1

Chapter 25Chapter 25MetabolismMetabolism

Functions of food Functions of food source of energysource of energy

essential nutrients essential nutrients stored for future usestored for future use

Metabolism is all the chemical Metabolism is all the chemical reactions of the bodyreactions of the body some reactions produce the energy stored some reactions produce the energy stored

in ATP that other reactions consumein ATP that other reactions consume all molecules will eventually be broken all molecules will eventually be broken

down and recycled or excreted from the down and recycled or excreted from the bodybody

2

Catabolism and Catabolism and AnabolismAnabolism

Catabolic reactions breakdown complex Catabolic reactions breakdown complex organic compoundsorganic compounds providing energy (exergonic)providing energy (exergonic) glycolysis, Krebs cycle and electron transportglycolysis, Krebs cycle and electron transport

Anabolic reactions synthesize complex Anabolic reactions synthesize complex molecules from small molecules molecules from small molecules requiring energy (endergonic)requiring energy (endergonic)

Exchange of energy requires use of ATP Exchange of energy requires use of ATP (adenosine triphosphate) molecule.(adenosine triphosphate) molecule.

3

ATP Molecule & EnergyATP Molecule & Energy

Each cell has about 1 billion ATP molecules that last Each cell has about 1 billion ATP molecules that last for less than one minutefor less than one minute

Over half of the energy released from ATP is Over half of the energy released from ATP is converted to heatconverted to heat

4

Energy TransferEnergy Transfer Energy is found in the bondsEnergy is found in the bonds between between

atomsatoms Oxidation is a decrease in the energy Oxidation is a decrease in the energy

content of a moleculecontent of a molecule Reduction is the increase in the energy Reduction is the increase in the energy

content of a molecule content of a molecule Oxidation-reduction reactions are Oxidation-reduction reactions are

always coupled within the bodyalways coupled within the body whenever a substance is oxidized, whenever a substance is oxidized,

another is almost simultaneously reduced.another is almost simultaneously reduced.

5

Mechanisms of ATP Mechanisms of ATP GenerationGeneration

Phosphorylation is Phosphorylation is bond attaching 3rd phosphate group bond attaching 3rd phosphate group

contains stored energy contains stored energy Mechanisms of phosphorylation Mechanisms of phosphorylation

within animalswithin animals substrate-level phosphorylation in cytosolsubstrate-level phosphorylation in cytosol oxidative phosphorylation in mitochondriaoxidative phosphorylation in mitochondria

in chlorophyll-containing plants or bacteriain chlorophyll-containing plants or bacteria photophosphorylation.photophosphorylation.

6

Phosphorylation in Phosphorylation in Animal CellsAnimal Cells

In cytoplasm (1)In cytoplasm (1) In mitochondria (2, 3 & 4) In mitochondria (2, 3 & 4)

7

Carbohydrate Metabolism--Carbohydrate Metabolism--In ReviewIn Review In GI tractIn GI tract

polysaccharides broken down into simple polysaccharides broken down into simple sugars sugars

absorption of simple sugars (glucose, absorption of simple sugars (glucose, fructose & galactose)fructose & galactose)

In liver In liver fructose & galactose transformed into fructose & galactose transformed into

glucoseglucose storage of glycogen (also in muscle)storage of glycogen (also in muscle)

In body cells --functions of glucoseIn body cells --functions of glucose oxidized to produce energyoxidized to produce energy conversion into something elseconversion into something else storage energy as triglyceride in fat storage energy as triglyceride in fat

8

Fate of GlucoseFate of Glucose ATP production during cell respirationATP production during cell respiration

uses glucose preferentially uses glucose preferentially Converted to one of several amino acids in Converted to one of several amino acids in

many different cells throughout the body many different cells throughout the body GlycogenesisGlycogenesis

hundreds of glucose molecules combined to hundreds of glucose molecules combined to form glycogen for storage in liver & skeletal form glycogen for storage in liver & skeletal musclesmuscles

Lipogenesis (triglyceride synthesis)Lipogenesis (triglyceride synthesis) converted to glycerol & fatty acids within liver converted to glycerol & fatty acids within liver

& sent to fat cells& sent to fat cells

9

Glucose Movement into Glucose Movement into CellsCells In GI tract and kidney tubules, In GI tract and kidney tubules,

Na+/glucose symportersNa+/glucose symporters Most other cells, GluT facilitated Most other cells, GluT facilitated

diffusion transporters move diffusion transporters move glucose into cellsglucose into cells insulin increases number of GluT insulin increases number of GluT

transporters in the membrane of transporters in the membrane of most cellsmost cells

in liver & brain, always lots of GluT in liver & brain, always lots of GluT transporterstransporters

Glucose 6-phosphate forms Glucose 6-phosphate forms immediately inside cell (requires immediately inside cell (requires ATP) thus, glucose hidden in cellATP) thus, glucose hidden in cell

Concentration gradient favorable Concentration gradient favorable for more glucose to enterfor more glucose to enter

10

Glucose CatabolismGlucose Catabolism Cellular respirationCellular respiration

4 steps are involved4 steps are involved glucose + O2 producesglucose + O2 produces

H2O + energy + CO2H2O + energy + CO2 Anaerobic respirationAnaerobic respiration

called glycolysis (1)called glycolysis (1) formation of acetyl CoA (2)formation of acetyl CoA (2)

is transitional step to Krebs cycleis transitional step to Krebs cycle Aerobic respirationAerobic respiration

Krebs cycle (3) and electron transport chain (4)Krebs cycle (3) and electron transport chain (4)

11

Glycolysis of Glucose & Fate of Glycolysis of Glucose & Fate of Pyruvic AcidPyruvic Acid

Breakdown of six-carbon Breakdown of six-carbon glucose molecule into 2 three-glucose molecule into 2 three-carbon molecules of pyruvic carbon molecules of pyruvic acidacid 10 step process occurring in cell 10 step process occurring in cell

cytosolcytosol produces 4 molecules of ATP after produces 4 molecules of ATP after

input of 2 ATPinput of 2 ATP utilizes 2 NAD+ molecules as utilizes 2 NAD+ molecules as

hydrogen acceptorshydrogen acceptors If O2 shortage in a cell If O2 shortage in a cell

pyruvic acid is reduced to lactic pyruvic acid is reduced to lactic acid so that NAD+ will be still acid so that NAD+ will be still available for further glycolysisavailable for further glycolysis

rapidly diffuses out of cell to bloodrapidly diffuses out of cell to blood liver cells remove it from blood & liver cells remove it from blood &

convert it back to pyruvic acidconvert it back to pyruvic acid

12

Formation of Acetyl Formation of Acetyl Coenzyme ACoenzyme A Pyruvic acid enters the Pyruvic acid enters the

mitochondria with help of mitochondria with help of transporter proteintransporter protein

DecarboxylationDecarboxylation pyruvate dehydrogenase pyruvate dehydrogenase

converts 3 carbon pyruvic acid converts 3 carbon pyruvic acid to 2 carbon fragment (CO2 to 2 carbon fragment (CO2 produced)produced)

pyruvic acid was oxidized so pyruvic acid was oxidized so that NAD+ becomes NADHthat NAD+ becomes NADH

2 carbon fragment (acetyl 2 carbon fragment (acetyl group) is attached to group) is attached to Coenzyme A to form Acetyl Coenzyme A to form Acetyl coenzyme A which enter coenzyme A which enter Krebs cycleKrebs cycle coenzyme A is derived from coenzyme A is derived from

pantothenic acid (B vitamin).pantothenic acid (B vitamin).

13

Krebs Cycle (Citric Acid Krebs Cycle (Citric Acid Cycle)Cycle) Series of oxidation-Series of oxidation-

reduction & reduction & decarboxylation reactions decarboxylation reactions occurring in matrix of occurring in matrix of mitochondriamitochondria

It finishes the same as it It finishes the same as it starts (4C)starts (4C) acetyl CoA (2C) enters at top acetyl CoA (2C) enters at top

& combines with a 4C & combines with a 4C compoundcompound

2 decarboxylation reactions 2 decarboxylation reactions peel 2 carbons off again when peel 2 carbons off again when CO2 is formedCO2 is formed

14

Krebs CycleKrebs Cycle Energy stored in bonds is released step by Energy stored in bonds is released step by

step to form several reduced coenzymes step to form several reduced coenzymes (NADH & FADH2) that store the energy(NADH & FADH2) that store the energy

In summary: each Acetyl CoAIn summary: each Acetyl CoAmolecule that enters the Krebsmolecule that enters the Krebscycle producescycle produces 2 molecules of C022 molecules of C02

one reason O2 is neededone reason O2 is needed 3 molecules of NADH + H+3 molecules of NADH + H+ one molecule of ATPone molecule of ATP one molecule of FADHone molecule of FADH2 2

Remember, each glucoseRemember, each glucoseproduced 2 acetyl CoA moleculesproduced 2 acetyl CoA molecules

15

The Electron Transport The Electron Transport ChainChain

Series of integral Series of integral membrane proteins in membrane proteins in the inner mitochondrial the inner mitochondrial membrane capable of membrane capable of oxidation/reductionoxidation/reduction

Each electron carrier is Each electron carrier is reduced as it picks up reduced as it picks up electrons and is oxidized electrons and is oxidized as it gives up electronsas it gives up electrons

Small amounts of energy Small amounts of energy released in small steps released in small steps

Energy used to form Energy used to form ATP by chemiosmosisATP by chemiosmosis

16

ChemiosmosisChemiosmosis Small amounts of energy Small amounts of energy

released as substances released as substances are passed along inner are passed along inner membranemembrane

Energy used to pump Energy used to pump H+ ions from matrix H+ ions from matrix into space between into space between inner & outer membraneinner & outer membrane

High concentration of High concentration of H+ is maintained H+ is maintained outside of inner outside of inner membranemembrane

ATP synthesis occurs as ATP synthesis occurs as H+ diffuses through a H+ diffuses through a special H+ channel in special H+ channel in inner membraneinner membrane

17

Steps in Electron TransportSteps in Electron Transport

Carriers of electron transport chain are clustered into Carriers of electron transport chain are clustered into 3 complexes that each act as proton pump (expel H+)3 complexes that each act as proton pump (expel H+)

Mobile shuttles pass electrons between complexesMobile shuttles pass electrons between complexes Last complex passes its electrons (2H+) to a half of Last complex passes its electrons (2H+) to a half of

O2 molecule to form a water molecule (H2O) O2 molecule to form a water molecule (H2O)

18

Proton Motive Force & Proton Motive Force & ChemiosmosisChemiosmosis

Buildup of H+ outside the inner membrane creates Buildup of H+ outside the inner membrane creates + charge+ charge electrochemical gradient potential energy is called proton electrochemical gradient potential energy is called proton

motive forcemotive force ATP synthase enzyme within H+ channel uses proton ATP synthase enzyme within H+ channel uses proton

motive force to synthesize ATP from ADP and Pmotive force to synthesize ATP from ADP and P

19

Summary of Cellular Summary of Cellular RespirationRespiration

Glucose + O2 is broken down Glucose + O2 is broken down into CO2 + H2O + energy used into CO2 + H2O + energy used to form 36 to 38 ATPsto form 36 to 38 ATPs 2 ATP are formed during glycolysis 2 ATP are formed during glycolysis 2 ATP are formed by 2 ATP are formed by

phosphorylation during Krebs cyclephosphorylation during Krebs cycle electron transfers in transport chain electron transfers in transport chain

generate 32 or 34 ATPs from one generate 32 or 34 ATPs from one glucose moleculeglucose molecule

Summary in Table 25.1Summary in Table 25.1 Points to remember Points to remember

ATP must be transported out of ATP must be transported out of mitochondria in exchange for ADPmitochondria in exchange for ADP

uses up some of proton motive forceuses up some of proton motive force Oxygen is required or many of these Oxygen is required or many of these

steps can not occursteps can not occur

20

Carbohydrate LoadingCarbohydrate Loading

Long-term athletic events Long-term athletic events (marathons) can exhaust glycogen (marathons) can exhaust glycogen stored in liver and skeletal musclesstored in liver and skeletal muscles

Eating large amounts of complex Eating large amounts of complex carbohydrates (pasta & potatoes) for carbohydrates (pasta & potatoes) for 3 days before a marathon maximizes 3 days before a marathon maximizes glycogen available for ATP glycogen available for ATP productionproduction

Useful for athletic events lasting for Useful for athletic events lasting for more than an hourmore than an hour

21

Glycogenesis & Glycogenesis & GlycogenolysisGlycogenolysis

GlycogenesisGlycogenesis glucose storage as glycogenglucose storage as glycogen 4 steps to glycogen4 steps to glycogen

formation in liver orformation in liver orskeletal muscleskeletal muscle

stimulated by insulinstimulated by insulin GlycogenolysisGlycogenolysis

glucose release not a simpleglucose release not a simplereversal of stepsreversal of steps

enzyme phosphorylase splits off a glucose molecule by enzyme phosphorylase splits off a glucose molecule by phosphorylation to form glucose 1-phosphatephosphorylation to form glucose 1-phosphate

enzyme only in hepatocytes so muscle can’t release enzyme only in hepatocytes so muscle can’t release glucoseglucose

enzyme activated by glucagon (pancreas) & epinephrine enzyme activated by glucagon (pancreas) & epinephrine (adrenal)(adrenal)

22

GluconeogenesisGluconeogenesis

Liver glycogen runs low if fasting, starving or not eating Liver glycogen runs low if fasting, starving or not eating carbohydrates forcing formation from other substancescarbohydrates forcing formation from other substances lactic acid, glycerol & certain amino acids (60% of available)lactic acid, glycerol & certain amino acids (60% of available)

Stimulated by cortisol (adrenal) & glucagon (pancreas)Stimulated by cortisol (adrenal) & glucagon (pancreas) cortisol stimulates breakdown of proteins freeing amino acidscortisol stimulates breakdown of proteins freeing amino acids thyroid mobilizes triglycerides from adipose tissuethyroid mobilizes triglycerides from adipose tissue

23

Transport of Lipids by Transport of Lipids by LipoproteinsLipoproteins

Most lipids are nonpolar and must be combined Most lipids are nonpolar and must be combined with protein to be tranported in bloodwith protein to be tranported in blood

Lipoproteins are spheres containing hundreds Lipoproteins are spheres containing hundreds of moleculesof molecules outer shell polar proteinsouter shell polar proteins

(apoproteins) & phospholipids(apoproteins) & phospholipids inner core of triglyceride & inner core of triglyceride &

cholesterol esterscholesterol esters Lipoprotein categorized byLipoprotein categorized by

function & densityfunction & density 4 major classes of lipoproteins4 major classes of lipoproteins

chylomicrons, very low-density, low-density & high-chylomicrons, very low-density, low-density & high-density lipoproteinsdensity lipoproteins

24

Classes of LipoproteinsClasses of Lipoproteins Chylomicrons (2 % protein)Chylomicrons (2 % protein)

form in intestinal epithelial cells to transport dietary fatform in intestinal epithelial cells to transport dietary fat apo C-2 activates enzyme that releases the fatty apo C-2 activates enzyme that releases the fatty

acids from the chylomicron for absorption by acids from the chylomicron for absorption by adipose & muscle cellsadipose & muscle cells

liver processes what is leftliver processes what is left VLDLs (10% protein)VLDLs (10% protein)

transport triglycerides formed in liver to fat cellstransport triglycerides formed in liver to fat cells LDLs (25% protein) --- “bad cholesterol”LDLs (25% protein) --- “bad cholesterol”

carry 75% of blood cholesterol to body cellscarry 75% of blood cholesterol to body cells apo B100 is docking protein for receptor-mediated apo B100 is docking protein for receptor-mediated

endocytosis of the LDL into a body cellendocytosis of the LDL into a body cell if cells have insufficient receptors, remains in blood if cells have insufficient receptors, remains in blood

and more likely to deposit cholesterol in artery walls and more likely to deposit cholesterol in artery walls (plaque)(plaque)

HDLs (40% protein) --- “good cholesterol” HDLs (40% protein) --- “good cholesterol” carry cholesterol from cells to liver for eliminationcarry cholesterol from cells to liver for elimination

25

Blood CholesterolBlood Cholesterol Sources of cholesterol in the bodySources of cholesterol in the body

food (eggs, dairy, organ meats, meat)food (eggs, dairy, organ meats, meat) synthesized by the liversynthesized by the liver

All fatty foods still raise blood cholesterolAll fatty foods still raise blood cholesterol liver uses them to create cholesterolliver uses them to create cholesterol stimulate reuptake of cholesterol containing bile stimulate reuptake of cholesterol containing bile

normally lost in the fecesnormally lost in the feces Desirable readings for adultsDesirable readings for adults

total cholesterol under 200 mg/dL; triglycerides total cholesterol under 200 mg/dL; triglycerides 10-190 mg/dL10-190 mg/dL

LDL under 130 mg/dL; HDL over 40 mg/dLLDL under 130 mg/dL; HDL over 40 mg/dL cholesterol/HDL ratio above 4 is undesirable risk cholesterol/HDL ratio above 4 is undesirable risk

Raising HDL & lowering cholesterol can be Raising HDL & lowering cholesterol can be accomplished by exercise, diet & drugsaccomplished by exercise, diet & drugs

26

Fate of LipidsFate of Lipids Oxidized to produce ATPOxidized to produce ATP Excess stored in adipose tissue or liverExcess stored in adipose tissue or liver Synthesize structural or important Synthesize structural or important

moleculesmolecules phospholipids of plasma membranesphospholipids of plasma membranes lipoproteins that transport cholesterollipoproteins that transport cholesterol thromboplastin for blood clottingthromboplastin for blood clotting myelin sheaths to speed up nerve myelin sheaths to speed up nerve

conductionconduction cholesterol used to synthesize bile salts cholesterol used to synthesize bile salts

and steroid hormones.and steroid hormones.

27

Lipid Anabolism: Lipid Anabolism: LipogenesisLipogenesis

Synthesis of lipids by liver cells = Synthesis of lipids by liver cells = lipogenesislipogenesis from amino acids from amino acids

converted to acetyl CoA & then to triglyceridesconverted to acetyl CoA & then to triglycerides from glucosefrom glucose

from glyceraldehyde 3-phosphate to triglyceridesfrom glyceraldehyde 3-phosphate to triglycerides

Stimulated by insulin when eat excess Stimulated by insulin when eat excess caloriescalories

28

KetosisKetosis Blood ketone levels are usually very lowBlood ketone levels are usually very low

many tissues use ketone for ATP productionmany tissues use ketone for ATP production Fasting, starving or high fat meal with few Fasting, starving or high fat meal with few

carbohydrates results in excessive beta carbohydrates results in excessive beta oxidation & ketone productionoxidation & ketone production acidosis (ketoacidosis) is abnormally low blood acidosis (ketoacidosis) is abnormally low blood

pHpH sweet smell of ketone body acetone on breathsweet smell of ketone body acetone on breath occurs in diabetic since triglycerides are used occurs in diabetic since triglycerides are used

for ATP production instead of glucose & insulin for ATP production instead of glucose & insulin inhibits lipolysisinhibits lipolysis

29

Fate of ProteinsFate of Proteins Proteins are broken down into amino acidsProteins are broken down into amino acids

transported to the livertransported to the liver UsageUsage

oxidized to produce ATPoxidized to produce ATP used to synthesize new proteins used to synthesize new proteins

enzymes, hemoglobin, antibodies, hormones, enzymes, hemoglobin, antibodies, hormones, fibrinogen, actin, myosin, collagen, elastin & keratinfibrinogen, actin, myosin, collagen, elastin & keratin

excess converted into glucose or triglyceridesexcess converted into glucose or triglycerides no storage is possibleno storage is possible

Absorption into body cells is stimulated by Absorption into body cells is stimulated by insulinlike growth factors (IGFs) & insulininsulinlike growth factors (IGFs) & insulin

30

Protein CatabolismProtein Catabolism Breakdown of protein Breakdown of protein

into amino acids into amino acids Liver cells convert Liver cells convert

amino acids into amino acids into substances that can substances that can enter the Krebs cycleenter the Krebs cycle deamination removes the deamination removes the

amino group (NH2)amino group (NH2) converts it to converts it to

ammonia (NH3) & ammonia (NH3) & then ureathen urea

urea excreted in the urea excreted in the urineurine

Converted substances Converted substances enter the Krebs cycle to enter the Krebs cycle to produce ATPproduce ATP

31

Protein AnabolismProtein Anabolism Production of new proteins by formation of peptide bonds Production of new proteins by formation of peptide bonds

between amino acidsbetween amino acids 10 essential amino acids are ones we must eat because we can 10 essential amino acids are ones we must eat because we can

not synthesize themnot synthesize them nonessential amino acids can be synthesized by transamination nonessential amino acids can be synthesized by transamination

(transfer of an amino group to a substance to create an amino (transfer of an amino group to a substance to create an amino acid)acid)

Occurs on ribosomes in almost every cellOccurs on ribosomes in almost every cell Stimulated by insulinlike growth factor, thyroid hormone, Stimulated by insulinlike growth factor, thyroid hormone,

insulin, estrogen & testosteroneinsulin, estrogen & testosterone Large amounts of protein in the diet do not cause the Large amounts of protein in the diet do not cause the

growth of muscle, only weight-bearing exercisegrowth of muscle, only weight-bearing exercise

32

Phenylketonuria (PKU)Phenylketonuria (PKU) Genetic error of protein metabolism that Genetic error of protein metabolism that

produces elevated blood levels of amino produces elevated blood levels of amino acid phenylalanineacid phenylalanine causes vomiting, seizures & mental retardationcauses vomiting, seizures & mental retardation normally converted by an enzyme into tyrosine normally converted by an enzyme into tyrosine

which can enter the krebs cycle which can enter the krebs cycle Screening of newborns prevents retardationScreening of newborns prevents retardation

spend their life with a diet restricting spend their life with a diet restricting phenylalaninephenylalanine

restrict Nutrasweet which contains restrict Nutrasweet which contains phenylalaninephenylalanine

33

Metabolic AdaptationsMetabolic Adaptations Absorptive stateAbsorptive state

nutrients entering the bloodstreamnutrients entering the bloodstream glucose readily available for ATP productionglucose readily available for ATP production 4 hours for absorption of each meal so 4 hours for absorption of each meal so

absorptive state lasts for 12 hours/dayabsorptive state lasts for 12 hours/day Postabsorptive statePostabsorptive state

absorption of nutrients from GI tract is absorption of nutrients from GI tract is completecomplete

body must meet its needs without outside body must meet its needs without outside nutrientsnutrients late morning, late afternoon & most of the eveninglate morning, late afternoon & most of the evening assuming no snacks, lasts about 12 hours/dayassuming no snacks, lasts about 12 hours/day more cells use ketone bodies for ATP productionmore cells use ketone bodies for ATP production

maintaining a steady blood glucose level is maintaining a steady blood glucose level is criticalcritical

34

Metabolism During Fasting & Metabolism During Fasting & StarvationStarvation

Fasting means going without food for Fasting means going without food for hours/dayshours/days

Starvation means weeks or monthsStarvation means weeks or months can survive 2 months or more if drink enough can survive 2 months or more if drink enough

waterwater amount of adipose tissue is determining factoramount of adipose tissue is determining factor

Nutritional needsNutritional needs nervous tissue & RBC need glucose so amino nervous tissue & RBC need glucose so amino

acids will be broken down for gluconeogenesisacids will be broken down for gluconeogenesis blood glucose stabilizes at 65 mg/100 mLblood glucose stabilizes at 65 mg/100 mL lipolysis releases glycerol used in gluconeogenesislipolysis releases glycerol used in gluconeogenesis

increase in formation of ketone bodies by liver increase in formation of ketone bodies by liver cells due to catabolism of fatty acidscells due to catabolism of fatty acids by 40 days, ketones supply 2/3’s of brains fuel for by 40 days, ketones supply 2/3’s of brains fuel for

ATPATP

35

Absorption of AlcoholAbsorption of Alcohol Absorption begins in the stomach but is Absorption begins in the stomach but is

absorbed more quickly in the small absorbed more quickly in the small intestineintestine fat rich foods keep the alcohol from leaving fat rich foods keep the alcohol from leaving

the stomach and prevent a rapid rise in the stomach and prevent a rapid rise in blood alcoholblood alcohol

a gastric mucosa enzyme breaks down some a gastric mucosa enzyme breaks down some of the alcohol to acetaldehydeof the alcohol to acetaldehyde

Females develop higher blood alcoholsFemales develop higher blood alcohols have a smaller blood volumehave a smaller blood volume have less gastric alcohol dehydrogenase have less gastric alcohol dehydrogenase

activityactivity

36

Metabolic RateMetabolic Rate

Rate at which metabolic reactions use Rate at which metabolic reactions use energyenergy energy used to produce heat or ATPenergy used to produce heat or ATP

Basal Metabolic Rate (BMR) Basal Metabolic Rate (BMR) measurements made under specific conditionsmeasurements made under specific conditions

quiet, resting and fasting conditionquiet, resting and fasting condition

Basal Temperature maintained at 98.6 Basal Temperature maintained at 98.6 degreesdegrees shell temperature is usually 1 to 6 degrees lowershell temperature is usually 1 to 6 degrees lower

37

Heat ProductionHeat Production Factors that affect metabolic rate and Factors that affect metabolic rate and

thus the production of body heatthus the production of body heat exercise increases metabolic rate as much as exercise increases metabolic rate as much as

15 times15 times hormones regulate basal metabolic ratehormones regulate basal metabolic rate

thyroid, insulin, growth hormone & testosterone thyroid, insulin, growth hormone & testosterone increase BMRincrease BMR

sympathetic nervous system’s release of sympathetic nervous system’s release of epinephrine & norepinephrine increases BMRepinephrine & norepinephrine increases BMR

higher body temperature raises BMRhigher body temperature raises BMR ingestion of food raises BMR 10-20%ingestion of food raises BMR 10-20% children’s BMR is double that of an elderly children’s BMR is double that of an elderly

personperson

38

Mechanisms of Heat Mechanisms of Heat TransferTransfer

Temperature homeostasis requires Temperature homeostasis requires mechanisms of transferring heat from mechanisms of transferring heat from the body to the environmentthe body to the environment conduction is heat exchange requiring conduction is heat exchange requiring

direct contact with an objectdirect contact with an object convection is heat transfer by movement convection is heat transfer by movement

of gas or liquid over bodyof gas or liquid over body radiation is transfer of heat in form of radiation is transfer of heat in form of

infrared rays from bodyinfrared rays from body evaporation is heat loss due to conversion evaporation is heat loss due to conversion

of liquid to a vapor (insensible water loss)of liquid to a vapor (insensible water loss)

39

Hypothalamic Hypothalamic ThermostatThermostat

Preoptic area in anterior hypothalamusPreoptic area in anterior hypothalamus receives impulses from thermoreceptorsreceives impulses from thermoreceptors generates impulses at a higher frequency when generates impulses at a higher frequency when

blood temperature increasesblood temperature increases impulses propagate to other parts of impulses propagate to other parts of

hypothalamushypothalamus heat-losing centerheat-losing center heat-promoting centerheat-promoting center

Set in motion responses that either lower or Set in motion responses that either lower or raise body temperatureraise body temperature

40

ThermoregulationThermoregulation Declining body temperatureDeclining body temperature

thermoreceptors signal thermoreceptors signal hypothalamus to produce TRHhypothalamus to produce TRH

TRH causes anterior pituitary TRH causes anterior pituitary to produce TSH resulting in to produce TSH resulting in

vasoconstriction in skinvasoconstriction in skin adrenal medulla stimulates cell adrenal medulla stimulates cell

metabolic ratemetabolic rate shiveringshivering release of more thyroid hormone release of more thyroid hormone

raises BMRraises BMR

Increases in body Increases in body temperaturetemperature sweating & vasodilationsweating & vasodilation

41

HypothermiaHypothermia

Lowering of core body temperature to 35°C Lowering of core body temperature to 35°C (95°F) (95°F)

CausesCauses immersion in icy water (cold stress)immersion in icy water (cold stress) metabolic diseases (hypoglycemia, adrenal metabolic diseases (hypoglycemia, adrenal

insufficiency or hypothyroidism)insufficiency or hypothyroidism) drugs (alcohol, antidepressants, or sedatives)drugs (alcohol, antidepressants, or sedatives) burns and malnutritionburns and malnutrition

Symptoms that occur as body temperature Symptoms that occur as body temperature dropsdrops shivering, confusion, vasoconstriction, muscle rigidity, shivering, confusion, vasoconstriction, muscle rigidity,

bradycardia, acidosis, hypoventilation, coma & deathbradycardia, acidosis, hypoventilation, coma & death

42

Regulation of Food Regulation of Food IntakeIntake

Hypothalamus regulates food intakeHypothalamus regulates food intake feeding (hunger) centerfeeding (hunger) center satiety centersatiety center

Stimuli that decrease appetiteStimuli that decrease appetite glucagon, cholecystokinin, epinephrine, glucagon, cholecystokinin, epinephrine,

glucose & leptinglucose & leptin stretching of the stomach and duodenumstretching of the stomach and duodenum

Signals that increase appetiteSignals that increase appetite growth releasing hormone, opioids, growth releasing hormone, opioids,

glucocorticoids, insulin, progesterone & glucocorticoids, insulin, progesterone & somatostatinsomatostatin

43

Guidelines for Healthy Guidelines for Healthy EatingEating

Nutrients include water, carbohydrates, Nutrients include water, carbohydrates, lipids, proteins, vitamins and mineralslipids, proteins, vitamins and minerals

Caloric intakeCaloric intake women 1600 Calories/day is neededwomen 1600 Calories/day is needed active women and most men 2200 Caloriesactive women and most men 2200 Calories teenage boys and active men 2800 calories teenage boys and active men 2800 calories

Food guide pyramid developed by U.S. Food guide pyramid developed by U.S. Department of AgricultureDepartment of Agriculture indicates number of servings of each food indicates number of servings of each food

group to eat each daygroup to eat each day

44

Food Guide PyramidFood Guide Pyramid

45

MineralsMinerals InorganicInorganic substances = 4% body weightsubstances = 4% body weight FunctionsFunctions

calcium & phosphorus form part of the matrix of calcium & phosphorus form part of the matrix of bonebone

help regulate enzymatic reactionshelp regulate enzymatic reactions calcium, iron, magnesium & manganesecalcium, iron, magnesium & manganese

magnesium is catalyst for conversion of ADP to magnesium is catalyst for conversion of ADP to ATPATP

form buffer systemsform buffer systems regulate osmosis of waterregulate osmosis of water generation of nerve impulsesgeneration of nerve impulses

46

VitaminsVitamins Organic nutrients needed in very small Organic nutrients needed in very small

amountsamounts serve as coenzymesserve as coenzymes

Most cannot be synthesized by the bodyMost cannot be synthesized by the body Fat-soluble vitaminsFat-soluble vitamins

absorbed with dietary fats by the small intestineabsorbed with dietary fats by the small intestine stored in liver and include vitamins A, D, E, and Kstored in liver and include vitamins A, D, E, and K

Water-soluble vitamins are absorbed along Water-soluble vitamins are absorbed along with water in the Gl tractwith water in the Gl tract body does not store---excess excreted in urinebody does not store---excess excreted in urine includes the B vitamins and vitamin Cincludes the B vitamins and vitamin C

47

Antioxidant VitaminsAntioxidant Vitamins C, E and beta-carotene (a provitamin)C, E and beta-carotene (a provitamin) Inactivate oxygen free radicalsInactivate oxygen free radicals

highly reactive particles that carry an highly reactive particles that carry an unpaired electronunpaired electron

damage cell membranes, DNA, and damage cell membranes, DNA, and contribute to atherosclerotic plaquescontribute to atherosclerotic plaques

arise naturally or from environmental arise naturally or from environmental hazards such as tobacco or radiationhazards such as tobacco or radiation

Protect against cancer, aging, Protect against cancer, aging, cataract formation, and cataract formation, and atherosclerotic plaqueatherosclerotic plaque

48

Vitamin and Mineral Vitamin and Mineral SupplementsSupplements

Eat a balanced diet rather than taking Eat a balanced diet rather than taking supplementssupplements

ExceptionsExceptions iron for women with heavy menstrual iron for women with heavy menstrual

bleedingbleeding iron & calcium for pregnant or nursing iron & calcium for pregnant or nursing

womenwomen folic acid if trying to become pregnantfolic acid if trying to become pregnant

reduce risk of fetal neural tube defectsreduce risk of fetal neural tube defects calcium for all adultscalcium for all adults B12 for strict vegetariansB12 for strict vegetarians antioxidants C and E recommended by someantioxidants C and E recommended by some

49

FeverFever Abnormally high body temperature Abnormally high body temperature

toxins from bacterial or viral infection = pyrogenstoxins from bacterial or viral infection = pyrogens heart attacks or tumorsheart attacks or tumors tissue destruction by x-rays, surgery, or traumatissue destruction by x-rays, surgery, or trauma reactions to vaccinesreactions to vaccines

Beneficial in fighting infection & increasing Beneficial in fighting infection & increasing rate of tissue repair during the course of a rate of tissue repair during the course of a diseasedisease

ComplicationsComplications----dehydration, acidosis, & brain dehydration, acidosis, & brain damage.damage.

50

ObesityObesity Body weight more than 20% above Body weight more than 20% above

desirable standarddesirable standard Risk factor in many diseasesRisk factor in many diseases

cardiovascular disease, hypertension, cardiovascular disease, hypertension, pulmonary disease,pulmonary disease,

non-insulin dependent diabetes mellitus non-insulin dependent diabetes mellitus arthritis, certain cancers (breast, uterus, arthritis, certain cancers (breast, uterus,

and colon),and colon), varicose veins, and gallbladder disease. varicose veins, and gallbladder disease.