Microbial Metabolism

It is a type of metabolic reaction that results in the formation of adenosine triphosphate (ATP) or guanosine triphosphate (GTP) by the direct transfer and donation of a phosphoryl (PO3) group to adenosine diphosphate or guanosine diphosphate from a phosphorylated reacted intermediate. Unlike oxidative phosphorylation, oxidation and phosphorylation are not coupled in the process of substrate level phosphorylation, although both types of phosphorylation result in the formation of ATP. Oxidative phosphorylation occurs in the cytoplasm as a part of glycolysis and in mitochondrial as a part of Krebs's cycle.

Summary

It is a type of metabolic reaction that results in the formation of adenosine triphosphate (ATP) or guanosine triphosphate (GTP) by the direct transfer and donation of a phosphoryl (PO3) group to adenosine diphosphate or guanosine diphosphate from a phosphorylated reacted intermediate. Unlike oxidative phosphorylation, oxidation and phosphorylation are not coupled in the process of substrate level phosphorylation, although both types of phosphorylation result in the formation of ATP. Oxidative phosphorylation occurs in the cytoplasm as a part of glycolysis and in mitochondrial as a part of Krebs's cycle.

Things to Remember

  • ATP is the most important high-energy phosphate compound and its phospho- anhydride bond is referred to as high energy bonds and is created in the process of oxidative phosphorylation in mitochondria.
  • However, oxidative phosphorylation only occurs in mitochondrial. Substrate level phosphorylation is independent of aerobic or anaerobic condition whereas oxidative phosphorylation only occurs in the aerobic condition.
  • The NADH and FADH2 formed during glycolysis, -oxidation and the TCA cycle give electrons to reduce molecular oxygen to water. These electrons are transferred through a series of protein electron carriers in the electron transport chain.
  • The accompanying protons (H+) are released. A part of free energy harvested during the ETC is used to pump protons out of the mitochondrial matrix. 

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Q1:

What are the advantages of breast milk ?


Type: Long Difficulty: Easy

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Answer: <ul>
<li>Breast milk has anti infective properties that protect the infant from infection in the early months. Colostrum contains cellular anti-infective immunoglobulin substances like lymphocytes and microphages and enzymes, lysozyme enzyme. The antibody in colostrum protect against protect against gastro intestinal and respiratory infection.</li>
</ul>
<p>Breast milk also contains a factors called &ldquo;bifidus factors&rdquo;, which encourage the growth of lactrobacillus bifidus. This result in a high quantity of lactic acid and formic acid suppressing the growth of enteropathogenic E coli. It is well known that E.coli case gastro enteritis in the newborn and the neonates so not have immunity against this pathogen.</p>
<ul>
<li>Breast milk is a complete food and provides all nutrients needed to the infant in the first few months. Protein, fat and other nutrients contained in breast milk is easily digestible; the composition is maintained as per need of neonate.</li>
<li>Breastfeeding is much cheaper than other feeding, the cost of the extra food needed by the mother is negligible compared with cost of feeding milk formula.</li>
<li>Mother who is on breastfeeding usually has longer periods of birth spacing than non-lactating mother so it also helps in spacing of children i.e. lactational Amenorrhea Method</li>
<li>Breast fed infants are less likely to get colic, infantile allergies and eczema than those bottle fed.</li>
<li>Breastfeeding milk is always sterile and warm as per need of baby.</li>
<li>Breast milk is always available and no utensils or water which may carry germ or fuel is needed to prepare it.</li>
<li>Breastfeeding immediately after delivery encourage the contraction of uterus which helps the mother to regain her figure quickly.</li>
<li>Breastfeeding mother have less chance of having breast cancer non lactating mother.</li>
<li>It establishes good and close relationship between mother and baby.</li>
<li>It has laxative action this helps un elimination of meconium.</li>
<li>It also prevents hypoglycemia.</li>
</ul>
<p>It helps in contraction of uterus thus helps in separation of placenta, drainage of lochia and prevent from PPH.</p>
<p>&nbsp;</p>

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Microbial Metabolism

Microbial Metabolism

Microbial metabolism

The Energy is produced in the form of ATP.

ATP → ADP + Ppi +large amount of free energy

Free energy:

  1. It is the energy need to do work under constant temp and pressure.
  2. Free energy (–ve) → spontaneous → exergonic
  3. Free energy (+ve) → not spontaneous → endergonic
  4. Free energy ( o )→ equilibrium

→ Energy released in metabolism by

  1. Oxidative phosphorylation (ETC)
  2. Substrate-level phosphorylation

Oxidative phosphorylation:

The NADH and FADH2 produced during glycolysis, -oxidation and the electron is provided by TCA cycle to reduce molecular oxygen to water. These electrons are shifted through the series of protein electron carriers in the electron transport chain. O2 is the final electron acceptor which contact with H2 to form water. Electron transport chain found in inner mitochondrial membrane where all of the electron carriers are situated. The function of electron transport chain is to facilitate the controlled release of free energy that was stored in reduced co-factors during catabolism.

when electrons are transported from higher energy NADH/FADH2 to lower energy O2the energy is released. This energy is used to phosphorylate ADP. This coupling of ADP synthesis to NADH/FADH2 is called oxidative phosphorylation. Oxidative phosphorylation is important for 90% of total ATP synthesis in the cell.

The chemiosmotic theory of oxidative phosphorylation:

The mechanism of oxidative phosphorylation when electrons are transported along the components of ETC is explained by this theory. The accompanying protons (H+) are produced. A part of free energy collected or gained during the ETC is used to pump protons out from the mitochondrial matrix. The resulting uneven distribution of protons produces pH gradient and a charge gradient across the inner mitochondrial membrane. This gradient proton motive force is known as the electrochemical potential energy generated . The return of protons to the mitochondrial matrix is coupled to ATP synthesis. This type of theory is called a chemiosmotic theory of oxidative phosphorylation.

The components of ETC are NADH dehydrogenase, succinate dehydrogenase, co-enzyme O, cytochrome C , cytochrome oxidase , cytochrome reductase and ATP synthetase. The protons moving inside the mitochondrial membrane through ATP synthetase is responsible for forming ATP. For every 4 H+, that is pumped a single ATP is generated. From single NADH, 2.5 ATP and from FADH2, 1.5 ATP are generated.

Substrate level phosphorylation:

The type of metabolic reaction that results in the formation of adenosine triphosphate (ATP) or guanosine triphosphate (GTP) by the transfer and donation of a phosphoryl (PO3) group to adenosine diphosphate or guanosine diphosphate from a phosphorylated reacted intermediate. Different from the oxidative phosphorylation, oxidation and phosphorylation are not coupled in the process of substrate level phosphorylation, the formation of ATP result inboth types of phosphorylation . The process of Oxidative phosphorylation occurs in the cytoplasm as a part of glycolysis and in mitochondrial as a part of Krebs's cycle.

However, oxidative phosphorylation only occurs in mitochondrial. Substrate level phosphorylation is independent of aerobic or anaerobic condition whereas oxidative phosphorylation only occurs in the aerobic condition. Examples of substrate level phosphorylation are the transfer of phosphate group from 1,3-bi-phosphoglycerate to form 3-phosphoglycerate. During this transfer which is mediated by a kinase enzyme, a phosphate group is transferred to ADP to format. Similarly, pyruvate kinase enzyme transfers phosphate group from phosphoenolpyruvate to form pyruvate ADP is converted to ATP in a similar way.

High energy compounds:

For all useful activities like muscle contraction, cellular movements, metabolism ,etc. a cell required a large amount of free energy, these processes are energetically very demanding and cells use energy which is special for all living system such type of energy are released by hydrolysis of some compounds which are energetically very high. They contain some specific bonds which when to hydrolyse , release a large amount of free energy which is used to perform various cellular activities.

The most important high-energy phosphate compound is ATP and its phospho- anhydride bond is referred to as high energy bonds and is generated in the process of oxidative phosphorylation in mitochondria.

Energy release compound in cell comprises of five kinds of high energy bonds:

  1. Phosphor anhydride bond: It is formed between Two molecules of phosphoric acid (H3PO4) formed this type of bond. In hydrolysis of 1 mole of this bond approx. 30.5 KI energy is produced. These type of bond is present in ATP.
  2. Enol phosphate bond: when the phosphate group is attached to the hydroxyl group which is bonded to carbon with the double bond this type of bond is formed. This bond is energetically the richest bond in the hydrolysis of which 61 KI of energy is liberated. Such type of bond is present in phosphoenolpyruvate which is formed in the breakdown of glucose in glycolysis. This energy rich bond can be transferred by means of the kinase to ADP to form ATP.
  3. Acyl phosphate bond: It is formed by the reaction of the carboxylic acid with the phosphate group. In the hydrolysis of this type of bond approximately 49 KI of energy is released. This type of bond is present in 1,3-bisphosphoglycerate and is formed in the glycolysis and energy can be transferred from this compound to ADP to form ATP.
  4. Guanidine phosphate bond: It is formed when a phosphate group is attached to guanidine group. The energy released in the hydrolysis of this type of bond is 43 KI. The most important compound with this bond is phospho-- creatinine. The phospho- creatinine is present in muscles and serves as an energy reserve for the body.

Metabolism has four specific functions:

  1. To obtain chemical energy from fuel molecules or from absorbed sunlight.
  2. To convert exogenous nutrients into building blocks or precursors.
  3. To assemble such building blocks into proteins, nucleic acid , lipids and other cell components.
  4. To form and degrade such biomolecules.

References

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.

Debey, RC and D K Maheshwari. A textbook of Microbiology. India: s.chand and company Ltd., 1999.

Lesson

Metabolism

Subject

Microbiology

Grade

Bachelor of Science

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