Metabolism and temperature regulation

1. METABOLISM AND
TEMPERATURE REGULATION

2. METABOLISM is a set of chemical and physical
transformations that occur in the body and ensure
its vital activity in conjunction with the external
environment.
PURPOSE OF METABOLISM:
•Providing plastic needs
•Providing all vital functions of the body with ENERGY
•Anabolism is a set of reactions leading to the construction of
body tissues, the formation of complex organic substances
•Catabolism is a set of metabolic reactions leading to the
breakdown of substances in the body, based on dissimilation -
the process of destruction of organic substances.

3. Stages of
metabolism
processing
nutrients during
digestion
(fermentation)
interstitial metabolism
(transport of
monomers to tissues)
the formation of end
products of
metabolism and their
excretion from the
body

4. Types of work in the human
body
Chemical the synthesis of high molecular weight compounds from low
molecular weight, as well as the course of chemical reactions. The
synthesis of proteins, nucleic acids, polysaccharides proceeds with a
change in energy and the performance of work
Mechanical moving parts and organs of the body against mechanical forces.
Mechanical work is also done by muscles when they contract
Osmotic the transfer of various substances through membranes or membrane
envelope from an area of low concentration of these substances to an
area of higher concentration
Electrical the transfer of charged particles (ions) in an electric field. In the body,
electrical work is performed when cells generate biopotentials and
conduct excitation through the cells

5. Energy reserves of the human
body
Energy source
Energy value, kJ /
g
Concentration in
tissue
Tissue
mass
Energy
reserve, kJ
Skeletal muscle glycogen 17 18 g/kg 28 kg 8440
Liver glycogen 17 70 g/kg 2 kg 2345
Blood glucose 17 1 g/l 5 l 84
Triglycerides of adipose
tissue
38 900 g/kg 10 kg 339000
Muscle triglycerides 38 9 g/kg 28 kg 9496
Triglycerides and free fatty
acids in blood
38 1 g/l 5 l 188

6. The concentration of ATP should be in
the range from 2 to 5 mM for normal
muscle function
ATP = ADP + H3PO4+ 10
kcal Q
• ATP reserves are enough for 1-2 s of work, with a
lack of ATP - contracture, and with an excess -
muscle elasticity is lost!
• The concentration of ATP during work is
maintained at a relatively stable level due to the
mechanisms of resynthesis!

7. ATP resynthesis is due to anaerobic and
aerobic processes, the ratio of which
depends on the intensity and duration
of work
Anaerobic (when performing short-term
high-intensity exercise)
•Creatine phosphokinase reaction (phosphagenic or
alactate process)
•Myokinase (adenylate cyclase) reaction
•Glycolysis (lactacid anaerobic process)
Resynthesis of ATP in the aerobic
process (with prolonged work of
moderate intensity

8. PLASTIC EXCHANGE
THE CONCEPT OF
SUFFICIENT AND BALANCED
FOOD
BALANCED NUTRITION PROVIDES THE BODY WITH ALL
THE NECESSARY NUTRIENTS IN STRICTLY DEFINED
RATIOS, CORRELATIONS BETWEEN THE ABSORPTION OF
FOOD AND THE DEGREE OF BALANCE OF ITS CHEMICAL
COMPOSITION
• RATIO PROTEINS: FATS: CARBOHYDRATES = 1: 1: 4 (5)
• PROTEINS - 12-13%, FATS - 30-50%
• WITH HARD WORK - PROTEINS UP TO 11%, FATS UP TO
33%
• THE PRESENCE OF IRREPLACEABLE FOOD FACTORS

9. PROTEINS
• Daily allowance: men - 96-132 g, women - 82-92 g
• Nitrogen balance
• An adult needs 1.3-1.4 g of protein per 1 kg of body
weight per day
• For physical work - 1.5 g or more per 1 kg of weight
• The protein content should be higher in the diet of
children
Age
Protein amount, g / day
Age
Protein amount, g / day
total including animal total including animal
0,5-1 25 20-25 7-10 80 48
1-1,5 48 36 11-13 96 58
1,5-2 53 40 14-17
(boys)
106 64
3-4 63 44 14-17
(girls)
93 56
5-6 72 47

10. FUNCTIONS OF PROTEINS IN THE
BODY
Nitrogen balance

11. FATS
• Triglycerides, fatty acids, lipoids
• Energy function
• Fat-soluble vitamins A, D, K, E
• Daily - men - 84-90 g physical labor - 103-145
g
• Women - 70-77 g physical labor - 81-102 g
• 70% animal fats
Group
The amount of fat, g / day
Men Women
total including animal total including animal
Students 113 68 96 58
Athletes 154-171 77-86 120-137 60-69
Pregnant - - 109 65
Lactating - - 120 72

12. CARBOHYDRATES
• Plastic and energy functions
• Deposition as glycogen
• Daily - 344 - 440 g
• With especially hard work - 602 g
• For women the need is 15% lower than for men
• Should cover 50-55% of energy needs
Age
Amount, g/day
Men Women
18-40 382 329
41-60 355 303
61-70 320 228
71 and older 300 277
Students 451 383
Athletes 615-583 477-546

13. MICROELEMENTS
• Substances at a concentration of 1: 100,000
or less
• Part of vitamins, enzymes, hormones
1. Absolutely Necessary (Fe, Zn, Cu, I, F, Mn,
Co)
2. Probably necessary (Al, Cr, Mo, Se)
Microelement Sources Content in the diet, mg
Al Bakery products 20-100
B Bakery products, milk, beans 0,4-1,0
Fe Beans, meat, vegetables, liver 15-40
I Milk, meat, eggs, seafood 0,04-0,2
Co Milk, bakery products, vegetables 0,01-0,1

14. VITAMINS
Vitamin C in the human body provides the activity of certain
enzymes and hormones, improves the assimilation of
amino acids, stimulates the process of hematopoiesis,
phagocytic activity of leukocytes, promotes the production
of antibodies, thereby increasing the body's resistance to
infections.
The daily requirement for vitamin C for men up to 40 years
old is 50-100 mg, women - 65-85, depending on the
severity of physical work, children - 30-70 mg.

15. VITAMINS
Vitamin A (retinol) is one of the most important growth
vitamins required to maintain the protective function of the
mucous membranes and skin, to ensure normal vision.
Vitamin A is part of the visual pigments of the retinal rods
(rhodopsin) and cones (iodopsin). Main food sources: cod
liver, medicinal fish oil, summer butter, liver, kidneys, egg
yolks, milk. The source of carotene are vegetables and
fruits of yellow and red-orange color: carrots, tomatoes,
pumpkin, melon, red peppers, rose hips, apricots, plums,
green peas.
The daily requirement of a healthy adult for vitamin A is 1.5
mg, athletes - 4-5, children and adolescents - 0.5-1.5 mg

16. VITAMINS
Vitamin E (tocopherol). A number of compounds that are
similar in chemical structure and biological action are
combined under this name. Vitamin E protects unsaturated
lipids of cell and subcellular membranes from free radical
oxidation, promotes spermatogenesis, fetal development
and pregnancy; participates in oxidative processes,
promotes the accumulation of fat-soluble vitamins,
protects unsaturated fatty acids from oxidation. The daily
requirement for a healthy adult is 10-20 mg, for children,
0.5 mg / kg of body weight.
The main food sources: vegetable oils (sunflower, soybean,
cottonseed, corn), green leaves of vegetables.

17. VITAMINS
Vitamin B1 (thiamine) is involved in biochemical processes carbohydrate
metabolism, oxidative decarboxylation of keto acids, ensuring normal
growth. It plays an important role in the activity of the human nervous
system. The daily requirement for vitamin B1 in healthy men under the
age of 40 is 1.4-2.4 mg, women - 1.4-1.9, children - 0.5-2, 0, athletes
6-8 mg.
Vitamin B2 (riboflavin) is involved in redox processes (oxidation of fatty
acids) in the human body. The daily requirement of a healthy adult for
vitamin B2 is 1.9-3.0 mg, children - 1.0-3.0, athletes - 6 - 8 mg.
Vitamin B6 (pyridoxine) participates in nitrogen metabolism, in the
serotonin synthesis and fat metabolism, in the construction of enzymes
associated with the exchange of amino acids, ensures normal growth.
The daily requirement of a healthy adult is 1.5-2.8,children - 0.5-2.0
mg. Main dietary sources: yeast, liver, kidneys, meat, herring, cod,
legumes and cereals.

18. GENERAL HYGIENE REQUIREMENTS FOR DIET
Constant meal
time and
proportional
time of day
ratio of their
content and
calorie content
The optimal caloric
cost of the daily
diet: breakfast —
30-35%, lunch or
afternoon tea —
10-15%, lunch —
35-40%, dinner —
15-20%. It is
advisable to take
the bulk of protein
and fatty foods in
the first half of the
day
The relative
content of proteins
in breakfast should
be more - 20-22%,
fat – 35%,
carbohydrates -
43-45% (in the
daily diet - 15, 30
and 55%)
Lunch should
contain up to
40% of the
calories of the
total daily diet

19. FEATURES OF NUTRITION FOR ATHLETES
Regardless of the specialization and qualifications of
the athlete, proteins must provide at least 17% of the
total caloric intake of the diet.
Animal fats should make up 80-85% of all food fats, the rest -
vegetable oils
The carbohydrate part of the diet of athletes should consist of
64% starch and 36% simpler sugars.
The specificity of sports activity determines the increased need
of athletes for vitamins in comparison with non-athletes

20. BASAL METABOLISM IS
THE MINIMUM AMOUNT
OF ENERGY REQUIRED TO
MAINTAIN VITAL
PROCESSES, DETERMINED
UNDER STANDARD
CONDITIONS.
• CONDITIONS FOR
DETERMINING THE BM
(1700 KCAL / DAY):
• MUSCLE REST
• EMPTY STOMACH
• COMFORT
TEMPERATURE
• WAKING STATE
DEPENDS ON
• AGE
• GENDER
• HEIGHT,
• WEIGHT,
• AREA OF A BODY
SURFACE (RUBNER'S
LAW)
ENERGY
EXCHANGE

21. •"If heat is converted into work, then the amount of work produced by the system is
equivalent to the amount of absorbed heat"
1st law of thermodynamics of Helmholtz, Thomson and Claesius
•"The heat effect of a process that develops through a series of successive stages
depends on the heat content of the initial and final products of a chemical reaction, but
does not depend on the ways of their chemical transformations"
Hess's law

22. CALORIMETRY
INDIRECT
indirect determination of
heat generation in the
body. Gas analysis:
complete and incomplete
DIRECT
direct accounting of the
amount of heat released
by the body

23. ENERGY VALUE/CALORIC
COEFFICIENT OF A
SUBSTANCE
THE AMOUNT OF HEAT GENERATED DURING THE
COMBUSTION OF 1 G OF A SUBSTANCE IN AN
ATMOSPHERE OF PURE OXYGEN:
FATS - 9.3 KCAL; PROTEINS AND CARBOHYDRATES - 4.1
KCAL
THE CALORIC EQUIVALENT OF OXYGEN IS THE AMOUNT
OF HEAT RELEASED IN THE BODY FROM THE
COMBUSTION OF 1 G OF A SUBSTANCE WHEN 1 LITER OF
OXYGEN IS CONSUMED:
• FATS - 4.69 KCAL / L;
• PROTEINS - 4.46 KCAL / L;
M. Berthelot

24. ENERGY EXCHANGE
RESPIRATORY COEFFICIENT
(RC) - the ratio of the
volume of emitted carbon
dioxide to the volume of
oxygen consumed
RC for carbohydrates = 1.0
RC for proteins = 0.8
RK for fat = 0.7
WORK EXCHANGE - the value of
energy metabolism
characteristic of a certain type
of labor activity
WORKING INCREASE - the
difference between working
and basic exchange
Specifically dynamic action of
food - an increase in energy
expenditure levels 1-3 hours
after a meal:
for proteins - by 30%; for
carbohydrates and fats - by

25. EMPLOYEES GROUPS
1. Mainly mental workers: engineering staff, doctors (except surgeons),
workers in science and art, literature, managers, etc. - 2500-2800 kcal
/ day
2. Workers of light physical labor: engineering and technical personnel,
communications workers, radio-electronic industry, nurses, orderlies,
etc. - 2800-3000 kcal / day
3. Workers of medium severity: turners, locksmiths, railroad workers,
surgeons, vehicle drivers, food sellers, water workers - 3000 - 3200
kcal / day
4. Workers of heavy physical labor: construction workers, metallurgists and
foundry workers, machine operators, carpenters, oil and gas workers,
agricultural workers - 3400 - 3700 kcal / day
5. Workers of extra hard labor: miners, steelworkers, fellers, excavators,
loaders - 3900 - 4500 kcal / day

26. ENERGY EXCHANGE
 Energy value or caloric coefficient of a substance is
the amount of heat generated during the combustion
of 1 g of a substance in an atmosphere of pure
oxygen:
FATS - 9.3 kcal; PROTEINS and CARBOHYDRATES - 4.1
kcal
 The caloric equivalent of oxygen is the amount of
heat released in the body from the combustion of 1 g
of a substance when 1 liter of oxygen is consumed:
FATS - 4.69; PROTEINS - 4.46; CARBOHYDRATES - 5.05
kcal / l

27. REGULATION OF
TEMPERATURE

28. BODY TEMPERATURE
Normal Body Temperature (NBT) –98.60F (370C)
Range of NBT - (970F to 990F)
Rectal Temp -(0.50F to 10F) above the Oral. Rectal Temp reflects the internal
body Temp (Core Body Temp)
Core Body Temp remain almost constant
Skin Temp (Shell Temp) - Variable

29. HEAT BALANCE
In order to maintain a constant core
temperature, heat loss must match
heat gain

30. HEAT GAIN
• BASAL METABOLIC RATE
• SPECIFIC DYNAMIC ACTION OF FOOD
• ACTIVITY OF SKELETAL MUSCLE
• SHIVERING
• EXERCISE
• CHEMICAL THERMOGENESIS
• EPINEPHRINE &NOREPINEPHRINE
• THYROXINE ETC.
• BROWN FAT
• SOURCE OF CONSIDERABLE HEAT PRODUCTION
• ABUNDANT IN INFANTS

31. HEAT LOSS
• RADIATION
• CONDUCTION
• CONVECTION
• EVAPORATION
• PERSPIRATION
• RESPIRATION
• LOSS
THROUGH
URINE &
FECES

32. THERMOREGULATION
Temperature is regulated by
nervous feedback mechanisms
Thermoregulatory center located
in the Hypothalamus
Thermoregulatory regulatory
responses include:
• Autonomic
• Somatic
• Endocrine
• Behavioural changes
Feedback system:
1) Receptor
Sensor that responds to changes
2) Control Center
Sets range of values
Evaluates input and
Sends output
3) Effector
Receives output from control
center
Produces a response

33. THERMOREGULATION
The Hypothalamus: The body’s
thermostat
Increased core temperature
• Anterior hypothalamus
• Commencement of sweating
• Increased skin blood flow
Cold exposure
• Posterior hypothalamus
• Increase heat production
• Shivering
• Decrease heat loss
• Decreased skin blood flow

35. EXPOSURE TO COLD
SHIVERING
INCREASE VOLUNTARY ACTIVITY
INCREASE TSH SECRETION
INCREASE CATECHOLAMINES
VASOCONSTRICTION
HORRIPILATION
CURLING UP
EXPOSURE TO HEAT
VASODILATATION
SWEATING
INCREASE IN RESPIRATION
ANOREXIA
APATHY
DECREASE TSH SECRETION
REGULATORY RESPONSES

36. FEVER

37. A GREAT PROPORTION OF THE CHEMICAL
REACTIONS IN THE CELLS IS CONCERNED
WITH MAKING THE ENERGY IN FOODS
AVAILABLE TO THE VARIOUS PHYSIOLOGIC
SYSTEMS OF THE CELL. FOR INSTANCE,
ENERGY IS REQUIRED FOR MUSCLE ACTIVITY,
SECRETION BY THE GLANDS, MAINTENANCE
OF MEMBRANE POTENTIALS BY THE NERVE
AND MUSCLE FIBERS, SYNTHESIS OF
SUBSTANCES IN THE CELLS, ABSORPTION OF
FOODS FROM THE GASTROINTESTINAL
TRACT, AND MANY OTHER FUNCTIONS.
RELEASE OF ENERGY
FROM FOODS, AND THE
CONCEPT OF “FREE
ENERGY”

38. COUPLED REACTIONS
• ALL THE ENERGY FOODS—CARBOHYDRATES, FATS, AND
PROTEINS—CAN BE OXIDIZED IN THE CELLS, AND DURING
THIS PROCESS, LARGE AMOUNTS OF ENERGY ARE
RELEASED. THESE SAME FOODS CAN ALSO BE BURNED WITH
PURE OXYGEN OUTSIDE THE BODY IN AN ACTUAL FIRE,
ALSO RELEASING LARGE AMOUNTS OF ENERGY; IN THIS
CASE, HOWEVER, THE ENERGY IS RELEASED SUDDENLY, ALL
IN THE FORM OF HEAT. THE ENERGY NEEDED BY THE
PHYSIOLOGIC PROCESSES OF THE CELLS IS NOT HEAT BUT
ENERGY TO CAUSE MECHANICAL MOVEMENT IN THE CASE
OF MUSCLE FUNCTION, TO CONCENTRATE SOLUTES IN THE
CASE OF GLANDULAR SECRETION, AND TO EFFECT OTHER
FUNCTIONS. TO PROVIDE THIS ENERGY, THE CHEMICAL
REACTIONS MUST BE “COUPLED” WITH THE SYSTEMS
RESPONSIBLE FOR THESE PHYSIOLOGIC FUNCTIONS. THIS
COUPLING IS ACCOMPLISHED BY SPECIAL CELLULAR

39. “FREE
ENERGY”
• THE AMOUNT OF ENERGY
LIBERATED BY COMPLETE
OXIDATION OF A FOOD IS
CALLED THE FREE ENERGY
OF OXIDATION OF THE
FOOD, AND THIS IS
GENERALLY REPRESENTED BY
THE SYMBOL DG. FREE
ENERGY IS USUALLY
EXPRESSED IN TERMS OF
CALORIES PER MOLE OF
SUBSTANCE.
• FOR INSTANCE, THE
AMOUNT OF FREE ENERGY
LIBERATED BY COMPLETE
OXIDATION OF 1 MOLE (180
GRAMS) OF GLUCOSE IS

40. ROLE OF ADENOSINE
TRIPHOSPHATE IN
METABOLISM
• ADENOSINE TRIPHOSPHATE (ATP) IS AN ESSENTIAL LINK BETWEEN
ENERGY-UTILIZING AND ENERGY-PRODUCING FUNCTIONS OF THE
BODY. FOR THIS REASON, ATP HAS BEEN CALLED THE ENERGY
CURRENCY OF THE BODY, AND IT CAN BE GAINED AND SPENT
REPEATEDLY. ENERGY DERIVED FROM THE OXIDATION OF
CARBOHYDRATES, PROTEINS, AND FATS IS USED TO CONVERT
ADENOSINE DIPHOSPHATE (ADP) TO ATP, WHICH IS THEN CONSUMED
BY THE VARIOUS REACTIONS OF THE BODY THAT ARE NECESSARY FOR
• (1) ACTIVE TRANSPORT OF MOLECULES ACROSS CELL MEMBRANES;
• (2) CONTRACTION OF MUSCLES AND PERFORMANCE OF MECHANICAL
WORK;
• (3) VARIOUS SYNTHETIC REACTIONS THAT CREATE HORMONES, CELL
MEMBRANES, AND MANY OTHER ESSENTIAL MOLECULES OF THE BODY;
• (4) CONDUCTION OF NERVE IMPULSES;
• (5) CELL DIVISION AND GROWTH; AND (6) MANY OTHER PHYSIOLOGIC

41. • ATP IS A LABILE CHEMICAL
COMPOUND THAT IS
PRESENT IN ALL CELLS.
• IT CAN BE SEEN THAT ATP
IS A COMBINATION OF
ADENINE, RIBOSE, AND
THREE PHOSPHATE
RADICALS.
• THE LAST TWO PHOSPHATE
RADICALS ARE CONNECTED
WITH THE REMAINDER OF
THE MOLECULE BY HIGH-
ENERGY BONDS, WHICH ARE
INDICATED BY THE SYMBOL
~.
ATP

42. CENTRAL ROLE OF GLUCOSE
IN
CARBOHYDRATE
METABOLISM
• AFTER ABSORPTION FROM THE INTESTINAL TRACT, MUCH
OF THE FRUCTOSE AND ALMOST ALL THE GALACTOSE ARE
RAPIDLY CONVERTED INTO GLUCOSE IN THE LIVER.
• THEREFORE, LITTLE FRUCTOSE AND GALACTOSE ARE
PRESENT IN THE CIRCULATING BLOOD.
• GLUCOSE THUS BECOMES THE FINAL COMMON PATHWAY
FOR THE TRANSPORT OF ALMOST ALL CARBOHYDRATES
TO THE TISSUE CELLS.
• IN LIVER CELLS, APPROPRIATE ENZYMES ARE AVAILABLE
TO PROMOTE INTERCONVERSIONS AMONG THE
MONOSACCHARIDES — GLUCOSE, FRUCTOSE, AND
GALACTOSE

43. TRANSPORT OF GLUCOSE
THROUGH THE CELL
MEMBRANE
• GLUCOSE CANNOT EASILY DIFFUSE THROUGH THE PORES OF THE
CELL MEMBRANE BECAUSE THE MAXIMUM MOLECULAR WEIGHT OF
PARTICLES THAT CAN DIFFUSE READILY IS ABOUT 100, AND
GLUCOSE HAS A MOLECULAR WEIGHT OF 180.
• YET GLUCOSE DOES PASS TO THE INTERIOR OF THE CELLS WITH A
REASONABLE DEGREE OF FREEDOM BY THE MECHANISM OF
FACILITATED DIFFUSION.
• PENETRATING THROUGH THE LIPID MATRIX OF THE CELL
MEMBRANE ARE LARGE NUMBERS OF PROTEIN CARRIER
MOLECULES THAT CAN BIND WITH GLUCOSE. IN THIS BOUND
FORM, THE GLUCOSE CAN BE TRANSPORTED BY THE CARRIER
FROM ONE SIDE OF THE MEMBRANE TO THE OTHER SIDE AND
THEN RELEASED. THEREFORE, IF THE CONCENTRATION OF
GLUCOSE IS GREATER ON ONE SIDE OF THE MEMBRANE THAN ON
THE OTHER SIDE, MORE GLUCOSE WILL BE TRANSPORTED FROM
THE HIGH-CONCENTRATION AREA TO THE LOW-CONCENTRATION
AREA THAN IN THE OPPOSITE DIRECTION.

44. GLYCOGEN IS STORED IN
LIVER
AND MUSCLE
• AFTER ABSORPTION INTO A CELL, GLUCOSE CAN BE USED
IMMEDIATELY FOR RELEASE OF ENERGY TO THE CELL, OR
IT CAN BE STORED IN THE FORM OF GLYCOGEN, WHICH IS
A LARGE POLYMER OF GLUCOSE.
• ALL CELLS OF THE BODY ARE CAPABLE OF STORING AT
LEAST SOME GLYCOGEN, BUT CERTAIN CELLS CAN STORE
LARGE AMOUNTS, ESPECIALLY LIVER CELLS, WHICH CAN
STORE UP TO 5 TO 8 PER CENT OF THEIR WEIGHT AS
GLYCOGEN, AND MUSCLE CELLS, WHICH CAN STORE UP
TO 1 TO 3 PER CENT GLYCOGEN. THE GLYCOGEN
MOLECULES CAN BE POLYMERIZED TO ALMOST ANY
MOLECULAR WEIGHT, WITH THE AVERAGE MOLECULAR
WEIGHT BEING 5 MILLION OR GREATER; MOST OF THE
GLYCOGEN PRECIPITATES IN THE FORM OF SOLID

45. • BECAUSE COMPLETE OXIDATION OF 1 GRAM-MOLECULE
OF GLUCOSE RELEASES 686,000 CALORIES OF ENERGY
AND ONLY 12,000 CALORIES OF ENERGY ARE REQUIRED
TO FORM 1 GRAM-MOLECULE OF ATP, ENERGY WOULD BE
WASTED IF GLUCOSE WERE DECOMPOSED ALL AT ONCE
INTO WATER AND CARBON DIOXIDE WHILE FORMING ONLY
A SINGLE ATP MOLECULE. FORTUNATELY, ALL CELLS OF
THE BODY CONTAIN SPECIAL PROTEIN ENZYMES THAT
CAUSE THE GLUCOSE MOLECULE TO SPLIT A LITTLE AT A
TIME IN MANY SUCCESSIVE STEPS, SO THAT ITS ENERGY IS
RELEASED IN SMALL PACKETS TO FORM ONE MOLECULE
OF ATP AT A TIME, FORMING A TOTAL OF 38 MOLES OF
ATP FOR EACH MOLE OF GLUCOSE METABOLIZED BY THE
CELLS.
RELEASE OF ENERGY
FROM THE GLUCOSE
MOLECULE BY THE
GLYCOLYTIC PATHWAY

46. FORMATION OF LARGE QUANTITIES OF ATP
BY OXIDATION OF HYDROGEN
(THE PROCESS OF OXIDATIVE
PHOSPHORYLATION)
• DESPITE ALL THE COMPLEXITIES OF (1)
GLYCOLYSIS, (2) THE CITRIC ACID CYCLE, (3)
DEHYDROGENATION, AND (4) DECARBOXYLATION,
PITIFULLY SMALL AMOUNTS OF ATP ARE FORMED
DURING ALL THESE PROCESSES—ONLY TWO ATP
MOLECULES IN THE GLYCOLYSIS SCHEME AND
ANOTHER TWO IN THE CITRIC ACID CYCLE FOR
EACH MOLECULE OF GLUCOSE METABOLIZED.
INSTEAD, ALMOST 90 PER CENT OF THE TOTAL
ATP CREATED THROUGH GLUCOSE METABOLISM IS
FORMED DURING SUBSEQUENT OXIDATION OF THE
HYDROGEN ATOMS THAT WERE RELEASED AT
EARLY STAGES OF GLUCOSE DEGRADATION.
INDEED, THE PRINCIPAL FUNCTION OF ALL THESE

47. LIPID METABOLISM
• SEVERAL CHEMICAL COMPOUNDS IN FOOD AND IN THE BODY ARE CLASSIFIED AS
LIPIDS. THEY INCLUDE
• (1) NEUTRAL FAT, ALSO KNOWN AS TRIGLYCERIDES;
• (2) PHOSPHOLIPIDS;
• (3) CHOLESTEROL;
• (4) A FEW OTHERS OF LESS IMPORTANCE.
• CHEMICALLY, THE BASIC LIPID MOIETY OF THE TRIGLYCERIDES AND THE
PHOSPHOLIPIDS IS FATTY ACIDS, WHICH ARE SIMPLY LONG-CHAIN HYDROCARBON
ORGANIC ACIDS.

48. TRANSPORT OF LIPIDS IN
THE BODY FLUIDS
• DURING DIGESTION, MOST TRIGLYCERIDES ARE SPLIT INTO
MONOGLYCERIDES AND FATTY ACIDS. THEN, WHILE PASSING
THROUGH THE INTESTINAL EPITHELIAL CELLS, THE
MONOGLYCERIDES AND FATTY ACIDS ARE RESYNTHESIZED
INTO NEW MOLECULES OF TRIGLYCERIDES THAT ENTER THE
LYMPH AS MINUTE, DISPERSED DROPLETS CALLED
CHYLOMICRONS, WHOSE DIAMETERS ARE BETWEEN 0.08 AND
0.6 MICRON. A SMALL AMOUNT OF APOPROTEIN B IS
ADSORBED TO THE OUTER SURFACES OF THE CHYLOMICRONS.
THIS LEAVES THE REMAINDER OF THE PROTEIN MOLECULES
PROJECTING INTO THE SURROUNDING WATER AND THEREBY
INCREASES THE SUSPENSION STABILITY OF THE
CHYLOMICRONS IN THE LYMPH FLUID AND PREVENTS THEIR
ADHERENCE TO THE LYMPHATIC VESSEL WALLS.

49. THE CHOLESTEROL AND
PHOSPHOLIPIDS TRANSPORT
• MOST OF THE CHOLESTEROL AND
PHOSPHOLIPIDS ABSORBED FROM THE
GASTROINTESTINAL TRACT ENTER THE
CHYLOMICRONS. THUS, ALTHOUGH THE
CHYLOMICRONS ARE COMPOSED PRINCIPALLY OF
TRIGLYCERIDES, THEY ALSO CONTAIN ABOUT 9
PER CENT PHOSPHOLIPIDS, 3 PER CENT
CHOLESTEROL, AND 1 PER CENT APOPROTEIN B.
THE CHYLOMICRONS ARE THEN TRANSPORTED
UPWARD THROUGH THE THORACIC DUCT AND
EMPTIED INTO THE CIRCULATING VENOUS BLOOD
AT THE JUNCTURE OF THE JUGULAR AND