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Cellular Biochemistry and Metabolism (CLS 331). Dr. Samah Kotb Nasr Eldeen. Topics were covered in theoretical part. Introduction to Metabolism Digestion and absorption The role of vitamins in metabolism. Topics were covered in practical part. lab safety
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Cellular Biochemistry and Metabolism(CLS 331) Dr. Samah Kotb Nasr Eldeen
Topics were covered in theoreticalpart • Introduction to Metabolism • Digestion and absorption • The role of vitamins in metabolism
Topics were covered in practical part • lab safety • Hydrolysis of starch by salivary amylase
CHAPTER1 Metabolism
General Introduction: Metabolism is the study of the chemical reactions that occur inside living cells. Updates over 2000 such reactions have been documented. Although this is a large number, there is a high degree of organization and order that govern these reactions. Metabolic reactions do not occur at random inside cells but take the shape of chains or series known as Metabolic Pathways. • Some pathways are short made of 2 or 3 reactions or long made of 20, 30 or 40 reactions.
Types of Pathways There are 2 types of metabolic pathways that occur inside cells:- 1) Catabolic Pathways These are made of reactions through which energy rich nutrient molecules are broken down by chemical reactions into simple end products. As a result of catabolic pathways energy is produced and released to the cell.
2) Anabolic Pathways: These are pathways made of reactions that result in the synthesis of biomolecules using basic unit components. These biomolecules are either biologically or structurally important to the cells. • Anabolic reactions & pathways require an input of energy to take place.
Regulation of Cellular Metabolism:- Cells use 3 mechanisms to regulate (speed up or slow down) the rate of metabolic activity:- • Allosteric Enzymes. • Availability of Enzymes. • Hormonal Regulation.
1) Allosteric Regulation: This is done by the use of allosteric enzymes which are usually key enzymes of metabolic pathway. • Structure of enzymes:- Enzymes are globular proteins made of peptide chains that have folded on each other in a specific manner that results in the formation of a globular macro protein with an active site at the periphery of the protein molecule.
Allosteric Regulation Mechanism: Allosteric modulators are of 2 types:- • An allosteric stimulator module of the enzyme. • An allosteric inhibitor molecule of the enzyme.
2) Availability of Enzymes: Upon consumption of a meal rich in carbohydrate and as digestion in the GIT occurs, large amounts of glucose will be absorbed into the blood. As a result there will be an influx of glucose into cells. Cells react by synthesizing larger than usual amounts of glucose degradative enzymes in order to increase the rate of its catabolism. The levels of amino acids (a.a.) catabolic enzymes or fatty acids (f.a.) catabolic enzymes stays normal. If the meal was rich in proteins, a.a. catabolic enzymes will be synthesized in large amounts.
3) Hormonal Regulation: Hormones are organic type molecule synthesized and secreted by special type tissues known as endocrine glands. The hormones pour from the gland directly in to the blood and are transported in the blood until they reach what is known as target tissue cells. The hormone is recognized by its target cells; by way of receptors present the outer surface of the cell membrane. As a result of the binding between the hormone and its receptor a series of chemical reactions inside the cell occurs that result in either an increase or a decrease in the rate of a certain biochemical pathway.
3) Hormonal Regulation: Example for the hormonal regulation: Adrenaline is a hormone synthesized and secreted by the adrenal medullary cells. Adrenaline leaves the gland and is transported in the blood until it reaches its target cells which are liver and muscle cells. As the hormone binds to its target cells large amounts of an intracellular secondary messenger (Cyclic AMP) are synthesized. This will cause an increase in the catabolic pathway responsible for breaking down Glycogen into glucose (G).
The extra glucose leaves muscle and liver & is distributed to the various tissues. Adrenaline is released from the adrenal medulla under conditions of emotional or physical stress. The body under such conditions requires extra catabolism of G for extra energy production.
Other Hormones include:- Insulin synthesized and secreted by the β cells of the pancreas. Its target cells include muscle & adipose tissue. It acts to lower plasma glucose levels by: • Increase the rate of glycolysis. • Increase the rate of glycogenesis. • Increase the rate of entry of glucose into cells.
Chapter 2 digestion Dr Samah Kotb
Transport of glucose, fructose, and galactose across the intestinal epithelium. Dr Samah Kotb
Triacylglycerols Stomach gastric lipases 1,2-diacylglycerols + free fatty acids Pancreatic lipase small intestine 2-monoacylglycerols + free fatty acids hydrolysis Secreted as chylomicrons into the lymphatics, entering the blood stream via the thoracic duct . free fatty acids + glycerol Portal vein Dr Samah Kotb
Triacylglycerols Stomach gastric lipases 1,2-diacylglycerols + free fatty acids Pancreatic lipase small intestine 2-monoacylglycerols + free fatty acids hydrolysis Secreted as chylomicrons into the lymphatics, entering the blood stream via the thoracic duct . free fatty acids + glycerol Portal vein Dr Samah Kotb
A vitamin is both: • An organic compound (contains carbon). • An essential nutrient, the body cannot produce enough of on its own, so it has to get it (tiny amounts) from food.
Clinical conditions • Thiamin deficiency, called beribericaused by dietary deficiency of thiamine (vitamin B1 ). It affects the nerves to the limbs, producing pain, paralysis).
Clinical conditions • Riboflavin deficiency, also known as ariboflavinosis, occurs in areas with long periods of low intake. • Symptoms include the inflammation and breakdown of tissue, swollen and cracked lips, swollen tongue, and red, itchy eyes.
Newborn infants with jaundice that are treated with phototherapy have shown signs of riboflavin deficiency. • Toxicity is non-existent. Excess riboflavin is readily excreted in the urine.
