Carbohydrate is an organic compound that consists only of carbon (C), hydrogen & oxygen. The primary function of carbohydrates is to provide energy for the body. Simple carbohydrates have one or two sugar molecules. Complex carbohydrates have three or more sugar molecules, such as legumes, bread, rice, pasta.

1. CARBOHYDRATES
Miss AMANJOT KAUR
MSN, CCN.

2. CARBOHYDRATES
Carbohydrate is an organic compound that
consists only of carbon (C), hydrogen & oxygen.
The primary function of carbohydrates is to
provide energy for the body.
Simple carbohydrates have one or two sugar
molecules.
Complex carbohydrates have three or more sugar
molecules, such as legumes, bread, rice, pasta.

3. Classification of carbohydrates
•Monosaccharides
•Disaccharides
•Oligosaccharides
•Polysaccharides

4. 1. MONOSACCHARIDES
Monosaccharides are simple sugars which cannot be
hydrolyzed into a simpler form. Common
monosaccharides have functional group, i.e. aldoses
and ketoses.
Aldoses: Monosaccharide having an aldehyde group.
(CHO) as the functional group. For example,
glyceraldehyde, glucose, galactose, etc.
Ketoses: Monosaccharides having keto group (C=O) as
the functional group. For example, ribulose, fructose
etc.

5. 2. DISACCHARIDES
Disaccharides are carbohydrates that can be
hydrolyzed into two units of monosaccharides.
e.g. Maltose, Lactose & sucrose

6. 3. OLIGOSACCHARIDES
•They yield 2 to 10 monosaccharides molecules on
hydrolysis.
- An example is ABO blood type specificity. Fructose,
Mannose & Glucose residues attached on RBC cell
surface contribute to the antigenticity of ABO blood
groups.

7. 4. POLYSACCHARIDES
•They consist of repeated units of monosaccharides or
their derivatives held together by glycosidic bond.
They are of two types:
1. Monopolysaccharides: These are made-up of
same type of monosaccharides. E.g. starch,
cellulose etc.
2. Heteropolysaccharides: These are made-up of
different type of monosaccharides. E.g. hyaluronic
acid, heparin.

8. FUNCTIONS OF CARBOHYDRATES
•Carbohydrates are the main source of energy in the
body. When carbohydrates are oxidized, are they
liberate CO₂, water and energy.
•They serve as storage form of energy (glycogen).
•Certain carbohydrates are the starting materials for
the biological synthesis of fatty acids and amino
acids.
•Certain products of carbohydrate metabolism acts as
catalyst to promote oxidation of food stuffs.

9. FUNCTIONS OF CARBOHYDRATES
•Carbohydrates like glycoproteins and glycolipids
participate in the structure of cell membrane.
•Carbohydrates are the structural components of
many organisms. Example, cellulose of plants, cell
wall of microorganisms.
•Carbohydrates save proteins from being used in
the production of energy.

10. DIGESTION OF CARBOHYDRATES
•Digestion is the process of breakdown of large
and complex organic molecules into simpler
forms.
•Digestion of carbohydrates is mainly of three
types i.e. polysaccharides (starch and glycogen),
disaccharides (sucrose, lactose, maltose) and
monosaccharides (glucose and fructose).

11. Contd…
•The monosaccharide is absorbed without any
change while polysaccharides and disaccharides
need digestion process to be converted into
monosaccharide.
•Digestion happens at different levels in gastro-
intestinal tract by help of different digestive
enzymes which convert carbohydrates into
simpler forms.

12. DIGESTION OF CARBOHYDRATES
In mouth, salivary amylase converts polysaccharides
into simpler carbohydrates
Then, moves on to stomach and no such carbohydrate
digestion occurs there.
Further, pancreatic amylase converts complex
carbohydrates into simpler carbohydrates for digestion.

13. Contd…

14. ABSORPTION OF CARBOHYDRATES
Simplest form of carbohydrates, monosaccharide i.e.
glucose, fructose and mannose are absorbed at jejunum.
Fructose is absorbed more slowly then glucose and
galactose. The monosaccharide is absorbed through
following two mechanisms:
1. Facilitative transport (with the concentration
gradient): Generally, all the monosaccharide i.e. fructose,
glucose and galactose are absorbed by the diffusion with
concentration gradient by means of sodium-dependent
facilitative transporter.

15. Contd…
•Active transportation (against concentration
gradient): When concentration fall and not
favourable then, absorption of glucose is done by
active transportation. The active transportation
happen by the help of sodium linked glucose
transporter (SLGT-1). This transporter binds both
glucose and sodium at separate sites and transport
across plasma membrane and needs energy which is
provided from hydrolysis of ATPs.

16. METABOLISM OF CARBOHYDRATES
•Digestion process converts all carbohydrates like
polysaccharides and disaccharides to
monosaccharides into gut. Then these
monosaccharides are converted to glucose in the
liver. So liver is first filter of carbohydrates and
has major role in storage and distribution. There
are numerous metabolic pathways from
beginning to the end.

17. METABOLISM OF CARBOHYDRATES
•Carbohydrates are not only obtained from food but
are also produced in body. Amino acids, glycerol, etc.
are the different components from which synthesis of
carbohydrates takes place.
•The chemical reactions which occurs in the body are
mainly divided into three pathways:
a. Catabolic pathways: Catabolic pathways are those
which result in breaking down of compounds:
-Glycolysis
-Glycogenolysis

18. METABOLISM OF CARBOHYDRATES
b. Anabolic pathways: Anabolic pathways are
those which build compounds or synthesize
substances for the body:
-Gluconeogenesis
-Glycogenesis
c. Amphibolic pathway: It has a dual role: both
catabolic and anabolic.
- TCA cycle

19. GLYCOLYSIS
Glycolysis means breakdown of glucose or sugar. It is a
set of reactions in which one glucose molecule
produces two pyruvic acid molecules, 2 molecules of
ATP, 2 molecules of NADH (Nicotinamide adenine
dinucleotide) and 2 molecules of water. In the
glycolysis pathway, the breakdown of six-carbon
glucose (C₆H₁₂O₆) into two molecules of three-carbon
compound pyruvate (C₃H₆O₃) takes place.
Site: It occurs in the cytosol of the cell.

20. GLYCOLYSIS
Importance:
•It provides fuel in the form of ATP and
intermediates for metabolic pathways.
•It can operate both in aerobic and anaerobic
conditions forming different end products.
•It is the fastest pathway for supplying energy.

21. GLYCOLYTIC PATHWAY

22. Reactions of Aerobic Glycolysis or glucose
1. In the first step, the glucose is irreversibly activated to glucose-6-phosphate in the
cell. This step is catalyzed by hexokinase enzyme. This requires Mg2+ and ATP.
In liver, glucokinase is the specific enzyme which also catalyzes this reaction at
higher concentration of glucose. Glucose-6 phosphate is impermeable to the cell
membrane. It is a central molecule with a variety of metabolic fates, such as
glycolysis, cogenesis, gluconeogenesis and HMP shunt.
2. Next the glucose-6-phosphate is isomerized to fructose-6-phosphate by
phosphohexose isomerase enzyme.
3. Fructose-6-phosphate is then irreversibly phosphorylated by phosphofructokinase
enzyme to fructose 1,6-bisphosphate. Fructose 1,6-bisphosphate contains two
phosphoric acid groups at C1 and C6 via phosphate ester bond.
4. Later, fructose 1, 6-bisphosphate molecule (six carbon sugar) is cleaved by
aldolase enzyme to yield glyceraldehyde-3-phosphate and dihydroxy acetone
phosphate (2, 3-carbon sugars-trioses).
5. Dihydroxyacetone phosphate formed in the above step is converted back
glyceraldehyde 3-phosphate by phosphotriose isomerase enzyme.

23. Reactions of Aerobic Glycolysis or glucose
6. Now we have two molecules of glyceraldehyde-3-phosphate
molecules, which get oxidized to 1,3-bisphosphoglycerate by the action
of gluteraldehyde 3-phosphate dehydrogenase enzyme. This step utilizes
glyceraldehyde to convert glyceraldehyde 3-phosphate into 1, 3 bis
phosphoglycerate to convert inorganic phosphoglycerate.
In 1, 3-bisphosphoglycerate the phosphate group 3-bisphosphoglycerate.
at carbon atom number 1 is high-energy group. Iodoacetate and arsenite
inhibit the enzyme glyceraldehyde 3-phosphate dehydrogenase. During
oxidation of glyceraldehyde-3-phosphate the reducing equivalents are
transferred to the acceptor NAD (nicotinamide adenine dinucleotide)
enters into mitochondria and The (reduced) NADH under aerobic
conditions enters & produces three molecules of ATP through its passage
into electron transport or respiratory chain. This type of formation of
energy currency ATP chain or through respiratory chain is called as
oxidative phosphorylation.

24. Reactions of Aerobic Glycolysis or glucose
7. In the next step, the high-energy compound 1,3-bisphosphoglycerate
transfers its high-energy to ADP to form ATP resulting in the formation of 3-
phosphoglycerate. This reaction is catalyzed by phosphoglycerate kinase
enzyme. This type of formation of energy from ATP by high-energy substrate is
called as substrate level phosphorylation.
8. 3-phosphoglycerate is then isomerized to 2-phosphoglycerate by
phosphoglycerate mutase enzyme.
9. 2-phosphoglycerate is then converted to one more high-energy compound
called phosphoenolpyruvate. This reaction is catalyzed by enolase enzyme.
The activity of this enzyme is completely inhibited by fluoride. Hence, fluoride
is used during blood collection for glucose estimation. This prevents the
utilization of glucose by red blood cell (RBC).
10. Later phosphoenolpyruvate is converted to pyruvate by pyruvate kinase
enzyme. In this step one molecule of ATP is formed by substrate level
phosphorylation

25. Reactions of Aerobic Glycolysis
Under aerobic conditions pyruvate is the end
product of glycolysis. Hence, pyruvate is then
converted into acetyl-CoA or oxaloacetate in the
mitochondria.

26. Anaerobic glycolysis
Under anaerobic condition pyruvate is reduced to lactate by
lactate dehydrogenase enzyme. This step utilizes the reducing
equivalent from NADH (Nicotinamide adenine dinucleotide) formed
in the earlier step and regenerates NAD+. Thus, the number of
ATP produced will be less in anaerobic condition.
Lactate accumulation in muscle leads to muscle cramps and
fatigue. In thiamine deficient alcoholics, pyruvate is rapidly
converted to lactate resulting in lactic acidosis.

27. Energetics of Glycolysis
1. Anaerobic glycolysis:
Energy spent/molecule of glucose =
i. Hexokinase 1 ATP
ii. PFK 1 ATP
Total = 2 ATP
Energy generated/molecule of glucose =
i. Phosphoglycerate kinase 1 ATP × 2 = 2 ATP
ii. Pyruvate kinase 1 ATP x2 = 2 ATP
Total = 4 ATP
Therefore NET GAIN OF ATP= 4-2 = 2 ATP

28. Energetics of Glycolysis
2. Aerobic glycolysis
Energy spent/molecule of glucose =
i. Hexokinase 1 ATP
ii. PFK 1 ATP
Total = 2 ATP
Energy generated/molecule of glucose =
i. Glyceraldehyde 3-Ph DH 1 x NADH x 2 = 3x2 = 6 ATP
ii. Phosphoglycerate kinase 1 ATP x 2 = 2 ATP
iii. Pyruvate kinase 1 ATP x 2 = 2 ATP
Total = 10 ATP
Therefore NET GAIN = 10-2 = 8 ATP

29. TRICARBOXYLIC ACID CYCLE (KREB'S
CYCLE OR CITRIC ACID CYCLE)
Significance:
Tricarboxylic acid (TCA) is a final common pathway for
oxidation of carbohydrates, fats and proteins. It provides
abundant ATP for the body and also provides substrates
for respiratory chain. It is amphibolic in nature showing
both catabolic and anabolic features. Since final common
oxidation takes place in this cycle, it is called catabolic.
TCA cycle provides substrates for synthesis of heme,
nonessential amino acids, fats, glucose, etc., and hence
called anabolic.

30. TRICARBOXYLIC ACID CYCLE (KREB'S
CYCLE OR CITRIC ACID CYCLE)
Features:
TCA cycle oxidizes acetyl-CoA to CO₂, and H₂O with
liberation of energy. It is strictly aerobic and purely
mitochondrial.
Sources of Acetyl-CoA:
• Fatty acid
• Pyruvate
• Glucose
• Ketogenic amino acids

31. TRICARBOXYLIC ACID CYCLE (KREB'S
CYCLE OR CITRIC ACID CYCLE)

32. TRICARBOXYLIC ACID CYCLE (KREB'S
CYCLE OR CITRIC ACID CYCLE)

33. TRICARBOXYLIC ACID CYCLE (KREB'S CYCLE
OR CITRIC ACID CYCLE)

34. ENERGY LIBERATING STEPS

35. REACTIONS OF TCA CYCLE

36. GLUCONEOGENESIS
Gluconeogenesis is the synthesis of glucose
from noncarbohydrate precursors. Substrates
for gluconeogenesis are lactate, pyruvate,
glucogenic amino acids as major substrates
and to a lesser extent propionate and
glycerol.

37. GLUCONEOGENESIS

38. GLUCONEOGENESIS

39. Physiological significance of gluconeogenesis
•Maintenance of blood glucose level especially under
conditions of starvation.
•Brain has a minimum need of 120 grams of glucose
per day. The body stores of glycogen are depleted
within first 12-18 hours of fasting.
•On prolonged starvation, gluconeogenesis is speeded
up.

41. Cori’s Cycle or Lactic Acid Cycle
Lactic acid is the major end product in muscle in
anaerobic glycolysis. Muscle tissue is incapable of
resynthesizing glucose from lactate. The conversion
takes place entirely in the liver. Muscle lactate is
transported to the liver by the blood. In the liver, it is
converted to glucose and glycogen by the enzymes
concerned in gluconeogenesis.
Liver glycogen is converted to glucose which is carried
back to muscle by blood. This conversion of muscle
lactate to glucose in liver and its re-entry into muscle is
called "Cori's Cycle.

42. GLYCOGEN METABOLISM
•Glycogen is stored in liver and muscle in cytoplasm as
granules. Liver glycogen is concerned with export of
glucose for circulation to maintain blood sugar and
muscle glycogen provides glucose for glycolysis within
the muscle itself providing energy during exercise.
Metabolism of glycogen:
a. Synthesis (glycogenesis)
b. Breakdown (glycogenolysis)

43. Glycogenesis (Synthesis of
Glycogen)
Glycogenesis occurs in liver and muscle
when plenty of glucose is available. It is a
cytosolic pathway requiring ATP and UDP
glucose.
Glycogenesis is the formation of glycogen
from glucose.

44. Glycogenesis (Synthesis of Glycogen)

45. Glycogenesis (Synthesis of Glycogen)

46. Glycogenesis (Synthesis of Glycogen)
3. Formation of branches:
•It involves "branching enzyme” (glycosyl alpha 4-6
transferase)
•It transfers a linear chain of 6-8 glucose residues to
another chain of glucose, forming a- 1,6 linkage,
thus branching takes place.
•To the newly formed branch, glycogen synthase
again adds glucose units by a, 1-4 linkages with
further branching and elongation to form glycogen.

47. Glycogenesis (Synthesis of Glycogen)
•Then, this glucose is transferred to a
glycogen primer (glycogenin) molecule
which is the acceptor of glycosyl unit.
•Then, glucose unit is added to the outer
(non-reducing) end of glycogen primer to
form alpha 1,4 glycosidic linkage or glycogen
and UDP is liberated.

48. Glycogenolysis

49. Glycogenolysis

50. Glycogenolysis

51. Glycogenolysis
•Debranching enzyme has two activities:
i. Glucan transferase activity: It transfers a block of 3
glucose residues to another chain. Now branch point
is exposed.
ii. α, 1-6 glucosidase activity: It hydrolyses α, 1-6 linkage
at branch point, releasing free glucose.

52. BLOOD GLUCOSE AND ITS REGULATION
•Blood sugar regulation is the process by which the
levels of blood sugar, primarily glucose are
maintained by the body. The maintenance of
glucose level in blood within narrow limits is a
finely And efficiently regulated system. This is
important because it is essential to have
continuous supply compound, glucose to the
brain. Mechanisms of Blood Sugar Regulation:

53. BLOOD GLUCOSE AND ITS REGULATION
•Blood sugar levels are regulated by negative feedback
in order to keep the body in homeostasis. Levels of
glucose in the blood are monitored by the cells in the
pancreas's Islets of Langerhans.
•The blood glucose level falls to dangerous levels (as
in very heavy exercise or lack of food), the Alpha cells
of the pancreas release glucagon, a hormone whose
effects on cells act to increase blood glucose levels.
•They convert glycogen into glucose (this process is
called glycogenolysis). The glucose is released into
the bloodstream, increasing blood sugar levels.

54. BLOOD GLUCOSE AND ITS REGULATION
•When levels of blood sugar rise, whether as a
result of glycogen conversion, or from digestion of
a meal, a different hormone is released from beta
cells found in the Islets of Langerhans in
pancreas.
•This hormone, insulin, causes the liver to convert
more glucose into glycogen (this process is called
glycogenesis), and to force about 2/3 of body cells
(primarily muscle and fat cells) to take-up glucose
from the blood through the GLUT4 transporter,
thus decreasing blood sugar.

55. BLOOD GLUCOSE AND ITS REGULATION
•When insulin binds to the receptors on the cell surface,
vesicles containing the GLUT4 transporters come to the
plasma membrane and fuse together by the process of
exocytosis, thus enabling a facilitated diffusion of
glucose into the cell.
•As soon as the glucose enters the cell, it is
phosphorylated into Glucose-6-Phosphate in order to
preserve the concentration gradient so glucose will
continue to enter the cell.
•Insulin also provides signals to several other body
systems, and is the chief regulatory metabolic control in
humans.

56. BLOOD GLUCOSE AND ITS REGULATION
•There are also several other causes for an increase in
blood sugar levels. Among them are the 'stress'
hormones such as epinephrine (also known as
adrenaline), several of the steroids, infections, trauma,
and of course, the ingestion of food.

57. HYPOGLYCEMIA
•Hypoglycemia is a condition that occurs when
blood sugar (glucose) is too low. Blood sugar
below 70 mg/dl is considered low and termed as
Hypoglycemia.

58. Causes and Risk Factors of Hypoglycemia
•Taking insulin or diabetes medicine at the wrong time
•Taking too much insulin or diabetes medicine by
mistake
•Not eating enough during meals or snacks after taken
insulin or diabetes medicine
•Skipping meals
•Waiting to eat meals after insulin
•Exercising more or at a different time than usual
•Drinking alcohol

59. Symptoms of Hypoglycemia
•Double vision or blurred vision
•Fast heartbeat
•Feeling or acting aggressive
•Feeling nervous
•Headache
•Hunger
•Shaking
•Trouble in Sleeping

60. Symptoms of Hypoglycemia
•Sweating
•Tingling or numbness of the skin
•Tiredness or weakness
•Unclear thinking.
Sometimes blood sugar may be too low, even without
having symptoms. If blood sugar gets too low, patient
may:
•Faint
•Have a seizure or Go into a coma.

61. Diagnosis of Hypoglycemia
•Random Blood Sugar: Show readings lower than
70 mg/dL.

62. Treatment of Hypoglycemia
•Treatment primarily depends on the cause.
•If blood sugar is low (70 mg/dL), treat it right away.
•Give about 15 grams of carbohydrates. Examples are: A
1/2 cup (4 ounces) of fruit juice or regular, non-diet
soda, 5 or 6 hard candies, 1 tablespoon sugar, plain or
dissolved in water, 1 tablespoon honey or syrup. Wait
about 15 minutes before giving anything else. Be
careful not to over-treat by eating too much. This can
cause high blood sugar and weight gain.

63. Treatment of Hypoglycemia
•Check blood sugar again: If person does not feel
better in 15 minutes and blood sugar is still low
(less than 70 mg/dL), eat something that has 15
grams of carbohydrates again.
•Person may need to eat a snack that has
carbohydrates and protein if blood sugar is in a
safer range (over 70 mg/dL) and next meal is
more than an hour away. If these steps for raising
your blood sugar do not work, plan to administer
5% dextrose Intravenously.

64. GLUCOSE TOLERANCE TEST (GTT)
•The glucose tolerance test is a laboratory method
to check how the body breaks down (metabolizes)
sugar. The glucose tolerance test is aid to
diagnosis in diabetes mellitus. If the glucose level
peak at Higher than normal level at 1 and 2 hours
after injection or ingestion of glucose and are
slower than normal to return to fasting levels, then
diabetes mellitus is confirmed. The most common
glucose tolerance test is:

65. GLUCOSE TOLERANCE TEST (GTT)
•The oral glucose tolerance test (OGTT):
Person cannot eat or drink anything for at
least 8 hours before the test For the test,
after taking a fasting blood sample of patient,
he/she is asked to drink a liquid containing a
certain amount of glucose (usually 75 grams).
Then blood samples are taken every 30 to 60
minutes after drinking the glucose solution.
The test takes up to 3 hours.

66. GLUCOSE TOLERANCE TEST (GTT)
• The intravenous glucose tolerance test (IGT): It is rarely used, and is
never used to diagnose diabetes. In this test, glucose is injected into
vein. Blood glucose levels are measured before the injection, and again
at 1, 2 and 3 hours after the injection. However, the timing may vary.
• Indications of GTT:
• Glucose tolerance tests are one of the tools used to diagnose diabetes.
• Diabetic patients with untreated diabetes have high blood glucose
levels.
• The oral glucose tolerance test is used to screen pregnant women for
gestational diabetes tors between 24 and 28 weeks of pregnancy.
• It may also be used when the diabetes is suspected, even though the
fasting blood glucose level normal.

67. GLUCOSE TOLERANCE TEST (GTT)
•Preparation for the Test:
•Make sure that patient eat normally for several days
before the test.
•Ensure that patient has not consumed anything for 8
hours before the test and patient do not eat during test
also.
•Certain medicines also may be discontinued which may
affect the test results such as steroids, morning dose of
insulin or oral hypoglycemic medicines, etc.

68. GLUCOSE TOLERANCE TEST (GTT)
•Interpretations of GTT:
•Blood values for a 75-gram oral glucose tolerance test
used to check for type 2 diabetes:
•Fasting: 60 and 100 mg/dL
•1 hour: less than 200 mg/dL
•Between 140 and 200 mg/dL is considered impaired
glucose tolerance or prediabetes. A glucose level of 200
mg/dl. or higher is a sign of diabetes.
•Normal blood values for a 100-gram oral glucose
tolerance test used to screen for gestational diabetes:
•Fasting: less than 95 mg/dL

69. GLUCOSE TOLERANCE TEST (GTT)
• 1 hour: less than 180 mg/dL
• 2 hour: less than 155 mg/dL
• 3 hour: less than 140 mg/dL
• Nursing Considerations:
• Instruct the patient to eat a high-carbohydrate (200-300 g) diet for 3 days
before the test.
• Instruct the patient to avoid alcohol, coffee and smoking for 36 hours before
test.
• Instruct the patient to fast for 8 to10 hours before test.
• Instruct the patient to avoid strenuous exercise for 8 hours before test and
after the test.
• Instruct the patient with diabetes mellitus to withhold morning insulin or oral
hypoglycemia medications.
• Instruct the patient that the test may take 3 to 5 hours requires IV or oral
administration of glucose and multiple blood samples.