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    i understand the sodium ions are activley transported out of the PCT but from there where do they go? to the capillaries? and when they move back down their concentration gradient where do they go?
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    ^^ pheww lol thanks again
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    (Original post by 102102)
    Okay here i go

    loop of Henle, this is what you need to knw..

    longer the loop of henle, the lower the water potential of urine
    because ions pass out from ascending limb to the medulla (active transport)
    creates lower water potential in the medulla
    water is reabsorbed from collecting duct in medulla by osmosis
    the arrangement is hairpin countrecurrent multiplier, and this is to increase the efficiency os salts from ascending limb to the descending limb
    also remember that ascending limb is impermeabale to water, so prevents water from being passed out by osmosis.okkies..anyfink else?
    aah i think i get this lol
    so ions(sodium chloride ions) that pass into the medulla by active transport provides a water potential gradient, so water moves from the ascending limb into the medulla by osmosis making the fluid(urine) in the ascending limb more concentrated and low in water potential i think i get it now lol so the advantage of having a long loop of henle is more water is kept and not watsed in the urine
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    Can anyone help with this?

    'explain the difference in relative energy values of carbohydrates, lipid and protein respiratory substrates'
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    No, remember that the ascending limb is impermeable to water so water does not move out of that tubule..yh, so therefore the urine is more dilute
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    (Original post by thekooks)
    Can anyone help with this?

    'explain the difference in relative energy values of carbohydrates, lipid and protein respiratory substrates'
    I hate thiss!!

    Lipids have long hydrogencarbonate tails (more hydrogen and carbon atoms) so more acetyl coA can be made in the links reaction, consequently more acetate is offloaded into the Krebs cycle - so more ATP is produced when lipids are used as a respiratory substrate.
    Cant help with the other two im afraid!! x
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    (Original post by thekooks)
    Can anyone help with this?

    'explain the difference in relative energy values of carbohydrates, lipid and protein respiratory substrates'
    lol, i ignored all of this page..haha i seriosuli cba with it
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    Could anyone pretty please explain the control of heart rate by hormonal/neuronal mechanisms. I just don't get it.. : )
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    (Original post by 102102)
    lol, i ignored all of this page..haha i seriosuli cba with it
    Lol me neither. I will read it now and try to post a summary if u want?

    and thanks, NicolaBelle..U have started me off
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    (Original post by Zahraaaa)
    i understand the sodium ions are activley transported out of the PCT but from there where do they go? to the capillaries? and when they move back down their concentration gradient where do they go?
    Tissue fluid.. i think..tap me sum1 if it's wrong
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    (Original post by thekooks)
    Can anyone help with this?

    'explain the difference in relative energy values of carbohydrates, lipid and protein respiratory substrates'
    you get more energy from lipids because of the many fatty acids and hydrocarbon chains so breaking the bonds releases more energy than carbohydrate, however protein due to its many chains of amino acids and many nitrogenous bases it can release more energy than both lipid and carbohydrate. although carbohydrate and lipid have the same chemical ingredients mainly carbon, oxygen and hydrogen lipid has higher proportion of hydrogen and carbon compared to carbohydrate.
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    (Original post by thekooks)
    Lol me neither. I will read it now and try to post a summary if u want?

    and thanks, NicolaBelle..U have started me off
    yh go ahead, if u wish
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    (Original post by thekooks)
    Lol me neither. I will read it now and try to post a summary if u want?

    and thanks, NicolaBelle..U have started me off
    S'quite alright..
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    Is it foot processes or major processes?

    There both in my book for the same thing?
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    (Original post by NicolaBelle)
    Could anyone pretty please explain the control of heart rate by hormonal/neuronal mechanisms. I just don't get it.. : )
    Expand on what you trying to quote..maybe then i can my thinking cap on
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    (Original post by 102102)
    No, remember that the ascending limb is impermeable to water so water does not move out of that tubule..yh, so therefore the urine is more dilute
    wait so how is water extracted from the urine? is it re-absorbed in the descending loop?
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    (Original post by HELPME-ology)
    All i know..from memory atm..

    is photophosphyrlation uses light energy which excites a pair of electrons. These electrons flow through electron carriers and release energy. This energy is then used to move the H+ ions from the thylakoid membrane to the thylakoid space and creates a proton, electrochemical and pH gradient. The H+ions then move down the ATP synthase stalked particle down their potential gradient and cause a proton force that joins ADP + Pi to form ATP. The electrons lost from photosystem I are replaced and the electrons lost from the photosystem II ar replaced by thr electrons from photosystem I.

    I get confused between non cyclic and cyclic.. and dont know which one i just mentioned ^^^^^ :confused:

    for the Calvin Cycle.. all i know is:

    CO2 is fixed onto rubisco enzyme during carbon fixation and RuBP forms GP. GP split into 2 triose phosphates.. which then form a 5C compound and then a 4C compound. releases NADH? and ATP.
    then 4C compound forms a second 4C compound and releases NADH and the second 4C compound turns into a third 4C compound releases CO2 its dehydrogentated and decarboxylated each time. Its further decarboxylated and dehydrogenated to regenerate RUBP.
    Some TP can form hexose sugars like glucose that form sucrose and fructose. Some TP can form amino acids and fatty acids.

    I have no idea if im mixing up things and if this is even correct. Please correct me if im wrong!! Would really appreciate the helppp!!
    For the photophosphorylation, its mostly all correct, but the part where you talk about electrons is a bit jumbled up. The electrons lost by PSI are replaced by electrons released from PSII. The electrons lost by PSII are replaced by electrons produced in the photolysis of water. The electrons released by PSI are used to reduce NADP to NADPH. This is non-cyclic photophosphorylation as both photosystems are used and the products are oxygen, ATP and NADPH.

    Cyclic photophosphorylation is when all NADP carriers are reduced so there are no free carriers to pick up electrons lost by PSI. Hence PSII shuts down and the electrons lost by PSI are passed down the electron transport chain of PSII. This produces energy which is used to do the H+ ions pumping. Therefore ATP is produced. The process is cyclic because the electrons lost by PSI are continously passed down electron transport chain of PSII. But remember, cyclic photophosphorylation doesn't produce oxygen or NADPH.

    Your Calcin Cycle is a bit jumbled up as well. You need to know that CO2 combines with RuBP (5C compound) in presence of enzyme rubisco to form unstable 6C-compound intermediate which splits into 2 molecules of 3C-compound glycerate-3-phosphate/GP. GP is then reduced to 3C-compound triose-phosphate/TP using ATP where NADPH is oxidised to NADP. TP produces hexose sugars, fatty acids, glycerol, amino acids....
    TP then regenerates to RuBP using ATP and the cycle starts again!
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    Ooh no need now thanks to Remarqable M

    Thank you.
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    (Original post by dontkillhannah)
    Non cylic is when photosystems 1 and 2 are involved, whereas cyclic only involves photosystem 1. For cylic photophosphorylation, the excited electrons (once they have gone through the electron transported thingymebob and generated the ATP) are passed back to the pigment. In contrast, in non-cyclic photophosphorylation, both photosystems are involved and will emit electrons, but this time PSI absorbs the electrons emitted from PSII to replace the ones it lost when it's hit by the light, and PSII regains the electrons it loses via the photolysis of water. The hydrogen ions also produced in the photolysis of water are used to reduce NADP to form reduced NADP, and the oxygen left is released as a waste product.

    So the main differences are:
    *Cyclic only uses PSI, whereas non-cyclic uses both
    * The product of CPP is ATP, and the products of NCPP are ATP, reduced NADP and oxygen

    So in what you said, you've got all the details of cyclic photophosphorylation spot on

    I hope this helped
    Hi, the oxygen produced during NCPP is that due to the photolysis reaction which replaces the electrons, i.e. H2O --> 2H+ + 1/202 +2e-
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    (Original post by Remarqable M)
    wait so how is water extracted from the urine? is it re-absorbed in the descending loop?
    The descending limp is permeable to water, hence water diffuses down water potential gradient from high water potential in descending limb to low water potential in surrounding tissue of medulla by osmosis
 
 
 
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