Photosynthesis- Light reactions Flashcards
Biochemical energy in animals comes from the ??? (in mitochondria) of organic fuel from food
oxidation
Photosynthesis provides carbohydrate building blocks in the form of:
* ???
* coal deposits
* crude oil
* gas deposits
biomass
Photosynthesis liberates ??? and produces carbohydrates which are used by animals in the oxidative processes of respiration
oxygen
TRUE or FALSE: Almost all energy flow and all fixed carbon in the biosphere, originated from photosynthesis. Almost all oxygen in the atmosphere is generated by photosynthesis
TRUE
2H2O + hu + CO2 → (CH2O)n + O2 is the basic equation for ???
photosynthesis
Use of the stable isotope ??? proved that the oxygen involved in
photosynthesis is derived from water
18O
Photosynthetic bacteria eg. purple sulphur bacteria can use alternative electron donors such as ???
H2S
Pigments absorb light energy and convert it to ???, ATP and O2
NADPH
??? and ATP from photosynthesis are used to reduce CO2 to form (CH2O)n
NADPH
in a leaf cell, photosynthesis occurs in the ???. More specifically, the thylakoids found in this structure
chloroplast
“Light reactions” = electron transport/proton gradient which takes place in the ??? membranes. The pigments absorb light and solar energy is converted to ATP and NADPH
thylakoid
Photosynthesis Step 1: light converts H2O to a good electron DONOR or ACCEPTOR?
DONOR
Photosynthesis Step 2: electrons run through the transport chain on thylakoid membrane and the electron carriers pump H+ into thylakoid lumen as electrons flow to ??? which is an e- acceptor in the stroma
NADP+
Photosynthesis step 3: energy from flow of electrons is stored as ???
electrochemical potential
Photosynthesis Step 4: ATP synthase uses ??? to synthesise ATP
electrochemical gradient
What is the main photoreceptor in chloroplasts?
Chlorophyll is the main photoreceptor in chloroplasts
Chlorophyll have delocalised electrons that are easily excited by photons of VISIBLE or NONVISIBLE light.
VISIBLE
Chlorophyll absorbs light in the
blue, green or red regions of visible light?
Blue and Red
Secondary light absorbing pigments are called ???
carotenoids
The two most important carotenoids are:
* β-Carotene (red-orange)
* ??? (yellow)
Lutein
The carotenoid pigments, β-Carotene and Lutein, absorb light at wavelengths not absorbed by ???, thus serve as supplementary light receptors to expand the range of wavelengths absorbed
chlorophyll
TRUE or FALSE: Carotenoids also function as anti-oxidants
TRUE
light-absorbing pigments are
arranged in arrays called
photosystems embedded in the
thylakoid ???
thylakoid membrane
Absorption of light (photon) by
antenna chlorophyll leads to excitation of the ???
reaction centre
Specialized chlorophyll molecules
associated with the photochemical
reaction centre can transduce light
into ???
chemical energy
Excitation and Electron Transfer Step 1: light excites an ??? molecule (chlorophyll or accessory pigment), raising an electron to a higher energy level
antenna molecule
Excitation and Electron Transfer Step 2: excited antenna molecule passes energy to a neighbouring chlorophyll molecule, exciting it. this is called ???
excitation transfer
Excitation and Electron Transfer Step 3: excitation transfer energy is transferred to a chlorophyll of the ??? special pair, exciting it
reaction centre
Excitation and Electron Transfer Step 4: the excited reaction centre chlorophyll passes an electron to an electron ACCEPTOR or DONOR?
ACCEPTOR
Excitation and Electron Transfer Step 5: the electron hole in the reaction centre is filled with an electron from an electron ACCEPTOR or DONOR?
DONOR
TRUE or FALSE: Excitation and Electron Transfer = the absorption of a photon causes the separation of charge in the reaction centre
TRUE
Photosystem I and II have multiple antenna pigment molecules and a pair of reaction centre ??? + contain a series of electron transfer molecules
chlorophylls
TRUE or FALSE: PSII and PSI are linked by the cytochrome b6f complex
TRUE
Cytochrome b6f Complex: e-
transfer from PSII through
plastoquinone (PQ) to Cyt b6f and then to ???
PSI
how many protons (H+) are released by cyt b6f into lumen to contribute to proton gradient (to drive ATP
synthase to generate ATP)
4 H+
P680/P700 are the ??? PS which receives light energy
reaction centre
Cooperation between PSII and PSI creates an e- flow from ??? to NADP+ in a Z-like scheme between the two PS
water
ferredoxin drives a cyclic transfer of electrons by controlling whether NADP+ is reduced to ???. ferredoxin takes the electrons, when limited state of ATP, cycles electrons back through to start of cycle at Cyt b6f
NADPH
Plastocyanin: mobile electron carrier that shuttles electrons from ??? to PSI
cytochrome b6f
