UNDERSTANDING METABOLISM

Dr. Ayisha Qureshi Assistant Professor,

MBBS, Mphil

SIMPLIFYING METABOLISM

• Dietary fuel intake is intermittent, not continuous. • As a result excess energy from nutrients taken in

at meals must be stored and then released between meals.

• The food ingested meets one of three fates: 1. Energy2. Synthesis3. Storage

Stored Metabolic Fuel in the Body

ANABOLIC PATHWAYS:Pathways that synthesize larger molecules

from smaller ones. Usually energy in the form of ATP is required.

CATABOLIC PATHWAYS:Pathways that break large molecules into

smaller ones. Usually ATP is yielded.

FED/ ABSORPTIVE STATE:The period of time following a meal, when the products of digestion are being absorbed, used

and stored. This is an anabolic state in which energy of nutrients is transferred to larger mol.

FASTING/ POST-ABSORPTIVE STATE:The time period in between the meals when

nutrients are NOT present in the blood anymore & so NOT available for use by the tissues. Now the body taps into the stored

reserves. This is a catabolic state.

METABOLISMSum of all chemical

reactions in the body

Interconversions among Organic molecules

ALL FOOD EATEN (even CHO & Proteins) IS ULTIMATELY CONVERTED INTO FATS AND STORED IN THE ADIPOSE TISSUE.

MAINTAINING BLOOD GLUCOSE LEVELS DURING FASTING STATE

BLOOD GLUCOSE

LEVELS

PROTEINS serve as the last resort

for energy and providing glucose thru

Gluconeogenesis.

GLYCOGENthru Glycogenolysis

forms Glucose

FATS (TG) break down into

Glycerol (10%) & Fatty acids (90%). Glycerol

forms Glucose.

CARBOHYDRATE METABOLISM

The principal product of carbohydrate digestion & the principal circulating sugar is GLUCOSE.

• The breakdown of glucose to pyruvate or lactate (or both) is called Glycolysis.

• The conversion of non-glucose molecules to glucose is called Gluconeogenesis.

CARBOHYDRATE METABOLISM

• Glycolysis• Gluconeogenesis• Glycogenolysis• Glycogenesis

GLYCOGEN

• Glycogenesis: The process of glycogen formation is glycogenesis.

• Glycogenolysis: The process of glycogen breakdown is glycogenolysis.

Glycogen, the storage form of sugar, is present in most body tissues, but the major supplies are in the liver & skeletal muscles.