Carbohydrates (CHO):

Dr. Hisham Mohamed Osman, Assistant professor in Biochemistry.

Carbohydrates Metabolism

Carbohydrates digestion and absorption Mouth diet (starch) Salivary amylase

Dextrins Stomach (HCL stop amylase activity)Intestine pancreatic juice contains 1,4 amylase 1,6 glycosidaseDisaccharides

Brush border cell contain disaccharide enzymes which hydrolysis disaccharide to monosaccharide (to avoid high osmotic pressure in intestinal lumen) as following: Maltose maltase glucose + glucose

Sucrose sucrase glucose + fructose Lactose lactase glucose + galactose Some infants suffering from lactase deficiency, must not given mother milk and must be given lactose free milk.

Insulin dependent tissues:1- Adipose tissues 2- Muscle Non Insulin dependent tissues:1- Brain 3- Kidney 5- intestine 2-RBCs 4- Retina

Glycolysis pathway: Oxidation of glucose to Pyruvate +water+ NADH2 in steps wise (10 steps).It employ by most tissues, for the break down of glucose to provide energy.* Glycolysis pathway occurs in most cell in the presences of oxygen and called (aerobic glycolysis)An-aerobic glycolysis: occurs in the completely absent of oxygen or partial deficiency of oxygen.

An aerobic glycolysis found in: 1- Red blood cells (no mitochondria) 2-Labor (partial deficiency of oxygen)3-Exercise muscle (partial deficiency of oxygen)4-Cancer cells

1- Glucose Hexokinase [Glucokinase] Glucose-6-phosphate Mg++ ATP ADP

2- Glucose-6-phospha Fructose-6- phosphate phospho hexsose isomerase

phospho fructo kinase3- Fructose-6- phosphate Fructose 1-6 diphosphate ATP ADP

4- Fructose 1-6 diphosphate Aldolase

Glyceraldehyde -3- phosphate + Dihydroxy acetone phosphate

5-** Glyceraldehyde -3- phosphate Dihydroxy acetone phosphate phospho triose isomerase

6- 2x Glyceraldehyde -3- phosphate Pi + NAD Glyceraldehyde-3-phosphate dehydrogenase

NADH2

1 - 3 diphosphoglycerate

9

7- 1-3diphosphoglycerate

ADP Phosphoglycerate Kinase ATP8- 3- Phosphoglycerate Phosphoglycerate mutase

9- 2- Phosphoglycerate

10- 2- Phosphoglycerate

Enolase

phosphoenolpyruvate + H2O

11

10- phosphoenolpyruvate

ADP Pyruvate Kinase ATP

Pyruvate

Anaerobic glycolysis:- Pyruvate lactate dehydrogenase lactate NADH2 NAD

Citric acid cycle

Occur inside the mitochondria (house of energy).Note:End product of aerobic glycolysiswhich can not penetrate mitochondria membrane their for must be converted to Acetyl CoA

Pyruvate

pyruvate dehydrogenase complex

Acetyl CoA

Co-enzymes of pyruvate dehydrogenase complex:-1- Nicotinamide adenine dinucleotide (NAD)2- Falavin aminde dinucleotide (FAD)3- Co- enzyme A [COA]4- Lipoic acid5- Thiamine pyrophosphate

Citric acid cycleOccur inside the mitochondria (house of energy)1- Acetyl CoA + Oxaloacetate Citrate synthase Citrate 2- Citrate aconitase Iso-citrate +H2O

3- Iso-citrate +NAD Iso-citrate -Ketoglutarate +NADH2 +CO2 dehydrogenase

4- -ketoglutarate +NAD +COA

-Ketoglutarate dehydrogenase

Succinyl-COA + NADH2 +CO2

5-Succinyl-COA +ADP +Pi

Succinyl-coA thiokinase

Succinate +COA +ATP (substrate level phosphorylation)6-succinate + FAD succinate dehydrogenase

Fumarate + FADH2

7-Fumarate +H2O Fumarase Malate

8- Malate + NAD

Malate dehydrogenase

Oxaloacetate +NADH2

ATP: Adenosine tri-phosphate ADP: Adenosine di-phosphateNAD: nicotinamide adenine dinucleotideFAD: flavine adenine dinucleotide

AcetylCOA + 3NAD + FAD + ADP+Pi

C. A. C

3NADH2 + FADH2 + ATP +2CO2

3NADH2 FADH2 ATP Electron transport chains (E.T.C )33= 9 ATP 12= 2ATP ATP

Energy production from complete oxidation of glucose :-2 ATP (glycolysis) 2 ATP 2NADH2 (glycolysis) E.T.C 23 = 6 ATP

2NADH2 (Pyruvate dehydrogenase) E.T.C 23 = 6 ATP 2 Acetyl-coA(212 ATP) 24 ATP

Net energy from aerobic glycolysis:2 ATP + 6 ATP + 6 ATP + 24 ATP = 38 ATP

Electron transport chain (E.T.C): This pathway is found in inner mitochondria matrix, energy rich molecules, such as glucose or fatty acids are metabolized by series of oxidation reaction ultimately yielding co2 and H20.

Drugs inhibited E.T.C:- 1- OligomycinUncoupler: Stop phosphorylation in the occurs of oxidation i- 2,4- dinitrophenolii- High doses of aspirin

NADH2 FADH2

Complex 1 complex2 Complex 3

NAD FAD

O2 ADP + Pi

ATP SynthaseComplex 4 Complex 5

H2O ATP