Lecture 6 Flashcards
Photoautotrophs
Can convert light energy into organic molecules
Chloroplasts components and what they do
Thylakoid membrane - sites of light reactions (photosynthesis)
Stroma - calvin cycle
Outer and inner membrane - control entry
Grana - stacks of thylakoid membranes
What is the other name for LDR and LIR
LDR = Reaction type 1
LIR = Reaction type 2
Steps that contribute to H+ gradient in LDR
- Water is split by photosytem II on the side of the membrane facing the thylakoid space
- As plastoquinone (Pq) transfers electrons of the cytochrome complex, four protons are translocated across the membrane into the thylakoid space
- A hydrogen ion is removed from the stroma when it is taken up by NADP+
Formula of most simple sugars
Multiples of CH2O
Why is chloroplast green
Absorbs violet, blue and red light and reflects green light
What do chlorophyll a and chlorophyll b differ in
One of the functional groups bonded to the porphyrin ring
Why do chlorophyll have to be in groups
Alone the chlorophyll will be excited and then lose energy to be back to normal state whereas if there is neighbouring chlorophyll the excitment of electrons passes through. Once this hits a specalised chlorophyll (reaction centre) the electrons then pass down the chain
How a photosytem harvests light
When a photon strikes a pigment molecule in a light-harvesting complex, the energy is passed from molecule to molecule until it reaches the reaction-center complex. Here, an excited electron from the special pair of chlorophyll a molecules is transferred to the primary electron acceptor.
Photosytem I reaction centre
absorbs light energy at 700mn so the reaction centre is called p700
Photosystem II reaction centre
Absorbs light energy best at 680nm so the reaction centre is called p680
How linear electron flow during the light reactions generates ATP and NADPH
PSII splits water
Electrons replace those lost be P680
Generates O2 and H+
Excited electrons move down the electron transport chain and reduced
Reduced electrons release energy to generate ATP
PSI can’t split water so electrons from the ETC move to replace lost in P700 and there is linear movement of electrons
The electrons enter second ETC 2 which has a NADP+ reductase
Electrons reach NADP+ reductase and derives NADPH
What do photosytem I and photosystem II work together to do
Make ATP (create a H+ concentration gradient)
Make NADPH
Cyclic electron flow vs non cyclic
-Only uses PSI
-Only creates ATP
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Type 2: Calvin Cycle (3 phases)
Phase 1: Carbon fixation
3CO2 reacts with 3RuBP in the presence of rubisco to form 6 3-phosphoglycernate
Phase 3: Reduction
1. 6ATP used to phosphorylate 6 3-phosphoglycernate to 1,3-bisphosphoglycerate
2. 6 NADPH is oxidised and 6Pi released to form Glyceraldehyde-3-phosphate (G3P) (1 G3P is released to form organic compounds eg glucose)
Phase 3: Regeneration
5 G3P is phosphorylated by 3ATP to reform RuBP
