Saccharides (carbohydrates)

Biochemistry for nurses

1. Biochemistry for nurses
SACCHARIDES (carbohydrates)
A saccharide is a biological molecule consisting of carbon (C), hydrogen (H)
and oxygen (O
2
). The saccharides have the general formula (CH
2
O)
n
.
Saccharides are divided into 4 chemical groupes: monosaccharides,
dissacharides, polysaccharides and glycoconjugates.

2. Biochemistry for nurses
Monosaccharides
The monosaccharides have the general formula C
n
H
2
O
n
Most monosaccharides found in the cell have 5 or 6 carbones:
• monosaccharide with 5 carbones (C
5
H
10
O
5
) = PENTOSE
• monosaccharide with 6 carbones (C
6
H
12
O
6
) = HEXOSE
The most important pentoses are the RIBOSE and the DEOXYRIBOSE.
They are elements of the nucleic acid structures (DNA and RNA)

3. Monosaccharides
The most important hexoses are the GLUCOSE, FRUCTOSE and the
GALACTOSE. They have the same formula C
6
H
12
O
6
but they have
differents structures: They are ISOMERS
The hexoses are important FUEL MOLECULES!
Biochemistry for nurses

4. Monosaccharides
The most important hexoses are the GLUCOSE, FRUCTOSE and the
GALACTOSE. They have the same formula C
6
H
12
O
6
but they have
differents structures: They are ISOMERS
The hexoses are important FUEL MOLECULES!
Biochemistry for nurses

5. Disaccharides
A disaccharide is a sugar composed of
two monosaccharides. It is formed
when two sugars are joined together
and a molecule of water is removed.
The most important dissacharides are:
Biochemistry for nursesA SUCROSE AUAbrhRaC(1tDhRdaC(
A LACTOSE A UAbrhRaC(1bHrHRdaC(
A MALTOSE AUAbrhRaC(1brhRaC(
SUCROSE = glucose-fructose
LACTOSE = glucose-galactose
MALTOSE = glucose-glucose

6. Biochemistry for nurses
(Cereal grains, corn…)
(Milk…)
(Fruits, sugarcane,
sugar beet…)

7. Polysaccharides
Most of the polysaccharides are long chains of glucoses (= polymers of glucoses).
The most important polysaccharides are:
• STARCH
• GLYCOGEN
• CELLULOSE
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8. Starch
There are 2 types of Starch molecules:
• AMYLOSE = Long linear chains of glucoses.
• AMYLOPECTIN = Long linear and branched chains of glucoses.
Each starch can contain 100 to 20.000 molecules of glucose.
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The starch is a sugar coming from vegetables
(Cereals: rice, wheat, corn and potatoes)

9. Glycogen
The Glycogen structure is composed by long linear and branched chains of glucoses.
The Glycogen is a sugar coming from animals (Meats)
After a meal, our blood sugar increases.
The liver cells and muscular cells transform
the extra sugar into molecules of Glycogen
which causes a decrease of the blood
sugar.
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The extra sugar is stored as Glycogen in
our body. Our body can store up to 600 g of
glycogen

10. Cellulose
The Cellulose is also composed by long linear chains of glucoses but the glucoses are
linked by a different type of chemical bond.
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(Main component of Wood)

11. Glycoconjugate
•Glycoconjugates is the general classification for carbohydrates covalently linked
with other chemical species such as proteins, peptides and lipids.
•Most of the Glycoconjugates are GLYCOPROTEINS (= proteins linked with
polysaccharides). They are especially found in the cell membrane (the blood type
is defined by the type of glycoprotein).
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12. Biochemistry for nurses
Functions of the Carbohydrates
•Provide energy (ATP) to drive metabolic
processes (GLYCOLYSIS).
•Energy-storage molecules, e.g, GLYCOGEN.
•Structural component of cell wall.
•Component found in coenzyme (FAD) and
Nucleic Acids.

13. ATP molecule is
the source of
ENERGY!
CELL METABOLISM (cell respiration)
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14. ATP (Adenosine Triphosphate)
ATP is a molecule composed by
an organic base (adenine) and
a 3 phosphates group attached
to a sugar (ribose).
ATP is manufactured inside the
mitochondria from the transformation
of the energy coming from the
absorbed foods into a chemical
energy stored in the chemical bond
with the 3
rd
phosphate group.
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15. ATP
ADP+Pi
Energy
ATP hydrolyse provides energy
Each day, you
hydrolyse 10
25

ATP molecules in
your body
HydrolysePhosphorylation
Hydrolyse of ATP provides a
big energy (35 KJ)
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16. Biochemistry for nurses
GLYCOLYSIS:
Catabolism of Glucose (or Fructose, Mannose) to provide ATPs molecules. That
process is also called “Cell Respiration”, and it happens inside Mitochondria.

17. DIGESTION (Metabolism) of the polysaccharides
After absorption of the polysaccharides coming from the foods, the digestive system of
our body has to transform the long chains of polysaccharides into monosaccharides in
order to be absorbed by the blood. That reaction is done by enzymes (Ex: Amylase,
Maltase or Saccharase). Enzymes are biological catalysts. The breaking of a bond
joining 2 saccharides requires a molecule of water (H
2
0): That reaction is called the
« HYDROLYSIS of POLYSACCHARIDES
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18. Reminder: What is an enzyme?
• Enzymes are proteins produced in living cells.
• Enzyme are biological catalysts = They speed up the rate of chemical
reactions.
• Enzyme are specific to a particular substrate (Key-Lock: sucrose-sucrase,
maltose-maltase,…).
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19. Biochemistry for nurses
Digestion and absorption of carbohydrates

20. Biochemistry for nurses

21. Biochemistry for nursestIDr(CH Do h(raDydcr(IHR
Storage of carbohydrates
•Carbohydrates are stored in the form of Glycogen
•Glycogen is a multibranched polysaccharide of Glucose.
•Glycogen is stored in the cells of the Liver and the Muscles
•During starvation, Glycogen act as primary source of energy by
providing molecules of ATP

22. Biochemistry for nurses
Recommended dietary allowances (RDAs)
•Definition: Minimum required amount of the nutrient for the
maintenance of health in nearly all people.
• RDAs does not apply to sick people
Source: Food and Nutrition Board, Institute of Medicine, National Academies
(USA, CANADA)

23. Biochemistry for nurses
Diseases due to overconsumption of carbohydrates
•Obesity
•Diabete (Type 2: Non-Insulin Depedent Diabetes
Mellitus)
•Cardiovascular diseases (Heart disease and stroke)
•Dental caries

24. Biochemistry for nurses
Diseases due to deficiency of carbohydrates
•Usage of Fats as Energy Source
(underweight)
•KETOSIS: Accumulation of
Ketones in the body (in absence
of carbohydrates the body starts
using the proteins and converts it
to sugars)
•HYPOGLYCEMIA