3.2- Photosynthesis Flashcards
What is photosynthesis?
•where pigments trap light energy and convert it into chemical energy in the plant
Equation for photosynthesis
6CO2 + 6H2O ———> C6H12O6 + 6O2
Where does photosynthesis take place?
• in the THYLAKOID MEMBRANE of the chloroplast
What are the stages of photosynthesis?
There are 2 stages:
• light DEPENDENT
•light INDEPENDENT
Where do light DEPENDENT reactions take place?
in the THYLAKOIDS (stack called grana)
Where do the light INDEPENDENT reactions take place?
in the STROMA (fluid in the chloroplast)
Describe the features of a chloroplast
Label a chloroplast from internet
Where are chloroplasts mainly found?
In the palisade mesophyll layer (in the UPPER part of the leaf)
Also in the spongy mesophyll of the guard cell
Describe some structural features of a leaf & their significance for photosynthesis
•Large surface area → capture lots of light
•Thin → short diffusion pathway
•Stomatal pores → allows CO2 to diffuse into leaf
•Air spaces in spongy mesophyll and spaces between palisade cells → allows CO2 to diffuse into photosynthesising cells
Describe some structural features of a chloroplast & their significance for photosynthesis
•large surface area → more light absorbed
• move with palisade cell → move to TOP on dull days (capture max light) and moves to BOTTOM on bright days if light is too high (protects pigments)
• pigments in thylakoid in single layer at surface → maximise absorption of light
• rotate within palisade cell → maximise absorption of light
The absorption spectrum “shows how much light is __________ by a PIGMENT at ___________ wavelengths of light
Absorbed
Different
The action spectrum shows “ the _________ of photosynthesis at _____________ wavelengths of light
Rate
Different
What do photosynthetic pigments do?
Absorb specific wavelengths of light
Give examples of the main photosynthetic pigments
2 main classes: chlorophylls & carotenoids
•Chlorophylls→ chlorophyll a and b
•Carotenoids →ß carotene and xanthophylls
Describe both chlorophyll a and b
Chlorophyll a
• peak absorbed at 435,670 - 680
• pigment colour: blue-green
• occurs in ALL plants
Chlorophyll b
•peak absorbed at 480,650
• pigment colour: yellow -green
• occurs in HIGHER plants
