Nutrition, Metabolism, and Body Temperature Regulation

1
Chapter 24

• Nutrition, Metabolism, and Body Temperature
  Regulation

2
Nutrition

• Some food is used to build your body, but most is
  for ATP production
• Nutrients any substance in food used to promote
  growth, maintenance, and repair divided into
  six categories
• Major (Macro) Nutrients Carbs, Proteins, Lipids
• Micro Nutrients Vitamins, Minerals,
• Water 60 by volume of the food we eat
• Many nutrients are made or converted by the body
• Essential nutrients (45-50) cannot be made in
  diet
• Non-essential nutrients are needed but made from
  E.N.

3
http//www.mypyramid.gov/
4
Nutrition
Figure 24.1b
5
Carbohydrates

• Starches, sugars, glycogen, fiber needed in
  simple forms glucose, galactose, fructose in
  order to manufacture ATP
• Need 100g/d to maintain blood glucose, with
  125-175g/d recommended as adult maintenance diet
  (incl. complex carbs whole grains)
• We consume 200-300g/d - only 50-60 of your daily
  caloric intake should come from carbs empty
  calories are the result of refined sugars and
  soda/soft drinks

6
Carbohydrates

• Complex carbohydrates (starches) are found in
  bread, cereal, flour, pasta, nuts, and potatoes
• Simple carbohydrates (sugars) are found in soft
  drinks, candy, fruit, and ice cream
• Neurons and RBCs rely almost entirely upon
  glucose to supply their energy needs
• Excess glucose is converted to glycogen or fat
  and stored

7
Lipids

• Neutral fats mostly triglycerides (TGs)
• Saturated animal fats, butter
• Unsaturated plant oils, nuts, seeds, fish
• Essential Fatty Acids (FAs) omega-3, 6, 9
• Needed for fat soluble vitamin absorption,
  cholesterol in cell membrane, myelin, etc. and
  also protection, insulation, conc. energy
  storage
• Are a major energy fuel of hepatocytes and
  skeletal muscle

8
Lipids

• Cholesterol not for energy, but is to stabilize
  plasma membrane, steroids and steroid hormones,
  bile salts
• Prostaglandins function in
• Smooth muscle contraction
• Control of blood pressure
• Inflammation

9
Lipids Dietary Requirements

• Higher for infants and children than for adults
• The American Heart Association suggests that
• Fats should represent less than 30 of ones
  total caloric intake
• Saturated fats should be limited to 10 or less
  of ones total fat intake
• Daily cholesterol intake should not exceed 200 mg

10
Proteins

• Includes many different biochemical entities
• Collagen, keratin, elastin, muscle, hormones,
  enzymes, hemoglobin, cell membranes,
  neurotransmitters, DNA/RNA,
• Complete must have all essential AAs animal
• Incomplete plant, complimentary (combs)
• All-or-None Rule all essential AAs present and
  in adequate amount or NO protein is made
• Adequate caloric intake of carbs fat for ATP so
  protein is spared daily need 0.8 g/kg body
  weight
• Nitrogen balance protein synthesis is to
  destruction
• Hormonal controls anabolic accelerate synthesis
  (GH) vs. glucocorticoids that enhance breakdown

11
Essential Amino Acids
12
Vitamins

• Do NOT get metabolized for energy, but do provide
  catalyst for energy transformations as coenzymes
  (NAD, FAD)
• Water soluble vits 8 Bs and vit C only water
  soluble vitamin stored is B12
• Fat soluble are A, D, E, K and only K is not
  stored in fat or liver. Most are good
  antioxidants
• Too much of the fat soluble can create toxic
  effects e.g. vit.A - bone fragility,
  liver/spleen damage, vit.D - vomit, diarrhea,
  hypercalcemia, calcification, irreversible
  cardiac renal damage

13
Minerals

• Moderate amounts of 7 minerals macro are Ca,
  P, K, Na, S, Cl, Mg and a group of trace
  which incl F, Co, Cr, Cu, I, Fe, Mn, Se, Zn.
• These are NOT for direct energy production, but
  rather for ensuring smooth function and strength.
  e.g. Fe in Hb Ca P in bone, nerve muscle
  function, and clotting Na K for nerve function
  and I2 for thyroid function.
• Need to be balanced amounts to avoid toxicity
• Most found in veggies, legumes, milk, meats

14
Metabolism

• Biochemical reactions that build-up or tear down
  molecules while extracting energy to power
  processes
• Anabolism build up, small to large e.g. AA ?
  protein
• Catabolism breakdown complex to simple, e.g.
  the hydrolysis of polysaccharides to simple
  sugars or in the cellular respiration of glucose
  into ATP (energy)
• 3 stages in processing energy-containing
  nutrients
• Digestion and absorption GI ? blood ? cells
• Anabolic construction of lipids, proteins,
  glycogen in cytoplasm or catabolic pathways to
  pyruvic acid and acetyl CoA
• Catabolic w/in mitochondria, requires 02 to
  produce ATP
• 1o function of cellular respiration is stage 2
  glycolysis and all events of stage 3 to produce
  ATP

15
(No Transcript)
16
Oxidation-Reduction Reactions

• Oxidation is the gain of oxygen or loss of
  hydrogen, either way is represents the loss of
  electrons
• When this happens something gains electrons or it
  is reduced meaning that the charge is reduced, so
  the reactions are called redox reactions
• Oxidized substances lose energy, reduced gain
  energy from the energy rich e- so as foods are
  oxidized their lost energy is transferred to the
  formation of ATP from ADP
• Enzymes dehydrogenases (take H) or oxidases (add
  O)
• Coenzymes are H or e- acceptors which reduces
  them and they gain energy to later be used to
  create more ATP e.g. ADP ? ATP, NAD ?NADH, or
  FAD ?FADH2

17
Mechanisms of phosphorylation a) substrate level
w/ direct transfer of energy and Pi to ADP?ATP
or b) oxidative phosphorylation using e-
transport chain and proton pumps, powered by the
energy of oxidized food
18
Carbohydrate Metabolism 4kcal/g

• Oxidation of glucose is catabolic by the
  reaction
• C6H12O6 6O2 ? 6CO2 6H2O 36ATP heat
• Glycolysis - split glucose w/ or w/o O2
  (anaerobic) to make pyruvic acid and NAD ? NADH
• Krebs (TCA) Cycle - decarboxylation, remove CO2
  and make ATP while more NADH and FADH2 are
  created, and cycle intermediates are called keto
  acids
• Electron Transport Chain - oxidative
  phosphorylation H is added to O2 and energy
  created by reformation of NAD is added to ADP
  Pi ?ATP
• Net result 1 mole glucose creates 38 energy
  capture of ATP formation or 36ATP/glucose
  molecule

19
(No Transcript)
20
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
• Pyruvic acid
• Moves on to the Krebs cycle in an aerobic pathway
• Is reduced to lactic acid in an anaerobic
  environment

21
(No Transcript)
22
Glycolysis Phase 1 and 2

• Phase 1 Sugar activation
• Two ATP molecules activate glucose into
  fructose-1,6-diphosphate
• Phase 2 Sugar cleavage
• Fructose-1,6-bisphosphate is cleaved into two
  3-carbon isomers
• Bishydroxyacetone phosphate
• Glyceraldehyde 3-phosphate

23
Glycolysis Phase 3

• Phase 3 Oxidation and ATP formation
• The 3-carbon sugars are oxidized (reducing NAD)
• Inorganic phosphate groups (Pi) are attached to
  each oxidized fragment
• The terminal phosphates are cleaved and captured
  by ADP to form four ATP molecules

24
Glycolysis Phase 3

• The final products are
• Two pyruvic acid molecules
• Two NADH H molecules (reduced NAD)
• A net gain of two ATP molecules

25
Krebs Cycle Preparatory Step

• Occurs in the mitochondrial matrix and is fueled
  by pyruvic acid and fatty acids

26
Krebs Cycle Preparatory Step

• Pyruvic acid is converted to acetyl CoA in three
  main steps
• Decarboxylation
• Carbon is removed from pyruvic acid
• Carbon dioxide is released

27
Krebs Cycle Preparatory Step

• Oxidation
• Hydrogen atoms are removed from pyruvic acid
• NAD is reduced to NADH H
• Formation of acetyl CoA the resulting acetic
  acid is combined with coenzyme A, a
  sulfur-containing coenzyme, to form acetyl CoA

28
Krebs Cycle

• An eight-step cycle in which each acetic acid is
  decarboxylated and oxidized, generating
• Three molecules of NADH H
• One molecule of FADH2
• Two molecules of CO2
• One molecule of ATP
• For each molecule of glucose entering glycolysis,
  two molecules of acetyl CoA enter the Krebs cycle

PLAY
Krebs Cycle
29
(No Transcript)
30
Electron Transport Chain

• Food (glucose) is oxidized and the released
  hydrogens
• Are transported by coenzymes NADH and FADH2
• Enter a chain of proteins bound to metal atoms
  (cofactors)
• Combine with molecular oxygen to form water
• Release energy
• The energy released is harnessed to attach
  inorganic phosphate groups (Pi) to ADP, making
  ATP by oxidative phosphorylation

31
Mechanism of Oxidative Phosphorylation

• The hydrogens delivered to the chain are split
  into protons (H) and electrons
• The protons are pumped across the inner
  mitochondrial membrane by
• NADH dehydrogenase (FMN, Fe-S)
• Cytochrome b-c1
• Cytochrome oxidase (a-a3)
• The electrons are shuttled from one acceptor to
  the next

32
Mechanism of Oxidative Phosphorylation

• Electrons are delivered to oxygen, forming oxygen
  ions
• Oxygen ions attract H to form water
• H pumped to the intermembrane space
• Diffuses back to the matrix via ATP synthase
• Releases energy to make ATP

PLAY
InterActive Physiology Muscular System
Muscular Metabolism
33
(No Transcript)
34
Electronic Energy Gradient

• The transfer of energy from NADH H and FADH2
  to oxygen releases large amounts of energy
• This energy is released in a stepwise manner
  through the electron transport chain

35
Electronic Energy Gradient

• The electrochemical proton gradient across the
  inner membrane
• Creates a pH gradient
• Generates a voltage gradient
• These gradients cause H to flow back into the
  matrix via ATP synthase

PLAY
Electron Transport
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
Glycogenesis Glycogenolysis

• Glycogenesis occurs with rising blood ATP levels
  that stops glycolysis and adding glucoses
  together creates glycogen (or fat)
• If ATP levels fall then there is a stimulus to
  split glycogen and release glucose
  glycogenolysis
• Most body muscle cells trap phosphorylated
  glucose from glycogenolysis (except for liver,
  some kidney, and intestinal cells which have
  special enzyme that allows the glucose freed from
  glycogen to leave the cells)
• Therefore the liver can sustain blood glucose
  when we havent eaten
• Gluconeogenesis glucose made from glycerol or
  AAs

40
(No Transcript)
41
Lipid Metabolism 9kcal/g

• Chylomicrons absorbed via lacteals then into the
  BVs
• Oxidation of glycerol to glycolysis intermediate
  (½ glcs)
• ß-oxidation of fatty acid (FA) chains of
  triglycerides (TG) cleaves off 2-C acetic acids
  w/ coenzymes to make acetyl CoA for the TCA cycle
• Lipogenesis - the synthesis of TGs when there is
  glycerol and FAs from diet that are not needed
  for energy, that are recombined 50 stockpiled
  in body fat
• Occurs when cellular ATP glucose levels are
  high so acetyl CoAs are condensed to form FAs
• Therefore, excess glucose ?acetyl CoA ? FAs
  fat!

42
(No Transcript)
43
Lipolysis

• Breakdown of stored fats into glycerol and FAs
  to provide a good, long-term fuel for aerobic
  respiration
• liver, cardiac m. and resting skeletal m.
  prefer FAs
• Fats burn in a flame of carbohydrate low carb
  intake
• Lipolysis accelerated to provide energy
• TCA cycle needs oxaloacetic acid to work and if
  carbs are depleted then it is used to make
  glucose for the brain
• Deficient oxaloacetic acid causes acetyl CoA
  accumulation
• Liver converts the acetyl CoA to ketone bodies
  ketosis
• See in diabetic, starvation, Atkins diet - cause
  metabolic acidosis, fruity breath, ?RR, but w/o
  correction it results in coma and death via
  depressed nervous system

44
Metabolism of triglycerides when needed for
energy fats are catabolized (both glycerol and
FAs) when excess occurs they can be synthesized
45
Protein Metabolism 4kcal/g

• Uses approximately 100g/d and anything in excess
  above that is either converted to energy (stress)
  or converted to fat
• Deamination occurs (remove NH2) prior to
  oxidation
• Transamination AAs transferred to TCA cycle
  keto acid to make glutamic acid
• Oxidative deamination liver removes amine group
  of glutamic acid to make NH3 reforms original
  keto acid and NH3 combines with CO2 to make urea
• Keto acid modification converted to metabolites
  (pyruvic acid, acetyl CoA, oxaloacetic acid) that
  can be used in TCA cycle or can be converted to
  glucose

46
(No Transcript)
47
(No Transcript)
48
Protein Synthesis

• AAs are most important anabolic nutrient, form
  protein structures as well as the bodys
  functional molecules.
• Your body will make 500-1000 lbs in your
  lifetime! But you dont need to eat that amount
  as the body forms non-essential AAs in the liver
• Must have a complete set of essential AAs or
  the body doesnt make protein, and the others are
  converted to energy

49
Carbohydrate/Fat and AA Pool
50
Interconversion of carbohydrates, fats, and
proteins The liver, adipose tissue, skeletal
m. are 1o effector organs
51
Liver Metabolism

• Hepatocytes carry out over 500 intricate
  metabolic functions

52
Liver Metabolism

• A brief summary of liver functions
• Packages fatty acids to be stored and transported
• Synthesizes plasma proteins
• Produces blood clotting factors
• Forms nonessential amino acids
• Converts ammonia from deamination to urea
• Stores glucose as glycogen, and regulates blood
  glucose homeostasis
• Stores vitamins, conserves iron, degrades
  hormones, and detoxifies substances

53
Cholesterol

• Is the structural basis of bile salts, steroid
  hormones, and vitamin D
• Makes up part of the hedgehog molecule that
  directs embryonic development
• Is transported to and from tissues via
  lipoproteins

54
Cholesterol

• Lipoproteins are classified as
• HDLs high-density lipoproteins have more
  protein content
• LDLs low-density lipoproteins have a
  considerable cholesterol component
• VLDLs very low density lipoproteins are mostly
  triglycerides

55
Cholesterol
Figure 24.22
56
Lipoproteins

• The liver is the main source of VLDLs, which
  transport triglycerides to peripheral tissues
  (especially adipose)
• LDLs transport cholesterol to the peripheral
  tissues and regulate cholesterol synthesis
• HDLs transport excess cholesterol from peripheral
  tissues to the liver
• Also serve the needs of steroid-producing organs
  (ovaries and adrenal glands)

57
Lipoproteins

• High levels of HDL are thought to protect against
  heart attack
• High levels of LDL, especially lipoprotein (a),
  increase the risk of heart attack

58
Plasma Cholesterol Levels

• The liver produces cholesterol
• At a basal level of cholesterol regardless of
  dietary intake
• Via a negative feedback loop involving serum
  cholesterol levels
• In response to saturated fatty acids

59
Plasma Cholesterol Levels

• Fatty acids regulate excretion of cholesterol
• Unsaturated fatty acids enhance excretion
• Saturated fatty acids inhibit excretion
• Certain unsaturated fatty acids (omega-3 fatty
  acids, found in cold-water fish) lower the
  proportions of saturated fats and cholesterol

60
Non-Dietary Factors Affecting Cholesterol

• Stress, cigarette smoking, and coffee drinking
  increase LDL levels
• Aerobic exercise increases HDL levels
• Body shape is correlated with cholesterol levels
• Fat carried on the upper body is correlated with
  high cholesterol levels
• Fat carried on the hips and thighs is correlated
  with lower levels

61
Body Energy Balance

• Bond energy released from catabolized food must
  equal the total energy output
• Energy intake equal to the energy liberated
  during the oxidation of food
• Energy output includes the energy
• Immediately lost as heat (about 60 of the total)
• Used to do work (driven by ATP)
• Stored in the form of fat and glycogen

62
Body Energy Balance

• Nearly all energy derived from food is eventually
  converted to heat
• Cells cannot use this energy to do work, but the
  heat
• Warms the tissues and blood
• Helps maintain the homeostatic body temperature
• Allows metabolic reactions to occur efficiently

63
Regulation of Food Intake

• When energy intake and energy outflow are
  balanced, body weight remains stable
• The hypothalamus releases peptides that influence
  feeding behavior
• Orexins are powerful appetite enhancers
• Neuropeptide Y causes a craving for carbohydrates
• Galanin produces a craving for fats
• GLP-1 and serotonin make us feel full and
  satisfied

64
Feeding Behaviors

• Feeding behavior and hunger depend on one or more
  of five factors
• Neural signals from the digestive tract
• Bloodborne signals related to the body energy
  stores
• Hormones, body temperature, and psychological
  factors

65
Nutrient Signals Related to Energy Stores

• High plasma levels of nutrients that signal
  depressed eating
• Plasma glucose levels
• Amino acids in the plasma
• Fatty acids and leptin

66
Hormones, Temperature, and Psychological Factors

• Glucagon and epinephrine stimulate hunger
• Insulin and cholecystokinin depress hunger
• Increased body temperature may inhibit eating
  behavior
• Psychological factors that have little to do with
  caloric balance can also influence eating
  behaviors

67
Control of Feeding Behavior and Satiety

• Leptin, secreted by fat tissue, appears to be the
  overall satiety signal
• Acts on the ventromedial hypothalamus
• Controls appetite and energy output
• Suppresses the secretion of neuropeptide Y, a
  potent appetite stimulant
• Blood levels of insulin and glucocorticoids play
  a role in regulating leptin release

68
Hypothalamic Command of Appetite
Figure 24.23
69
Metabolic Rate

• Rate of energy output (expressed per hour) equal
  to the total heat produced by
• All the chemical reactions in the body
• The mechanical work of the body
• Measured directly with a calorimeter or
  indirectly with a respirometer

70
Metabolic Rate

• Basal metabolic rate (BMR)
• Reflects the energy the body needs to perform its
  most essential activities
• Total metabolic rate (TMR)
• Total rate of kilocalorie consumption to fuel all
  ongoing activities

71
Factors that Influence BMR

• Surface area, age, gender, stress, and hormones
• As the ratio of surface area to volume increases,
  BMR increases
• Males have a disproportionately high BMR
• Stress increases BMR
• Thyroxine increases oxygen consumption, cellular
  respiration, and BMR

72
Regulation of Body Temperature

• Body temperature balance between heat
  production and heat loss
• At rest, the liver, heart, brain, and endocrine
  organs account for most heat production
• During vigorous exercise, heat production from
  skeletal muscles can increase 3040 times

73
Regulation of Body Temperature

• Normal body temperature is 36.2?C (98.2?F)
  optimal enzyme activity occurs at this
  temperature
• Temperature spikes above this range denature
  proteins and depress neurons

74
Regulation of Body Temperature
Figure 24.24
75
Core and Shell Temperature

• Organs in the core (within the skull, thoracic,
  and abdominal cavities) have the highest
  temperature
• The shell, essentially the skin, has the lowest
  temperature
• Blood serves as the major agent of heat transfer
  between the core and shell
• Core temperature remains relatively constant,
  while shell temperature fluctuates substantially
  (20?C40?C)

76
Mechanisms of Heat Exchange

• Four mechanisms
• Radiation loss of heat in the form of infrared
  rays
• Conduction transfer of heat by direct contact
• Convection transfer of heat to the surrounding
  air
• Evaporation heat loss due to the evaporation of
  water from the lungs, mouth mucosa, and skin
  (insensible heat loss)
• Evaporative heat loss becomes sensible when body
  temperature rises and sweating produces increased
  water for vaporization

77
Role of the Hypothalamus

• The main thermoregulation center is the preoptic
  region of the hypothalamus
• The heat-loss and heat-promoting centers comprise
  the thermoregulatory centers
• The hypothalamus
• Receives input from thermoreceptors in the skin
  and core
• Responds by initiating appropriate heat-loss and
  heat-promoting activities

78
Heat-Promoting Mechanisms

• Low external temperature or low temperature of
  circulating blood activates heat-promoting
  centers of the hypothalamus to cause
• Vasoconstriction of cutaneous blood vessels
• Increased metabolic rate
• Shivering
• Enhanced thyroxine release

79
Heat-Loss Mechanisms

• When the core temperature rises, the heat-loss
  center is activated to cause
• Vasodilation of cutaneous blood vessels
• Enhanced sweating
• Voluntary measures commonly taken to reduce body
  heat include
• Reducing activity and seeking a cooler
  environment
• Wearing light-colored and loose-fitting clothing

80
(No Transcript)
81
Hyperthermia

• Normal heat loss processes become ineffective and
  elevated body temperatures depress the
  hypothalamus
• This sets up a positive-feedback mechanism,
  sharply increasing body temperature and metabolic
  rate
• This condition, called heat stroke, can be fatal
  if not corrected

82
Heat Exhaustion

• Heat-associated collapse after vigorous exercise,
  evidenced by elevated body temperature, mental
  confusion, and fainting
• Due to dehydration and low blood pressure
• Heat-loss mechanisms are fully functional
• Can progress to heat stroke if the body is not
  cooled and rehydrated

83
Fever

• Controlled hyperthermia, often a result of
  infection, cancer, allergic reactions, or central
  nervous system injuries
• White blood cells, injured tissue cells, and
  macrophages release pyrogens that act on the
  hypothalamus, causing release of prostaglandins
• Prostaglandins reset the hypothalamic thermostat
• The higher set point is maintained until the
  natural body defenses reverse the disease
  process, then reset is lower and we sweat it out

84
(No Transcript)
85
(No Transcript)
86
(No Transcript)
87
(No Transcript)
88
(No Transcript)
89
(No Transcript)
90
(No Transcript)