Digestion, Absorption and Metabolism of proteins

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