3.6 photosynthesis
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What is photosynthesis?
a series of enzyme controlled reactions that occur in a two stage process
What are the two stages of photosynthesis?
• light dependant stage (photolysis) - carbon fixation
What is the word equation for photosynthesis?
light energy carbon dioxide + water ————->glucose + oxygen chlorophyll
Name the energy conversion that takes place in photosynthesis, where is happens and what is produced in this conversion
• light -> chemical (in the form of ATP) • happens in the chloroplast (light is captured by the chlorophyll pigment) • ATP is produced
What is ATP used for in photosynthesis?
it is used to split water producing hydrogen and oxygen
Name a by-product of the light dependant stage and its fate
• oxygen - diffuses out the leaf
Describe the process of carbon fixation
the joining of hydrogen and carbon dioxide to make sugar (glucose) with ATP providing the energy
What can the chemical energy in the sugar (glucose) be used for by the plant?
• respiration • converted into starch (for storage) • converted into cellulose (structural)
What can carbohydrates be used for?
used to create fats and proteins
Name 3 limiting factors of photosynthesis
• carbon dioxide concentration • temperature • light intensity
What reduces the rate of photosynthesis?
the absence or reduction of any one of the limiting factors. A reduction in the rate of photosynthesis slows plant growth.
Name the substances produced in carbon fixation
sugar (glucose)
Name the substances used in carbon fixation
• hydrogen • ATP • carbon dioxide
Name the substances used in the light in the light dependant stage
• water - light energy
name the substances produced in the light dependant stage
• hydrogen • ATP • oxygen
Describe the light dependant stage of photosynthesis
• light energy is trapped by the chlorophyll • the energy is inverted to chemical energy and is stored in ATP • ATP is passed onto the second stage • water molecules are split into hydrogen and oxygen molecules • oxygen then diffuses out the leaf
What is the colour transformation in iodine solution when starch is present?
brown–>blue/black