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Unit II Metal ions in Biological systems

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Presentation on theme: "Unit II Metal ions in Biological systems"— Presentation transcript:

1 Unit II Metal ions in Biological systems
Dr. SS. Vutukuru, M.Tech., Ph.D, PG DEM

2 Nitrogen Fixation

3 Sources Lightning Inorganic fertilizers Nitrogen Fixation
Animal Residues Crop residues Organic fertilizers

4 Encyclopaedia Britannica, Encyclopaedia Britannica (1998)

5 Forms of Nitrogen Urea  CO(NH2)2 Ammonia  NH3 (gaseous)
Ammonium  NH4 Nitrate  NO3 Nitrite  NO2 Atmospheric Dinitrogen N2 Organic N

6 Global Nitrogen Reservoirs
Metric tons nitrogen Actively cycled Atmosphere 3.9*1015 No Ocean  soluble salts Biomass 6.9*1011 5.2*108 Yes Land  organic matter  Biota 1.1*1011 2.5*1010 Slow

7 Roles of Nitrogen Plants and bacteria use nitrogen in the form of NH4+ or NO3- It serves as an electron acceptor in anaerobic environment Nitrogen is often the most limiting nutrient in soil and water

8 Nitrogen is a key element for
amino acids nucleic acids (purine, pyrimidine) cell wall components of bacteria (NAM)

9 Nitrogen Cycle Ammonification/mineralization Immobilization
Nitrogen Fixation Nitrification Denitrification

10 Ammonification or Mineralization

11 Mineralization or Ammonification
Decomposers: earthworms, termites, slugs, snails, bacteria, and fungi Uses extracellular enzymes  initiate degradation of plant polymers Microorganisms uses: Proteases,lysozymes, nucleases to degrade nitrogen containing molecules

12 Plants die or bacterial cells lyse  release of organic nitrogen
Organic nitrogen is converted to inorganic nitrogen (NH3) When pH<7.5, converted rapidly to NH4 Example: Urea NH3 + 2 CO2

13 Immobilization The opposite of mineralization
Happens when nitrogen is limiting in the environment Nitrogen limitation is governed by C/N ratio C/N typical for soil microbial biomass is 20 C/N < 20 Mineralization C/N > 20 Immobilization

14 Nitrogen Fixation Energy intensive process :
N2 + 8H+ + 8e ATP = 2NH3 + H2 + 16ADP + 16 Pi Performed only by selected bacteria and actinomycetes Performed in nitrogen fixing crops (ex: soybeans)

15 Microorganisms fixing
Azobacter Beijerinckia Azospirillum Clostridium Cyanobacteria Require the enzyme nitrogenase Inhibited by oxygen Inhibited by ammonia (end product)

16 Rates of Nitrogen Fixation
N2 fixing system Nitrogen Fixation (kg N/hect/year) Rhizobium-legume Cyanobacteria- moss 30-40 Rhizosphere associations 2-25 Free- living 1-2

17 Bacterial Fixation Occurs mostly in salt marshes
Is absent from low pH peat of northern bogs Cyanobacteria found in waterlogged soils

18 Nitrification Two step reactions that occur together :
1rst step catalyzed by Nitrosomonas 2 NH O2  2 NO2- +2 H2O+ 4 H+ 2nd step catalyzed by Nitrobacter 2 NO2- + O2  2 NO3-

19 Optimal pH is between If pH < 6.0  rate is slowed If pH < 4.5  reaction is inhibited

20 Denitrification Removes a limiting nutrient from the environment
4NO3- + C6H12O6 2N2 + 6 H20 Inhibited by O2 Not inhibited by ammonia Microbial reaction Nitrate is the terminal electron acceptor

21 Metal ions Many metal ions have role in biological processes of the body The ions have different physical and chemical properties Complex formation Oxidation states Minerals in food

22 The most important ions
Ca2+ Mg2+ Fe2+ Cu2+ Zn2+ Co3+ Na+ K+ Role: 1.5-2% of body mass, bones, teeth Bones and teeth, intracellular activity Hemoglobin, O2 transfer Cofactor in enzymes Cofactor in enzymes,growth, healing In vitamin B12 Water balance, nerve impulses, fluids inside and outside cells

23 Oxygen transport proteins hemoglobin
Hemoglobin is a tetramer composed of two α and two β subunits Each subunit contains an iron-porphyrin ring that binds oxygen Oxygen binding is highly cooperative between each subunit

24 Oxygen transport

25 Hemoglobin as oxygen carrier
In each hemoglobin molecule there are four heme groups Heme = Fe2+ surrounded by phorphyrin group, As O2 carrier: O2 binds to Fe2+ as a ligand Reversible process

26 The transport of oxygen in blood - Haemoglobin

27 Oxygen Transport The resting body requires 250ml of O2 per minute.
We have four to six billion haemoglobin containing red blood cells. The haemoglobin allows nearly 70 times more O2 than dissolved in plasma.

28 Hemoglobin Binding of O2 alters the structure

29 Haemoglobin 4 x Haem group x Polypeptide chain

30 Hemoglobin Oxygen carrier protein 4 subunits = 2 alpha + 2 beta
Normal adult = HbA = a2b2 Four heme groups - iron-porphyrin compound at O2 binding site Iron containing porphyrin rings, only Fe2+ can bind O2 Each heme combines with one globin protein chain Molecular weight of hemoglobin is 64,000 Each gm of Hb can carry up to 1.31ml of O2, theoretically up to ml/gm

31 Chemical Binding of Hemoglobin & Oxygen
Hemoglobin combines reversibly with O2 Hemoglobin is the unoxygenated form Oxyhemoglobin is when O2 combined Association and dissociation of Hb & O2 occurs within milliseconds Critically fast reaction important for O2 exchange Very loose coordination bonds between Fe2+ and O2, easily reversible Oxygen carried in molecular state (O2) not ionic O2-

32 Haemoglobin Saturation
Haemoglobin saturation is the amount of oxygen bound by each molecule of haemoglobin Each molecule of haemoglobin can carry four molecules of O2. When oxygen binds to haemoglobin, it forms OXYHAEMOGLOBIN; Haemoglobin that is not bound to oxygen is referred to as DEOXYHAEMOGLOBIN.

33 Pathological Ligands of Hemoglobin
Ligands form covalent bonds to the ferrous iron in Hb These bonds have more affinity to iron than oxygen which binds weakly to Hb Carbon Monoxide 250 times the affinity than oxygen Does not dissociate readily Requires hours to rid body of CO Nitric Oxide Binds to Hb 200,000 times more strongly Hemoglobin binds irreversibly to NO Used to treat pulmonary hypertension

34 Hemoglobin & Myoglobin
Myoglobin is single chained heme pigment found in skeletal muscle Myoglobin has an increased affinity for O2 (binds O2 at lower Po2) Mb stores O2 temporarily in muscle

35 Myoglobin and Hemoglobin
Increases O2 solubility in tissues (muscle) Facilitates O2 diffusion Stores O2 in tissues Hemoglobin Transports O2 from lungs to peripheral tissues (erythrocytes)

36 Figure 7-17a

37 Sickle-cell

38 Capillary Blockage

39 Porphyrin Porphyrin rings are biological molecules used in a variety of essential chemical processes The two most well-known porphyrins are heme and chlorophyll

40 Heme Because of their large conjugated double bond system, porphyrins typically absorb visible light Chlorophyll’s green color, heme’s red, and the blue blood of some sea creatures are all a result of this absorbance Additionally, the 4 nitrogen atoms at the center of the ring are excellent at conjugating metals because of their lone pairs As a result, porphyrins are a common way to attach metals to proteins

41 Chlorophyll –porphyrins are important in plants, too!
Chlorophyll as a Photoreceptor Chlorophyll is the molecule that traps this 'most elusive of all powers' - and is called a photoreceptor. It is found in the chloroplasts of green plants, and is what makes green plants, green. The basic structure of a chlorophyll molecule is a porphyrin ring, coordinated to a central atom. This is very similar in structure to the heme group found in hemoglobin, except that in heme the central atom is iron, whereas in chlorophyll it is magnesium.

42 Chrophyll Porphyrin is also part of the chlorophyll, the key substance for the photosynthesis of green plants, some algae and some bacteria. Chlorophyll absorbs mainly violet-blue and orange-red light and reflect green colour which give plants their green colour Several kinds of chlorophyll exist (chl a,chl b etc.). They differ from each other in details of their molecular structure and absorb slightly different wavelengths of light.


44   Chlorophyll is composed of two parts; the first is a porphyrin ring with magnesium at its center, the second is a hyrophobic phytol tail.   The ring has many delocalized electrons that are shared between several of the C, N, and H atoms; these delocalized electrons are very important for the function of chlorophyll.  The tail is a 20 carbon chain stabilizes the molecule in the hydrophobic core of the thylakoid membrane.

45 Copyright © 2005 Pearson Education, Inc
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

46 Photosynthesis Overview
Two processes - each with multiple steps Light reactions convert solar energy to chemical energy light energy drives transfer of electrons to NADP+ forming NADPH ATP generated by photophosphorylation occur at the thylakoids

47 Photosynthesis Overview
Two processes - each with multiple stages Calvin cycle Named for Melvin Calvin who worked out many of the steps in the 1940s incorporates CO2 from the atmosphere into an organic molecule (carbon fixation) uses energy from the light reaction to reduce the new carbon to a sugar occurs in the stroma of the chloroplast

48 Interactions of light with chloroplast matter
Light may be reflected, absorbed, or transmitted by matter Pigments such as chlorophyll absorb photons of different wavelengths (energy) Plants are green because red and blue light are absorbed and green light is transmitted and reflected Light Reflected Light Absorbed Light Grana Transmitted Light Chloroplast Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

49 Light is composed of particles called photons that act like waves. 
Visible light is also called photosynthetically available radiation (PAR) . Changes in the wavelength of visible light (PAR) result in a change of color.  Light with a wavelength of 450 nm is blue while light with a wavelength of 650 nm is red. 

50 2. Each Cluster of Pigment Molecules is referred to as a PHOTOSYSTEM.
COVERTING LIGHT ENERGY TO CHEMICAL ENERGY 1. The Chlorophylls and Carotenoids are grouped in Cluster of a Few Hundred Pigment Molecules in the Thylakoid Membranes. 2. Each Cluster of Pigment Molecules is referred to as a PHOTOSYSTEM.  There are Two Types of Photosystems known as PHOTOSYSTEM I AND PHOTOSYSTEM II. 3. Photosystem I and Photosystem II are similar in terms of pigments, but they have Different Roles in the Light reactions. 4. The Light Reactions BEGIN when Accessory Pigment molecules of BOTH Photosystems Absorb Light. 5. By Absorbing Light, those Molecules Acquire some of the Energy that was carried by the Light Waves. 6. In each Photosystem, the Acquired Energy is Passed to other Pigment Molecules until it reaches a Specific Pair of CHLOROPHYLL a Molecules. .

51 Photosystem Photosystem is composed of the Light Harvesting Complex (LHC) and the reaction center.  The LHC is composed of hundreds of molecules of chlorophylls and accessory pigments.

52 How a photosystem harvests light
When any antenna molecule absorbs a photon, transferred to a particular chlorophyll a in the reaction center At the reaction center is a primary electron acceptor which removes an excited electron from the reaction center chlorophyll a Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

53 Reaction Center Closeup
Absorption of light boosts energy of an electron. Energy is passed from molecule to molecule in the light-harvesting complex until it reaches the reaction center Primary electron acceptor Chlorophyll a molecules Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

54 Two Types of Photosystems
Photosystem I reaction center chlorophyll a molecule P absorption peak at 700nm Photosystem II P680

55 Noncyclic Electron Flow
PS II PS I Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

56 A mechanical analogy for the light reactions
1) Photons of light boost energy of electrons. 2) Energy is extracted from electrons in the electron transport chain and used for ATP synthesis. 3) Another photon boosts energy of an electron which ultimately is transferred to NADPH 1) 2) 3) Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

57 Cyclic electron flow P700 Ferridoxin • No O2 generated
• No NADH generated • Only ATP generated P700 cyclic photophosphorylation Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings

58 Light (dependent)Reactions
Happen ONLY in sunlight Hence they depend on light! Light is absorbed by chlorophyll molecules The energy generates molecules of ATP Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto

59 Summary Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto

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