16) Photosynthesis Flashcards
Why do plants need energy for biological processes
Photosynthesis , active transport , DNA Replication , cell dicision and protein synthesis
Why do animals need energy for biological processes
Muscle contraction , body temperature ,active transport , DNA Replication , cell division , protein synthesis
What is phosphorylation , Photophosphorylation , Photolysis
Adding phosphate to a molecule
Adding phosphate to a molecule using light
Splitting a molecule using light energy
Explain a coenzyme involved in photosynthesis
NADP - transfer hydrogenfrom one to another , mean it can readuce or axidise a molecule
Describe the structure of the chlorplast
Thylakoids Fluid filled stacks
Grana Stacked up thylakoids
Lamellae bits of thylakoid membrane that links grana
Summarise Photosystem 1
Absorb light at 700nm wavelengths
Summarise Photosystem 2
Absorb light at 680 nm
What happens in the Light-dependent reaction
Light energy is absorbed by photosynthetic pigments ( eg , chlorophyll a / b ) in photosystems are converted to chemical energy
Light used to add phosphate group to ADP to form ATP and to reduce NADP to form reduced NADP
NADP transfer hydrogen to light-indepenent reaction .
What happens in the light-independent reaction
Called the calvin cycle
Rely on products from light-dependent reaction
Takes place in stroma
Atp + reduced NADP supply energy and hydrogen to make glucose from cO2
How are photo systems linked
Photosystems linked by electron carriers
WHat are electron carriers
Proteins (H+) that transfer electrons
What do photosystems and electron carriers form?
What is this?
Electron transport chain
-Chain of proteins through which excited electrons flow
What happens in the First stage of Non-cyclic Photophosphorylation
1) Light energy excites electrons in chlorophyll
Light is absorbed by PS2
Electron excite and move to a higher energy level
These high-energy electrons move along the electron transport chain to PS1
What happens in the 2nd stage of Non-cyclic photoposhporylation
2) Photolysis of water produces proton ( H+ ions ) , electrons and O2
Electrons move from chloryphyll leave PS2 and move along electron transport chain , these are replaced
Light energy splits water into Hydrogen ions and electrons and oxygen
What is the 3rd stage of Non-Cyclic Photophosphorylation
3) Energy from the excited electrons make ATP
Excited electrons lose energy and move along Electron transporter chain
ENergy used to transport protons into thylakoid by proton pumos
High conc of proton cause *Proton gradient *
Protons movw down gradient into stroma by ATP Synthase energy from this combines ADP and phosphate into ATP
What happens in the 4th datge of Non-cyclic Photophosphorylation
4) Generates reduced NADP
Light is absorbed by PS1 which excites electrons again to an even higher energy level
Electrons transfered to NADP along with reduced NADP
What is produced in cyclic photophosphorylation
Only produces ATP
Uses Ps1 , electrons are recycled and aren’t passed onto NADP so NADP or O2 is not made only ATP
What products are made / done in the light-dependent reaction
Atp from photophosphorylation
Reduced NADP from NADP + H ions
Splitting of water = > protons , electrons , oxygen by photolysis
What is the light independent reaction
Calcin cycle
Takes place in the stroma of the chloropasts
Camke triose phosphate from co2 , ribulose biphosphate.
Needs ATP an H+ ions
WHat is the first stage of the Calvin Cycle
1) Carbon dioxide is combined with ribulose biphosphate to form 2 molecules of glycerate 3-phosphate
CO2 enters leaf and diffuse into stroma
COmbines with Ribulose bisphosphate ** which breakks down by enzyme *rubisco into *Glycerate 3-phosphate
What happens in the 2nd stage of the Calvin Cycle
2) ATP and reduced NADP are required for the reduction of GP to triose phosphate
ATP from lDR provide energy to turn 2 Glycerate into 2 triose phosphate
Requite H+ ions and come from reduced NAFP .
NADP recycled to NADP
Triose phosphate converted into many useful organic compounds
What happens in the 3rd stage of the Calvin Cycle
3) Ribulose biphosphate is regenerated
Five out of 6 TP molecules arent made to make sugar but regenerate RuBP
Uses the rest of ATP by the light-depenedent reaction
What useful organic substances are produced by converting TP and GP
Carbohydrates
Lipids
AMino acids
How much of each product is made t make 1 hexose sugar
6 cycles
to make 2 molecules of TP
18 ATP
12 Reduced NADP
Describe the optimum conditions needed for photosynthesis
1) High light intensity of a certain wavelength
Light provide energy for LDR.
Higher intensity - more enrgy provided
Certain wavelength used , absorb red and blue , reflect green hence look green
**2) Temp around 25 **
Invlve enxymes , inactive when too low , denature when too high
Stomata closes at high
Thylakoid membranes may be damaged
Membrane around chloroplast damage - enzymes to be released into cell , reduce ror
Chlorophyll affected - red amount of light energy absorbed
3) Carbon dioxide at 0.4%
CO2 make up 0.04% of gas
Increases up to 0.4% give high rate of photosyntheses
How does light intensity affect levels of GP , RuBP and TP
reduced NADP , ATP will be in short supply
Conversion of GP to TP amd RuBP is slow
GP level will rise , levels of TP and RuBP will fall
How does temperature affect the levels of GP , RuBP and TP
Low temp , enzymes work slow
Levels of RuBP , GP , TP will fall
AFfect same way at high temp - denature
How does Carbon Dioxide affect the levels of GP , RuBP and TP
Low CO2 , Coversion of RuBP to GP is slow
Level of RuBP will rise and level of GP and TP will fall.
what are autotrophs
can make organic molecules from inorganic molecules
what are heterotrophs
relies on organic molecules made from another organism
Describe how light is absorbed in the chloroplast
There are different primary and accessory pigments in a photosystem.
For eg. Chlorophyll A and Chlorophyll B
Photon energy is absorbed by the pigments.
Cause an electron to be excited.
Electron is passed to different pigments
Accessory pigments can absorb a range of wavelengths.
where are photosynthetic pgiments found
photosystems in the thylakoid
