Download B4 Leaves and photosynthesis

Photosynthesis and Leaves – Revision Pack (B4)
Leaf Structure:
Sunlight will enter here
The wax cuticle
layer is there to
protect the leaf
without blocking
out sunlight
The above diagram shows the specialised cells in a green leaf – you should know
how to label a diagram like the one above. These cells are adapted to do certain
jobs:
Cell Adaption
The outer epidermis is transparent
because it lacks chloroplast (and as such
chlorophyll which is a green pigment)
Purpose
They allow light to reach the palisade
layer; they do not act as an obstacle to
light
Upper palisade layer contains most of
the leafs chloroplasts
Because this is where most of the light
from the sun will be received, it allows
the plant to absorb all of this light
1) This allows the diffusion of gases
between the cells and the
atmosphere to happen
2) It also creates a large surface
area to volume ratio – this means
that large amounts of gases can
enter and exit the cells
The spongy mesophyll cells are loosely
packed (there’s lots of air space)
Leaf adaptations for Photosynthesis:
Leaves are adapted so that photosynthesis is VERY efficient.
Photosynthesis and Leaves – Revision Pack (B4)
Broad
Leaf Adaption
Thin
Purpose
To maximise surface area so they can
get as much light as possible
Contain a variety of pigments (e.g.
chlorophyll a, b, carotene etc.)
1) So that gases (like CO 2 ) can
diffuse through easily
2) So that light can get to ALL cells
This allows the plant to absorb light from
a broad range of the light spectrum
They have loads of vascular bundles (or
veins)
This allows support and transport of
chemicals like water and glucose
Specialist guard cells
(see below)
These control the opening and closing of
the stomata, thus regulating the flow of
carbon dioxide, oxygen and water loss
When the stoma is open, the
guard cells are full of water
and are turgid.
When the stoma is closed, the
guard cells lose water and
become flaccid. They would
normally only close when it is
dark when no carbon dioxide
is needed for photosynthesis.
NOTE – Through having a variety of pigments (these being: chlorophyll a, chlorophyll
b, carotene and xanthophylls), the plants cells can maximise the use of the suns
energy. Each of these pigments absorbs light of different wavelengths.
Photosynthesis and Leaves – Revision Pack (B4)
Past Papers:
PPQ(1):
Photosynthesis and Leaves – Revision Pack (B4)
PPQ(2):
PPQ(3):
Photosynthesis and Leaves – Revision Pack (B4)
PPQ(4):
Photosynthesis and Leaves – Revision Pack (B4)
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
PPQ(4):