13 Photosynthesis Flashcards
two products of the light-dependent stage of photosynthesis are.
NADPH / reduced NADP;
ATP
RUBP is..
ribulose bisphosphate
Two uses for hexose sugars inside plant cells
- Translocation:Conversion into sucrose for transport around the plant
- Respiration to produce ATP
One other product that can be made during the Calvin cycle
- Lipids / glycerol / fatty acids = Which can be used to build cell membranes/the waxy cuticle;
- ADP / NADP= Can enter back into the LDR
An electron microscope rather than a light microscope is needed to view the internal structures of chloroplasts because
- EM higher resolution (than LM- resolution of 0.5 nm compared to a light microscope at 200 nm
-EM can distinguish between/resolve two objects that are close together /
Starch granules are present inside chloroplasts because
- Glucose produced during photosynthesis is converted into starch/amylose/
- Starch does not affect the water potential of the chloroplast INSOLUBALE
- Starch is a storage molecule- stores chemical energy
The role of photosynthetic pigments in the thylakoid membrane
- To absorb light energy for photosynthesis
The benefit of having various pigments is that +
Light of different wavelengths can be absorbed; [
- enables the absorption of a wider range of light wavelengths
Photoactivation involves the following…
- Light energy is absorbed by (photosynthetic/accessory) pigments (before being funnelled to the primary pigment)
- Electrons in the reaction centre/chlorophyll a are excited to higher energy levels
- Electrons are emitted/lost from the photosystem
Photolysis involves the following.
- Water is split into H+ ions/protons and electrons and oxygen
- reaction is catalysed by an enzyme/ oxygen-evolving complex
- in PS1
Oxidation and reduction occur in the LDR in the following ways…
-chlorophyll a/the reaction centre is oxidised when electrons are lost (during photoactivation) and passed to ETC
- Water is oxidised when it loses electrons during photolysis;
- Electron carriers are reduced when they accept/gain electrons from the photosystem
- Chlorophyll a is reduced when it gains/accepts electrons from an electron carrier during cyclic photophosphorylation
- NADP is reduced when it accepts/gains electrons (along with hydrogen ions), becoming reduced NADP or NADPH
ETC during non cyclic phosp…
- Energy is released as electrons pass down the ETC
- energy released via series of redox reactions, proton pump actively transports H+ (from the stroma) into the thylakoid lumen
- A H+ conc gradient is generated between the thylakoid lumen + stroma
- H+ move back across the membrane via FD via ATP synthase (channel protein) - CHEMIOSMOSIS
- ATP synthase catalyses the production of ATP- from ADP and Pi;
Non-cyclic photophosphorylation;
-involves photosystems I and II / photosystem II is present (rather than just PS I as in cyclic photophosphorylation);
- Electrons do not return to their starting point (as they do in cyclic photophosphorylation);
Describe functions of internal membranes of chloroplasts in photosynthesis
- photosyntheic pigments/ accessory pigments absorb light energy and pass energy to primary pigment chlorophyll a
- photosystems
- photoactivation/electrons excited
- picked up by electron carrier
- electrons move along ETC to PS1
- photophosp of ADP + Pi—-> /LDS
- 2e- raised to higher energy level so energetic electrons passed from C:C
- these electrons reduced by NADP= NADPH
- PSII unstable
- site of photolysis when light absorbed by water/ location of OEC, 2H+ and 2e- and 1/2 O2
- thlakoids stacked to form grana = large SA
- thlakoid space to form proton gradient/high conc of protons
- thlakoid membrane imperable to maintain proton gradient
- ATP synthase to make ATP
- chemiosmosis
Function of aernchyma
- O2 diffues into roots submerged underwater for aerobic respiration
