triglycerides and glycogen (10)
• Adipose tissues store fat take up blood glucose ?
  to triglycerides (40)
• Muscles take up glucose and store as glycogen
  (50)

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Absorptive State

• Events
• Amino Acids ? liver ? Kreb's cycle or
  gluconeogenesis or protein synthesis
• Lipids most packaged ? VLDL lipoproteins and are
  carried to adipose.
• Hormones -mostly, insulin hypoglycemic hormone

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Absorptive State
Figure 24.18a
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Principal Pathways of the Absorptive State
Figure 24.18b
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Postabsorptive State

• Need to maintain normal blood glucose level
  90-100mg/100mL
• Very important for nervous system - can only use
  glucose for energy.

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Postabsorptive State

• EVENTS
• Liver glycogen is converted to glucose - lasts
  about 4 hrs.
• Muscle glycogen is converted to lactic acid ?
  glucose in liver
• Adipose breaks triglycerides to glycerol ?
  glucose

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Postabsorptive State

• Muscle protein ? aa ? converted by liver into
  glucose gluconeogenesis
• Hormone glucagon Neural Control ANS via
  epinephrine

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Postabsorptive State
Figure 24.20a
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Principle Pathways in the Postabsorptive State
Figure 24.20b
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Metabolic Rate

• Basal metabolic rate BMR - rate of metabolism
  measured under standard conditions - awake,
  resting, fasting.
• Units Kcal/m2/hr. Can be indirectly measured
  by monitoring oxygen consumption per unit time.
  averages 2000 kcal/day

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Factors that Influence BMR

• Surface area, age, gender, stress, hormones.
• Ratio of surface area to volume if increases,
  BMR increases.
• Sex. Males have a high BMR.

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Factors that Influence BMR

• Stress. Increases BMR.
• Thyroxine increases oxygen consumption, cellular
  respiration, BMR.

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Thermoregulation

• Imbalances
• Hyperthermia elevated body temperature - Heat
  stroke, fever
• Hypothermia - too low --gt death

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Thermoregulation

• Body temperature
• Core temperature 37.2 - 37.6 oC can be higher
  with high activity
• Shell temperature 36.6 - 37.0 oC can be
  higher with high activity

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Mechanisms of Heat Exchange

• The body uses four mechanisms of heat exchange
• Radiation
• Conduction
• Convection
• Evaporation

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Regulation of Body Temperature
Figure 24.25
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Role of the Hypothalamus

• The chief thermoregulation center is the
  pre-optic region of the hypothalamus.
• Thermoregulatory areas include heat-loss
  heat-promoting centers.

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Heat-Promoting Mechanisms

• Activation of heat-promoting centers of the
  hypothalamus causes
• Vasoconstriction of cutaneous blood vessels.
• Shivering.
• Increased metabolic rate.
• Enhanced thyroxine release.

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Heat-Loss Mechanisms

• When core temperature rises, the heat-loss center
  is activated to cause
• Vasodilation of cutaneous blood vessels,
• Enhanced sweating

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