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    Calvin Cycle
    During photosynthesis, light energy is used in generating chemical free energy, stored in glucose. The light-independent Calvin cycle, also known as the "dark reaction" or "dark stage," uses the energy from short-lived electronically-excited carriers to convert carbon dioxide and water into organic compounds that can be used by the organism (and by animals that feed on it). This set of reactions is also called carbon fixation. The key enzyme of the cycle is called RuBisCO. In the following equations, the chemical species (phosphates and carboxylic acids) exist in equilibria among their various ionized states as governed by the pH.

    The enzymes in the Calvin cycle are functionally equivalent to many enzymes used in other metabolic pathways such as gluconeogenesis and the pentose phosphate pathway, but they are to be found in the chloroplast stroma instead of the cell cytoplasm, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. These regulatory functions prevent the Calvin cycle from being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions that have no net productivity.


    NOTE: IN THIS DIAGRAM IT HAS MISSED TRIOSE PHOSPHATE....WHICH SHOULD BE AFTER (G3P)
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    Limiting Factors in Photosynthesis
    Some factors affect the rate of photosynthesis in plants, as follows

    •Temperature plays a role in affecting the rate of photosynthesis. Enzymes involved in the photosynthetic process are directly affected by the temperature of the organism and its environment
    •Light Intensity is also a limiting factor, if there is no sunlight, then the photolysis of water cannot occur without the light energy required.
    •Carbon Dioxide concentration also plays a factor, due to the supplies of carbon dioxide required in the Calvin cycle stage.
    Overall, this is how a plant produces energy which supplies a rich source of glucose for respiration and the building blocks for more complex materials. While animals get their energy FROM food, plants get their energy FROM the sun.
    [IMG][/IMG]


    Note: if carbon dioxide concentration is low- AND- at high temperatures the enzyme rubisco will react with oxygen...(photorespiration)
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    (Original post by MadMaths)
    Limiting Factors in Photosynthesis
    Some factors affect the rate of photosynthesis in plants, as follows

    •Temperature plays a role in affecting the rate of photosynthesis. Enzymes involved in the photosynthetic process are directly affected by the temperature of the organism and its environment
    •Light Intensity is also a limiting factor, if there is no sunlight, then the photolysis of water cannot occur without the light energy required.
    •Carbon Dioxide concentration also plays a factor, due to the supplies of carbon dioxide required in the Calvin cycle stage.
    Overall, this is how a plant produces energy which supplies a rich source of glucose for respiration and the building blocks for more complex materials. While animals get their energy FROM food, plants get their energy FROM the sun.
    [IMG][/IMG]


    Note: if carbon dioxide concentration is low- AND- at high temperatures the enzyme rubisco will react with oxygen...(photorespiration)

    Yay thank you! +rep
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    I've only just found this thread. I've revised almost all of it, just got a bit of respiration to do. There seems to be so much content, considering there's only 4 modules.
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    (Original post by I Have No Imagination)
    Yay thank you! +rep
    thanks
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    (Original post by steph_v)
    I've only just found this thread. I've revised almost all of it, just got a bit of respiration to do. There seems to be so much content, considering there's only 4 modules.
    http://www.thestudentroom.co.uk/show....php?t=1159765

    :cyber:
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    Positive Feedback

    Positive feedback is a mechanism by which an output is enhanced, such as protein levels. However, in order to avoid any fluctuation in the protein level, Positive feedback mechanisms are designed to accelerate or enhance the output created by a stimulus that has already been activated.

    Unlike negative feedback mechanisms that initiate to maintain or regulate physiological functions within a set and narrow range, the positive feedback mechanisms are designed to push levels out of normal ranges. To achieve this purpose, a series of events initiates a cascading process that builds to increase the effect of the stimulus. This process can be beneficial but is rarely used by the body due to risks of the acceleration's becoming uncontrollable.

    One positive feedback example event in the body is blood platelet accumulation, which, in turn, causes blood clotting in response to a break or tear in the lining of blood vessels. Another example is the release of oxytocin to intensify the contractions that take place during childbirth.

    Negative Feedback
    Negative feedback mechanism consists of reducing the output or activity of any organ or system back to its normal range of functioning. A good example of this is regulating blood pressure. Blood vessels can sense resistance of blood flow against the walls when blood pressure increases. The blood vessels act as the receptors and they relay this message to the brain. The brain then sends a message to the heart and blood vessels, both of which are the effectors. The heart rate would decrease as the blood vessels increase in diameter (or vasodilation). This change would cause the blood pressure to fall back to its normal range. The opposite would happen when blood pressure decreases, and would cause vasoconstriction.
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    mad maths can you check if this is right about peritoneal and haemodialyses i think you posted it before so guess youve revised it.

    Haemodialysis

    1) a stunt is inserted into the arterial vessel to conect this vessel to the venus vessel and together blood is passed from here into small tubes made up of partial permeable membrane
    2) the tube containing the blood enters the dialyses machine were dialyses fluid runs along the otherside of the mebrane
    3) Dialysisi fluid is adjusted to have normal concentration of salts , nutriens, glucose with no waste products
    4) substances of higher concentration in the blood than normal diffuse down their concetration gradient across the partial permeable membrane and into the dialysis fluid.( this includes urea)
    5) blood cells and plasma proteins in the blood are to large to diffuse across the membrane so remain in the blood
    6) this process takes up to 2 to 4 hours a day for upto 4 times a week.

    Peritoneal dialysis
    1) the peritoneum is a layer of tissue that lines the abdominal cavity
    2)this cavity contains fluid which bathes the internal organs
    3) a catheter is insterted into the peritoneal cavity and dialysis fluid is passed through it filling the cavity
    4) time is allowed for exchange of molecules between the blood and the fluid in the cavity , note that the dialysis fluid contains normal level of salts and nutrients with no waste products.
    5) it takes abour 30 -45 mintutes for fluid to be introduced into the cavity , for exchange to take place and then the dialysis fluid is drained off.
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    (Original post by MG.GULED)
    mad maths can you check if this is right about peritoneal and haemodialyses i think you posted it before so guess youve revised it.

    Haemodialysis

    1) a stunt is inserted into the arterial vessel to conect this vessel to the venus vessel and together blood is passed from here into small tubes made up of partial permeable membrane
    2) the tube containing the blood enters the dialyses machine were dialyses fluid runs along the otherside of the mebrane
    3) Dialysisi fluid is adjusted to have normal concentration of salts , nutriens, glucose with no waste products
    4) substances of higher concentration in the blood than normal diffuse down their concetration gradient across the partial permeable membrane and into the dialysis fluid.( this includes urea)
    5) blood cells and plasma proteins in the blood are to large to diffuse across the membrane so remain in the blood
    6) this process takes up to 2 to 4 hours a day for upto 4 times a week.

    Peritoneal dialysis
    1) the peritoneum is a layer of tissue that lines the abdominal cavity
    2)this cavity contains fluid which bathes the internal organs
    3) a catheter is insterted into the peritoneal cavity and dialysis fluid is passed through it filling the cavity
    4) time is allowed for exchange of molecules between the blood and the fluid in the cavity , note that the dialysis fluid contains normal level of salts and nutrients with no waste products.
    5) it takes abour 30 -45 mintutes for fluid to be introduced into the cavity , for exchange to take place and then the dialysis fluid is drained off.
    yep your all correct, the only thing i can add is that:
    haemodialysis:im pretty sure that its never arterial vessel, because of the pressure being extremly high. yet veins and venus vessels. also that heparin is added to prevent clotting, plus pump for additional pressure.
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    Haha you did it. Thanks very much man. I need to rep you again in a month. :p:
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    (Original post by MadMaths)
    yep your all correct, the only thing i can add is that:
    haemodialysis:im pretty sure that its never arterial vessel, because of the pressure being extremly high. yet veins and venus vessels. also that heparin is added to prevent clotting, plus pump for additional pressure.
    Thanks ! hope this comes up. you know your post about detecting for anabolic steriods do we have to know it in that much detial.....my ocr book only mentions a tinny bit.
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    Yay I've finished exams for this week so I can focus on Biology! Well done for getting this to 26 pages!!
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    Wow, thanks for this.
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    (Original post by MG.GULED)
    Thanks ! hope this comes up. you know your post about detecting for anabolic steriods do we have to know it in that much detial.....my ocr book only mentions a tinny bit.
    i dont think you have to remember that, in that much detail, but it is a good idea to have a rough outline of how an anabolic steriods can be detected in urine, i.e the gas chromatography method.

    i think the mary jones book concentrates on the affects of the drug rather than the testing.
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    OMG! I finally understand photosynthesis! Just got to cover limiting factors today. And try and get it stuck in my brain!
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    jus got a place at university of leicester...wooooooh
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    No matter how hard I try to summarise and learn the light dependent reaction, it doesn't stick! The independent one is fine!

    And neurons.. sensory/motor! Don't understand. Mylinated/non mylinated?! ARGH. Stress.
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    (Original post by nbailey8)
    No matter how hard I try to summarise and learn the light dependent reaction, it doesn't stick! The independent one is fine!

    And neurons.. sensory/motor! Don't understand. Mylinated/non mylinated?! ARGH. Stress.
    just calm down, im sure u'll be fine
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    (Original post by nbailey8)
    No matter how hard I try to summarise and learn the light dependent reaction, it doesn't stick! The independent one is fine!

    And neurons.. sensory/motor! Don't understand. Mylinated/non mylinated?! ARGH. Stress.
    Ahhh I know not sure if you want them but here's my notes for light dependent:

    Non-cyclic photophosphorylation:

    1) light energy is absorbed by PS2, exciting the electron, it becomesa higher energy level electron and passed down the electron transport chain to PS1

    2) as they do this, these electrons then need to be replaced. Water is used to replace them. Light energy splits the H2O into protons, electrons and O2.

    3) As the electrons move down the electron transport chain, the energy is 'rung' out of them and used to pump H+ into the thylakoid. Because there is a higher concentration of H+ in the thylakoid than in the stroma there is a proton gradient.

    4) The protons move back into the stroma down the concentration gradient via ATP syntahase. This movement gives the energy to combine ADP + Pi into ATP

    5) Light energy is absorbed by PS1, the electrons are excited to an even higher energy level. The electrons are then transfered to NADP, along with a proton to give NADPH (reduced NADP)


    Cyclic photophosphorylation:

    * Only uses PS1
    * Electrons aren't passed to NADP but instead, passed back to PS1again via electron carriers.
    * So the electrons are 'recycled'
    * This process doesn't produce any NADPH or O2
    * Only produces small amounts of ATP
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    (Original post by MadMaths)
    jus got a place at university of leicester...wooooooh
    Well done what for ?
 
 
 
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