5.2.1 - photosynthesis Flashcards
thylakoid membranes
folded membranes in chloroplast
contain chlorophyll and electron carrier proteins (photosystems) are found in membranes - both for LDR
granum
stack of thylakoids
lamella
connect thylakoids
stroma
fluid centre containing enzymes involved in LIR
inner and outer membrane of chloroplast
control what can enter/leave organelle
example of primary pigment
chlorophyll a - blue/green
examples of accessory pigments
chlorophyll b - yellow/green
caratenoids - orange
xanthophylls - yellow
why do we need pigments
each absorbs a slightly different wavelength of visible light so increases amount of light energy absorbed
why do we need accessory pigments
embedded in thylakoid membrane to form light harvesting system - light energy of different wavelengths absorbed, this then transferred to reaction centre containing chlorophyll a
what makes up a photosystem
light harvesting system and reaction centre
thin layer chromatography (TLC) for photosynthetic pigments
pigments added to TLC plate, placed in solvent
more soluble the pigment, further it travels
Rf value = distance moved by pigment/distance from origin to solvent front
light dependent stage purpose
to harvest light
to split water
to create ATP and reduced NADP for LIR
where does the LDR occur
thylakoid membranes
key stages of LDR
- non-cyclic phosphorylation
- cyclic phosphorylation
- photolysis
- chemiosmosis
what are photosystems in non-cyclic phosphorylation
uses PSII (absorbs light at wavelength 700nm) and then PSI (light at 680nm)
Non cyclic phosphorylation steps
*Light energy that is absorbed causes electrons in reaction centres to become excited and released
* the electrons released from PSII and PSI move along electron transport chain
* this results in ATP production by chemiosmosis
* electrons lost from PSII are replaced by electrons from photolysis
* electrons lost from PSI are replaced by electrons at end of electron transport chain from PSII
* at the end of the electron transport chain from PSI the electrons are accepted by the coenzyme NADP which accepts the electrons and H+ from photolysis to form reduced NADP
cyclic phosphorylation
some of the electrons that are released from PSI are not picked up by NADP, and instead are recycled back to PSI
transport of electrons still makes ATP through chemiosmosis so this results in ATP production but not NADPH
photolysis of water
‘light’ ‘splitting’ water
what is the process of photolysis
- light energy is absorbed by chlorophyll and splits water into oxygen, H+ and e-
- H+ picked up by NADP to form NADPH and used in LIR
- e- passed along a chain of electron carrier proteins
- oxygen either used for respiration/diffuses out through stomata
what is the process of chemiosmosis
- electrons that gained energy and left chlorophyll move along a series of proteins embedded in thylakoid membrane
- as they move along they release energy and some of the energy from electrons is used to pump the protons across chloroplast membranes
- electrochemical gradient created
- protons pass through enzyme ATP Synthase which results in ATP production
- protons combine with coenzyme NADP to become reduced NADP, because protons move from a high to low conc gradient this is chemiosmosis
what is the LIR also known as
the calvin cycle
where does the LIR occur
stroma
this fluid contains the enzyme RuBisCo which catalyses this reaction
