Plants and Xylem Revision Notes (Biol 2 AS AQA Spec)

My plants and Xylem tissue revision notes. There's the lack of xerophytic adaptations, they're covered in my gas exchange pack that i have also uploaded.

Hope they help

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Plant Cells & Water Transport

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Cellulose ­ Uses & Comparison
Plant Cells
Palisade Mesophyll Cells
Plant Transport
Uptake of water across a root
Uptake of Water up the Xylem
How water moves through a plant
How water moves through a leaf
Potometer Experiments
Factors Affecting Transpiration Rate
Summary of the Pathway Taken By Water…read more

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Cellulose is the primary component of plant cell walls. To do
this job, it needs to be able to bond to other cellulose
molecules and be extremely strong.
Cellulose is made from beta-glucose rather than alpha-glucose,
which is used as a source of energy.
The only
difference between
the two is the
hydroxyl (OH)
group on carbon-1
is inverted in
however this
seemingly minor
change changes everything.…read more

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Cellulose ­ Uses & Comparison
Cellulose is the main
component of plant cell
walls and when molecules
of it are arranged together,
they form microfibrils that
then form fibers.
This is only possible due
The linear structure
due to inverted
The hydrogen bonds
forming in between
layers that hold it
Polym Monom
Structure Function
er er
Long, Provides
straight, rigidity to plant
un-branched cell walls
chains.…read more

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Compact, can
alpha-helix fit lots of it in a
shape small space
Highly Carbohydrate
branched store in animals
Large & Readily
Glyco Alpha-G
insoluble hydrolysed
gen lucose
Inert Less dense &
more soluble
than starch
In questions always talk about `tensile strength' is it asks about the rigidity
of cell walls.
Try and remember most of Unit 1 regarding polysaccharides despite them
not being on Unit 2, they might give you a `tick the box' table and ask you to
compare them.…read more

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The cell wall consists of a primary cell wall, and older ones
may have a secondary inner one as well. The middle lamella, a
thin outer layer, cements adjacent cells together.
In cell walls there are small gaps known as plasmodesmata that
allow for communication and transport between cells. We will
see this in more detail later.
Plant cells have a large, permanent vacuole whilst animal cells
only have small, temporary ones.…read more

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Chlorophyll is located inside the thylakoid membranes
The stroma is an aqueous matrix that contains starch
Trapping Light
The thylakoid membrane & grana provide a large surface
area for chlorophyll electron carriers and enzymes that
carry out photosynthesis.
The large number of grana mean there is a large surface
area for photosynthesis.
The matrix in the stroma contains all the enzymes
needed for photosynthesis.…read more

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There are long, thin cells that form a continuous layer to
absorb sunlight.
There are numerous chloroplasts that collect light.
The large vacuole pushes the cytoplasm and chloroplasts
to the edge of the call.
Plant Transport
Basically there are two transportation
systems in a plant, the xylem & phloem
vessels. The xylem is concerned with
water transport and the phloem sugars
and ions etc. The xylem tubes are what
concerns us.
The passage is as follows:
Water moves into the roots hair
cells by osmosis.…read more

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Uptake of water across a root
Throughout water's passage through a root it will meet:
Root hair cells ­ Epidermal cells
with a large surface area for
water uptake
Epidermis ­ Single outer layer
of cells
Cortex ­ Tissue making the
bulk of the root
Endodermis ­ Single layer of
cells around the vascular
bundle.…read more

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Water can move through the cortex in two different ways:
Symplastic Pathway
Water can move through the cortex via this path. It moves
through the membranes and cytoplasms by osmosis down a
water potential gradient. Plasmodesmata are channels through
the cell wall that connect plant cells together and form
continuous cytoplasmic bridges that increases the rate of
movement between cells.
Water can diffuse
through cell walls,
as they are
permeable.…read more


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