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Carbohydrates

Major Pathway of Glucose

Absorption

movement of molecules across the gastrointestinal (GI) tract into the circulatory system

Most of the end-products of digestion are absorbed in the small intestinal by four mechanisms for absorption :

facilitative diffusion

endocytosis, and

passive diffusion

active transport

requires energy

classified

polysaccharides

Starch

glycogen

Cellulose

oligosaccharides

Complex carbohydrates

Raffinose

Stachyoses

Verbascose

sugars

Simple carbohydrates

Disaccharides

Maltose

Lactose

Sucrose

Monosaccharides

Mannose

Galactose

Fructose

Glucose

Deoxyribose

Ribose

Carbohydrate Metabolism

Minor Pathways for Glucose oxidation

HMP shunt

a pathway by which pentose phosphate is produced from glucose

Site

Cytoplasm

Major pathway for Glucose oxidation

Citric Acid Cycle

Complete oxidation of acetyl-CoA to 2 molecules of CO2 and generating energy

Functions

Anabolic Function

Catabolic for glucose, fat &proteins

Energy production

All cells that contain mitochondria

Glycolysis

means oxidation of glucose to give pyruvate or lactate

Location

in all cells

GLUCONEOGENESIS

It is synthesis of glucose from non-carbohydrate sources

It occurs mainly in the liver cells and to lesser extent in kidneys

Cytoplasm except for the first step (carboxylation of pyruvate) occurs in the mitochondria.

Glycogenolysis

is the breakdown of glycogen to glucose

Glycogenolysis is inhibited by insulin

Glycogenolysis is activated by glucogon in the liver and epinephrine in muscles

- in the liver and kidneys, glucose-6-phosphate can be hydrolized to glucose

Phosphorylated glucose can’t be absorbed into cells

Glucose-1-phosphate can be converted to glucose-6-phosphate, which can enter glycolysis

The glucose is phosphorylated as it is cleaved from the glycogen to form glucose-1-phosphate

Glycogenesis

is the synthesis of glycogen from glucose-6-phosphate

it does not operate when glycogen stores are full, which means that additional glucose is converted to body fat

it occurs when high levels of glucose-6-phosphate are formed in the first reaction of glycolysis

Glycogen stores are used to keep the blood sugar level steady between meals

Glycogen is a highly branched glucose polymer used for carbohydrate storage in animals

Unavailable carbohydrates are not hydrolyzed by endogenous human enzymes

Available carbohydrates are those that are hydrolyzed by enzymes of the human

In terms of their physiological there are available and unavailable carbohydrates

40-75% of energy intake