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
