What are the Functions of Lymph?

1. Lymph acts as a “middle man” which transports oxygen, food materials, hormones, etc., to the body cells and brings carbon dioxide and other metabolic wastes, from the body cells to blood and then finally pours the same into the venous system.

2. Body cells are kept moist by the lymph.

3. Lymph nodes produce lymphocytes. Lymph takes lymphocytes and antibodies from the lymph nodes to the blood.’

4. It destroys the invading microorganisms and foreign particles in the lymph nodes.

5. It absorbs and transports fat and fat soluble vitamins from the intestine. Lymph capillaries present in the intestinal villi are called lacteals which are associated with absorption and transportation of fat and fat soluble vitamins.

6. It brings plasma portein macromolecules synthesized in the liver cells and hormones produced in the endocrine glands to the blood. These molecules cannot pass into the narrow blood capillaries but can diffuse into the lymphatic capillaries.

7. Lymph maintains the volume of the blood, as soon as the volume of the blood reduces in the blood vascular system, the lymph rushes from the lymphatic systems to the blood vascular system.

Blood Groups :

The term blood group is applied to any well-defined system of red blood corpuscle antigens which are inherited characteristics. Over 20 blood group systems having approximately 400 blood group antigens are currently recognised. Some blood groups are mentioned below:

(i) ABO blood group, the classical blood group systems defined by the agglutination reactions of erythrocytes to the natural is antibodies anti A and anti B and related anti sera (Landsteiner 1900).

(ii) Rh blood group (erythrocyte antigens defined originally by reactions to serum from rabbits or guinea pigs immunized with blood of rhesus monkey, Landsteiner and Wiener 1940)

(iii) Auberger blood group (it was found in the serum of a Madame Auberger who had received many transfusions).

(iv) Diego blood group (the antigen systems is controlled by two alleles,).

(v) Dombrock blood group (the Do antigen exhibits autosomal dominant ‘inheritance).

(vi) Duffy blood group (the erythrocyte antigens defined by reactions to an immune serum called anti first found in a haemophilic patient named duffy).

(vii) I blood group (the erythrocyte antigens defined by antigens to antibodies designated antigen).

(viii) Kell blood group (the erythrocytic antigens defined by an immune anti body, anti-K first found in the serum of a Mrs. Kell.)

(ix) Kidd blood group (the erythrocyte antigens defined by reactions to an antibody designated anti discovered in the serum of a Mrs. Kidd, who had delivered an infant with erythroblast sis?

(x) Lew is blood group (the antigens of erythrocytes, saliva and certain other body fluids defined by reactions to anti-Le^a anti body, first found in the serum of a Mrs. Lewis).

(xi) Lutheran blood group (the blood group antigens defined by reactions to an antibody designated anti-Lu first found in serum of a patient who had received many transfusions).

(xii) MNSs blood group (the system of erythrocyte antigens originally defined by reactions to immune rabbit sera designated anti-M and anti-N (Landsteiner and Levine 1927) and since extended by reaction to sera anti-S, anti-s and certain others).

(xiii) P blood group (the erythrocyte antigens originally defined by reactions to immune rabbit serum designated anti P (Landsteiner and Levine 1927).

(xiv) Sutter blood group (the erythrocyte antigen defined by reaction to an antibody designated anti- found in the serum of a Mrs. Sutter who had been previously transfused).

(xv) Xg blood group (the erythrocyte antigen defined by reaction to an antibody designated anti-Xg which was found in the serum of a patient who had received many transfusions).

The ABO and rhesus (Rh) blood groups are of major clinical significance. Other blood groups are minor and are clinically less important.

ABO Blood Group. A, B and O blood groups were discovered by Landsteiner in 1900 and he got Nobel Prize in 1930 for the discovery of ABO blood group. AB blood group was discovered later by Castello and Steini (1902).

Phosphorylation occurs in the mitochondria. As electrons are passed from NADH and FADH₂ along the electron transport system. ATP molecules are made from energy released by a process called chemiosmosis. (it) Glucose Catabolism: Glycolysis, also known as the Embden- Myerh of pathway is the central pathway of carbohydrate metabolism and occurs in the cytosol of all cells. The pathway consists of 10 reactions that convert glucose to two molecules of private.

13. Entry and Trapping Glucose in the Cell: We have seen that the entry of glucose into cells is carrier-mediated by membrane proteins that move glucose down a [] gradient. Once inside the cell glucose is rapidly phosphorylated to G6P. This ensures that the [] gradient is maintained and that, glucose doesn’t leak back out of the cell.

Regulation of Glycolysis: The primary site of regulation of glycolysis is Phosphofructokinase -1. Two other sites of regulation are less important. Phosphofructokinase-1 is an enzyme that catalyzes the conversion of F6P to Fl, 6P” it is under allosteric control. When [ATP] high then activity of enzyme is” reduced, when [ATP] is low, then activity of enzyme is increased. This is a simplistic view of the action of this enzyme, but for our purposes it will suffice.

When activity of enzyme low, such as when ATP is abundant, most G6P is converted to glycogen for storage or it goes into other pathways.

Substrate level phophorylation in glycolysis: Notice that 4 molecules of ATP are formed in glycolysis by substrate level phosphorylation. Recall that it requires two molecules of ATP for glycolysis, hence the net production of ATP is 2 molecules per molecule of glucose. Example of substrate level phosphorylation-1,3, bisphosphoglycerate to 3-Phosphoglycerate.

19. Fate of Pyruvate: The fate of the pyruvate molecule depends on the availability of oxygen. If oxygen concentration is low, for example during vigorous exercise, or as in RBC which have no mitochondria, the pyruvate converted to lactate. The reaction is:

20. This reaction is catalyzed by lactate dehydrogenase (LDH). Notice that NAD+ is produced, a necessary molecule if glycolysis is to proceed.

21. Lactate diffuses out of cell, into blood stream, then to liver, where lactate is converted back to pyruvate.

22. If oxygen concentration high, pyruvate is taken into mitochondria where converted to acetyl CoA. A transporter in membrane of mitochondria is required to get pyruvate into mitochondrial matrix

23. Balance sheet for Glycolysis

Glucose +2 ATP + 2 NAD + 4 ADP + 2 Pi -> 2 pyruvate + 2 ADP +2 NADH + 2 H + 4 ATP

24. Net gain: under aerobic conditions

2ATP and 2NADH per mole glucose

25. The final step of oxidation of metabolic fuels is carried out by the electron transport system (ETS), which oxidizes NADH and FADH, to NAD+ and FAD.

26. The electrons are transferred through a series of carriers to molecular oxygen forming water.

27. The ETS is the major consumer of oxygen within the cell.

28. Coenzyme Q collects electrons from both complex 1 and complex 2 and transfers them to complex 3.

29. Cytochrome c is mobile in the membrane and transfers electrons from complex 3 to complex 4. The terminal electron acceptor is oxygen.

30. The reduction of each atom of oxygen to water requires two electrons.

31. FMN and FAD-FMN is a cofactor for complex 1, which oxidizes NADH to NAD with the concomitant reduction of FAD to FADH,. FAD is a cofactor for complex 2, which oxidizes succinate to fumarate with the formation of FADH_r

32. CoQ-small lipophilic cofactor that moves in the lipid bilayer. Transfers electrons to cytochrome-b.

33. Iron-sulfur centres-contain iron atoms. Proteins with iron sulfur centres are found in complex 1,3,4.

34. Heme-the prosthetic group of cytochromes has a central iron atom that participates in electron transfer.

35. The chemiosmotic theory has two postulates.

(i) As electrons flow through the ETS, the energy released is used to create a H⁺ gradient across the inner mitochondrial membrane. (ii) And the movement of protons back across the membrane releases energy that can be used to drive ATP synthesis.

36. Complexes 1,3,4 are H⁺ pumps that transfer H⁺ from the mitochondrial matrix into the space between the IMM and the OMM.

37. ATP synthesis is catalyzed by ATP synthase. H⁺ ions apparently move through this protein complex driving the phosphorylation of ADP to ATP.

38. For each NADH, 3 ATP are formed. For each FADH₂, 2 ATP are formed.