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Transcript
Chapter 19 blood biochemistry What makes up our blood? What makes up our blood? • PLASMA – This is the yellowish liquid portion of blood that contains electrolytes, nutrients and vitamins, hormones, clotting factors, and proteins such as antibodies to fight infection. • RED BLOOD CELLS (Erythrocytes) – The most abundant cells in our blood; they are produced in the bone marrow and contain a protein called hemoglobin that carries oxygen to our cells. • WHITE BLOOD CELLS (Leukocytes) – They are part of the immune system and destroy infectious agents called pathogens. • PLATELETS (Thrombocytes) – The clotting factors that are carried in the plasma; they clot together in a process called coagulation to seal a wound and prevent a loss of blood. We will learn: - Composition of plasma - Metabolism of Red blood cells Section 1 Composition of plasma • Composition • Non-protein nitrogen (NPN) • Plasma proteins Components of Plasma • Liquid part of blood, made up of 92% water, 8% soluble substances. • soluble substances include organic compounds and inorganic compounds. • Electrolyses are the major inorganic compounds including Na+, K+, Ca2+, Mg2+ and Cl-, HCO3- etc, which are responsible for maintain of crystal osmotic pressure, acid-base balance, and normal neuromuscular excitability. Components of Plasma • Organic compounds include proteins, organic nutrients, hormones and waste products. • NPN (non-protein nitrogen): It includes urea, uric acid, creatinine, creatine, bilirubin and ammonia, the nitrogen in which is termed NPN. • 50% of NPN is blood urea nitrogen (BUN). Significance of NPN • NPN has little nutrition and is transported to the kidneys for excretion from the urine. • NPN is an index of renal function. • 50% of NPN is blood urea nitrogen (BUN), clinically, determinate BUN rather than NPN to reflect renal function. Difference between plasma and serum • Serum: After blood clotting, the liquid separated from the clot. No fibrinogen • Serum has the same composition as plasma except for fibrinogens, which are used up during clotting. Classes of Plasma Proteins • Plasma proteins are very complicated mixture • Main protein can be divided into: -Albumins (60%) -Globulins (35%) -Fibrinogen (4%) Separation of plasma protein • The plasma proteins are usually classified according to the source, separation methods and physiological functions. • The general methods of proteins separation are electrophoresis and ultracentrifugation. Separation of plasma protein electrophoresis • It is the most common method to separate plasma proteins. • Separate proteins based on their physical characteristics, such as pI (Isoelectric point), molecular weight and size. Separation of plasma protein electrophoresis - Using cellulose acetate electrophoresis, plasma protein can be separated into six groups. anode cathode Albumin α1globulin α2globulin βglobulin fibrinogen γglobulin If serum is separated using this method, how many bands will be appear ? What are they? Section 2 Metabolism of red blood cells Structure of RBC -Small and highly specialized disc -Thin in middle and thicker at edge Red blood cells (erythrocytes) • They are the most important cells in blood, formed through direct differentiation of haemopoietic stem cells in marrow. • Erythropoiesis refers to as the production of erythrocytes. • The procedure of cell transformation: proerythroblast, erythroblast, intermediate erythroblast, later erythroblast, reticulocyte. • The overall transformation from the proerythroblast to reticulocyte involves a reduction in cell size, an increase in cell number and the synthesis of hemoglobin. Metabolic characteristics of mature erythrocytes • Mature erythrocyte does not possess other organelles, except plasma membrane and cytoplasma. • Its metabolism is simpler and only contains four basic classical pathways: glycolysis, pentose phosphate pathway, adenine nucleotide metabolism and 2, 3-BPG shunt. • The task of these metabolisms is to produce the necessary cofactors ( ATP, NADPH and NADH) for maintaining its osmotic balance and electroneutrality and fighting oxidative stresses. Metabolic characteristics of mature erythrocytes glycolysis • Erythrocytes consume about 30g glucose each day, of which 90-95% enter into glycolysis and 2, 3-BPG shunt, 5%-10% through pentose phosphate pathway. • Mature erythrocytes depend on glycolysis for ATP production. • ATP is used to maintain the biconcave disk shape, ion balance, and so on. Metabolic characteristics of mature erythrocytes (1,3-BPG) (2,3-BPG) 2,3-BPG pathway Role of 2,3-bisphosphoglycerate (2,3-BPG) • Activity of diphosphoglycerate mutase is much high than that of diphosphoglycerate phosphatase, so the concentration of 2,3-BPG is very high in erythrocytes. 1 heme : 1 O2 Release oxygen T state T state R state R state Role of 2,3-bisphosphoglycerate (2,3-BPG) • 2,3-BPG is a potent allosteric effector on the oxygen binding properties of hemoglobin. • In the deoxygenated T conformer, 2,3-BPG can occupy a cavity which locate in the center of the hemoglobin. • 2,3-BPG stabilizes the T state of hemoglobin, causes the release of more oxygen • Its main function is regulating the ability of transporting oxygen of hemoglobin. Biochemical features of RBC • • • • Lifespan is about 120 days Lack nuclei, mitochondria, and ribosomes Essential component is hemoglobin Function -Transport oxygen from lungs to tissues and carbon dioxide from tissues to lungs Hemoglobin • Consist of 4 globular protein subunits: – each with 1 molecule of heme – each heme contains 1 iron ion – Each iron ion with 1 O2 • Iron ions easily: 1 Hb : ? O2 1 Hb : 4 O2 – associate with oxygen (oxyhemoglobin) – or dissociate from oxygen (deoxyhemoglobin) Hemoglobin Biosynthesis of hemoglobin Globin: The synthesis is similar to other proteins Consist of 4 subunits (2+2 ) Heme: is not only the prosthetic group of Hb, but also the prosthetic group of myoglobin, cytochrome and peroxydase. Heme synthesis • The principal sites of synthesis are erythroid cells (~85%) and hepatocytes (accounting for nearly all the rest of heme synthesis). • Mitochondrion and cytoplasm are involved in heme synthesis. • Materials needed in synthesis are succinylCoA, glycine and Fe2+. • Synthesis of heme can be divided into four steps. Heme synthesis pathway Heme synthesis pathway The First step • take place in mitochondria -aminolevulinate • ALA synthase synthase catalyze this reaction • It is the rate-limiting reaction in heme synthesis Regulation of heme biosynthesis • Negative Feedback control: heme inhibit synthesis and activity of ALA synthase. • Erythropoietin(EPO): increase heme synthesis to carry more oxygen. EPO Scandal • EPO is a hormone involved in red blood cell production and increases the body's oxygen delivery. For this reason, it's usually used in endurance sports like cycling, distance running, and boxing. • However, EPO is thought as a blood doping by the World Anti-doping Agency. Although EPO has been banned since the 1990s, the first screening test was used at the 2000 Summer Olympic Games in Sydney. EPO Scandal Lance Armstrong • He is an American former professional road racing cyclist. • He had won the Tour de France a record seven consecutive times between 1999 and 2005. • On August 24, 2012 it announced a lifetime ban from competition, applicable to all sports which follow the US Anti-Doping Agency (USADA) code, as well as the stripping of all titles won since August 1998.[ Because USADA detected EPO in his urine samples which keeped before. The formed elements in blood include , and . The nitrogen in , , , and which is an index of function. is termed NPN, Difference between plasma and serum is plasma containing , which is absent in serum. The general methods of proteins separation are and . Using cellulose acetate electrophoresis, serum protein can be separated into , , cathode ). and groups, they are respectively (from anode to , • Which the following statements about serum protein separation by electrophoresis is not right? A. It is the most common method to separate plasma proteins. B. It separate proteins based on their pI, molecular weight and size. C. After electrophoresis, there are six bands on cellulose acetate membrane. D. The band nearest to anode is albumin. E. The migration speed of -globulin is slowest. In mature RBC, pathway produces ATP. Pentose Phosphate pathway can provide . In mature RBC, there is a shunt, the product of this pathway can stimulate hemoglobin to release more . The function of hemoglobin is to Transport to tissues and from tissues to lungs . from lungs Heme synthesis mainly occurs in and of cells. The synthesis Materials include , and , the rate-limiting enzyme is .