Y2: Photosynthesis Flashcards
What are leaves adapted to do?
Bring together H2O, CO2 and light and remove O2 and glucose
Name three adaptations of leaves?
- Arrangement?
- Surface area?
- Thickness?
- Leaves are arranged for minimum overlapping so they don’t shadow each other
- Large surface area so more light is absorbed
- Thin so most of the light is absorbed in the first few micrometers so sort diffusion distance
Name three adaptations of leaves?
- Cuticle?
- Chloroplasts and mesophyll?
- Stomata?
- Transparent cuticle and epidermis to let light into the mesophyll cells
- Upper mesophyll cells packed w/ chloroplasts
- Lots of stomata so all mesophyll close to one so short diffusion distance
Name three adaptations of leaves?
- stomata in light?
- air spaces?
- transport?
- Stomata open and close depending on light intensity
- air spaces in lower mesophyll to allow for rapid gas diffusion
- xylem and phloem to transport substances
Structure and role of grana in the chloroplasts?
Stacks of up to 100 thylakoids
hold chlorophyll in a way that maximises absorption of light
light dependent stage of photosynthesis
structure and role of thylakoids in the chloroplasts?
Contain photosynthetic pigment- chlorophyll
Have intergranal lamellae- tubular extensions join thylakoids
Have large surface area for attachment of chloropyll and e- carriers etc.
Structure and role of the stroma in the chloroplasts?
Fluid-filled matrix
Contains DNA and Ribosomes to make proteins for light independent reaction
contains enzymes
Surrounds thylakoids for easy diffusion
Site of light independent reaction
Light dependent stage: Photoionisation and photoexcitation 1
Full version
- Photons of light hit photosystem II
- Light energy causes photoexcitation of 2e- in the chlorophyll
- leads to photoionisation of chlorophyll
- chlorophyll has become oxidised - 2e- raised in energy level move into e- carrier in the electron transport chain
- e- carrier reduced - Reduced e- carrier passes e- onto carrier becoming oxidised when they leave
Light dependent stage: proton pump
Full version
- Energy released from e- used to actively transport h+ ions against the conc gradient from the stroma to the lumen of the thylakoid
- This creates and maintains chemiosmotic gradient of H+ ions- highest in the thylakoid
- Allows chemiosmosis to occur
Light dependent stage: Photoionisation and photoexcitation 2
what forms as a result?
Full version
- When e- reach photosystem I, another photon of light excites the e- so they can combine with NADP+ and H+ to form NADPH (reduced NADP)
Light dependent stage: Chemiosmosis
Full version
- H+ ions move down the chemiosmotic gradient through ATP synthase which catalyses the reaction between ADP and Pi to form ATP
Light dependent stage: Photolysis
Full version
- for chlorophyll of PSII to be used again it needs to be reduced- replace lost e-
- E- provided for by the photolysis of water
- photon of light is used
- H2O –> 2H+ + 2e- + 1/2O2
H+ ions used to reduce NADP+
Light dependent stage:
Summary 5 marker
Photoexcitation and ionisation
Proton pump
Photoexcitation and formation of ?????
Chemiosmosis
Photolysis
- Photons of light hit photosystem II causes photoexcitation of 2e- in the chlorophyll, 2e- raised in energy level move into the electron transport chain, chlorophyll has been photoionised
- Energy released from e- used to actively transport h+ ions against the conc gradient from the stroma to the lumen of the thylakoid. This creates and maintains chemiosmotic gradient of H+ ions- highest in the thylakoid
- When e- reach photosystem I, another photon of light excites the e- so they can combine with NADP+ and H+ to form NADPH (reduced NADP)
- H+ ions move down the chemiosmotic gradient through ATP synthase which catalyses the reaction between ADP and Pi to form ATP
- Photolysis of water to reduce chlorophyll and replace lost e- and H+ ions used in reduction of NADP+
Light dependent stage: Bullet point summary
Photoexcitation and ionisation
Proton pump
Photoexcitation and formation of NADPH
Chemiosmosis and formation of ATP
Photolysis
Calvin cycle 5 marker
RuBP combines with CO2 to form 2 x GP
This is catalysed by rubisco
GP is reduced into TP
Using NADPH and ATP
Some TP is used to make hexose sugars and some is used to regenerate RuBP
What does RuBP stand for?
Ribose Bisphosphate
What does GP stand for?
Glycerate 3 phosphate
What does TP stand for?
Triose Phosphate
What is the role of ATP in the calvin cycle?
It provides energy
What is the role of NADPH in the calvin cycle?
Reducing agent
What does the light dependent stage of photosynthesis do? What is its purpose?
Think energy
It transfers light energy to chemical energy in ATP and NADPH
What does the light independent stage of photosynthesis do? What is its purpose?
Think energy
It transfers chemical energy in ATP and NADPH into chemical energy in glucose
What is carbon fixation?
Converting inorganic carbon eg: CO2 into organic molecules eg: glucose
