Metabolism and Bioenegetics

1. Course: B.Sc. Biochemistry
Sub: introduction to biochemistry
Unit -4

2. Metabolic Concepts
 Metabolism, the sum of all the chemical transformations
taking place in a cell or organism, occurs through a series of
enzyme-catalyzed reactions that constitute metabolic
pathways.
 Each of the consecutive steps in a metabolic pathway brings
about a specific, small chemical change, usually the removal,
transfer, or addition of a particular atom or functional group.
 The precursor is converted into a product through a series of
metabolic intermediates called metabolites.
 The term intermediary metabolism is often applied to the
combined activities of all the metabolic pathways that
interconvert precursors, metabolites, and products of low
molecular weight (generally, Mr 1,000).

3.  Catabolism is the degradative phase of metabolism in
which organic nutrient molecules (carbohydrates, fats, and
proteins) are converted into smaller, simpler end products
(such as lactic acid, CO2, NH3).
 Catabolic pathways release energy, some of which is
conserved in the formation of ATP and reduced electron
carriers (NADH, NADPH, and FADH2); the rest is lost as
heat.
 In anabolism, also called biosynthesis, small, simple
precursors are built up into larger and more complex
 molecules, including lipids, polysaccharides, proteins,
 and nucleic acids.

4.  Anabolic reactions require an input of energy, generally in
the form of the phosphoryl group transfer potential of ATP
and the reducing power of
 NADH, NADPH, and FADH2 (Fig. 3).
 Some metabolic pathways are linear, and some are
branched, yielding multiple useful end products from a
single precursor or converting several starting materials
into a single product. In general, catabolic pathways are
convergent and anabolic pathways divergent .
 Some pathways are cyclic: one starting component of the
pathway is regenerated in a series of reactions that converts
another starting component into a product.

6. Three types of nonlinear metabolic pathways. (a) Converging, catabolic; (b) diverging,
anabolic; and (c) cyclic, in which one of the starting materials (oxaloacetate in this
case) is regenerated and reenters the pathway. Acetate, a key metabolic intermediate,
is the breakdown product of a variety of fuels (a), serves as the precursor for an array
of products (b), and is consumed in the catabolic pathway known as the citric acid
cycle (c).

8. Bioenergetics
 Life is an energy intensive
process.
 It takes energy to operate
muscles, extract wastes, make
new cells, heal wounds, even
to think.

9. Bioenergetics
A discipline within
biochemistry
dedicated to the
study of energy flow
within living
systems

10. Why Study Bioenergetics?
The understanding of metabolism provides
the directions to better understand how skeletal
muscles generate energy, and how and why the
body responds to exercise the way it does.
The study of metabolism is aided by studying
Bioenergetics.
The Laws of Bioenergetics provide the rules
upon which metabolism functions.

11. Thermodynamics
 The study of energy transformations that occur in a
collection of matter.
 Two Laws:
1. First Law of Thermodynamics
2. Second Law of Thermodynamics

12. First Law of Thermodynamics
Energy cannot be created or
destroyed, but only converted to
other forms.
This means that the amount of energy
in the universe is constant.

13. The First Law is not much help...
What prevents a melting ice cube from
spontaneously refreezing?
Why doesn’t water flow uphill?
Will L-alanine convert into D-alanine?
The energy of the system and its surrounds won’t
change.
If it does not occur, what is driving force?

14. What can we learn from the 1st law of
bioenergetics
1. The main forms of energy within the body are;
• heat light mechanical
• chemical
• “free energy”
• entropy
2. Entropy is a form of energy that cannot be re-used in chemical
reactions, and is defined synonomously with increased
randomness or disorder.
3. “Free energy” is referred to as Gibb’s free energy, and is
abbreviated “G”. Typically, during energy transfers there is a
change in energy forms, which is indicated by the “∆“ symbol.
Thus, a change in Gibb’s free energy is expressed as a “∆G”.

15. The Second Law helps resolve problem
Only those events that result in a net
increase in disorder will occur
spontaneously

16. Second Law of Thermodynamics
 All energy transformations are inefficient
because every reaction results in an increase in
entropy and the loss of usable energy as heat.
 Entropy: the amount of disorder in a system.

17. Second law:
 The second law of thermodynamics, which can be
stated in several forms, says that the universe always
tends toward increasing disorder: in all natural
processes, the entropy of the universe increases.
 Living organisms consist of collections of molecules
much more highly organized than the surrounding
materials from which they are constructed, and
organisms maintain and produce order, seemingly
oblivious to the second law of thermodynamics. But
living organisms do not violate the second law; they
operate strictly within it.

18. Lessons learnt from the 2nd law of
bioenergetics
1. All reactions proceed in the direction of:
a) ↑ entropy
b) a release of free energy (-∆G,(Kcal/Mol))
2. The more negative the ∆G, the greater the release of free
energy during a chemical reaction.
3. Chemical reactions that have a -∆G are termed exergonic
reactions.
4. By convention, reactions that require free energy input to
proceed are termed endergonic reactions, but there are no
such reactions in the human body!
5. The free energy not used to do work is expressed as heat.

19. 6. Reactions that have no net change in substrate or
product are termed equilibrium reactions, and have no
change in free energy (∆G=0).
7. All reactions are potentially reversible.
8. The directionality and amount of free energy release of
a chemical reaction can be modified by altering
substrate and product concentrations.
- ↑’ing products may reverse the direction of the reaction
- ↑’ing substrates can make the ∆G more negative
Of course, if the reaction is reversed, what were the
products are now the substrates, and vice-versa

20. The second Law; The entropy (disorder) of the
universe is increasing
3

21. Mitochondria:
1

22. STATE STANDARD:
“Students know that in both plants and animals,
mitochondria make stored chemical bond
energy available to cells by completing the
breakdown of glucose to carbon dioxide!”

23. Mitochondria:
1

24. • have complex folded inner membranes
(cristae), increasing their surface area
Mitochondria:

25. • have complex folded inner membranes
(cristae), increasing their surface area
• have a fluid-filled interior (the matrix)
Mitochondria:

26. • have complex folded inner membranes
(cristae), increasing their surface area
• have a fluid-filled interior (the matrix)
• act like combustion chambers in an engine,
a ‘safe’ place to ‘burn’ fuel with oxygen
Mitochondria:

27. A Combustion Chamber?

28. A Combustion Chamber?
LET’S COMPARE!
A gasoline engine . . . . and a mitochondria,
in cross-section.
2

29. Before combustion can
occur, however, we have to
get some “fuel” !

30. For that, we will need to break down glucose
(or other sugars) OUTSIDE
the mitochondria, in a process called . . . .

33.  is the breakdown of glucose (or
other sugars)

34.  is the breakdown of glucose (or
other sugars)
 requires an activation energy

35.  is the breakdown of glucose (or
other sugars)
 requires an activation energy
 occurs in the cytoplasm

36. Polymers of glucose, like starch, are first
broken into individual sugars through
hydrolysis

37. The single sugars produced contain
stored energy in their chemical bonds,
but they are still too big to pass
through the mitochondrial membrane.

38. ATP provides the initial activation
energy. The 6-carbon sugar will
be broken down in a series of steps
that do not involve oxygen.

40. There will be a net gain of 2 ATP. The
final products of glycolysis are two 3-
carbon molecules of pyruvate (pyruvic
acid)
C3H3O3
3

41. Pyruvate is small enough to
be easily transported through the mitochondrial
membrane, where a new series of chemical reactions
take place. . .
C3H3O3

42. The
Krebs
Cycle

43. The Krebs Cycle:
• takes place in the matrix
4

44. The Krebs Cycle:
• takes place in the matrix
• begins by converting each of the 3-carbon
pyruvates into a special complex called
acetyl CoA
C3H3O3 “acetyl CoA”
. . Co-enzyme A is added
Pyruvate enters
the matrix. . . . . .a waste product ,
CO2 , is released . . .

45. The Krebs Cycle:
Acetyl CoA
begins the cycle
Acetyl CoA

46. The Krebs Cycle:
Acetyl CoA
begins the cycle
As the cycle
proceeds, CO2
are removed
CO2
CO2

47. The Krebs Cycle:
There is a net
gain in ATP,
and . . .
. . .an electron
transport chain
is charged!
ATP
CO2
CO2
e-
e-

48. Electron Transport:
• takes place in the cristae

49. Electron Transport:
• takes place in the cristae

50. Electron Transport:
• takes place in the cristae
• will draw in H+, creating a high
concentration which can be used to
drive a proton pump
Electron Transport:

51. Proton Pumping:
• powers the enzyme, ATP synthase

52. Proton Pumping:
• powers the enzyme, ATP synthase
…which is then used to make ATP

53. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP

54. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP
Krebs Cycle, in matrix, no O2 2 ATP

55. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP
Krebs Cycle, in matrix, no O2 2 ATP
Electron transport chains, with O2 32 ATP

56. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP
Krebs Cycle, in matrix, no O2 2 ATP
Electron transport chains, with O2 32 ATP
TOTAL: 38 ATP

57. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP*
Krebs Cycle, in matrix, no O2 2 ATP
Electron transport chains, with O2 32 ATP
TOTAL: 38 ATP
(-2 ATP)*
---------------
(*minus 2 ATP used for activation energy in glycolysis)

58. DOING THE MATH:
Glycolysis, in cytoplasm, no O2 4 ATP*
Krebs Cycle, in matrix, no O2 2 ATP
Electron transport chains, with O2 32 ATP
TOTAL: 38 ATP
(-2 ATP)*
---------------
NET YIELD, 1 glucose: 36 net ATP
(*minus 2 ATP used for activation energy in glycolysis)

60. MINERALS
 A mineral is a naturally occurring substance that is
solid and stable at room temperature, representable by
a chemical formula, usually abiogenic, and has an
ordered atomic structure. It is different from a rock,
which can be an aggregate of minerals or non-minerals
and does not have a specific chemical composition.
The exact definition of a mineral is under debate,
especially with respect to the requirement a valid
species be abiogenic, and to a lesser extent with regard
to it having an ordered atomic structure. The study of
minerals is called mineralogy.

61. Functions of Minerals
 Some participate with enzymes in metabolic
processes (cofactors, e.g. Mg, Mn, Cu, Zn, K)
 Some have structural functions (Ca, P in bone;
S in keratin)
 Acid-base and water balance (Na, K, Cl)
 Nerve & muscle function (Ca, Na, K)
 Unique functions: hemoglobin (Fe), Vitamin B12
(Co), thyroxine (I).

62. Classification
 Macro or Major minerals
 Sodium (Na), potassium
(K), magnesium (Mg),
calcium (Ca), phosphorus
(P), sulfur (S), chloride (Cl)
 Present in body tissues at
concentrations >50 mg/kg
 requirement of these is
>100 mg/d
 Micro or Trace minerals
(body needs relatively less)
 Manganese(Mg), iron(Fe),
cobalt(Co), chromium(Cr),
molybdenum(Mo),
copper(Cu), zinc(Zn),
fluoride(F), iodine(I),
selenium(Se)
 Present in body tissues at
concentrations <50 mg/kg
 requirement of these is ﹤100
mg/d

63. Nutritionally Important Minerals
Macro Trace
Element g/kg Element mg/kg
Ca
P
K
Na
Cl
S
Mg
15
10
2
1.6
1.1
1.5
0.4
Fe
Zn
Cu
Mo
Se
I
Mn
Co
20-50
10-50
1-5
1-4
1-2
0.3-0.6
0.2-0.5
0.02-0.1

64. Minerals in Foods
 Found in all food groups.
 More reliably found in animal
products.
 Often other substances in foods
decrease absorption
(bioavailability) of minerals
 Oxalate, found in spinach, prevents
absorption of most calcium in
spinach.
 Phytate, form of phosphorous in
most plants makes it poorly available
Oxalate
Phytate

65. Factors Affecting Requirements
 Physiological state/level of production
 Interactions with other minerals
4

66. Deficiencies and Excesses
 Most minerals have an optimal range
 Below leads to deficiency symptoms
 Above leads to toxicity symptoms
 Mineral content of soils dictates mineral status of
plants (i.e., feeds)
 May take many months to develop

67. Requirements and Toxicities
Element Species Requirement,
mg/kg
Toxic level,
mg/kg
Cu Cattle
Swine
5-8
6
115
250
Co Cattle 0.06 60
I Livestock 0.1 ?
Se Cattle
Horses
0.1
0.1
3-4
5-40

68. Calcium (Ca)
 Most abundant mineral in
animal tissues
 99% Ca in skeleton
 1% Present in:
 Blood & other tissues
 Lots of functions
 Bone structure
 Nerve function
 Blood clotting
 Muscle contraction
 Cellular metabolism
5

69. Dietary requirements
 Dietary requirements:
 Adult : 800 mg/day;
 Women during pregnancy, lactation and post-
menopause: 1.5 g/day;
 Children (1-18 yrs): 0.8-1.2 g/ day;
 Infants: (< 1 year): 300-500 mg /day
 Food Sources:
 Best sources: milk and milk product;
 Good sources: beans, leafy vegetables, fish, cabbage, egg
yolk.

70. Major minerals
Sodium-sources- table salt, processed foods
-metabolism- water balance
-acid base balance
(excretion of
hydrogen ions in
exchange for
sodium ions in
kidney)

71. Major minerals
Chloride-sources- table salt, processed foods
-metabolism- water balance
-hydrochloric acid

72. Major minerals
Potassium-
-sources-all whole foods, meats, milk,
fruits, grains
-metabolism- water balance
-supports cell integrity
-promotes steady heartbeat

73. Major minerals
Calcium
-sources-milk and milk products,
small fish with bones,
tofu, broccoli, chard
-metabolism- bone and teeth
formation
-cell signalling

74. Major minerals
Phosphorous
-sources-all animal tissues
-metabolism- buffers
-part of DNA/RNA
-phosphorylation of many
enzymes and B vitamins
to make them
biochemically active
-ATP
-phospholipids-cell signalling

75. Major minerals
Magnesium
-sources-nuts, legumes, whole grains,
dark green vegetables,
seafood, chocolate
-metabolism- enzyme co-factor (glucose
use in body plus
synthesis of protein,
lipids and nucleic acids)
-part of enzyme that
transforms ADP to ATP

76. Major minerals
Sulphur
-sources-all protein containing foods
-metabolism- protein structure
-part of thiamine and
biotin

77. Minor minerals
Definition of minor minerals
-present in body in amounts less than
5 grams

78. Minor minerals
Inorganic elements
•Iron
•Zinc
•Iodine
•Selenium
•Copper
•Manganese
•Fluoride
•Chromium
• Molybdenum

79. Minor minerals
Body's handling of minerals
-iron uses carriers for absorption, transport and
proteins for storage-no free iron- oxidation issue-
example of minor mineral requiring no carriers or
storage proteins iodine
Variable Bioavailability
-phytates reduce iron absorption

80. Minor minerals
Nutrient Interactions
-slight manganese overload may
exacerbate iron deficiency
-combined iodine and selenium
deficiency reduces thyroid hormone
function more than just iodine
deficiency alone
Varied roles
-iron-oxygen carrying
-zinc- part of enzymes

81. Minor minerals
Iron
-sources-red meats, fish, poultry,
shellfish, eggs, legumes,
dried fruits
-metabolism- oxygen carrier
-part of electron carriers
in electron transport
chain

82. Minor minerals
Zinc
-sources-protein containing foods:meats
fish, poultry, whole grains,
vegetables
-metabolism- part of many enzymes
-synthesis of DNA/RNA
-heme synthesis
-fatty acid metabolism
-release hepatic stores of
vitamin A
-carbohydrate metabolism
-synthesis of proteins
-dispose of damaging free radicals
-oxygen carrying

83. Minor minerals
Iodine
-sources-iodised salt, seafood, bread,
dairy products, plants grown on iodine
rich soil and animals that eat such
plants
-metabolism- thyroid hormones-
metabolic rate(rate of oxygen use),body
temperature

84. Minor minerals
Selenium
-sources-seafood, meat, whole grains, and
depending on soil selenium
content- vegetables
-metabolism- anti-oxidation (via enzyme)
- regulates thyroid hormone

85. Minor minerals
Copper
-sources-seafood, nuts, whole grains, seeds,
legumes
-metabolism- part of many enzymes all of
which have common feature of
consuming oxygen or oxygen radicals
-eg -hemoglobisynthesis
-collagen synthesis
-free radical control
-electron transport
chain

86. Minor minerals
Manganese
-sources-nuts, whole grains, leafy
vegetables
-metabolism- essential for iron
absorption and use in formation of hemoglobin
-part of several enzymes

87. Minor minerals
Fluoride
-sources-fluoridated drinking water, tea,
seafood
-metabolism- formation of bones and teeth,
resistance to tooth decay

88. Minor minerals
Chromium
-sources-meat, unrefined foods, fats,
vegetable oils
-metabolism- enhancing insulin activity

89. Minor minerals
Molybdenum
-sources-legumes, cereals, organ meats
-metabolism- co-factor for several
enzymes

90. References/Sources
 All images are from Lehninger Principles of biochemistry by Nelson and Cox except
1.https://lh4.ggpht.com/0HlIrSFqDcCtidmS1T6x70CquY2CThQM6i_eY3ZuxEt4lC0_yLvjFTwsBiuS6isLH
Azb=s123
2.https://lh4.ggpht.com/J4qU9fcv42V2pQj7Wt99lTqMZQZedjEaafMd4CahkTo9euleEuWRbjwSTcnDK1
VIzPbTLg=s93
3. https://lh5.ggpht.com/CYhZcxlIn01H7O77jW4gz-
6MPxYJ59IzvMJbV6utSh2FX0505P7Ab1fLHQcFE2Zxbv-JBVk=s85
4.https://lh3.ggpht.com/cc8HBCMzPlDFxXgQKwjk9ZYkOJLotGmbUa4ZzwusqvslbQY7W2UVhXUgVd_
Oj8YGtK6wWw=s139
5.
https://lh3.ggpht.com/cHAfbDE2a1aKZfi_VuC9uzkrvK2YjakVMmONrNPcchJcwcsOaYYgOk4wXL_Y
zeX0E15iEw=s97
6.https://lh3.ggpht.com/eWm_hMna_I6Wapkaq33984aHnCZk8cjgh354pbqKU1BNtZ9kAcNNnaEwGVU
ZT5FtwR27eow=s85
Books/ Web resources
 Lehninger Principles of biochemistry by Nelson and Cox
 www.nlm.nih.gov/medlineplus/minerals.html
 https://chemistry.osu.edu/~woodward/ch121/ch5_law.htm
 biochem.co/2010/02/glycolysis
 www.elmhurst.edu/~chm/onlcourse/CHM103/Rx24citricacidcycle