5A photosynthesis Flashcards
What is the equations for photosynthesis?
6CO2 + 6H2O + Energy –> C6H1206 + 602
Why is photosynthesis an example of a metabolic pathway?
process occurs in a series of small reactions controlled by enzymes
Where does photosynthesis take place?
In the chloroplasts
What is the structure of a chloroplasts?
- Thylakoids : fluid filled sacs that are stacked up into chloroplasts into structures called grana
- Grana are linked together by bits of thylakoid membrane called Lamallae
- Photosynthetic pigments eg Chlorophyll are found in the thylakoid membrane attatched to a protein
- Photosystem : protein + pigment –> capture light energy
- Stroma : Gel like substance containing enzymes, sugars, amino acids, starch grains (carbs) are stored in inner membrane and surrounding thylakoid
What is a redox reaction?
- Reduced : gain electrons , gain hydrogen , lost oxygen
- Oxidised : lost electrons, lost hydrogen, gained oxygen
What is a coenzyme?
Molecule that aids the function of an enzyme
- NADP transfers hydrogen from one molecule to another so it can reduce or oxidise a molecule
Where does the light dependent reaction occur?
Thylakoid membrane of the chloroplasts
What is the process of the light dependant reaction?
- Photoionisation : Light energy absorbed by chlorophyll which excites electrons causing them to be released from chlorophyll molecule so it now is positively charged.
- Photophosphorylation : Making ATP from ADP and inorganic phosphate
- Making reduced NADP from NADP
- Splitting water into protons, electrons and oxygen
What is non cyclic phosphorylation?
- Light energy excites electrons in chlorophyll
- absorbed by PSII
- excites electrons in chlorophyll
- electrons move to a higher energy level and move down to PSI - Photolysis of water produces protons, electrons and oxygen
- Energy from excited electrons makes ATP
- excited electrons lose energy as they move down chain
- the energy is used to transport protons into thylakoid so it has a higher concetration than the stroma
- forming a proton gradient against thylakoid membrane
- move via ATP synthase channel in stroma which creates ATP - Energy from excited electrons generates reduced NADP
- energy absorbed by psI
- excites electrons to an even higher energy level
- electrons transferred to NADP with a proton to form reduced NADP
What is cyclic phosphorylation?
- produces ATP but only uses PSI
- electrons arent passed onto NADP but back to PSI via electron carriers so the electrons can be recycled and flow through PSI
- only produces ATP
What is the chemiosmotic theory?
This is where electrons flow down electron transport chain and create a protein gradeint against membrane to drive ATP synthesis
What is the Calvin cycle? - LIGHT DEPENDENT REACTION
- Formation of GP
- co2 enters and diffuses into stroma where it combines with ribulose biphosphate
- catalysed by enzyme rubisco
- unstable 6c compound which breaks down into two molecules of GP
- Formation of triose phosphate
- Hydrolysis of ATP provides energy to reduce GP into TP
- Requires H+ which come from RED NADP making NADP - Regeneration of RUBP
- 1/6 make useful compounds- carbs,lipids, amino acids
- 5/6 regenerate usinf atp from light dependant
Why does the calvin cycle need to be turned 6 times to make one hexose sugar?
- 3 turns produces 6 molecules of TP
- 5 out of 6 used to regenerate
- 3 turns of the cycle only 1tp is produced to make hexose sugar
- cycle must turn 6 times to produce 2 molecules of TP that can make one hexose sugar
so you can get 18ATP and 12 reduced NADP
What are the limiting factors of photosynthesis?
light intensity
co2
water
temp
