Metabolism encompasses all chemical processes in an organism and is organized into metabolic pathways, which involve converting molecules to produce various substances. These pathways include catabolic reactions that break down molecules for energy and anabolic reactions that synthesize complex molecules from simpler ones, which are crucial for maintaining homeostasis. Metabolic rate, influenced by factors such as age, sex, and physical activity, measures the energy released from food catabolism and is essential for bodily functions.

1. METABOLISM
• The sum of all the chemical processes
occurring in an organism at one time
• Concerned with the management of
material and energy resources within the
cell

2. • The chemistry of life is organized into metabolic
pathways.
• A metabolic pathway involves the step-by-step
modification of an initial molecule to form another
product.
• The resulting product can be used in one of three
ways:
1.Be used immediately,
2.Initiate another metabolic pathway, called a flux
generating step
3.Be stored by the cell
• A specific enzyme catalyzes each step of the pathway.

3. •Chemical reactions occurring within a cell.
•Principal chemical is modified by a series
of chemical reactions.
•Enzymes catalyze these reactions.
•Require dietary minerals, vitamins, and
other cofactors in order to function properly.
•Numerous distinct pathways co-exist within a
cell.
•This collection of pathways is called
the metabolic network.

4. • Important to the maintenance of homeostasis.
• Catabolic (break-down) and Anabolic (synthesis)
pathways work interdependently to create new
biomolecules as the final end-products

5. •A molecule called a substrate enters a
metabolic pathway depending on the needs
of the cell and the availability of the
substrate.
•An increase in concentration
of anabolic and catabolic intermediates
and/or end-products may influence the
metabolic rate for that particular pathway

6. Catabolic and anabolic reactions
© Michael Palmer 2014

7. Catabolic Pathways
• Pathways that release energy by breaking
down complex molecules into simpler
compounds
• Cellular respiration
• C6H1206 + 6O26CO2 +6H20 + ENERGY

8. Anabolic Pathways
• Pathways that consume energy to build
larger, complicated molecules from
simpler ones
• Polymerization
• Photosynthesis
6CO2 +6H20 + light  C6H1206 + 6O2

9. • Catabolic pathways release energy by
breaking down complex molecules to simpler
compounds.
–A major pathway of catabolism is cellular
respiration, in which the sugar glucose is
broken down in the presence of oxygen to
carbon dioxide and water.

10. The place of glycolysis in glucose degradation
© Michael Palmer 2014

11. •Most of the structures that make up animals,
plants and microbes are made from three basic
classes of molecule:
•amino acids,
•Carbohydrates
• lipids (often called fats).
•Metabolic reactions either focus on making these
molecules during the construction of cells and
tissues,
•Breaking them down and using them as a source
of energy, by their digestion.
•These biochemicals can be joined together to
make polymers such as DNA and proteins,
essential macromolecules of life

12. Type of molecule
Name of
monomer forms
Name of polymer
forms
Examples of
polymer forms
Amino acids Amino acids
Proteins (also
called
polypeptides)
Fibrous proteins
and globular
proteins
Carbohydrates Monosaccharides Polysaccharides
Starch, glycogen
and cellulose
Nucleic acids Nucleotides Polynucleotides DNA and RNA

13. •Catabolic reactions in animals can be
separated into three main stages.
•In the first, large organic molecules such
as proteins polysaccharides or lipids are
digested into their smaller components
outside cells.

14. • Smaller molecules are taken up by cells and
converted to yet smaller molecules, usually acetyl
coenzyme A (acetyl-CoA), which releases some
energy.
• Finally, the acetyl group on the CoA is oxidised to
water and carbon dioxide in the citric acid
cycle and electron transport chain, releasing the
energy that is stored by reducing the
coenzyme nicotinamide adenine
dinucleotide (NAD+
) into NADH

15. Stages of Catabolism
Catabolic reactions are organized into three stages:
• In Stage 1, digestion breaks down large molecules
into smaller ones that enter the bloodstream
• In Stage 2, molecules enter the cells and are broken
down into two- and three-carbon compounds
• In Stage 3, compounds are oxidized in the citric
acid cycle to provide energy (ATP) for anabolic
processes

16. Stages of Catabolism (Diagram)

17. Eukaryotic Cell Structure
• Metabolic reactions occur at specific sites within the cell

18. •Anabolism is the set of constructive
metabolic processes where the energy
released by catabolism is used to synthesize
complex molecules.
•Complex molecules that make up cellular
structures are constructed step-by-step from
small and simple precursors.

19. Three basic stages.
• Firstly, the production of precursors such as amino
acids, monosaccharides, isoprenoids and nucleotide
s,
• Secondly, their activation into reactive forms using
energy from ATP,
• Thirdly, the assembly of these precursors into
complex molecules such
as proteins, polysaccharides, lipids and nucleic
acids

20. •In carbohydrate anabolism, simple organic acids can
be converted into monosaccharides
•Then used to assemble polysaccharides such
as starch.
•The generation of glucose from compounds
like pyruvate, lactate, glycerol, glycerate 3-
phosphate and amino acids is called gluconeogenesis.
• Gluconeogenesis converts pyruvate to glucose-6-
phosphate through a series of intermediates, many of
which are shared with glycolysis
• However, this pathway is not simply glycolysis run
in reverse, as several steps are catalyzed by non-
glycolytic enzymes.

21. © Michael Palmer 2014

22. Glucose phosphorylation cycling involves two
separate compartments
© Michael Palmer 2014

23. • Metabolic Rate
• The amount of energy liberated by the catabolism of
food in the body is the same as the amount liberated
when food is burned outside the body.
• The energy liberated by catabolic processes in the
body is used for maintaining body functions
•

24. • Digesting and metabolizing food,
• thermoregulation, and physical activity.
• It appears as external work , heat, and
energy storage:
• The amount of energy liberated per unit of
time is the metabolic rate.
• Isotonic muscle contractions perform work
at a peak efficiency approximating 50%:

25. • Factors affecting the metabolic rate.
• Muscular exertion during or just before measurement
• Recent ingestion of food
• High or low environmental temperature
• Height, weight, and surface area
• Sex Age Growth Reproduction Lactation Emotional
state
• Body temperature
• Circulating levels of thyroid hormones
• Circulating epinephrine and norepinephrine levels

26. • The metabolic rate determined at rest in a room at a
comfortable temperature in the thermoneutral zone 12-14
hours after the last meal is called the basal metabolic rate
(BMR).
• This value falls about 10% during sleep and up to 40%
during prolonged starvation.
• The rate during normal daytime activities is, of course, higher
than the BMR because of muscular activity and food intake.
• The maximum metabolic rate reached during exercise is
often said to be ten times the BMR, but trained athletes can
increase their metabolic rate as much as 20-fold.

27. Metabolic Rate and Caloric
Requirements
• Metabolic rate is the total rate of body metabolism.
– Metabolic rate measured by the amount of oxygen
consumed by the body/min.
• BMR:
– Oxygen consumption of an awake relaxed person 12–14
hours after eating and at a comfortable temperature.
• BMR determined by:Age.
 Age.
 Gender.
 Body surface area.
 Thyroid secretion

28. Anabolic Requirements
• Anabolism:
– Food supplies raw materials for synthesis reactions.
• Synthesize:
– DNA and RNA.
– Proteins.
– Triglycerides.
– Glycogen.
• Must occur constantly to replace molecules that
are hydrolyzed.

29. Aerobic Requirements
• Catabolism:
– Hydrolysis (break down monomers down to
C02 and H20.):
• Hydrolysis reactions and cellular respiration.
• Gluconeogenesis.
• Glycogenolysis.
• Lipolysis.

30. Components of Eukaryotic Cells

31. ATP and Energy
• In cells, energy is stored in adenosine triphosphate (ATP)
- there are other cellular energy sources, but ATP is the
main one

32. Hydrolysis of ATP
• The hydrolysis of ATP to ADP releases 7.3 kcal (31 kJ/mole)
ATP  ADP + Pi + 7.3 kcal (31 kJ/mole)
• The hydrolysis of ADP to AMP releases 7.3 kcal (31 kJ/mole)
ADP  AMP + Pi + 7.3 kcal (31 kJ/mole)

33. ATP and Muscle Contraction
• Muscle fibers contains
filaments of actin and
myosin
• When a nerve impulse
increases [Ca2
+], the
filaments slide closer
together to contract the
muscle
• The hydrolysis of ATP in
muscle provides the
energy for contraction
• As Ca2+
and ATP decrease,
the filaments return to the
relaxed position

34. Coenzyme NAD+
• When a compound is oxidized by an enzyme, 2H as 2H+
and 2e-
are removed by a coenzyme, which is reduced
• NAD+
(nicotinamide adenine dinucleotide) participates in
reactions that produce a carbon-oxygen double bond (C=O)
• For example, NAD+
participates in the oxidation of ethanol:
Overall Reaction:
OH
H
O
+ NADH + H +
+ NAD+
Alcohol
dehydrogenase
Oxidation:
OH
H
O
+ 2H+
+ 2e -
Reduction:
NAD+
+ 2H +
+ 2e -
NADH + H +

35. Structure of Coenzyme NAD+
• NAD+
(nicotinamide adenine dinucleotide) contains ADP, ribose,
and nicotinamide (from niacin, B3)
• NAD+
reduces to NADH when the nicotinamide group accepts
H+
and 2e-

36. Coenzyme FAD
• FAD participates in reactions that produce a carbon-carbon
double bond (C=C)
Oxidation
—CH2—CH2—  —CH=CH— + 2H+
+ 2e-
Reduction
FAD + 2H+
+ 2e-
 FADH2

37. Structure of Coenzyme FAD
• FAD(flavin adenine dinucleotide) contains ADP and riboflavin
(vitamin B2)
• FADreduces to FADH2 when flavin accepts 2H+
and 2e-

38. Coenzyme A (CoA)
• CoA activates acyl groups, such as the two-carbon acetyl group
for transfer to other compounds
• It consists of pantothenic acid (vitamin B5), phosphorylated ADP
and an aminoethanethiol

39. Digestion of Carbohydrates (Stage 1)
• In the mouth, salivary amylase hydrolyzes -glycosidic bonds
in polysaccharides to give smaller polysaccharides (dextrins),
maltose, and some glucose
• In the small intestine, pancreatic amylase hydrolyzes dextrins
to maltose and glucose
• The disaccharides maltose, lactose, and sucrose are hydrolyzed
to monosaccharides in the small intestine
• The monosaccharides enter the bloodstream
- fructose and galactose are transported to the liver, where they
are isomerized to glucose
- glucose is transported to cells for metabolism

40. Overview of Stage 1 of Carbohydrate Catabolism

41. Glycolysis (Stage 2)
• In Stage 2 of carbohydrate
catabolism, the metabolic
pathway called glycolysis
degrades glucose (6C)
obtained from digestion to
pyruvate (3C)
• Glycolysis is an anaerobic
process that takes place in
the cytoplasm

42. Energy-Investing Phase of Glycolysis
In reactions 1-5 of glycolysis:
• Energy is used to add phosphate groups to glucose and fructose
• Glucose is converted to two three-carbon molecules

43. Energy-Producing Phase of Glycolysis
• In reactions 6-10, the hydrolysis of phosphates generates
four ATP molecules
• Two NAD+
coenzymes are also reduced

44. Glycolysis, Overall Reaction
• Glycolysis generates 2 ATP and 2 NADH
• Two ATP are used in energy-investment to add phosphate groups
to glucose and fructose-6-phosphate
• Four ATP are formed in energy-generation by direct transfers of
phosphate groups to four ADP
Overall Reaction:
Glucose + 2ADP + 2Pi + 2NAD+

2Pyruvate + 2ATP + 2NADH +
4H+

45. Regulation of Glycolysis
• The amount of glucose that goes through glycolysis is
regulated based on relative levels of ATP, ADP and AMP,
as well as other glycolysis intermediates
• This regulation takes place at three steps:
- Reaction 1: Hexokinase is inhibited by high levels of
glucose-6-phosphate, which prevents the phosphorylation of
glucose
- Reaction 3: Phosphofructokinase, an allosteric enzyme, is
inhibited by high levels of ATP and activated by high levels
of ADP and AMP
- Reaction 10: Pyruvate kinase, another allosteric enzyme
is inhibited by high levels of ATP or acetyl CoA