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Unit 2 Carbohydrates
1. Program: B.Sc Nursing, Second Year
BNSG-201 Nutrition & Biochemistry
Unit No.2 Carbohydrates
Topic-Carbohydrates
Lecture No. 1
Dr. Sudharani B Banappagoudar
Professor, SONS/OBG
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3. Carbohydrates
Composed of carbon, hydrogen, and oxygen, and “constitute the main source of energy for
all body functions, particularly brain functions, and are necessary for the metabolism of other
nutrients” (Mosby 260).
Carbohydrate providing 4 Kcals per one gram Carbohydrate is also essential for the
oxidation of fats and for the synthesis of certain non-essential amino acids
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<SELO: 1,4,9,13>
<Reference No.: R1,R3>
5. Can you live without sugar?
Soda/Punch
Cookies
Candy
Chocolate
Desserts
Sugary Cereals
Ice cream
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<SELO: 1,4,9,13>
<Reference No.: R1,R3>
6. Carbohydrates
It is the easiest form of food to convert into energy.
Ingested carbohydrates are turned into glucose, which circulates in the bloodstream being readily
available, and into glycogen which is stored in the liver and muscle cells, for later use.
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<SELO: 1,4,9,13>
<Reference No.: R1,R3>
7. Carbohydrates
Energy Food
Starch, Sugar
Least Expensive
Plentiful Available
Easily Digested
Organic Compound,CnH2nOn
Widely distributed in plant food
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<SELO: 1,4,9,13>
<Reference No.: R1,R3>
8. CARBOHYDRATES
Carbohydrates give the body energy. They are the best source of fuel for the body.
Carbohydrates also help to digest protein and fat.
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<SELO: 1,4,9,13>
<Reference No.: R1,R3>
9. CARBOHYDRATES
Carbs
Protein
Fats
45-65% of our food should come from carbohydrates.
If we eat more carbohydrates than are needed for energy, the extra is stored in the liver or
in the tissues as fat.
11. Carbohydrate
Carbohydrate, class of naturally occurring carbonyl compounds (aldehydes or ketones) that
also contain several hydroxyl groups. It may also include their derivatives which produce such
compounds on hydrolysis. They are the most abundant organic molecules in nature and also
referred to as “saccharides”.
The carbohydrates which are soluble in water and sweet in taste are called as “sugars”.
They are the most abundant organic molecules in nature and also referred to as “saccharides”.
12. Objectives
<SELO: 1,4,9,13> <Reference No.: R1,R2>
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By the end of this chapter, you will be able to:
• Carbohydrates, Types, Digestion, Absorption, Metabolism
• Sources , Functions, RDA
• Deficiency
13. Introduction
Carbohydrates are one of the three main classes of foods and a source of energy.
Carbohydrates are mainly sugars and starches that the body breaks down into glucose
(a simple sugar that the body can use to feed its cells).
Carbohydrates are probably the most abundant and widespread organic substances in nature,
and they are essential constituents of all living things. Carbohydrates are formed by
green plants from carbon dioxide and water during the process of photosynthesis.
Carbohydrates serve as energy sources and as essential structural components in organisms; in
addition, part of the structure of nucleic acids, which contain genetic information, consists of
carbohydrate.
14. Carbohydrate
Composition
A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O)
atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with
the empirical formula Cm(H2O)n
.
15. Structural Representation of Carbohydrates
The carbohydrates can be structurally represented in any of the three forms:
1.Open chain structure.
It is the long straight-chain form of carbohydrates.
2.Hemi-acetal structure.
Here the 1st carbon of the glucose condenses with the -OH group of the 5th carbon to form a ring
structure.
3.Haworth structure.
It is the presence of the pyranose ring structure
16. Properties of Carbohydrates
1.Physical Properties of Carbohydrates
a. Stereoisomerism – Compound sharing the same structural formula but they differ in spatial
configuration. Example: Glucose has two isomers with respect to the penultimate carbon atom.
They are D-glucose and L-glucose.
b. Optical Activity – It is the rotation of plane-polarized light forming (+) glucose and (-) glucose.
c. Diastereo isomers – It the configurational changes with regard to C2, C3, or C4 in glucose.
Example: Mannose, galactose.
d. Annomerism – It is the spatial configuration with respect to the first carbon atom in aldoses and
second carbon atom in ketoses.
17. 2.Chemical Properties of Carbohydrates
a.Osazone formation: Osazone are carbohydrate derivatives when sugars are reacted with an excess
of phenylhydrazine. eg. Glucosazone
b.Benedict’s test: Reducing sugars when heated in the presence of an alkali gets converted to
powerful reducing species known as enediols. When Benedict’s reagent solution and reducing sugars
are heated together, the solution changes its color to orange-red/ brick red.
c.Oxidation: Monosaccharides are reducing sugars if their carbonyl groups oxidize to give carboxylic
acids. In Benedict’s test, D-glucose is oxidized to D-gluconic acid thus, glucose is considered a
reducing sugar.
d.Reduction to alcohols: The C=O groups in open-chain forms of carbohydrates can be reduced to
alcohols by sodium borohydride, NaBH4, or catalytic hydrogenation (H2, Ni, EtOH/H2O). The
products are known as “alditols”.
Properties of Carbohydrates
20. Simple Sugars
Glucose or blood sugar is the basic source of energy for all living things.
Sucrose or table sugar is made from sugar beets or sugar cane.
Fructose is sugar found in fruit, honey and vegetables.
Maltose is grain starch broken down into sugar.
Lactose is milk sugar.
23. Although a number of classification schemes have been devised for carbohydrates, the
division into four major groups—
1.Monosaccharides,
2.Disaccharides,
3.Oligosaccharides, and
4.Polysaccharides.
Classification of Carbohydrates
24. Monosaccharide
One Sugar Unit
Important Single Sugar are Glucose, Fructose, Galactose
Glucose (Dextrose):
Give Energy for body Activity
It is primary Fuel of Cell
It usually not found in Diet (Corn Syrup)
Produce from Starch.
26. Monosaccharides
Monosaccharides
The building blocks of all simplest group carbohydrates are simple sugars called monosaccharides
since they cannot be further hydrolyzed . A monosaccharide can be a polyhydroxy aldehyde (aldose)
or a polyhydroxy ketone (ketose). Colorless, crystalline solid which are soluble in water and
insoluble in a non-polar solvent. These are compound which possesses a free aldehyde or ketone
group. Most monosaccharides, or simple sugars, are found in grapes, other fruits, and honey.
Although they can contain from three to nine carbon atoms, the most common representatives
consist of five or six joined together to form a chainlike molecule. Three of the most important
simple sugars—glucose(also known as dextrose, grape sugar, and corn sugar), fructose (fruit sugar),
and galactose—have the same molecular formula, (C6H12O6), but, because their atoms have different
structural arrangements, the sugars have different characteristics; i.e., they are isomers.
27. The general formula is Cn(H2O) nor CnH2nOn. These are compound which possesses a free
aldehyde or ketone group.
They are classified according to the number of carbon atoms they contain and also on the basis
of the functional group present.The monosaccharides thus with 3,4,5,6,7… carbons are called
trioses, tetroses, pentoses, hexoses, heptoses, etc., and also as aldoses or ketoses depending upon
whether they contain aldehyde or ketone group.
Examples: Glucose, Fructose, Erythrulose, Ribulose.
Monosaccharides
28. Properties of Monosaccharides
Most monosaccharides have a sweet taste (fructose is sweetest; 73% sweeter than sucrose).
They are solids at room temperature.
They are extremely soluble in water: – Despite their high molecular weights, the presence of
large numbers of OH groups make the monosaccharides much more water-soluble than most
molecules of similar MW.
Glucose can dissolve in minute amounts of water to make a syrup (1 g / 1 ml H2O).
Monosaccharides
29. Are Simple Single Sugar
Which require no Digestion
Quickly absorbed from Intestine to Blood and carried to the Liver
In Liver Converted into Glycogen and stored.
Characteristics of Monosaccharide
30. Disaccharide
Are Simple Double Sugar
Which Link with two Single Sugar
Important Disaccharides are Sucrose, Lactose &Maltose
Sucrose = Glucose + Fructose
e.g. Sugar, Brown Sugar Sugarcane, Sugar beet.
31. Disaccharide
Lactose = Glucose + Galactose
e.g. Milk Sugar Lactose is less soluble
Less Sweet than Sucrose
Maltose = Glucose + Glcose Starch => Maltose => Glucose
Sugar alcohols such Sorbitol Used in Candies, Beverages.
32. Disaccharides
Disaccharides
Two molecules of a simple sugar that are linked to each other form a disaccharide, or double
sugar. The disaccharide sucrose, or table sugar, consists of one molecule of glucose and one
molecule of fructose; the most familiar sources of sucrose are sugar beets and cane sugar. Milk
sugar, or lactose, and maltose are also disaccharides. Before the energy in disaccharides can be
utilized by living things, the molecules must be broken down into their respective
monosaccharides.
33. Oligosaccharides
Oligosaccharides
Oligosaccharides are compound sugars that yield 2 to 10 molecules of the same or different
monosaccharides on hydrolysis are rather infrequently found in natural sources, although a few
plant derivatives have been identified. .The monosaccharide units are joined by glycosidic
linkage.
Based on the number of monosaccharide units, it is further classified as disaccharide,
trisaccharide, tetrasaccharide etc.
34. Oligosaccharides yielding 2 molecules of monosaccharides on hydrolysis is known as a disaccharide, and
the ones yielding 3 or 4 monosaccharides are known as trisaccharides and tetrasaccharides respectively and
so on.
The general formula of disaccharides is Cn(H2O)n-1and that of trisaccharides is Cn(H2O)n-2 and so on.
Examples: Disaccharides include sucrose, lactose, maltose, etc.
Oligosaccharides
35. Polysaccharides(the term means many sugars)
Polysaccharides(the term means many sugars)
They are also called as “glycans”. Polysaccharides represent most of the structural and
energy-reserve carbohydrates found in nature. Large molecules that may consist of as many
as 10,000 monosaccharide on hydrolysis & these units are linked together, polysaccharides
vary considerably in size, in structural complexity, and in sugar content. Polysaccharides
differ from each other in the identity of their recurring monosaccharide units, in the length of
their chains, in the types of bond linking units and in the degree of branching.
36. Cellulose, the principal structural component of plants, is a complex polysaccharide
comprising many glucose units linked together; it is the most common polysaccharide. The starch
found in plants and the glycogen found in animals also are complex glucose polysaccharides.
Starch (from the Old English word stercan, meaning “to stiffen”) is found mostly in seeds, roots,
and stems, where it is stored as an available energy source for plants. Plant starch may be processed
into foods such as bread, or it may be consumed directly—as in potatoes, for instance. Glycogen,
which consists of branching chains of glucose molecules, is formed in the liver and muscles of
higher animals and is stored as an energy source.
They are primarily concerned with two important functions ie.
1. Structural functions
2. The storage of energy.
Polysaccharides(the term means many sugars)
39. Action of Fiber in the Body
Insoluble Fiber
• Accelerate GI Transit
• Increase Fecal Weight
• Promotes bowel
movement
• Slow Starch
Hydrolysis
• Delays Glucose
Absorption.
Soluble Fiber
• Delays GI Transit
• Lowers blood
Cholesterols
• Delays Glucose
absorption.
40. Digestion and absorption of carbohydrates
Digestion and absorption of carbohydrates
The digestion of carbohydrates begins in the mouth by Ptyalin (amylase) produced by the salivary
glands. No carbohydrate digestion takes place in the stomach. Digestion occurs mainly in the small
intestine through the action of pancreatic and intestinal juices: ƒ
Amylase ƒ
Lactase ƒ
Sucrase ƒ
Maltase
Dextrin is degradation products of starch in which the glucose chains have been broken down to
smaller units by partial hydrolysis. ƒ Dextran is a carbohydrate polymer obtained from bacterial cell
wall. This has no part in dietetics but is used in medicine as plasma expander.
41. Digestion
Mouth
Salivary amylase
Stomach
Fibers and satiety
Small Intestine
-Maltase, sucrase, lactase
Pancreas
Pancreatic amylase
Large Intestine
-Fermentation of viscous fibers
Water, gas, short-chain fatty
acid production
46. Summary of carbohydrate digestion
Site of action Carbohydrate Enzyme End – product
Mouth Starch Amylase in saliva
(ptyalin)
Dextrin- maltose
Glucose
Small intestine Starch Amylase in pancreatic
juice
Dextrin- maltose
glucose maltose
Glucose
Dextrin Enzyme in brush
border of small
intestine
Maltose Sucrose
Lactose
Maltase
Sucrase
Lactase
Glucose Glucose &
fructose Glucose &
Galactose
49. Metabolism
Glucose in the Body
Used for energy – fuels most of the body’s cells
Stored as glycogen – 1/3 in the liver and 2/3 in muscles
Made from protein – gluconeogenesis
Converted to fat – when in excess of body’s needs
50. Constancy of Blood Glucose
Regulating hormones – maintain glucose homeostasis
1. Insulin – moves glucose from the blood into cells
2. Glucagon – signals the liver to release glucose into the blood
3. Epinephrine – released when emergency fuel needed
52. Absorption
Carbohydrates are absorbed from small intestine mainly as monosaccharides, namely glucose,
galactose & fructose. Through sodium co-transport mechanism glucose and galactose are
absorbed into portal blood.
Fructose absorption takes place through the epithelium of intestine which is facilitated by
diffusion.
glucose, galactose & fructose absorbed in the intestines pass through the portal circulation to
the liver. In liver galactose ,fructose and some part of glucose into glycogen. A part of glucose
passess into the general circulation & to the various tissues for being oxidized and used as
energy. Some part of glucose is stored in liver & muscles and some portion converted to fat
which is stored in adipose tissues. This oxidation occurs in 2 stages ie Glycolysis and a series
of reaction of Kreb Cycle
53. In Health and with normal diet, the available carbohydrate is digested and absorbed completely in
the small intestine. If an excess of unabsorbed carbohydrate arise due to a disorder of the
absorption mechanisms or occasionally to excessive intake, the osmotic pressure (effects) leads to
retention of fluids in the lumen and as the result there will be watery diarrhoea. This diarrhoea is
known as osmotic diarrhoea. The tissues use as fuel a mixture of glucose and fatty acids. But the
brain normally uses only glucose and requires around 80g daily. In starvation glucose may be
provided by gluconeogenesis from the amino acids in tissues proteins, mainly from muscle
proteins, but fats cannot be converted into glucose. With prolonged starvation the brain adapts
and can then utilize fatty acids and ketone.
Absorption
54. The two hormones, which control the metabolisms of carbohydrates, are insulin and glucagons
ƒ Insulin is secreted by the beta cells of the islets of Langerhans and the secretion is stimulated
by: – Hyperglycemias – Parasympathetic nervous activity Function of insulin To facilitate
glucose transport to the liver and muscle cells To facilitate formation of glycogen in the liver
and muscle cells To incorporate formation of protein from the amino acids.
Absorption
55. Functions
Functions
Carbohydrates are widely distributed molecules in plant and animal tissues. In plants and
arthropods, carbohydrates from the skeletal structures, they also serve as food reserves in plants
and animals. They are important energy source required for various metabolic activities, the
energy is derived by oxidation.
56. Functions
Some of their major functions include:
1. Living organisms use carbohydrates as accessible energy to fuel cellular reactions. They are the
most abundant dietary source of energy (4kcal/gram) for all living beings.
2. Carbohydrates along with being the chief energy source, in many animals, are instant sources
of energy. Glucose is broken down by glycolysis/ Kreb’s cycle to yield ATP.
3. Serve as energy stores, fuels, and metabolic intermediates. It is stored as glycogen in animals
and starch in plants.
4. Stored carbohydrates act as an energy source instead of proteins.
5. They form structural and protective components, like in the cell wall of plants and
microorganisms. Structural elements in the cell walls of bacteria (peptidoglycan or murein),
plants (cellulose) and animals (chitin).
57. Functions
1. Carbohydrates are intermediates in the biosynthesis of fats and proteins.
2. Carbohydrates aid in the regulation of nerve tissue and are the energy source for the brain.
3. Carbohydrates get associated with lipids and proteins to form surface antigens, receptor
molecules, vitamins, and antibiotics.
4. Formation of the structural framework of RNA and DNA (ribonucleic acid and
deoxyribonucleic acid).
5. They are linked to many proteins and lipids. Such linked carbohydrates are important in cell-
cell communication and in interactions between cells and other elements in the cellular
environment.
6. In animals, they are an important constituent of connective tissues.
7. Carbohydrates that is rich in fiber content help to prevent constipation.
8. Also, they help in the modulation of the immune system.
58. Energy Supply Brain,Cell
SpareProteins
Synthesis of Substances Non-essentialAminoacids
Glycoproteins
Glycolipids
Promote complete lipid metabolism
Provide Bulk Fiberin the Diet.
Functions
59. Energy Supply for body function
Essential for the Oxidation of Fats
Proteins sparing action
Provide Carbon for synthesis of Non-essential Amino acids
Are present in some tissue Constituents
Add flavour to Diet
Nucleic acid of Connective tissue Matrix , Galactosides of Nerve Tissue
Necessary for proper functioning of CNS
Adequate hepatic Glycogen Storage enhances normal liver detoxification ability.
Functions
60. Caloric Value
One Kilo Calorie is defined as the amount of heat required to raise the temperature of 1 kg of
water by 1 degree Celsius. 1 gm of carbohydrates on complete oxidation yields 4 kcal of
energy.
Recommended Dietary Allowances
Normally 60-70 per cent of our total calories should come from carbohydrates. 275-300 grams
of carbohydrates in 2000 kcal
Functions
63. Dietary Sources
All sources like wheat, rice, jowar, bajra, ragai etc
Roots and tubers like potato and sweet potato.
Sugarcane, honey, jaggery, and sago.
Vegetables like beans, peas, carrots, tomatoes, cabbage, & spinach
Fruits like bananas, grapes, oranges & strawberries.
64. Constancy of Blood Glucose
Diabetes
Type 1 diabetes
Failure of insulin production
Type 2 diabetes
Obesity
Hypoglycemia
Rare in healthy people
Glycemic response
Glycemic index
66. Health Effects of Sugar
Sugar in excess
1. Contains no nutrients and may contribute to malnutrition
2. Causes dental caries (tooth decay)
3. Does not cause, but can contribute
to: obesity, diabetes, heart
disease, & behavorial problems
69. Recommended Intakes of Sugars
DRI
No more than 25% of total daily
energy intake
-Limit added sugars to <10% of
total energy intake
Copyright 2005 Wadsworth Group, a division of Thomson Learning
70. Health Effects
• Complex carbohydrates &
fiber may reduce
the risk of:
-Heart disease
-Diabetes
-GI health
-Cancer
-Weight
Management
71. Health Effects
How?
Diets high in complex CHO tend to be:
1. Lower in fat and calories
2. Higher in fiber, vitamins, & minerals
72. Soluble Fibers
Lower blood cholesterol by binding dietary cholesterol so less absorbed
Slow glucose absorption
Slow transit of food through upper GI tract
Holds moisture in stools, softening them
Lower risk of heart disease
Lower risk of diabetes
73. Soluble Fibers
Gums & mucilages, pectins, psyllium
Sources
Whole-grains, fruits, legumes, seeds and husks, vegetables
Extracted and used as food additives
74. Insoluble Fibers
Increase fecal weight - helps form soft, bulky stools which improves G.I. motility
& reduces risk of constipation, hemorrhoids,
diverticulosis & colon cancer
Speed fecal passage through colon
Provide bulk and feelings of fullness
(satiety)
75. Insoluble Fibers
Cellulose, lignins, hemiculloses
Sources
Brown rice, fruits, legumes, seeds,
vegetables, wheat bran, whole grains
Extracted and used as food additives
76. Recommended Intakes
of Carbohydrates & Fibers
RDA for carbohydrate
130 g/day
45% - 65% total daily energy intake
with emphasis on complex
-Daily Value: 300 g/day
Fiber
Daily Value: 25 g/day
AI: 14 g/1000 kcal/day
77. Dietary Recommendations
Example:
If 2000 kcal diet, then:
1100-1200 kcals as CHO
(275-300 grams)
with < 200 kcals as “added sugar”
(50 grams)
One 12 oz. soft drink has 36-40 gms sugar
0ne tsp. sugar weighs 4 gms = 9-10 tsps!
78. Malnutrition ofCarbohydrate
Deficiency :
Low body weight
Accumulation of large amount of ketone bodies in the body
Overconsumption :
• Increase dental caries
• Cause Obesity
• Large amount of sugar – Gastric ulcer
• Depress appetite – Soft Drink
• Increase blood Triglyceride – Lead to Heart Disease.
79. Alternative Sweeteners
Two Categories
1. Sugar Alcohols – mannitol, sorbitol,
xylitol
2. Artificial sweeteners – sugar substitutes
(calorie-free); in moderation, useful for
blood sugar & weight control
80. Alternative Sweeteners
Sugar Alcohols
1. CHOs that provide less energy than
sucrose (2-3 kcals/gm) because not
completely absorbed
2. May cause gas, abdominal discomfort,
diarrhea
3. Less cariogenic than sugar
83. Student effective learning outcome
1.Application of concepts of topic & it’s technological application.
2.Ability to interpret and analyze data into information and to design and conduct experiments.
3.Understanding available tools and products and ability to use it effectively.
4.Adaptive Thinking Skills
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84. Reference
1.Essentials of nutrition and biochemistry for basic B sc nursing I clement
2. Food & nutrition for nurses (B sc nursing) by Ruma Singh
3. A textbook of nutrition B.Sc(n) first year Darshan Soni
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