B4c: Leaves and photosynthesis Flashcards
Why are chloroplasts not found in all plant cells?
because not all plant cells (e.g. root cells) are exposed to light so cannot trap light using chlorophyll
Entry points of materials required for photosynthesis (2)
water through root hairs
carbon dioxide through stomata
What absorbs light energy for photosynthesis?
chlorophyll pigments in chloroplasts
Exit point of materials produced in photosynthesis
oxygen through stomata
Leaf structure (7)(top to bottom)
cuticle
upper epidermis
palisade mesophyll layer
vascular bundle
spongy mesophyll layer - contains large air spaces
lower epidermis - contains stomata(small holes between two guard cells) and guard cells
lower cuticle
Explain how leaves are adapted for efficient photosynthesis(5)
broad so large surface area - absorbs more light
thin so short distance for gases to diffuse
contain chlorophyll and other pigments to absorb light from different parts of the spectrum - absorbs as much of Sun’s energy as possible
have a network of vascular bundles for support and transport of raw materials (water) and products (glucose) of photosynthesis
guard cells which open and close the stomata therefore regulating the flow of carbon dioxide and oxygen and water loss
Explain how the cellular structure of a leaf is adapted for efficient photosynthesis(4)
epidermis is transparent - no barriers to the entry of light
palisade layer at the top containing most of the chloroplasts as they will receive most of the light
air spaces in the spongy mesophyll allow diffusion between stomata and photosynthesising cells
internal surface area to volume ratio very large so that large amounts of gases can enter and exit the cells
Explain how plants maximise the use of energy from the Sun(2)
peaks in absorption spectrum show amounts of light absorbed by different pigments
several chloroplast pigments (a, b, catorene, xanthophyll) allow plants to absorb light across a greater range of colour wavelengths in the spectrum
