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    Describe the functions of glycoproteins in cell surface membrane? Anyone? - also dont understand cell signalling
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    (Original post by pastpaper-guy)
    lol revise in bed then.
    great tip

    cheers.
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    (Original post by xMaGic)
    Describe the functions of glycoproteins in cell surface membrane? Anyone? - also dont understand cell signalling
    Acts as receptor sites for hormones due to its complementary shape

    Cell Adhesion- binds tissues together providing stability

    Forms OH bonds with water- again stability

    Regulates what enters and leaves (pores/channels/carrier proteins)

    Cell signalling- Recognises cells as "self" so involved in the immune system

    Think thats about it. Correct me if im wrong anyone
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    ok my go now,
    please some1 explain to me in simple coherent english, about CARRIAGE OF OXYGEN & CARRIAGE OF CARBON DIOXIDE
    all about the graphs & bohr shift blablablabala
    i dont get ittttttt
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    (Original post by fahimak)
    hey can anyone xplain transpiration 2 me....i still dont get it :confused:

    water evaporates from the leaf because of gas exchange that takes place when the stomata opens.
    water travels up the xylem because of cohesion of the water molecules and adhesion with the lignin.

    someone continue, dont know how to word the rest.
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    (Original post by xMaGic)
    Describe the functions of glycoproteins in cell surface membrane? Anyone? - also dont understand cell signalling
    For your glycoproteins one, It came up in 2009 I think; the markscheme answer was:

    -acts as antigens
    - used in cell adhesion
    - identification and recognition of cells
    -attaches to water molecules to stabilise membrane
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    (Original post by xMaGic)
    Describe the functions of glycoproteins in cell surface membrane? Anyone? - also dont understand cell signalling
    If you have the mark scheme for JAN 2010 paper, there was a 5/6 marker on this.. you'll find exactly what you need to write.
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    Im unsure if you use the same reasons for glycolipids too?
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    (Original post by 786girl)
    ok my go now,
    please some1 explain to me in simple coherent english, about CARRIAGE OF OXYGEN & CARRIAGE OF CARBON DIOXIDE
    all about the graphs & bohr shift blablablabala
    i dont get ittttttt
    Carriage of CO2

    CO2 transported in blood in 3 main ways:
    1) 85% in the form of Hydrogen carbonate ions
    2) 5% dissolves directly in plasma
    3) 10% combines with haemoglobin to form carbaminohaemoglobin

    When there is a HIGH PARTIAL PRESSURE OF C02 so basically lots of C02 for eg. during exercise (cells respiring more), C02 will combine with water to form carbonic acid. Enzyme called CARBONIC ANHYDRASE catalyses this.

    Carbonic acid dissociates forming HCO3- and H+.
    HCO3- diffuses out red blood cells. Chloride ions enter to maintain charge. This is called CHLORIDE SHIFT. To stop the red blood cell becoming too acidic, haemoglobin accepts the H+ forming HAEMOGLOBINIC ACID.

    Now this does 2 things:
    1) Acts as a buffer so maintains PH cos remember H+ makes environment acidic.
    2) H+ COMPETE with OXYGEN for a place in the haemolgobin molecule. So Haemoglobinic acid causes OXYHAEMOGLOBIN to dissociate more releasing more oxygen.

    This is really useful when your doing lots of exercise so in muscle cells. More exercise so more CO2 (increased respiration) so more H2CO3 (carbonic acid) so more H+ so more HAEMGLOBINIC ACID so more oxygen to muscle cells.

    Thats CO2 carriage
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    Thanks everyone and @786girl i dont understand that either but inshallah we should do good tomorrow.

    Do you mean the % of co2 and stuff
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    (Original post by rasklatz)
    Im unsure if you use the same reasons for glycolipids too?
    I always used to get muddled up with that. Its basically the same so they usually ask functions of glycoproteins AND glycolipids.
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    hows everyone feeling right now? anyone pulling an all-nighter?
    =/
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    Transpiration
    Transpiration is the loss of water vapour by the aerial part of the plant, throught stomata, by diffusion. This is started by a push from the roots. The root pressure hyothesis is where solutes are actively transported into the xylem, this lowers the water potential in the xylem so water is drawn in by osmosis from the soil to the xylem. This creates a high pressure in the xylem causing a push from the roots. When water is lost from the leaf water is pulled up through the stem to replace water lost. In the stem there is cohesion between water molecules. This is a result of the slight dipoles water molecules have, therefore they attract each other and form a long column of water molecules that are puller up as a continuous column when water is lost at the leaf. This is a pull from above. In addition to cohesion there is adhesion in the stem, which is an attraction between the water molecules and the walls of the xylem. This is called capillary action and creates a high pressur, enabling water and solutes to flow. When the xylem passes near the leaf, the leaf is more negative in water potential than the xylem in the stem. Therefore, water moves, by osmosis, from the stem to the leaf down the water potential gradient. Water then evaporates to form water vapour and collects in the spongy mesophlyy layer in the air spaces. The water vapour then diffuses out of the leaf through the stomata, this is transpiration. Hope this helps
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    (Original post by CullenLoverX)
    hows everyone feeling right now? anyone pulling an all-nighter?
    =/
    Na that would mess you up!
    Just read Wake up early and revise
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    (Original post by 786girl)
    ok my go now,
    please some1 explain to me in simple coherent english, about CARRIAGE OF OXYGEN & CARRIAGE OF CARBON DIOXIDE
    all about the graphs & bohr shift blablablabala
    i dont get ittttttt
    O2 breathed into the lungs by inspiration*
    Low partial pressure of Oxygen in lungs as they're well supplied with capillaries, so it maintains a steep diffusion gradient. O2 binds with a haem group, 4 haem groups per haemoglobin molecule.
    Blood pumped round body, Oxygen dissociates in areas of low partial pressure of O2, meaning the cells there are respiring.
    CO2 is released from cells as metabolic waste. majority of CO2 enters blood and reacts with Water in plasma to form Carbonic Acid.(H2CO3)
    Carbonic acid dissociates (enzyme carbonic anhydrase used) to Hydrogen Carbonate Ions and H+ ions. HCO3- ions transported to lungs.
    The H+ ions compete with O2 for space on haem groups, and form Haemoglobinic Acid (HHb). This is know as the Bohr Effect, as more active cells produce more CO2, producing more H+ ions, meaning more O2 dissociates, meeting the requirements of the respiring cells.

    *intercostal muscles and diaphragm contract, pushing down on digestive organs. Volume of chest cavity increases, pressure inside thorax goes below atmospheric, and air flows into the lungs.

    quote me if you want to know anything else
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    (Original post by 786girl)
    ok my go now,
    please some1 explain to me in simple coherent english, about CARRIAGE OF OXYGEN & CARRIAGE OF CARBON DIOXIDE
    all about the graphs & bohr shift blablablabala
    i dont get ittttttt
    i like this bit.

    bohr shift happens when the amount of co2 increases. it shifts to the right because the o2 is DISPLACED by the co2.

    Example: a tissue in the body is respiring alot causing alot of CO2 to be released. the oxygen in the blood gets to this area.
    Co2 replaces the O2 so that the o2 can be used in this tissue.

    when the CO2 enters the blood cell, a enzyme called carbonic anhydrase converts the co2 into carbonic acid.
    carbonic acid disociates into hydrogencarbonate ions and hydrogen ions.

    when it reaches the lungs the H+ ions and hydrogencarbonate ions recombine into CO2.

    CO2 diffuse into alveoli
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    (Original post by Rosi M)
    Carriage of CO2

    CO2 transported in blood in 3 main ways:
    1) 85% in the form of Hydrogen carbonate ions
    2) 5% dissolves directly in plasma
    3) 10% combines with haemoglobin to form carbaminohaemoglobin

    When there is a HIGH PARTIAL PRESSURE OF C02 so basically lots of C02 for eg. during exercise (cells respiring more), C02 will combine with water to form carbonic acid. Enzyme called CARBONIC ANHYDRASE catalyses this.

    Carbonic acid dissociates forming HCO3- and H+.
    HCO3- diffuses out red blood cells. Chloride ions enter to maintain charge. This is called CHLORIDE SHIFT. To stop the red blood cell becoming too acidic, haemoglobin accepts the H+ forming HAEMOGLOBINIC ACID.

    Now this does 2 things:
    1) Acts as a buffer so maintains PH cos remember H+ makes environment acidic.
    2) H+ COMPETE with OXYGEN for a place in the haemolgobin molecule. So Haemoglobinic acid causes OXYHAEMOGLOBIN to dissociate more releasing more oxygen.

    This is really useful when your doing lots of exercise so in muscle cells. More exercise so more CO2 (increased respiration) so more H2CO3 (carbonic acid) so more H+ so more HAEMGLOBINIC ACID so more oxygen to muscle cells.

    Thats CO2 carriage
    that makes so much more sense! thanx!
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    (Original post by 786girl)
    that makes so much more sense! thanx!
    No problem & one more thing, 'cos INCREASED CO2 causes more oxygen to be released, the graph for the BOHR EFFECT, has the sigmoid shaped curve under the one already drawn.
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    (Original post by xMaGic)
    Na that would mess you up!
    Just read Wake up early and revise
    lool i wasn't planning on an all-nighter anyway :P thankfully, i've never felt the need to do that but i was just wondering if anyone else was.

    im planning on doing loads of past paper questions (ExamQuest ftw :P ) until about 11 tonight, then taking a shower and relaxing before going over the notes one last time before *trying* to sleep early lol
    then waking up tomorrow and just skim reading the revision guide just to refresh my memory before the exam... then having a mental breakdown silently in my seat while the exams are handed out before *hopefully* enjoying that calm and serene feeling i know i'll get as soon as i start question 1(a) lol


    wow i sound like a right weirdo.
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    (Original post by CullenLoverX)
    lool i wasn't planning on an all-nighter anyway :P thankfully, i've never felt the need to do that but i was just wondering if anyone else was.

    im planning on doing loads of past paper questions (ExamQuest ftw :P ) until about 11 tonight, then taking a shower and relaxing before going over the notes one last time before *trying* to sleep early lol
    then waking up tomorrow and just skim reading the revision guide just to refresh my memory before the exam... then having a mental breakdown silently in my seat while the exams are handed out before *hopefully* enjoying that calm and serene feeling i know i'll get as soon as i start question 1(a) lol


    wow i sound like a right weirdo.
    Haha mental breakdown silently.. is that possible?
 
 
 
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