1. 2-Energy Metabolism During Rest
and Exercise
Nutrition and Fitness
semester V
Dr. Siham Gritly

2. Human cell
Dr. Siham Gritly

3. Definitions related to the subject
• -AdenosineTriphosphate (ATP), a chemical
compound found in all cells that store energy
• *ATP or adenosine tri-phosphate is
intermediary compound that has the ability to
enter in many reactions. it is nucleotide
compound composed of adenine (nitrogen
base), ribose (pentose sugar) and three
phosphate radicals.
Dr. Siham Gritly

4. • -Adenosine Diphosphate ADP, a nucleotide
involved in energy metabolism it is produced
by hydrolysis of ATP and converted back to
ATP by the process of oxidative phosphrylation
• -Creatine Phosphate CP, an important storage
form of high energy phosphate in muscle cells
Dr. Siham Gritly

5. Objective; By the end of this lecture students should be
understand the following terms;
• glycolysis, citric acid cycle, oxidative phospholylation
• (electron transport system)
• The ATP-CP system (phosphagen)
• Glycogenolysis
• Glycogenesis
• Gluconeogenesis
• Pentose phosphate pathway.
Dr. Siham Gritly

6. Energy in nutrition
• *In nutrition, energy deals with chemical
energy that locked in food staff by chemical
bonding present in nutrients. energy is
derived from energy producing nutrients CHO,
fats and proteins.
• *All living cells need energy to continue living.
The main source of energy derived from solar
energy or sun energy. Human body obtains
energy by indirect way from the sun through
the process of photosynthesis.
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7. Uses of energy
• 1-muscular secretion
• 2-secretion of the glands
• 3-synthesis of new substances
• 4-regulation of body temperature
• 5-absorption of food from gastro-intestinal
tract
• 6-for the basal metabolism e.g. heart beat,
respiration etc.
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8. Sources of energy (ATP)
• Sources of ATP
• 1- glycolysis,
• 2- citric acid cycle
• 3-oxidative phospholylation (electron
transport system)
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9. 1-Glycolysis pathway;
• *Glycolysis is the process of energy releasing
from glucose molecules in cytoplasm of cells. in
the cytoplasm glucose bind with 6 phosphate
radicals this occur by the action of specific
enzymes.
• *Glycolysis is splitting of glucose molecule to
form 2 molecules of pyruvic acid (pyruvate). This
process occurs by 10 steps of chemical reactions,
each reaction is catalysed by one specific protein
enzyme. It has 2 phases in the first phase energy
is needed and the second phase energy is released
(ATP),
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10. • *Glycolysis also define as; the net formation of 2
high energy phosphate result from formation of
lactate or lactic acid from one molecule of
glucose under an-aerobic condition.
• *Glucose---------oxidation-------------2lactic acid
(the end product of glycolysis under anaerobic
condition) or
• *pyruvate (under aerobic condition) + 2ATP (net
formation of glucose oxidation).
Dr. Siham Gritly

11. • *pyruvic acid is the second main phase or step
in glycolysis process for production of ATP,
then enter the mitochondria (power house of
the cell)for total oxidation of glucose
molecules to water, carbon dioxide and energy.
• *in the fist phase of glycolysis energy is
required. energy obtained directly from the
chemical compound ATP
Dr. Siham Gritly

12. Glycolysis is a central pathway are important
part of glucose metabolism because;
• -It produces large amount of energy,
• -occur in all cells,
• -common pathway in breaking down all
macro-nutrients (proteins, fats and
carbohydrates)
Dr. Siham Gritly

13. Glycolysis Pathway
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14. 2-Citric acid cycle;
• *It is known also by Kerb's cycle or tri-
carboxylic acid cycle. it represent the second
and final process in glucose metabolism.
The cycle is discovered by kerb in 1937.
• *Under anaerobic condition mainly in
muscle cells, pyruvic acid is converted into
lactic acid.
Dr. Siham Gritly

15. • *Under aerobic conditions, pyruvic acid is
oxidized through kerb's or tri-carboxylic acid
cycle in the mitochondria of the cell to
energy, carbon dioxide and water.
• *kerb's cycle is a series of reactions in the
Mitochondria that bring about the catabolism of
acetyl residues, liberating hydrogen equivalent
(2H) which on oxidation lead to the release of
most of the free energy of tissue fuels. The acetyl
residues are in the form of acetyl Co-enzyme A
(active acetate).
Dr. Siham Gritly

16. Citric acid cycle
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17. • *the cycle is the major route for the generation of ATP and
is located in the matrix of mitochondria adjacent to the
enzymes of respiratory chain.
• *It is the final pathway for oxidation of glucose, lipids and
protein.
• *It catalyzed the combination of their common metabolite--
--acetyl Co-enzyme A with oxaloacetate to form citrate by
series of dehydrogenation and decarboxylation
• *citrate or citric acid is degraded (break down) releasing
reducing equivalent (energy in the form of H molecules)
and 2 carbon dioxide and regenerating oxaloacetate
Dr. Siham Gritly

18. 3-Electron transport system
• Electron transport chains;
• *are the cellular mechanisms used for
extracting energy through redox (reduction –
oxidation ) reactions, such as the oxidation of
sugars (glucose to water, carbon dioxide and
ATP) during the process of cellular respiration
in mitochondria (Kerb cycle).
Dr. Siham Gritly

19. • *In a simple words it is the oxidation of glucose
(C6H12O6) in the human body through a series of
complex electron transfer processes (transfer of
electrons between spaces) by specific electrons
receptors NAD and FAD.
• -Electron transport chains are redox reactions
that is; that transfer electrons from an electron
donor (NADH) to an electron acceptor (O2) with
the transfer of H ions (proton) across a cell
membrane releasing energy.
Dr. Siham Gritly

20. Electron transport system
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21. • Reduced electron carriers NADH & FADH2 reduce
oxygen to water via the electron transport chain.
• The energy released is used to set up a proton gradient
across the inner mitochondrial membrane.
• The protons flow down this concentration gradient back
across the inner mitochondrial membrane through the
ATPase .The energy released is used to generate ATP.
• The citric acid cycle and fatty acid oxidation supply
NADH and FADH2 for production of more through
electron
Dr. Siham Gritly

22. Glycogenesis
• *Glycogenesis is the formation of glycogen from
glucose. Glycogen synthesize is depending on the
demand for glucose and ATP (energy).
• *If both are present in relatively high amounts, then
the excess of insulin promotes the glucose conversion
into glycogen for storage in liver and muscle cells.
• *Glycogen is a large polymer of glucose it is the storage
form of glucose. Several enzymes involved in
conversions of extra glucose to glycogen
Dr. Siham Gritly

23. glucose after absorption can be used immediately
for release of energy to the cell or it can be stored
in the form of glycogen
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24. Glycogenolysis
• Glycogenolysis
• *is the process of breakdown of glycogen to re-
form glucose in the cells
• *glycogen stored in the liver and muscles, is
converted first to glucose-1- phosphate and then
into glucose-6-phosphate.
• *Two hormones which control glycogenolysis are
a peptide, glucagon from the pancreas and
epinephrine from the adrenal glands.
Dr. Siham Gritly

25. • *Glucagon is released from the pancreas in
response to low blood glucose and epinephrine
is released in response to a threat or stress.
• Both hormones act upon enzymes to stimulate
glycogen phosphorylase to begin
glycogenolysis and inhibit glycogen synthetase
(to stop glycogenesis)
Dr. Siham Gritly

26. • *In the next step the phosphate is moved to the C-
6 position to give glucose 6-phosphate, a cross
road compound or intermediate compound.
• *Glucose-6-phosphate is the first step of the
glycolysis pathway if glycogen is the
carbohydrate source and further energy is needed.
If energy is not immediately needed, the glucose-
6-phosphate is converted to glucose for
distribution in the blood to various cells such as
brain cells
Dr. Siham Gritly

27. Glycogenolysis; break down of glycogen to
release glucose
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28. Gluconeogenesis
• *Gluconeogenesis is the process or
mechanisms of synthesizing glucose from non-
carbohydrate sources.
• *The starting point of gluconeogenesis is
pyruvic acid, although oxaloacetic acid and
dihydroxyacetone phosphate also provide entry
points.
Dr. Siham Gritly

29. • * Lactic acid, some amino acids from
protein and glycerol from fat can be
converted into glucose.
• Gluconeogenesis is similar but not the exact
reverse of glycolysis, some of the steps are the
identical in reverse direction and three of them
are new ones
Dr. Siham Gritly

30. Gluconeogenesis is the process of synthesizing
glucose from non-carbohydrate sources
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31. • Energy and Exercises
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32. Energy and Exercises
• The energy needs of endurance athletes are high.
Every athlete’s calorie needs are different mainly
depend on;-
• - gender,
• - age,
• -body composition,
• -types of training
• - daily activities.
• During heavy training and racing cycles, extreme
changes in weight should be avoided
Dr. Siham Gritly

33. • Younger athletes in light training may need
fewer than 1,600 calories per day; larger
athletes and those in heavy training may need
well over 5,000 calories per day. Calories
should come from a variety of sources.
Dr. Siham Gritly

34. Energy metabolism in rest and exercise
• in the resting state
• energy expenditure varies according to physical
activity among individuals
• -in the resting state energy is expended in
mechanical activities necessary to sustain life
(respiration, circulation, synthesis, nervous
system
• - when body at rest energy used is known as basal
energy expenditure (BEE) or resting energy
expenditure (REE)
Dr. Siham Gritly

35. • -exercise and physical activity, muscle exercise
increase heat production of the body and thus
increase metabolic rate
• -body size and composition
• -daily activity
-metabolic rate MR-is the rate of heat liberation
during the chemical reaction (metabolism)
Dr. Siham Gritly

36. During heavy exercise and activity energy is derived
from;
During heavy exercise
1- ATP present in muscle cells
2-storedd creatine phosphate in the cells
3-anaerobic energy released by glycolytic
breakdown of glycogen to lactic acid
4-by oxidative process in the cells (glycolysis)
Dr. Siham Gritly

37. 1- ATP present in muscle cells
• * ATP is a source of high-energy phosphate
present everywhere in the cytoplasm and
nucleoplasma of all cells and essentially for all
the physiological mechanisms that required
energy.
• *ATP is known as energy currency of the cells
Dr. Siham Gritly

38. • * Anaerobic energy in the muscle produces
energy for short, high-intensity bursts of activity
lasting no more than several minutes before the
lactic acid build-up reaches a threshold known as
the lactate threshold.
• *The lactic acid or anaerobic glycolysis system
converts glycogen of the muscles to glucose.
Then, with the action of enzymes glucose is
broken down an-aerobically to produce lactic
acid;
Dr. Siham Gritly

39. • *this process creates enough energy to reform
ATP molecules, but due to the detrimental
effects of lactic acid and H+ ions building up
and causing the pH of the blood to become
more acidic,
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40. 2-storedd creatine phosphate in the cells
The ATP-CP system (phosphagen)
• *creatine phosphate (CP) is another high
energy rich compound and is considered the
reservoir of high energy phosphate. this
compound is stored in the body in large
quantities than ATP.
• - Creatine phosphate, also known as ATP-
PC or ATP-CP system, is the first source of
energy used;
Dr. Siham Gritly

41. • -The ATP-CP system is related system in
muscle cells by using high-energy phosphate
bond of creatine phosphate together with ATP
• -it works by forming ATP and then by breaking
down a creatine phosphate which creates and
which then will reform ATP.
Dr. Siham Gritly

42. • This is not used for muscle contraction, but is
mainly used for resynthesising ATP and to
maintain a constant supply of energy.
• These reactions occur very rapidly and only
last up to high intensity (this only lasts for a
short period of time).
Dr. Siham Gritly

43. • The ATP-CP energy pathway do not require
any oxygen to create ATP. It first uses up any
ATP stored in the muscle (about 2-3 seconds)
and then it uses creatine phosphate (CP) to
resynthesize ATP until the CP runs out
(another 6-8 seconds).
•
• After the ATP and CP are used the body will
move on to either aerobic or anaerobic
metabolism (glycolysis) to continue to create
ATP to fuel exercise.
Dr. Siham Gritly

44. 3-anaerobic energy released by glycolytic
breakdown of glycogen to lactic acid
• *During physical activity the energy is met by
the presence of ATP
• *Most of extra energy required during
strenuous activity derived from anaerobic
glycolysis
Dr. Siham Gritly

45. • *The anaerobic energy pathway, or glycolysis,
creates ATP exclusively from carbohydrates,
with lactic acid being a by-product.
• *Anaerobic glycolysis provides energy by the
(partial) breakdown of glucose without the
need for oxygen.
Dr. Siham Gritly

46. 4-by oxidative process in the cells
(Aerobic glycolysis)
• * Aerobic metabolism is used primarily during
moderate exercise, which is generally less intense
and can continue for long periods of time.
• *within the cells the nutrients amino acids, fatty
acids and glucose react with oxygen (oxidation) to
form carbon dioxide, water, pyruvate and energy.
Energy produced used to form adenosine tri-
phosphate
Dr. Siham Gritly

47. • Aerobic metabolism fuels most of the energy
needed for long duration activity. It uses
oxygen to convert nutrients (carbohydrates,
fats, and protein) to ATP.
• This system is a bit slower than the anaerobic
systems because it relies on the circulatory
system to transport oxygen to the working
muscles before it creates ATP.
Dr. Siham Gritly

48. • During exercise, ATP is produced via anaerobic
metabolism. With an increase in breathing and heart
rate, there is more oxygen available and aerobic
metabolism begins and continues until the lactate
threshold is reached.
• If this level is exceed, the body can not deliver
oxygen quickly enough to generate ATP and
anaerobic metabolism kick in again.
• Since this system is short-lived and lactic acid levels
rise, the intensity can not be sustained and the athlete
will need to decrease intensity to remove lactic acid
build-up.
Dr. Siham Gritly

49. References
• Sareen Gropper, Jack Smith and James Groff, Advanced Nutrition
and Human Metabolism, fifth ed. WADSWORTH
• Melvin H Williams 2010; Nutrition for Health, Fitness and Sport. 9th
ed, McGraw Hill
•
• Heymsfield, SB.; Baumgartner N.; Richard and Sheau-Fang P. 1999.
Modern Nutrition in Health and Disease; Shils E
Maurice, Olson A. James, Shike Moshe and Ross A. Catharine
eds. 9th edition
• Guyton, C. Arthur. 1985. Textbook of Medical Physiology. 6th
edition, W.B. Company
Dr. Siham Gritly