This ppt refers to the Digestion and metabolism of carbohydrates

1. ROMAN ARSHAD
CARBOHYDRATE DIGESTION
& METABOLISM.
PRINCIPLES OF ANIMAL NUTRITION
SUBMITTED TO:- DR ABDUL JABBAR
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2. INTRODUCTION
CARBOHYDRATES:-
“Carbohydrates are polyhydroxy
aldehydes or ketones or complex substances which, on hydrolysis give aldehydes
or ketones”
STRUCTURALLY….
Carbohydrates are organic compounds having
general formula Cx(H2Oy).
They may be;
1. Monosaccharaides.
2. Oligosaccharides.
3. Polysaccharides.
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3. DIGESTION:-
“Digestion is the process of breaking down of complex
molecules with the help of enzymes inside a stomach to eventually release
energy”
CARBOHYDRATE DIGESTION:-
Carbohydrate digestion occurs in
mouth where enzymes reach by Saliva and the rest occurs in stomach.
A polysaccharide is converted to smaller subunits and ultimately to
monosaccharaides(glucose, fructose, lactose).
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4. CARBOHYDRATE DIGESTING ENZYMES:-
Carbohydrate
digesting enzymes include;
1. Amylase(Ptyalin).
 Salivary.
 Pancreatic.
2. Maltase.
3. Lactase.
4. Sucrase.
DIGESTION IN MOUTH:-
Amylase is released in saliva and when food enters oral cavity, bolus gets
coated with saliva and carbohydrate component of food is broken down.
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5. Food starches are broken down into maltose and dextrin. About 5% of the
starch digestion occurs in mouth. More than this can result in degrading of
teeth.
Starch digestion in mouth occurs only in monogastric species of animals i.e.
Non-Ruminants.
DIGESTION IN RUMINANTS:-
Ruminants don’t secrete Salivary
Amylase in saliva instead they rely upon the Microbes in their Rumen. These
microbes account for the carbohydrate digestion in Ruminants. Microbes
digest carbs by a process called fermentation.
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6. Ruminal digestion of carbs is highly efficient as the food being ingested is
grass or feed high in roughage and starch.
STEPS OF DIGESTION IN RUMINANTS:-
1. Engulfing of food.
2. Mastication.
3. Chewing.
4. Rumination of food for several hours.
5. Regurgitation and chewing.
6. Passing of regurgitated food to next compartments.
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7. 7
Site of
fermentation
of starch.
Diagram
showing
digestive tract
of ruminant.

8. DIGESTION IN INTESTINE:-
After the initial 5% of digestion mouth
or Rumen, rest of carbohydrate digestion occurs in the small intestine.
MECHANISM:-
Chime or chyme from stomach when enters small
intestine, Intestinal walls sense the acidity and trigger pancreas to release
Pancreatic juice comprising Trypsin, chymotrypsin, carboxypeptidase-A
and Pancreatic Amylase.
This juice is mixed with Chyme to further digest carbohydrates. Maltase,
Sucrase and lactase are also released into chyme which breakdown sucrose,
maltose and lactose respectively.
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9. These oligosaccharides are broken to monosaccharaides i.e. glucose, fructose
etc. And absorbed into the bloodstream.
NUTRITIVE DISEASES ASSOCIATED:-
Lactose Intolerance is
the most common nutritive disorder in Felines and Canines specifically in
Domestic Cats and Dogs. Upon ingestion of lactose containing(Dairy
Products), lactose can not be digested as LACTASE is absent. Thus causing
the following symptoms;
1. Watery Diarrhea.
2. Vomiting.
3. Stomach bloat.
4. Cramps in abdomen.
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10. The digested carbohydrates need to be absorbed into bloodstream before
Metabolism.
ABSORPTION:-
Small intestine has Villi which increase the surface area of
small intestine, these have capillaries which absorb glucose from lumen and
pass onto main blood stream. Glucose and other monosaccharaides are then
transported to liver where excess is converted to glycogen.
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11. 11
Figure showing
absorption of
Glucose into
bloodstream.

12. METABOLISM OF CARBOHYDRATES:-
After the absorption
of carbohydrates in blood they need to metabolized either broken further
down to release energy or to be stored for future use.
The energy releasing process from glucose is called glycolysis.
1. GLYCOLYSIS(Catabolism):-
“Glycolysis is the breakdown of glucose to release energy”
It is an energy releasing process(Net ATP=6) whose product is pyruvic acid.
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13. STEPS OF GLYCOLYSIS:-
1. Glucose is phosphorylated to form glucose 6 phosphate.
2. Glucose rearranges with the action of enzyme isomerase to form fructose
6 phosphate.
3. F6P splits into Dihydroxyacetone phosphate and glyceraldehyde 6
phosphate.
4. Phosphorylation of G3P forms 1-3 Bisphosphoglycerate.
5. Phosphate is added to ADP to form 3 Phosphoglycerate.
6. Rearrangement to form 2 Phosphoglycerate.
7. Dehydration to form Phosphoenopyruvate.
8. Removal of high energy phosphate to form pyruvate.
(Energy is released on several steps of glycolysis)
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14. 14
Phases of Glycolysis

15. 2. GLYCOGENESIS(Anabolism):-
“Conversion of glucose
to glycogen is called glycogenesis”
CONDITIONS FOR GLYCOGENESIS:-
 High blood sugar level.
 Excess glucose in body than requirement.
STEPS OF GLYCOGENESIS:-
1. Phosphorylation of glucose to form glucose 6 phosphate.
2. G6P conversion to Glucose 1 phosphate with help of enzyme.
3. Uridine tri phosphate attaches to glucose to form UDP glucose.
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16. 4. Action of glycogen synthase to form glycogen.
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Flowchart
showing
glycogenesis
cycle

17. 3. CONVERSION TO FAT:-
Excess glucose can also be converted
to fats i.e. Adipose Tissue. This adipose tissue layer helps in protection and
insulation of the body and again broken down to glucose during fasting or
exercise.
BLOOD GLUCOSE CONCENTRATION:-
Blood glucose
concentration is the level of glucose in blood in concentration units.
UNITS:-
1. mg/dL →milligrams per deciliter.
2. mmol/L→millimoles per litre.
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18. 18
Animal Specie Normal Blood Sugar Range
(mmo/L)
Horse 3-6
Cattle 2-4
Sheep 2-4
Goat 2-4
Dog 8-6
Chicken 2-14
Table showing
glucose levels of
animals

19. HORMONES INVOLVED:-
In carbohydrate metabolism two
main hormones are involved which either catabolize or anabolize the glucose.
These hormones are:-
1. Insulin.
Insulin release decreases the glucose concentration of blood by initiating
glycogenesis when glucose conc increases from normal.
2. Glucagon.
Glucagon release increases the blood glucose concentration by initiating
glycolysis during fasting.
In fact insulin and glucagon are antagonists to each other.
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20. 20
Depiction of antagonistic nature of
insulin and glucagon

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