Photosynthesis Flashcards
How are photosynthesis and respiration related
Carbon dioxide and water are raw materials for photosynthesis and products of respiration
O2 and glucose are the raw materials for photosynthesis and the products of respiration
Describe the structure of a chloroplast
Usually disc shaped
Double membrane
Thylakoids- flattened discs stack to form grana
Intergranal LAMELLAE - tubular extensions attach thylakoids in adjacent grana
Stroma fluid filled matrix with high enzyme and substrate concentration of own loop of DNA
How are chloroplast adapted to photosynthesis
Strong- gel like fluid contains enzymes that catalyse the reactions of the light independent stage
Grana - granal stack creates a large SA for the prescient of many photosystems
DNA- chloroplast DNA contains genes that code for some protein and enzymes used in photosynthesis
How many stages does photosynthesis occur
Light dependent stage, takes place in the thylakoids
Light independent stage- takes place in the stroma
What occurs during the light dependent stage
Light energy breakdown water to produce hydrogen ions,electrons and oxygen in the thylakoid lumen
Proton gradient is formed
Define photosynthetic pigment
Coloured substances that absorb the light energy needed for photosynthesis
E.g chlorophyll a,chlorophyll b
Found in the thylakoid membranes
What are photosystem
Pigments attached to proteins
Contains two types - primary and accessory
Primary - reaction centres, electrons are excited
Accessory - light harvesting systems, transfer light energy,
What are the two photosystem that are used to capture light energy
Photosystem 1 - absorb light wavelength of 700nm
Photosystem 2- absorb light best at 680nm
Name the processes in the light dependent reaction
Photoionsation Electron transfer chain Chemiosmosis Non cyclic Reduction of NADP photolysis of water
Define photoionisation
Excites electrons
Explain the role of light in photoionisation
Chlorophyll molecules absorb energy from photons of light
Excites 2 electrons(raises them to a higher energy level) causing them to be released from the chlorophyll
What happens in the electron transfer chain
Electrons releases from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane and undergo a series of redox reactions, releases energy
How does chemiosmosis produce ATP in the light dependent stage
Some energy releases from the ETC is couples in active transport of H+ ions from the stroma into thylakoid space
H+ moves down concentration gradient from thylakoid space into stroma via transmembrane protein ATP synthase
ATP synthase catalyse ADP+ pi -> ATP
Describe non cyclic photophosphorylation
Uses PS1 and 2
Excites electrons enter ETC to produce ATP
NADP acts as final electron acceptor and is reduced
Water is photolysed to release electrons to replace those lost from PS 2
Produce ATP and reduced NADP
Describe cyclic photophosphorlyation (adding phosphate using light)
Uses PS1
Excited electrons enter ETC to produce ATP the return directly to phosystem
Purpose- produce additional ATP
What happens to the products of the photolysis of water
H+ ions move out of thylakoid spaces via ATP synthase and are used to reduce the co enzyme NADP
E- replace electrons lost from chlorophyll
O2 used for respiration or diffuses out of leaf as waste product
How and where is reduced NADP produced in the light dependent reaction
NADP+2H+(from photolysis of water) + 2e- (from acting as final electron acceptor in ETC)- reduced NADP
Catalysed by dehydrogenase enzymes
Stroma of chloroplast
Name the 3 main stages in light dependent reaction
Carbon fixation
Reduction
Regeneration
Explain how ribulose bisphosphate (RuBP) is regenerated in the Calvin cycle
Regenerated from triose phosphate
ATP provides the energy to do this
Name the products of the light dependent stage of photosynthesis
Reduced NADP
ATP
Oxygen
Explain why it is incorrect to say energy is produced
Energy cannot be created or destroyed instead energy is transferred and ATP is produced
Explain why ATP is not a good energy storage molecule but why organic molecules, like lipids and carbohydrates are
ATP is not very stable, easy to remove phosphate group, organic molecules are more stable and OM such as glycogen are more energy dense
Explain the interrelationship between respiration and photosynthesis in organisms
Photosynthesis: light energy is converted into chemical energy, inorganic molecules are converted into organic molecules, water and CO2 are converted to glucose and oxygen
Respiration: uses o2 prod. in photosynthesis, organic molecules broken down into inorganic molecules, energy released to synthesis ATP
Explain the importance of ATP to living organisms
Universal energy currency, energy transfer is quick, ATP can be re synthesised
Describe the properties of cell membrane necessary for the formation of a proton gradient
Contains embedded protein such as ATP synthase which is responsible for the synthesis of ATP
Name the type of diffusion which enables protons to move through ATP synthase and explain the role of ATP synthase in the production of ATP
Facilitated diffusion, ATP synthase provides hydrophilic channel for diffusion of protons, catalyses the synthesis of ATP, lowers activation energyb
ATPase and ATP synthase are the same enzyme,explain how this is possible
Reversible reaction, the products formed from reaction in one direction are the substrates of reaction in reverse direction
Active site is complementary to both substrates and products
Explain the meaning of the term photophosphorylation
Syntheiss of ATP/addition of phosphate group to ADP by using energy from light
Explain why photoysntheis stops when plants are exposed to green light
Green is reflected and not absorbed. No energy for light dependent stage, no ATP and reduced NADP for light independent stage
Explain what is meant by the term fixation
Inorganic carbon added to organic molecule
Explain why the alternate name of the Calvin cycle, the light independent stage, is also not completley accurate
Calvin cycle requires ATP and reduced NADP, supplied from light dependent stage
Suggets the possible benefits of cyclic photophosphoryation
ATP produced and reduced NADP not produced, electrons not required from PS2, less ATP used in calvin cycle
Describe how RuBP is regenerated from TP in the Calvin cycle
One glucose molecule to be produced = 6 CO2 enter calvin cycle
Result in 12 TP, two will be removed to make glucose molecule
10 x three carbon TP =30
