10Ammonification or Mineralization NH4NO2R-NH2NONO2NO3
11Mineralization or Ammonification Decomposers: earthworms, termites, slugs, snails, bacteria, and fungiUses extracellular enzymes initiate degradation of plant polymersMicroorganisms uses:Proteases,lysozymes, nucleases to degrade nitrogen containing molecules
12Plants die or bacterial cells lyse release of organic nitrogen Organic nitrogen is converted to inorganic nitrogen (NH3)When pH<7.5, converted rapidly to NH4Example:Urea NH3 + 2 CO2
13Immobilization The opposite of mineralization Happens when nitrogen is limiting in the environmentNitrogen limitation is governed by C/N ratioC/N typical for soil microbial biomass is 20C/N < 20 MineralizationC/N > 20 Immobilization
14Nitrogen Fixation Energy intensive process : N2 + 8H+ + 8e ATP = 2NH3 + H2 + 16ADP + 16 PiPerformed only by selected bacteria and actinomycetesPerformed in nitrogen fixing crops(ex: soybeans)
15Microorganisms fixing AzobacterBeijerinckiaAzospirillumClostridiumCyanobacteriaRequire the enzyme nitrogenaseInhibited by oxygenInhibited by ammonia (end product)
17Bacterial Fixation Occurs mostly in salt marshes Is absent from low pH peat of northern bogsCyanobacteria found in waterlogged soils
18Nitrification Two step reactions that occur together : 1rst step catalyzed by Nitrosomonas2 NH O2 2 NO2- +2 H2O+ 4 H+2nd step catalyzed by Nitrobacter2 NO2- + O2 2 NO3-
19Optimal pH is betweenIf pH < 6.0 rate is slowedIf pH < 4.5 reaction is inhibited
20Denitrification Removes a limiting nutrient from the environment 4NO3- + C6H12O6 2N2 + 6 H20Inhibited by O2Not inhibited by ammoniaMicrobial reactionNitrate is the terminal electron acceptor
21Metal ionsMany metal ions have role in biological processes of the bodyThe ions have different physical and chemical propertiesComplex formationOxidation statesMinerals in food
22The most important ions Ca2+Mg2+Fe2+Cu2+Zn2+Co3+Na+K+Role:1.5-2% of body mass, bones, teethBones and teeth, intracellular activityHemoglobin, O2 transferCofactor in enzymesCofactor in enzymes,growth, healingIn vitamin B12Water balance, nerve impulses, fluids inside and outside cells
23Oxygen transport proteins hemoglobin Hemoglobin is a tetramer composed of two α and two β subunitsEach subunit contains an iron-porphyrin ring that binds oxygenOxygen binding is highly cooperative between each subunit
27Oxygen 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.
30Hemoglobin Oxygen carrier protein 4 subunits = 2 alpha + 2 beta Normal adult = HbA = a2b2Four heme groups - iron-porphyrin compound at O2 binding siteIron containing porphyrin rings, only Fe2+ can bind O2Each heme combines with one globin protein chainMolecular weight of hemoglobin is 64,000Each gm of Hb can carry up to 1.31ml of O2, theoretically up to ml/gm
31Chemical Binding of Hemoglobin & Oxygen Hemoglobin combines reversibly with O2Hemoglobin is the unoxygenated formOxyhemoglobin is when O2 combinedAssociation and dissociation of Hb & O2 occurs within millisecondsCritically fast reaction important for O2 exchangeVery loose coordination bonds between Fe2+ and O2, easily reversibleOxygen carried in molecular state (O2) not ionic O2-
32Haemoglobin Saturation Haemoglobin saturation is the amount of oxygen bound by each molecule of haemoglobinEach 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.
33Pathological Ligands of Hemoglobin Ligands form covalent bonds to the ferrous iron in HbThese bonds have more affinity to iron than oxygen which binds weakly to HbCarbon Monoxide250 times the affinity than oxygenDoes not dissociate readilyRequires hours to rid body of CONitric OxideBinds to Hb 200,000 times more stronglyHemoglobin binds irreversibly to NOUsed to treat pulmonary hypertension
34Hemoglobin & Myoglobin Myoglobin is single chained heme pigment found in skeletal muscleMyoglobin has an increased affinity for O2 (binds O2 at lower Po2)Mb stores O2 temporarily in muscle
35Myoglobin and Hemoglobin Increases O2 solubility in tissues (muscle)Facilitates O2 diffusionStores O2 in tissuesHemoglobinTransports O2 from lungs to peripheral tissues (erythrocytes)
39PorphyrinPorphyrin rings are biological molecules used in a variety of essential chemical processesThe two most well-known porphyrins are heme and chlorophyll
40HemeBecause of their large conjugated double bond system, porphyrins typically absorb visible lightChlorophyll’s green color, heme’s red, and the blue blood of some sea creatures are all a result of this absorbanceAdditionally, the 4 nitrogen atoms at the center of the ring are excellent at conjugating metals because of their lone pairsAs a result, porphyrins are a common way to attach metals to proteins
41Chlorophyll –porphyrins are important in plants, too! Chlorophyll as a PhotoreceptorChlorophyll 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.
42ChrophyllPorphyrin 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 colourSeveral 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.
46Photosynthesis Overview Two processes - each with multiple stepsLight reactionsconvert solar energy to chemical energylight energy drives transfer of electrons to NADP+ forming NADPHATP generated by photophosphorylationoccur at the thylakoids
47Photosynthesis Overview Two processes - each with multiple stagesCalvin cycleNamed for Melvin Calvin who worked out many of the steps in the 1940sincorporates CO2 from the atmosphere into an organic molecule (carbon fixation)uses energy from the light reaction to reduce the new carbon to a sugaroccurs in the stroma of the chloroplast
49Light 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.
502. Each Cluster of Pigment Molecules is referred to as a PHOTOSYSTEM. COVERTING LIGHT ENERGY TO CHEMICAL ENERGY1. 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..
51PhotosystemPhotosystem 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.
58Light (dependent)Reactions Happen ONLY in sunlightHence they depend on light!Light is absorbed by chlorophyll moleculesThe energy generates molecules of ATPImage from: Biology 11: College Preparation. Pg 74. Nelson, Toronto
59SummaryImage from: Biology 11: College Preparation. Pg 74. Nelson, Toronto