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Biology Topic 6 - Plant Structures and Their Functions (6a -…
Biology Topic 6 - Plant Structures and Their Functions
6a - Photosynthesis
plants and algae are types of protists
they can trap energy transfered by light from the sun
this energy is transferred to molecules of suger -
glucose
in a process called photosynthesis
glucose and substances made from glucose are stores of energy
animals then eat these stores of energy
materials in organism are called
biomass
Photosynthesis
series of chemical reactions, catalyzed (speeded up) by enzymes
carbon dioxide + water => glucose + oxygen
products => reactants
photosynthesis happens in the chloroplast which contains chlorophyll that traps energy transferred by light
energy enters from the surroundings so the reactants have more energy than the products so
endothermic
glucose link together to make a
polymer
called
starch
- this stays in the chloroplasts until photosynthesis stops
starch is broken down into simpler substances which move to cytoplasm to make sucrose
sucrose is transported around the plant and used to make:
starch (in storage organ)
other molecules for the plant (cellulose, lipids and proteins)
glucose for respiration (to release energy)
Leaf Adaptations
the
palisade
cells near the top of a leaf are full of chloroplasts - absorbing lots of lights
leaves contain microscopic pores called stomata (stoma) - allowing carbon dioxide to diffuse into the leaf
stomata are opened and closed by specialized cells called
guard cells
in the light water flows into pairs of guard cells making them rigid, opening the stoma
at night water flows out of the guard cells, lose rigidity and stoma shuts
stomata also allows oxygen produced by photosynthesis to go into air (& water vapour) - the flow of different gases is called
gas exchange
leaves are often broad and flat giving them a large surface area