17.3 Photosynthesis Flashcards
What types of organisms photosynthesise
Autotrophic
What are chloroplasts and what is there structure
Where photosynthesis takes place in plants
Large surface area to maximise their light absorption
Membrane has flattened sacs
What is the structure of chloroplasts membrane
Forms flattened sacs called thylakoids which are stacked to form grana and these grana are joined by channels called lamellae
Where is the light absorbed in chloroplasts
By chlorophyll which are embedded in the thylakoid membrane
What are the types of chlorophyll
Chlorophyll A
Chlorophyll b
Xabthophylls
Carotenoids
What is chlorophyll A
Primary pigment that absorb light located in reaction centre
What are the roles of chlorophyll B, xanthophylls & carotenoids
Where are they in chloroplast
Absorb different wavelengths of light than chlorophyll a
They are embedded in the thylakoid membrane and form the light harvesting system
What is the light harvesting system
Absorbs light energy of different wave lengths and transfers this energy efficiently to the reaction centre
What is used to investigate photosynthetic pigments
Chromatography which is used to seperate pigments in a plant extract
What is the light dependent stage
The first stage of photosynthesis
Which absorbs energy from the sunlight and uses it to form ATP
It also uses hydrogen from water to reduce coenzyme NADP to reduced NADP
What is involved in the light dependent stage of photosynthesis
Non-cyclic phosphorylation
Photolysis
Cyclic phosphorylation
What happens in the first 2 stages of non-cyclic phosphorylation
Light is absorbed and excited electrons in photo system 2
The excited electrons are then released from the reaction centre of PSII and passed to the electron transport chain where ATP is produced by chemiosmosis
What happens at Photosystem 1 after photosystem 2 in noncyclic phosphorylation
More excited electrons are released from the reaction centre at PSI
And passed into another electron transport chain producing more ATP
the electrons lost from the reaction centre at PSI are replaced by the electrons that came from PSII
Electrons that leave ETC after PSI are accepted along with hydrogen ions by coenzyme NADP forming reduced NADP
What is photolysis
Water molecules are split into hydrogen ions, electrons and O2 using energy from the sun
How are the electrons lost at PSII replaced in non-cyclic phosphorylation
Electrons released from water in photolysis
O2 is released as a by product
What happens in cyclic phosphorylation in the light dependent stage of photosynthesis
Electrons that leave the electron transport chain after PSI can be returned to PSI instead of being used to form reduced NADP
What is the light independent stage of photosynthesis
Abs where does it take place
This takes place in the stroma of chloroplasts
The products from the light dependent stage -ATP AND REDUCED NADP are required
What are the products of the light dependent stage of photosynthesis
ATP
Reduced NADP
What is the process that takes place in the light dependent stage
Calvin cycle
What are the main 3 steps of the Calvin cycle
Fixation - co2 is fixed
Reduction - glycertate phosphate is reduced to triose phosphate by hydrogen from red NADP by ATP
Regeneration - RuBP is regenerated from recycled Triose phosphate
What are the first 2 stages of the Calvin cycle
Co2 enters the inter cellular spaces within the spongy mesophyll of leaves by diffusion
Co2 then diffuses into stroma of chloroplasts where it combines with Ribulose bisphosphate (5carbon)
What catalyses the reaction between co2 and ribulose bisphosphate
And what does this produce
In Calvin cycle
Ribulose bisphosphate carboxylate
( RuBisCo )
This produces an unstable 6 carbon intermediate
What happens to the unstable 6 carbon intermediate produced by the reaction between co2 and Ribulose bisphosphate in teh first stage of the Calvin cycle
It immediately breaks down into 2 3carbon glycerate 3-phosphate molecules (GP)
What happens to the two glycerate 3 phosphate molecules in the Calvin cycle
Each GP molecule is converted to another 3 carbon molecule - triose phosphate
