AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

Could someone just clarify if this is right about water transport in plants:
1) The Root:
- Ions are actively transported into the xylem
- This reduces water potential in the xylem
- Water moves down a water potential gradient from the soil to the root hair cells by osmosis
- This creates root pressure
2) The Routes:
- The symplast pathway involves travelling through living parts of the cell - the cytoplasm
- Cells are connected by plasmodesmata
- The apoplast pathway involves travelling through the non-living parts of the cell - the cell wall.
- Once endodermis cells are reached, a waxy casparian strip prevents the water from moving through the cell wall, so its forced to travel through the cell membrane (which allows for more control over water movement)
- Water molecules then reach the xylem
3) The Xylem:
- Water evaporates at the leaf of the plant
- This creates tension (suction) which forces more water molecules into the leaf
- Water molecules are cohesive due to hydrogen bonding, so when one is sucked up, a whole column follows
- As water enters via the roots, it pushes water already in the xylem further upwards (root pressure)

Much appreciated, need to get this!

I second that...

does anyone have a mnemonic for learning the taxonomy groups

That is absolutely beautiful, but I would recommend you say WATERPROOF casparian strip over 'waxy', because that word has been rejected in the past!

Could someone just clarify if this is right about water transport in plants:
1) The Root:
- Ions are actively transported into the xylem
- This reduces water potential in the xylem
- Water moves down a water potential gradient from the soil to the root hair cells by osmosis
- This creates root pressure
2) The Routes:
- The symplast pathway involves travelling through living parts of the cell - the cytoplasm
- Cells are connected by plasmodesmata
- The apoplast pathway involves travelling through the non-living parts of the cell - the cell wall.
- Once endodermis cells are reached, a waxy casparian strip prevents the water from moving through the cell wall, so its forced to travel through the cell membrane (which allows for more control over water movement)
- Water molecules then reach the xylem
3) The Xylem:
- Water evaporates at the leaf of the plant
- This creates tension (suction) which forces more water molecules into the leaf
- Water molecules are cohesive due to hydrogen bonding, so when one is sucked up, a whole column follows
- As water enters via the roots, it pushes water already in the xylem further upwards (root pressure)

Much appreciated, need to get this!

Does DNA half in mitosis?


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They won't ask you that amigo. All you need to know is that the chromosomes line up at the equator in homologous pairs. At this point, crossing over(rare) and independent segregation occur that increase variation. You don't need to really explain the stages of meiosis

Also can someone tell me what we need to know about glycogen and do we need to know anything about lipids/ fatty acids??? I'll be eternally grateful!

Does DNA half in mitosis?


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Just to add at the end, water molecules also stick to the xylem walls. This is called adhesion. The force is so strong it pulls the walls of the xylem inwards.
And when you talk about cohesion and tension use the phrase 'cohesion-tension'. You often get a mark just for that before you explain it the rest seems right

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