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    So, someone asks a question, then the person who answers it asks another. Go. Define homeostasis
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    (Original post by MrBean1994)
    So, someone asks a question, then the person who answers it asks another. Go. Define homeostasis
    The manintance of internal optimal conditions for cellular reactions

    PCT adaptations?
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    (Original post by lilGem)
    The manintance of internal optimal conditions for cellular reactions

    PCT adaptations?
    Contain large number of mitochondria for active transport.
    It's long and winding nature along with a brush border of microvilli increase surface area from which selective reabsorbtion can occur.
    Describe and explain photosynthesis.
    Also heres a question, does cyclic take place whilst non-cyclic is going on. Is it just part of non-cyclic?
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    (Original post by piers.townsend)
    Contain large number of mitochondria for active transport.
    It's long and winding nature along with a brush border of microvilli increase surface area from which selective reabsorbtion can occur.
    Describe and explain photosynthesis.
    Also heres a question, does cyclic take place whilst non-cyclic is going on. Is it just part of non-cyclic?
    I don't cover cyclic/ non cyclic or in as much detail in human bio

    Light dependent- takes place in thykaloid

    light hits chlorophyll causing a photoexcitation of an electron. The electron is passed to an electron acceptor molecule. the acceptor passes it to a chain of electron carriers as with the chemiosmotic theory, as the electron is passed ATP is produced by photophosphorylation (trapping of chemical energy from sunlight)

    Water is split by photolysis into oxygen (released as a waste gas) hydrogen which reduces NADP to NADPH2 and an electron which reduces the chlorophyll

    Calvin cycle- takes place in the stroma:

    CO2 (fixed) combines with RuBP by a catalysed reaction using the enzyme rubisco to form an unstable 6C molecule which quickly splits into 2 3C molecules of GP. ATP and NAPH2 reduce and phosphorylate it into triose phosphate, 5/6 of which is regenerated into RuBP whilst the remaining amount can be converetd into glucose, amino acids which are used in the plants metabolism
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    Cyclic phosphorylation - Photons of light absorbed by accessory pigments in antenna complex then passed to chl-A in reaction centre in PSII. This excited two high energy electons which are picked up by an electron acceptor to reduce it. The electrons pass down electron carriers and gradually lose energy. The energy lost is used to synthesise ATP from ADP + Pi.Non Cyclic- Photons of light absorbed by accessory pigments in antenna complex then passed to chl-A in reaction centre in PSII. This excited two high energy electons which are picked up by the first electon acceptor to reduce it. The electrons pass down electron carriers and gradually lose energy. The energy lost is used to synthesise ATP from ADP + Pi. Electrons move to PSI. Electrons are excited to high energy level and are picked up by second electron acceptor. Then passed down electron carriers and via redox reactions, NADP is reduced. Photolysis splits water to H+, e- and o2. The H+ reduced NADP to NADPH2 What do inhibitory drugs do?
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    (Original post by lilGem)
    I don't cover cyclic/ non cyclic or in as much detail in human bio

    Light dependent- takes place in thykaloid

    light hits chlorophyll causing a photoexcitation of an electron. The electron is passed to an electron acceptor molecule. the acceptor passes it to a chain of electron carriers as with the chemiosmotic theory, as the electron is passed ATP is produced by photophosphorylation (trapping of chemical energy from sunlight)

    Water is split by photolysis into oxygen (released as a waste gas) hydrogen which reduces NADP to NADPH2 and an electron which reduces the chlorophyll

    Calvin cycle- takes place in the stroma:

    CO2 (fixed) combines with RuBP by a catalysed reaction using the enzyme rubisco to form an unstable 6C molecule which quickly splits into 2 3C molecules of GP. ATP and NAPH2 reduce and phosphorylate it into triose phosphate, 5/6 of which is regenerated into RuBP whilst the remaining amount can be converetd into glucose, amino acids which are used in the plants metabolism
    That's pretty good knowledge for not doing it in detail, there isn't a great more in our syllabus to be perfectly honest!
    Another question?
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    (Original post by piers.townsend)
    That's pretty good knowledge for not doing it in detail, there isn't a great more in our syllabus to be perfectly honest!
    Another question?
    why do farmers plough the soil after each harvest?
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    Umm anyway, back BY4, describe the population growth curve
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    (Original post by lilGem)
    why do farmers plough the soil after each harvest?
    Improve aeration of the soil, and too encourage nitrogen fixation.
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    (Original post by MrBean1994)
    Umm anyway, back BY4, describe the population growth curve
    For bacteria (as that's the most common)

    Lag phase - Adapting to environment, high metabolic rate, protein synthesis. Little or no population growth.

    Log phase - Rapid population growth. Birth rate > Death rate. Sufficient nutrients etc

    Stationary phase - Stable population, no growth. Birth rate = Death rate. Population limited by nutrients etc

    Death Phase - Decline in population due to death of cells. Death rate > Birth rate. Due to lack of nutrients etc.

    Question; Describe and explain the effect on nerve transmission of each of the following; Myelin, Axon Diameter
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    (Original post by piers.townsend)
    Improve aeration of the soil, and too encourage nitrogen fixation.
    Yep, also prevents Pseudomonas bacteria involved in denitrification as they are anaerobes (love waterlogged ground).
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    (Original post by Bord3r)
    For bacteria (as that's the most common)Lag phase - Adapting to environment, high metabolic rate, protein synthesis. Little or no population growth.Log phase - Rapid population growth. Birth rate > Death rate. Sufficient nutrients etcStationary phase - Stable population, no growth. Birth rate = Death rate. Population limited by nutrients etcDeath Phase - Decline in population due to death of cells. Death rate > Birth rate. Due to lack of nutrients etc.Question; Describe and explain the effect on nerve transmission of each of the following; Myelin, Axon Diameter
    Myelin increased speed of impulse transmission because of salt story conduction. The impulse jumps between each node of ranvier. The larger the axon diameter the faster the impulse because of the increase in velocity?
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    Hey! Quick question!

    In the Nitrogen cycle is the process called "Putrefaction" or "Putrefication" simply because in the student guide they use "Putrefaction" however just looking through the mark scheme for Jan 12 and they use "Putrefication"...So not sure which one to use!

    Thank you!
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    (Original post by Lysipud)
    Hey! Quick question!

    In the Nitrogen cycle is the process called "Putrefaction" or "Putrefication" simply because in the student guide they use "Putrefaction" however just looking through the mark scheme for Jan 12 and they use "Putrefication"...So not sure which one to use!

    Thank you!
    Hey use putrefaction
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    (Original post by MrBean1994)
    Myelin increased speed of impulse transmission because of salt story conduction. The impulse jumps between each node of ranvier. The larger the axon diameter the faster the impulse because of the increase in velocity?
    The larger axon diameter reduces resistance and ion leakage, but I don't think that's actually part of syllabus come to think of it.
    But yeah myelination=saltatory conduction=faster transmission
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    (Original post by MrBean1994)
    Hey use putrefaction
    Thought as much, Thanks!
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    I have a quick question! Ultrafiltration, driven by hydrostatic pressure - the pressure's generated by changes in diameter between afferent and efferent arterioles and then apparently due to the water potential of the blood or something - could someone explain how the water potential of the blood generates pressure? It was never explained to us and I find it so much easier to remember things if I completely understand it!

    Thanks!
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    (Original post by hopefulmedic28)
    I have a quick question! Ultrafiltration, driven by hydrostatic pressure - the pressure's generated by changes in diameter between afferent and efferent arterioles and then apparently due to the water potential of the blood or something - could someone explain how the water potential of the blood generates pressure? It was never explained to us and I find it so much easier to remember things if I completely understand it!

    Thanks!
    I've never heard that second one to be a reason. The other one I've got in my notes is that the narrowness of the capillaries forces blood through at high hydrostatic pressure.
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    (Original post by Bord3r)
    I've never heard that second one to be a reason. The other one I've got in my notes is that the narrowness of the capillaries forces blood through at high hydrostatic pressure.
    Ahh okay thanks! I think I'll just steer clear of it in my answers though I've seen it come up in a couple of mark schemes before but it's only usually a couple of marks tagged onto say a five marker on ultra filtration and you can get the full marks without mentioning it so...
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    Describe the process of selective reabsorption
 
 
 
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