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    What is the transpiration stream
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    (Original post by Abuzar133)
    What is the transpiration stream
    Is it when water and other molecules travel up the xylem contiuously? Is that right?
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    (Original post by hafsa473)
    Is it when water and other molecules travel up the xylem contiuously? Is that right?
    i dont know
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    (Original post by Abuzar133)
    i dont know
    Oh k well in the revision guide it says water and minerals are carried up the xylem from the roots to the stem and leaves. As water is lost when it evaporates, water also enters the plant from the roots at the same time.
    I didn't rly know that myself
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    where does active transport take place
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    (Original post by siobhanx13)
    How does the iron lung work in comparison to how ventilators work now?
    The iron lung is a negative pressure system. Air is pulled in and drawn out, this changes atmospheric pressure outside the lungs, causing air to rush in and out of the person's body. A modern ventilator however, is a positive pressure system and works by mechanically forcing air into the lungs of a person.
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    (Original post by Abuzar133)
    where does active transport take place
    in the gut, in root hair cells
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    How do plants use glucose?
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    (Original post by hafsa473)
    Oh k well in the revision guide it says water and minerals are carried up the xylem from the roots to the stem and leaves. As water is lost when it evaporates, water also enters the plant from the roots at the same time.
    I didn't rly know that myself
    Transpiration stream is when water is diffused into the plant from root hair cells and carried up the xylem to leaves where it is lost to the surroundings by evaporation.
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    (Original post by hafsa473)
    How do plants use glucose?
    Respiration
    Growing shoots and seeds (storage?)
    Other than that idk


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    How do stents work?(2 marks)
    B3
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    The transpiration stream is the movement of water from the roots through the xylem and out of the leaves.
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    Can someone explain why Arteries have walls made up of muscles and elastic fibres.

    Also why Veins have thinner walls with valves to prevent backflow?
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    (Original post by miapeters)
    Respiration
    Growing shoots and seeds (storage?)
    Other than that idk


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    to make cellulose for cell walls
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    (Original post by Federerr)
    Can someone explain why Arteries have walls made up of muscles and elastic fibres.

    Also why Veins have thinner walls with valves to prevent backflow?
    Arteries pump blood away from the hearts (Arteries begins with an A - that's how i remember) and this blood is under high pressure because it's just come from the heart. Therefore, it needs thick muscular walls to make it strong and elastic fibres which can stretch and spring back,

    Veins pump blood back to the heart so are therefore under lower pressure meaning that the walls can be thinner and they have valves so the blood goes in the right direction.

    I hope this helps
    And I'm not quite sure why veins have valves but arteries don't?
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    (Original post by hafsa473)
    How do plants use glucose?
    Store as seeds, turned into lipids first
    Proteins, building into proteins from amino acids using nitrate ions
    Respiration, glucose + oxygen --> CO2 + water
    Stored as starch, to use when photosynthesis isn't happening, because starch is insoluble, unlike glucose so doesn't draw in loads of water
    Cell walls, into cellulose for strong cell walls
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    (Original post by rlb2000)
    Except from proteins are used for growth and development so they build things i have no idea... Help?
    remember CASH

    Catalysts
    Antibodies
    Structural components of tissue
    Hormones
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    And I'm not quite sure why veins have valves but arteries don't?[/QUOTE]

    Arteries travel away from the heart so naturally towards the direction of gravity, whilst veins travel towards the heart against the force of gravity so veins need valves to prevent the blood from flowing in the wrong directions
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    (Original post by siobhanx13)
    Arteries pump blood away from the hearts (Arteries begins with an A - that's how i remember) and this blood is under high pressure because it's just come from the heart. Therefore, it needs thick muscular walls to make it strong and elastic fibres which can stretch and spring back,

    Veins pump blood back to the heart so are therefore under lower pressure meaning that the walls can be thinner and they have valves so the blood goes in the right direction.

    I hope this helps
    And I'm not quite sure why veins have valves but arteries don't?
    Veins have valves to stop back flow as the blood travels back up to the heart against the force of gravity. The valves are two lines from either side of the vein, which face upwards. This means, when the blood flow up the vein, it cannot flow back in the other direction due to the two lines which is the valve. I hope the diagram below helps.
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    (Original post by siobhanx13)
    Arteries pump blood away from the hearts (Arteries begins with an A - that's how i remember) and this blood is under high pressure because it's just come from the heart. Therefore, it needs thick muscular walls to make it strong and elastic fibres which can stretch and spring back,

    Veins pump blood back to the heart so are therefore under lower pressure meaning that the walls can be thinner and they have valves so the blood goes in the right direction.

    I hope this helps
    And I'm not quite sure why veins have valves but arteries don't?
    Also arteries don't have valves as the blood flowing through them is already under high pressures. This means the blood does not need valves as the blood flows to the rest of the body through the arteries. I hope this has answered your question.
 
 
 
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