1) Carbohydrates are composed of carbon, hydrogen, and oxygen. They can be classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides depending on their sugar unit composition. 2) Carbohydrates provide dietary energy and are important for energy storage. They also participate in cellular structure and function. 3) Glycolysis and the citric acid cycle are key pathways in carbohydrate metabolism that generate energy through the oxidation of glucose. Glycolysis yields pyruvate which feeds into the citric acid cycle in the mitochondria to fully oxidize glucose.

1. CARBOHYDRATES
-Dr. Rushikesh K Joshi
MPT ( Neuro.)

2. Introduction
 Carbohydrates are composed of carbon,
hydrogen and oxygen.
 CARBOHYDRATES – “hydrates of carbon..“
 Emperical formula for carbohydrates can be
written as (CH2O)n… n=1,2,3…….

3. Contd..
 Examples-
Glucose
Fructose
galactose
Starch
cellulose etc....

4. Functions of carbohydrates
 Dietary sources of energy (calorific value
4cal/gm) for all organisms.
 Precursors of organic compounds like fats,
amino acids...
 Carbohydrates ( as glycoprotein and
glycolipids) participate in the structure of cell
membrane and cellular functions..

5. Contd..
 These are storage form of energy for energy
in the form of GLYCOGEN..
 Structural components of many organisms
like cell walls of bacteria, cellulose of plants.

6. Sources of carbohydrates

8. Classification of
carbohydrates
 Carbohydrates are divided into FOUR main
groups depending upon the number of
MONOMER units (e.g- CH2O) present in the
molecule.
 Broadly the carbohydrates are classified into
four groups as follows -->

10. Monosaccharides
 Also called as ‘SIMPLE’ SUGARS…
 They are the simplest form of carbohydrates,
which cannot be further hydrolysed into
simpler forms.
 Emperical formula – Cn H2n On
 Monosaccharides can be further divided into
following…

11. Contd..
 Depending upon the number of carbon
atoms , they can be subdivided into 
Monosaccharides
Trioses Tetroses Pentoses Hexoses
Heptose
s

12. Contd..
 Trioses – 3 carbons
 Tetroses – 4 carbons
 Pentoses- 5c
 Hexoses – 6 c
 Heptoses- 7c
Further if we see, if this can combine with either
an aldehyde or with ketone group.. 

15. Disaccharides
 These are those sugars which gives 2
molecules of monosaccharides on hydrolysis.
 These two units of monosaccharides are
joined by a GLYCOSIDIC BOND.. !!!
 Examples –
maltose
lactose
sucrose

16. Contd..
 Maltose  glucose + glucose
 Lactose  glucose + galactose
 Sucrose  glucose + fructose

17. Oligosaccharides
 These are those sugars which yield 3-10
monosaccharide units on hydrolysis..
 Examples-
 Raffinose
 Stachyose

18. Contd..
 Raffinose  fructose + galactose + glucose
 Stachyose  2(galactose) + glucose +
fructose

19. Polysaccharides
 These are those sugars which yield more than
10 molecules of monosaccharides on
hydrolysis.
 Polysaccharides can be further classified into
two types based on the type of
monosaccharide units present in the chain of
molecules.

21. Contd..
 Homopolysaccharides –
Also known as ‘ homoglycans’.
These are the polymers of the same monosaccharide
units.
Examples-
Starch
Glycogen
Inulin
Cellulose
dextrin

22. Contd..
 Heteropolysaccharides –
also known as ‘ heteroglycans’ .
these are polymers of different
monosaccharide units.
Examples-
heparin
chondroitin sulphate

23. In short…

25. Metabolism
 Metabolism  all chemical reactions in the
body.
 But, further it is important to understand that
reactions can be of mainly two types.
 They can either be synthetic in nature or they
can be reactions which breakdown
 Based on this concept, there are two main
types 

26. Contd..
Reactions
Anabolic
( synthetic)
Catabolic
(breakdown)

27. Anabolism
 Chemical reactions that combine simple
substances into more complex molecules
 This reactions help in the synthesis of
substances in the body
 E.g – Formation of peptide bonds between
amino acids  formation of PROTEINS..
-Glucose into GLYCOGEN..

28. Catabolism
 The chemical reactions that breakdown
complex organic compounds into simple
ones.
 E.g – Digestion of food molecules
breakdown of bonds  release of energy.
- generally these reactions are hydrolysis
reactions that release chemical energy..

29. Carbohydrate metabolism
 This includes the metabolism of glucose.
 During digestion, polysaccharides and
disaccharides are HYDROLYSED into
monosaccharides ( glucose), fructose and
galactose.
 These monosaccharides are ultimately
converted into glucose in the LIVER cells.

30. Fate of carbohydrates
 ATP Production- calorific value of glucose is
4Kcal/gm..
 Amino acid synthesis- glucose used to form
amino acids  proteins.
 Glycogenesis- liver stores excess glucose by
converting it into glycogen by Glycogenesis.
Later, when decrease in blood glucose 
glycogen converted to glucose by
glycogenolysis.

31. Contd..
 Lipogenesis- if glycogen storage is filled up,
liver cells can transform the glucose to
glycerol and fatty acids  formation of
triglycerides ( lipogenesis)

32. Glycolysis
 It is also known as EMP pathway ( Embden-
Meyerhof Parnas pathway)
 In glycolysis, a molecule of glucose is
degraded in a series of enzyme catalyzed
reactions to yield two molecules of
PYRUVATE.
 During this reactions, some of the free energy
liberated from glucose is conserved in the
form of ATP.

33. Contd..
 This process of catabolism of glucose occurs
either in presence of oxygen to pyruvic
acid(i.e pyruvate ) ( AEROBIC GLYCOLYSIS) or
during the lack of oxygen to lactate ( i.e lactic
acid) (ANAEROBICGLYCOLYSIS).
 GLYCOLYTIC ENZYMES are present in the
extramitochondrial compartment of the cell.
 Aerobic glycolysis occurs in all the tissues like
liver, kidney and erythrocytes.
 While anaerobic glycolysis takes place only in
MUSCLE.

35. Importance of glycolysis
 Energy production
 ProducesATP even in absence of Oxygen
(anaerobic glycolysis).This allows skeletal
muscles to perform efficiently even when
aerobic oxidation becomes insufficient.
 Deficiency of pyruvate kinase produces the
disease haemolytic anemia.

36. Energy production
 Glucose to glucose-6-phosphate  -1 ATP
 Fructose-6-phosphate to fructose 1,6-
diphosphate  -1 ATP
 Glyceraldehyde 3-phosphate to 1,3-
biphosphoglyecradehyde  2NADH2
2*3ATP= 6ATPs
 Phosphoglycerate kinase 2ATP
 Pyruvate kinase2ATP
 NET YIELD= 6+2+2-1-1=8ATPs.

37. Metabolism as a whole..

38. TCA cycle(Kreb’s/Citric
acid)
 Site of reaction- mitochondria
 Consists of a series of reactions in
mitochondria which catalyses the oxidation
of Acetyl CoA and giving out ENERGY..
 It is the FINAL COMMOM PATHWAY for
metabolism of carbohydrates, fats and
proteins.
 It is mechanism by which much of free energy
is liberated .

40. Production of Acetyl coA
from pyruvate(AEROBIC
CONDITION)
• Pyruvate
2molecules
• 2NAD+2N
ADH2
Pyruvate
dehydrogenase
• Acetyl
co-A
2molecules

41. Production of Lactic acid
from pyruvate(AN-AEROBIC
CONDITION)
• PYRUVATE • NADH2N
AD
LACTATE
DEHYDROGEN
ASE • LACTIC
ACID

42. Major functions of kreb’s
cycle
 most of the CO2 made in human tissues
through this cycle.
 Source of coenzymes for further chain
reactions
 Provides precursors for the synthesis of
proteins and fatty acids.
 Components of this cycle controls the other
enzyme systems.

43. Energy production
 Isocitrate Alpha keto glutarate -
1NADH23ATPs
 Alpha keto glutaratesuccinyl CO-
A1NADH23ATPs
 Succinyl coAsuccinate 1GTP1ATP
 Succinatefumarate1FADH22ATPs
 Malateoxaloacetate1NADH23ATPs
 NETYIELD OF ATP 3+3+1+2+3= 12ATPs

44. Contd..
 So, now we know that 1molecule of pyruvate
gives 12ATPs.
 As we know that in glycolysis, 2pyruvate
molecules are produced.
 So, 2molecules of acetyl coA is produced.
 NET PRODUCTION from 2acetyl coA will be
12*2= 24ATPs

45. NET YIELD DURING COMPLETE
OXIDATION OF 1 MOLECULE OF
GLUCOSE
 38 MOLECULES OF ATP
 Glycolysis8ATP
 Pyruvateacetyl coA  6ATP
 TCA Cycle  24 ATP

46. Biological significance of
citric acid cycle
 Plays dual role  oxidation + synthesis
 Catabolic + anabolic
 Catabolic  oxidation of carbohydrates.
Lipids and proteins  release of energy
 Anabolic  biosynthesis of amino acids and
glucose.