Photosynthesis Flashcards
What is the equation for photosynthesis?
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
How is the leaf adapted for photosynthesis?
-Palisade layer- cells close to the leaf upper surface (where most light enters the leaf), tightly packed together, numerous chloroplasts in their cytoplasm to maximise light absorption
-Spongy mesophyll layer- less tightly packed and has numerous large air spaces to facilitate gas exchange
-Waxy cuticle to prevent water loss by transpiration
-Stomata- facilitate gas exchange and reduces water loss by transpiration
How are chloroplasts adapted for photosynthesis?
-The chlorophyll is arranged in a system of flattened membranes called thylakoids
-Thylakoids contain chlorophyll and other plant pigments that absorb light energy
-They also contain systems of electron carriers and associated enzymes involved in the photosynthesis reactions
-Thylakoids arranged in clumps or “stacks” of membranes called grana (singular granum). As grana contain concentrated areas of light-absorbing photopigments, most light harvesting takes place here.
-Thylakoids are linked together by intergranal lamellae.
-Carbon dioxide is used (“fixed”) and sugars and other compounds are made in a cyclical series of reactions that take place in the stroma.
What does photosynthesis involve?
-Photosynthesis involves two distinct, but interlinked phases, which take place in the thylakoids and the stroma.
-The reactions that take place in the stroma are dependent on a steady supply of products from the reactions associated associated with the absorption of light energy
What is the absorption spectrum?
-The absorption spectrum can be represented as a graph that shows the relative absorption of light at particular wavelengths.
-It can show the overall absorption of light by all the pigments that absorb light in photosynthesis and/ or show the the light absorbed by individual pigments.
What does the absorption spectra of individual pigments show?
-Shows that the pigments complement each other by absorbing light over a different range of wavelengths.
-This ensures that by absorbing light over as great a range of wavelengths as possible, more light energy can be harvested.
What is the action spectrum?
-The action spectrum is the rate of photosynthesis that takes place at different wavelengths
What is the correlation between the action spectrum and the absorption spectrum?
-The rate of photosynthesis is high for those wavelengths over which most light is absorbed.
What are the 3 main stages of photosynthesis?
1 ) Light harvesting- the absorption of light in the thylakoid, a consequence of which is to raise the energy level of the electrons in the chlorophyll
2) Light-dependent stage- energised electrons are used to make the energy-rich compounds ATP and reduced NADP. These reactions take place in or on the thylakoid membranes of the grana.
3) Light-independent stage- the products of the light reaction are used to make simple carbohydrate. Carbon dioxide is fixed as part of the cyclical series of reactions that take place in the stroma
Where is chlorophyll and other pigments located in?
The thylakoid membranes
