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BIOL 2360

6.Discuss what are good characteristics of critical thinkers.

Critical thinking is a developing concept for the past 2500 years. It is conceptualizing thoughts in a well disciplined and intellectual manner so analyzing gathered information would have accurate, relevant and fair opinions. Hence, critical thinkers must demonstrate honesty and acknowledge their errors when it is seen by other individuals. They also see debatable issues or topics interesting and exciting so they would spend time to understand and resolve the matter. Even if a critical thinker disagrees with someone’s opinion they are still ready to listen to their views and correct themselves if errors are seen. By doing this a balance is created and everyone is happy and the right things would be demonstrated. Furthermore, critical thinkers do not let emotions control them rather they control it and think before an inappropriate action is done. Finally, judgments are made on solid evidence so biasness would not be seen when compared to personal inclination. When new evidence are discovered and errors are shown in the old judgment, it is revised.

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BIOL 1362 PART 3

THE PRESYNAPTIC NEURON AND THE MONOCYTE

The presynaptic neuron in the brain and the monocyte which is found in the immune system are communicated through the hypothalamic pituitary adrenal axis and the synaptic nervous system by neuroimmune interactions. In this neuroimmune interaction, norepinephrine transmits these local signals via the synaptic pathway to the lymphoid organs. Hence, when the body receives a stimulus the norepinephrine is released from the sympathetic nerve terminals in the neurons to the monocytes which then express adrenoreceptors to accept the long distance signal through the endocrine pathway. This affects monocyte cell traffic, circulation, cytokine production and it alters the function of their activity. When norepinephrine is produced this stimulates the β2-adrenoreceptor-cAMP-protein kinase A pathway which then inhibit the production of helper cells and stimulate the production of inflammatory monocyte cells. During an immune response the synaptic nervous system aims to specify the inflammatory response by initiation of the neutrophil accumulation and increase specific humoral immune response. This process of communication occurs through cell to cell interaction and chemical signals. At the end of the stimulus the monocyte together with the neurons aid in preventing damage to muscle cells or any part of the body that is affected when the monocyte invades the inflamed wound from the signals from the presynaptic neurons.

Reference: http://pharmrev.aspetjournals.org/content/52/4/595.full#title11

 

Blogging Assignment Part_II

COMMUNICATION BETWEEN ASTROCYTES, NEURONS AND MUSCLE CELLS

Astrocytes are star-like glia cells which hold neurons together, supply them with nutrients and digest the damaged parts of dead neurons. They communicate with each other via extracellular molecules, gap junctions, and intercellular channels. There is a chain reaction that occurs allowing the molecules to be passed on from one astrocyte to the other. Certain molecules inclusive of neurotransmitter glutamate creates an increase of Ca2+ in the cytoplasm of the astrocyte, also initiates secretion of ATP from the astrocyte, as well as causes calcium-dependent secretion of glutamate. The ATP that is now released out of the cell (Extracellular ATP) disperses to the neighbouring astrocytes activating membrane receptors which creates an increase of the Ca2+ in the neighbouring astrocyte. This then spreads to the neighbouring astrocytes. This extracellular mechanism allows synaptic signals to vibrate through the brain via glia cells. Studies show that ATP release and membrane permeability is associated with a transient outcome.

Excitatory neurotransmitters such as, glutamate and adenosine triphosphate (ATP) are released from the astroglia cells. These astro glia cell contact many presynaptic neurones through gap junctions and by the release of ATP so Ca2+ signals can cause the release of transmitters from the astro glia cells to stimulate neuronal activity at synapses that are distant to the initiating synaptic event. Astroglia, presynaptic neurons and purkjne cells work together to transport electrical impluses and integrate from extracellular signals. For these signals to have an effect on the mouse it must be passed on to the pheripheral nervous system (muscle cells). The nerve cells meet with the muscle cells through neuromuscular junctions in which the chemical signal is transmitted. Vesicles containing neurotransmitters are released due to the influx of ions at the channel forming junction. It diffuses across a gap and bind to the receptors of the muscle cells in mouse thus a response such as jumping, running or fright and flight action is seen as interpreted by the mouse brain.

INTRODUCTION: Part 1

The presynaptic neuron was originated from the glutamatergic neuron which is found in the forebrain of the mouse. The presynaptic neuron releases a mass of vesicles containing neurotransmitters which would be accepted by the postsynaptic cell to transport the signals. In the nervous system the presynaptic cell would only transport electrical messages in a lifetime. The main features in this cell are:    

  1. Vesicles: Acts like the nucleus containing the signals in the form of neurotransmitters.
  2. Neurotransmitters: Contains electrical messages that are similar to DNA which codes for a characteristic.
  3. Presynaptic membrane: Insulate the vesicles and nerves.
  4. Axon terminal: The vesicles attach themselves to the terminal and release the necessary hormones through the transporter to across the synaptic cleft. 

the synapse

http://science.education.nih.gov/supplements/nih2/addiction/guide/lesson2-1.htm

Information:

  1. http://intl.pharmrev.org/content/54/1/43.full
  2. http://www.jneurosci.org/content/26/21/5794.full

LIPIDS

–          Unsaturated fat is in the liquid form, has at least one double bond and it comes from plant sources.

–          Saturated fat is in the solid form, has no double bond and comes from animal sources. These fats cause heart diseases.

–          They are used as an insulator and fuels.

–          Fats release more energy than carbohydrates because it is in the more reduced form and fats have more hydrogen.

–          Saturated fatty acids such as palmitic has 16C and stearic has 18C

–          Unsaturated fatty acids such as oleic has 18C, arachidonic has 18C, alpha-linolenic has 20C (omega 3) and linoleic has 18C (omega 6).

–          Fatty acid can be named using the ∆ designation and ῳ omega designation

 –          The iodine index test is used to detect unsaturated fat or oil.

   

–          Oxidative phosphorylation occurs to produce carbon dioxide and water with the release of energy in the form of ATP.

–          As the electrons move from the inner membrane to the matrix an electrochemical gradient is established which generates a proton motive force?

–          There are four complexes in the inner membrane: I, II, III,IV

–          These complexes pump H+ ions to the intermembrane space form the matrix EXCEPT complex II.

–          Protons are impermeable to the inner membrane so only the complexes can carry it.

–          ATP synthesase which change in shape and use the energy to add a phosphate group to ADP to form ATP allows the H+ to go through for this ATP to form.

–          1 molecule of NADH produces 3 ATP molecules

–          1 molecule of FADH2 forms 2ATP molecules

–           When electron reaches complex IV, it takes protons from the matrix to form water in the presence of oxygen.

–          Rotenone and cyanide binds to the complexes a stop the electron transport chain. Hence, ATP synthesase would stop because the complexes are tightly coupled. 

–          Alpha-ketoglutarate will also use the five cofactors: CoA-SH, NAD+, TPP, Lipoate and FAD.

–          All enzymes are found in the matrix EXCEPT succinate dehydrogenase which is found in the inner membrane to supply the FADH2.

–          It is anabolic and would occur in the presence of mitochondria and oxygen.

–          Oxygen is important to accept the electrons

–          It is universal because it occurs in bacteria, yeast and humans.

–          Both anaerobic and aerobic organisms utilize glycolysis.

–          Ten enzymes are involved in the process, five in the energy investment phase and five in the pay-off phase.

–          Takes place in the cytosol of the matrix found in the mitochondria.

–          There are 3 irreversible and 7 reversible reactions.

–          Oxidation and phosphorylation occurs when glyceraldehydes-3-phosphate is oxidized to 1,3-bisphosphoglycerate.

–          The liver is the metabolic hub which clears 2/3 of glucose after a meal.

–          The pH of body fluids is 7.4

–          Di: phosphate group is on the carbon and bis: phosphate group is on C (1&6)

–          PFK-1 is important for regulation

–          2 primary reactions increase energy and make it more reactive for the reaction to go forward.

–          NADH is reduced to NAD+ because it is scarce in the cell.

–          The reverse reaction has higher activation energy so that ensures that the reaction proceeds.

–          Mg2+ stabilizes the negative charge.

–           In the presence of oxygen the pyruvate from glycolysis enters the TCA cycle through the link reaction. That is, pyruvate is converted to acetyl-CoA by pyruvate dehyrogenase, losing CO2 and using the five cofactors; CoA-SH, NAD+, TPP, Lipoate and FAD.

–          In anaerobic conditions the pyruvate would be converted to lactate or ethanol.

–          Other sugars excluding glucose can enter the glycolytic pathway but it must be converted to one form of the sugar in the pathway for it to enter  for the formation of pyruvate.

–          Fructose 6- phosphate is found in the fat tissues, muscle and kidney EXCEPT the liver.

–          They are biological protein catalysts that speed up the rate of a reaction by lowering the activation energy. This activation energy is the minimum energy for the reaction to proceed.

–          Most enzymes are proteins and some include RNA molecules.

–          Ribozymes (catalytic RNA) are substrate specific, they enhance the rate of a reaction and they are unchanged at the end of the reaction.

–          Antibodies that have catalytic power are known as abzymes.

–          For example sucrose is oxidized in the cell to produce carbon dioxide and water through respiration and with the aid of enzymes.

–          The most important reaction in nature to sustain life is photosynthesis.

–          In an energy profile diagram the transition state is when the atoms have the highest amount of energy between the intermediates of the reactants and products.

–          The enzyme does not change the free energy of the reactants or products, hence, the equilibrium of the reaction does not change but is accelerates the rate at which the equilibrium is reached.

–          Enzymes are versatile biochemical’s that can be distinguished by their catalytic power, specificity and regulation.

–          Each second an enzyme can covert 100 to 1000 substrates to products. This is known as the turnover number or Kcat which is the number of molecules of substrate converted to product per enzyme molecule per second.

–          Enzymes are classified into six major classes and they are given enzyme commission numbers. The six classes are:

1)      Oxidoreductases

2)      Tranferases

3)      Hydrolases

4)      Lyases

5)      Isomerases

6)      Ligases

–          In order for enzymes to function properly they must be accompanied by cofactors. There are inorganic and organic cofactors. Organic can be sub divided to transiently and permanently cofactors.

–          Holoenzyme is an active enzyme.

–          Cofactor is a non protein part and an apoenzyme is an inactive protein part.

–          An apoenzyme and a cofactor combine to form a holoenzyme.

–          Inorganic catalysts are used to make ammonia (finely divided iron catalyst) in the Haber process and sulphuric acid (vanadium (v) oxide catalyst) in the Contact process.

–          An enzyme interacts with its substrate through molecular recognition which is based on structural complmentarity.

–          Substrate binds to the enzyme’s active site.

–          Two different hypotheses were taught in class to explain the enzyme specificity and catalysis. They are Fisher’s lock and key and koshland’s induced fit hypothesis.

                              

–          There are four factors that affect the reaction velocity. Namely, [S], [E], temperature and pH.

– The graph of initial velocity vs. [S] hyperbolic curve is similar in shape to that of the oxygen – dissociation curve of myoglobin.

–           Allosteric enzymes show a sigmodial curve which is similar to the shape of the oxygen-dissociation curve for hemoglobin.

–          The assumptions of the Michaelis- Menten were relative concentrations of enzymes and substrates, steady-state assumption and the initial velocity.

–          Conclusions about the Michealis- Menten kinetics were:

1)      Km is numerically equal to the substrate concentration at which the reaction velocity is equal to ½ Vmax. Small Km has the higher affinity and large Km has the lower affinity of enzyme for the substrate.

2)      The order of the reaction: when [S] is much less than Km , the velocity of the reaction is approximately proportional to the [S] and when the [S] is much greater than Km , the velocity is constant and equal to Vmax.

–          The Line Weaver- Burk plot can also be used to calculate Km and Vmax.

–          There are two types of inhibition on enzyme activity:

1)      Irreversible: binds to enzymes through covalent bonds

2)      Reversible: binds to enzymes through non- covalent bonds.

–          In class we learnt about reversible inhibition. They include competitive, non-competitive, uncompetitive and mixed inhibition.

mixed inhibition: 

–          Competitive inhibition: the Vmax is reversed by increasing the [S] and Km increases.

–          Non- competitive inhibition:  the Vmax is decreased and the Km is the same.

–          Uncompetitive inhibition: both the Vmax and Km are reduced to the same amount.

–          Mixed inhibition: the Vmax is always reduced and the Km may be increased or decreased.

The genetic material known as DNA which is linear in most cells are packaged and stored safely in the nucleus since it is the control centre  The nucleus has a double membrane which gives additional protection to the DNA. This double membrane is also found in the mitochondria which is the power house of the cell and in chloroplasts that is found in plants.

When a cell divides, the nuclear membrane that surrounds the nucleus breaks down and two daughter cells are formed. Researchers have used these characteristics of the double membrane and cell division to understand the reformation of membranes. It is known that proteins control the membrane transformation but studies have shown that variations in lipids from a big group of fat related compounds could be the key used in fighting cancer or some other rare genetic disorders. Experiments have been done to explain how changes in lipids and the fact that protein has the messenger codes for membrane transformation. This has failed because the lipids at different levels were difficult to alter in specific compartments of the cells affecting other cellular processes.

However, Banafshe Lariiani from the Cancer Research UK’s London Research Institute and her colleagues developed a technique that converts the lipid diacylglycerol (DAG) into another lipid all within the nuclear membrane. In this technique, two fragments of DNA are inserted in the nucleus of a cell. The cell then produces two proteins; one which is attached to the nuclear membrane and the other floats around in the cell.

When the drug rapalogue was added to the same cell, the floating protein stocked to the protein that is attached to the nuclear membrane. This caused the transformation of the DAG into a distinctively new lipid. The other processes occurring in the cell was not affected because the type of DAG used does not bind to proteins. The new lipid was then tested in monkeys and human cancer cells. When low levels of DAG present in the nuclear membrane, the risk of membrane malformation and the destruction of cancer cells was higher. It has proven that lipids are important in the formation of the nuclear membrane without being dependent on proteins. Lipid composition changes cause curves in the fragment after division.  This can be used to treat rare disorders such as Hutchinson-Gilford progeria syndrome which is ageing premature in children. This is caused by irregular cell divisions so understanding membrane deformities can explain and assist in the problem.

http://www.newscientist.com/article/dn22592-chemical-key-to-cell-division-revealed.html