Photosynthesis Flashcards
Photosynthesis
Converts solar energy into chemical energy. This process allows photo-autotrophs to synthesize organic compounds from inorganic
Light (Short vs Long Wavelength)
Travels in waves called photons
Short wavelength- High Energy
Long wavelength- Low energy
What light do plants use?
Plants use white light (mixture of all colours of visible light)
Chlorophyll (Absorption/Action Spectrum)
Chlorophyll absorbs photons
Chart: Peaks at blue and red wavelengths meaning that they are most absorbed and maximum photosynthesis occurs in red and blue light. Line in graph dips at green wavelength meaning that green light is reflected and not absorbed hence the green colour of plants (photosynthesis is slowest in green light)
Stroma
Gel like enzyme rich substance filling chloroplast
Thylakoid
Pouch like structure containing chlorophyll
Granum
Stacks of thylakoid discs
Lamella
Unstacked thylakoids connecting adjacent grana
Products of Photosynthesis: ATP
Provides an immediate source of energy for cellular processes
ATP= ADP + P + Energy
Products of Photosynthesis: NADPH
Involved during energy transfer
NADP+ accepts 1 H+ ion and 2 e- to form NADPH (Its an electron donor so it becomes NADP+ again)
Products of photosynthesis: Glucose
Transport molecule with medium term energy storage bonds
Light Dependent Reaction Step 1
Photo excitation (PSII)- Photon from sun strikes chlorophyll in PSII. Electron gains energy and gets excited causing it to leave PSII and travel towards PSI via ETC
Light Dependent Reaction Step 2
Electron transport chain- Electron moves through proteins in ETC and release energy (potential energy decreases). This attracts H+ into thylakoid
Light Dependent Reaction Step 3
Photolysis- Light breaks down water molecule into hydrogen oxygen and an electron
2H2O + solar energy = 4H+ + 4e- + O2: 2 water needed for a whole oxygen
Oxygen gets released into air
Electron replaces missing one in PSII
Hydrogen continues to build up
Light Dependent Reaction Step 4
Chemiosmosis- Process of making ATP using energy from H+ concentration gradient (REDOX)
ATP Synthesis Complex- protein complex embedded in thylakoid that allow H+ to escape from lumen and uses resulting energy to generate ATP
Light Dependent Reaction Step 5
Reduction (ADP-ATP)- Occurs after H+ passes through ATP synthase
ADP + P= ATP (Phosphorylation)
Light Dependent Reaction Step 6
ETC (PSI- Stroma)- Once e- in PSI absorbs a lot of energy via photo-excitation it leaves PSI and goes towards stroma (e- that left PSII replaces it)
Light Dependent Reaction Step 7
Reduction (NADP- NADPH)- NADP is reduced and NADPH is oxidized (used in Calvin cycle)
OIL RIG- Oxidation is loss, reduction is gain (electrons)
NADP +H+ +2e-= NADPH
Calvin Cycle
Does not require REQUIRE energy from sun
Occurs in stroma
Does not make glucose it makes G3P
Calvin Cycle Step 1
Carbon Fixation- Uses the enzyme Rubisco to convert CO2 into organic componds
CO2 + RuBP= 6 carbon= 3- PGA + 3-PGA (occurs 3 times= 3 CO2)
Rubisco breaks the 6 unstable carbon into 2 3-PGA
Calvin Cycle Step 2
Activation and Reduction- Requires 6 ATP and NADPH (obtained from light dependent)
3PGA+ATP=active 3PGA + NADPH=G3P (occurs 6 times)
ATP activates 3-PGA and NADPH donates electron to reduce the 3 carbon intermediate to make G3P
Calvin Cycle Step 3
Replacement of RuBP- It takes 3 RuBP to make 6 G3P but it takes 5 G3P to make 3 RuBP so only one G3P leaves the cycle (cost 9 ATP and 6 NADPH)
Regeneration of RuBP makes 1/2 a glucose (3 ATP and 2 NADPH consumed for every 1 CO2. Carbon fixation used 3 CO2 meaning 9 ATP and 6 NADPH are used but this only makes 1/2 of a glucose so 18 ATP and 12 NADPH are needed to make 1 glucose)
Limiting Factor: Temperature
High temp= collision between Rubisco, RuBP and CO2 until enzyme de-natures
Limiting Factor: Light Intensity
Light increase= Chlorophyll becomes more activated until it’s all activated and reaches a plateau
