Digestion, Absorption and Metabolism of proteins

Sunday, November 28, 2010



The dietary proteins are formed by long chains of amino acids bound together by peptide linkages

Diet containing protein are

Wheat        -      Glutenin, gliadin

Milk             -     Casein, albumin, lactalbumin and myosin

Egg              -      Albumin and vitelin

Meat            -      Collagen, albumin and myosin

Digestion of proteins

The enzymes responsible for digestion of proteins are called proteolytic enzymes

Mouth                     -  No digestion

Stomach                -  Pepsin is the only proteolytic enzymes in gastric juice
                                     Rennin is also present in gastric juice
                                     But rennin is absent in human

SI                             -  Most of the proteins are digested in SI  by photolytic enzymes

Pancreatic juice   - Trypsin, chymotrypsin and carboxy poptidases
                                     These break down the bonds of the protein molecules


Succus Entericus   -DI, tri and amino peptidases

Absorption of protein

The final products of protein digestion are the amino acids which are absorbed into blood from intestine

The levo amino acids are actively absorbed by means of sodium co- transport, whereas the dextro amino acids are absorbed by means of facilitated diffusion

It contains di, tri , amino peptidases
 
DIGESTION OF PROTEINS
                                                    
AREA

JUICE

ENZYME
SUBSTRATE
END POINT

MOUTH
SALIVA
NO
PROTEOLYTIC
ENZYME
STOMACH
GASTRIC JUICE
PEPSIN
PROTEINS
PROTEOSES
PEPTONES








SMALL INTESTINE





PANCREATIC JUICE















SUCCUS ENTERICUS



TRYPSIN


CHYMO
TRYPSIN





CARBOXY PEPTIDASES  A & B





DIPEPTIDASES


TRIPEPTIDASES


AMINO PEPTIDASES





PROTEOSES
PEPTONES






DIPEPTIDES
TRIPEPTIDES
POLYPEPTIDES





DIPEPTIDES


TRIPEPTIDES


LARGE POLYPEPTIDES




DI, TRI  &
POLYPEPTIDES






AMINO ACIDS










AMINO ACIDS


Digestion & absorption of carbohydrates

Carbohydrates
Human diet contains 3 types of carbohydrates

Polysaccharides
Glycogen,  amylase and amylopectin
Glycogen -- non vegetarian diet
Amylase and amylopectin --- vegetarian sources

Disaccharides
Sucrose
which is called cane sugar
Glucose   +   Fructose

Lactose –available in milk

Glucose  +   Galactose

Monosaccharide

Glucose ,&  Fructose  

Digestion

Mouth

Saliva---Amylolytic enzymes
Polysaccharides –cooked starch
Stomach
Contains weak amylase
Digestion of carbohydrates

Intestine
Pancreatic amylase—polysaccharides---Disaccharides (dextrin and maltose)

Sucrase --- sucrose---glucose + fructose

Maltase --- maltose----glucose

Lactase ----Lactose---glucose  +  galactose

Dextrinase---dextrin, maltose----glucose

Absorption carbohydrates

Glucose and galactose
These are transported from  the intestinal lumen into the cells by Na dependent co transport in the luminal membrane
This sugar is transported uphill and Na is transported downhill
These are then transported from cell to blood by diffusion
Sodium ion moves laterally into the intercellular space
From here , it is transported into blood by active transport
In this process the energy is utilized which is liberated by breakdown of ATP

Fructose
It is absorbed into the blood by means of facilitated diffusion
Some molecules of fructose are converted into glucose
The glucose is absorbed

DIGESTION OF CARBOHYDRATES


AREA

JUICE

ENZYME
SUBSTRATE
END POINT

MOUTH
SALIVA
SALIVARY AMYLASE
POLYSACCHARIDES
COOKED STARCH
DISACCHARIDES
DEXTRIN    & MALTOSE
STOMACH
GASTRIC JUICE
GASTRIC AMYLASE
WEAK AMYLASE
ACTION  IS NEGLIGIBLE

PANCREATIC JUICE


PANCREATIC AMYLASE

POLYSACCHARIDES



DISACCHARIDES
DEXTRIN, MALTOSE
MALTRIOSE




SMALL INTESTINE









SUCCUS ENTERICUS







SUCRASE



MALTASE



LACTSE



DEXTRINASE






SUCROSE



MALTOSE



LACTOSE



DEXTRINE
MALT OSE
MALTRIOSE





GLUCOSE & FRUCTOSE


GLUCOSE



GLUCOSE &
GALACTOSE


GLUCOSSE

ANATOMY AND PHYSIOLOGY

Anatomy
A branch of biochemical science dealing with normal structure, shape,size and location of various parts of the body

Physiology
A branch of biomedical science dealing with normal functioning of various organs in the in the body,

Cell
 Structural and functional unit of body

Tissue
The group of cells which have same structure function of body

Organ
Different tissues combined together to form particular function or functions
System
 Varies organs working in co- ordination for the particular function or functions

Symmetric
 Their arrangement on the left side  and right side are similar.
                        Ex – Limbs, eyes, ears and lungs.

Asssymmetric
 No two equal portions
                         Ex – Spleen and liver. Spleen lies entirely in the left side.    
                                  Liver lies mostly on the right side.
Medial line
(Mid saggittal plane)  the central plane which divides the body two halves – right and left

Medial
Nearer to the median line

Lateral
Away from the median line

Inferior
Nearer to the head

Anterior
Nearer to  the head.
Anterior (Ventral)
Toward front of body or limbs

Posterior (dorsal)
Toward back of body or limbs

Proximal
The upper part nearest to the trunk  Proximal part or proximal end of a            
Structure  or an organ is the one from where it originates or attached to the  body.

Distal
The lowest portion away from the trunk

Superficial
Nearer to the skin surface.

Deep
Deeper  from the skin surface.

External
The relationship to outer surface of the body.

Internal
The relationship to the inner surface of the body.

T. S - Transverse section

V .S- Vertical section

L . S – Longitudinal section

H. S – Horizontal section

S. S – Saggital section

C. S- Cross section

Cytology – Study of cell .

Histology – Study of cell at a microscopic level

Cardiology – Study of heart

Neurology  - Study of nervous system.

Nephrology – Study  of excretory system

Otology – Study of ears.

Ophthalmology – Study of eyes.

Odontalogy – study of teeth

Osteology  - Study of skeleton (Bones)

Orthology – Study of bone joints.

Myology -   Study of muscles.

Endocrinology  - Study of endocrine glands.

Haematology  - Study of blood.

Angiology  - Study of blood circulation.

Arthology – Study of joints.

Serology –Study of serum.

Skeletal system – It is formed by bones. It provides a frame work for the body       
                             It  protects the soft tissues and allows movements at joints.

Muscular system  - It is made of numbers of muscles. It effects movements of
                               the body.

CVS – Heart and blood vessels -  Pumping of the blood.

Respiratory system  – Purification of the blood.

Digestive system  - Digestion and absorption of  food and elimination of
                               waste materials.

Endocrine glands  - It consists of ductless glands. It is concerned with the
                                production of hormones which regulates a variety of
                                functions of the body.



Urinary system – For excretion of waste metabolic products

Nervous system – it consists of brain ,spinal cord and nerves.
                                   The system creates awareness of the environment such that                                  
                                    the body cab respond by adapting.

Reproductive system – It consists of genital organs which are different in males and
                                              females. This system is responsible for the survival of the
                                              species by reproduction.

Organs of special sense 
Organs for taste – Tongue
Organs for sight – Eyes
Organs for hearing – Ear
Organ for touch – Skin
Organ for smell - Nose

Digestion and absorption of lipids

Lipids are mostly consumed in the form of natural fats, which are also known as triglycerides

The triglycerides are made up of a glycerol molecules and free fatty acids

Triglycerides are more in animal food and less in food of plant origin

Diet also contains small amount of cholesterol and cholesterol esters


Dietary fats are classified into two types

Saturated  fatty acids

Contains triglycerides

Maximum amount of hydrogen ions

Without any double bonds between carbon atoms

Unsaturated fatty acids

Dehydrogenation of saturated fatty acids


Digestion of lipids

Stomach

In the stomach, mixing breaks lipids into droplets to droplets to increase the surface area for digestion by pancreatic enzymes

Lingual lipases digest some of the ingested triglycerides to monoglycerides and fatty acids

The most of the ingested lipids are digested in the intestine by pancreatic lipases

Small intestine

Bile acids emulsify  lipids in the small intestine, increasing the surface area for digestion

Pancreatic lipases hydrolyze lipids to fatty acids, monoglycerides, cholesterols and lysolecithin

The enzymes are pancreatic lipase, cholesterol ester hydrolase’s and phospholipase A
The hydrophobic produces of lipid digestion are solubilized in micelles by bile acids
 
Absorption of lipids
Monoglycerides, cholesterol and fatty acids from the micelles enter the cells of intestinal mucosa by simple diffusion

In the mucosal cells,  most of the monoglycerides are converted into triglycerides.

The triglycerides and some of the cholesterol is esterified

The triglycerides and cholesterol esters are coated with a layer of protein, cholesterol and phospholipids to form the particles called chylomicrons

Chylomicrons cannot pass through the membrane of the blood  capillaries because of the larger size

So these lipid particles enter the lymph vessels and then are transferred into blood from lymph

Fatty acids containing less than 10-12 carbon atoms enter the portal blood from mucosal cells and are transported as free fatty acids or unesterified fatty acids

Most of the fats are absorbed in upper part of small intestine

The presence of bile is essential for fat absorption

 
DIGESTION OF FATS

 
AREA

JUICE

ENZYME
SUBSTRATE
END POINT

MOUTH
SALIVA
LINGUAL LIPASE
TRIGLYCERIDES
FATTY ACIDS  &

GLYCEROL
STOMACH
GASTRIC JUICE
GASRIC LIPASE
(WEAK LIPASE)
TRYGLICERIDES
FATTY ACIDS  &

GLYCEROL











SMALL INTESTINE










PANCREATIC JUICE










SUCCUS ENTERICUS


PANCREATIC LYPASE



CHOLESTEROL ESTER HYDROLASE



PHOSPHOLIPASE
A

&

PHOSPHOLIPASE
B




INTESTINAL LIPASE




TRIGLYCERIDES




CHOLESTEROL ESTER




PHOSPHOLIPIDES




LYSO PHOSPHOLIPIDES




TRIGLYCERIDES
MONOGLYCERIDES
FATTY ACIDS



FREE CHLOESTEROL  &   FATTY ACIDS



LYSO PHOSPHOLIPIDES



PHOSPHORYL CHOLINE
FREE FATTY ACIDS



FATTY ACIDS  &

GLYCEROL


 
FATS METABOLISM