The document discusses carbohydrate metabolism. It defines metabolism as all the chemical reactions occurring inside a cell and divides it into catabolism, the breakdown of molecules, and anabolism, the synthesis of molecules. Glucose is an important carbohydrate that can be broken down through glycolysis and the Krebs cycle to generate energy. The major pathways of carbohydrate metabolism include glycolysis, the Krebs cycle, gluconeogenesis, glycogenesis, and glycogenolysis. Glucose metabolism and the role of the liver in regulating blood glucose levels are also described.

1. Mr. Abhijit Bhoyar
Assistant Professor
Department of
Child Health Nursing
Metabolism
CARBOHYDRATE
Part-I

2. Specific Learning Objectives
At the end of the lecture, the students will be able to
• Define the metabolism.
• List down categories of metabolism
• Enumerate basic functions of metabolism.
• Explain the biomedical importance of Glucose.
• Describe the metabolism of carbohydrates.
• Explain the major pathways of carbohydrate metabolism.

3. Introduction
• Hundreds of reactions simultaneously take place in a
living cell, in a well-organized and integrated manner.
• The entire spectrum of chemical reactions, occurring in
the living system, are collectively referred to as
metabolism.

4. Definition of Metabolism
All the chemical
reactions taking
place inside a
cell are
collectively
known as
METABOLISM

5. A metabolic pathway (or metabolic map)
It constitutes a series of
enzymatic reactions to produce specific products.
The term metabolite is applied to a substrate or
an intermediate or a product in the metabolic
reactions.

7. Metabolism is broadly divided into two
categories
The degradative processes
concerned with the breakdown of
complex molecules to simpler
ones, with a concomitant release
of energy.
The biosynthetic reactions
involving the formation of
complex molecules from simple
precursors.
CATABOLISM ANABOLISM
Metabolism

8. Amphibolism
The term amphibolism is also in
use for reactions which are both catabolic and anabolic
in nature.

9. Catabolism occurs in three stages
1. Conversion of complex molecules into their
building blocks :
• Polysaccharides are broken down to monosaccharides,
• Lipids to free fatty acids and glycerol
• Proteins to amino acids.

10. Cont….
2. Formation of simple intermediates :
• The building blocks produced in stage (1) are
degraded to simple intermediates such as pyruvate
and acetyl CoA.
• These intermediates are not readily identifiable as
carbohydrates, lipids or proteins.
• A small quantity of energy (as ATP) is captured in stage
2.

11. Cont….
3. Final oxidation of acetyl CoA :
• Acetyl CoA is completely oxidized to CO2, liberating NADH
(Nicotinamide Adenine Dinucleotide) and FADH2 (Flavin
adenine dinucleotide) that finally get oxidized to release
large quantity of energy (as ATP).
• Krebs cycle (or citric acid cycle) is the common metabolic
pathway involved in the final oxidation of all energy-rich
molecules.
• This pathway accepts the carbon compounds (pyruvate,
succinate etc.) derived from carbohydrates, lipids or
proteins.

12. Basic
functions of
metabolism

13. Biomedical Importance Of Glucose
• Glucose is a major carbohydrate
• It is a major fuel of tissues
• It is converted into other carbohydrates
Glycogen for storage.
Ribose in nucleic acids.
Galactose in lactose of milk.

14. Cont….
They form glycoproteins & proteoglycans
They are present in some lipoproteins (LDL) .
Present in plasma membrane.

15. Metabolism of Carbohydrates
• It is a fundamental biochemical process that
ensures a constant supply of energy to living cells.
• The most important carbohydrate is glucose, which can
be broken down via glycolysis, enter into the Kreb's
cycle and oxidative phosphorylation to generate
ATP.

16. Cont….
• Carbohydrates are the major source of energy for
the living cells.
• As such, carbohydrates are the first cellular
constituents, synthesized by green plants during
photosynthesis from carbon dioxide and water, on
absorption of light.
• Thus, light is the ultimate source of energy for all
biological processes.

17. Cont….
• The monosaccharide glucose is the central
molecule in carbohydrate metabolism since all the
major pathways of carbohydrate metabolism are
connected with it.
• Glucose is utilized as a source of energy, it is
synthesized from non-carbohydrate precursors and
stored as glycogen to release glucose as and when
the need arises.
• The other monosaccharides important in carbohydrate
metabolism are fructose, galactose and mannose.

18. Cont….
• The fasting blood glucose level in normal individuals
is 70-100 mg/dl (4.5-5.5 mmol/l).
• Liver plays a key role in monitoring and stabilizing
blood glucose levels.
• Thus liver may be appropriately considered as
glucostat monitor.

19. Major pathways of carbohydrate metabolism
1. Glycolysis (Embden-Meyerhof Parnas) EMP
Pathway : Glycolysis is the process in which glucose is
broken down to produce energy. The oxidation of
glucose to pyruvate and lactate.
2. Citric acid cycle (Krebs cycle or tricarboxylic acid
cycle) : The oxidation of acetyl CoA to CO2. Krebs
cycle is the final common oxidative pathway for
carbohydrates, fats or amino acids, through acetyl CoA.

20. Cont….
3. Gluconeogenesis : The synthesis of glucose from non-
carbohydrate precursors (e.g. amino acids, glycerol etc.).
4. Glycogenesis : The formation of glycogen from glucose.
5. Glycogenolysis : The breakdown of glycogen to
glucose.
6. Hexose monophosphate shunt (pentose phosphate
pathway or direct oxidative pathway) : This pathway is
an alternative to glycolysis and TCA cycle for the
oxidation of glucose (directly to carbon dioxide and
water).

21. Cont….
7. Uronic acid pathway : Glucose is converted to
glucuronic acid, pentoses and, in some animals, to
ascorbic acid (not in man). This pathway is also an
alternative oxidative pathway for glucose.
8. Galactose metabolism : The pathways concerned
with the conversion of galactose to glucose and the
synthesis of lactose.

22. Cont….
9. Fructose metabolism : The oxidation of fructose to
pyruvate and the relation between fructose and glucose
metabolism.
10. Amino sugar and mucopolysaccharide metabolism :
The synthesis of amino sugars and other sugars for the
formation of mucopolysaccharides and glycoproteins.

23. Summary
So far today we have discussed
definition, categories of metabolism, basic functions of
metabolism, biomedical importance of Glucose,
metabolism of carbohydrates and major pathways of
carbohydrate metabolism.

24. Expected Questions
LAQ
Describe the metabolism of carbohydrates.
SAQ
• Explain the biomedical importance of Glucose.
• Describe the metabolism of carbohydrates.
• Explain the major pathways of carbohydrate metabolism.

25. Cont.….
Very Short
• Define the metabolism.
• List down categories of metabolism
• Enumerate basic functions of metabolism.

26. • Jacob Anthikad, Biochemistry for nurses.
• Pankaja Naik, Essentials of Biochemistry.
• Satyanarayan, Essentials of Biochemistry.
• A. C. Deb, Biochemistry.
References