Photosynthesis Flashcards
1
Q
activities that need enegy
A
- active transport (selective reabsorption of glucose + Aa in the kidney)
- anabolic reactions (growth)
- movement of cilia/flagella
2
Q
chemiosmosis
A
- diffusion of protons from high to low
- movement of protons releases energy
- used to attach P to ADP = ATP
3
Q
how are electrons excited
A
- absorbing light
- when chemical bonds are broken in respiratory substrate mol (glucose)
4
Q
electron transport chain
A
- series of electron carriers
- each have lower energy levels
- excited electron moves from one carrier to the next
- releases energy
- pumps protons across a membrane
- proton gradient
- PG maintained bc membrane is imperm to H+
- H+ move through hydrophilic channel linked to enzyme ATP synthase
- catalyses ATP formation
- flow of protons provides energy to synthesis ATP
5
Q
chloroplast structure
A
- network of membranes = large SA
- maximises absorption of light
- membranes form flattened sacs = thylakoids
- thylakoids stacked = grana
- grana joined by lamellae
- chlorophyll embedded in thylakoid membrane
- fluid in chloroplast = stroma
6
Q
chlorophyll
A
- primary pigment = chlorophyll a
- a is in the reaction centre
- diff pigments absorb diff wavelengths of light
- pigments in the photosystems
- chlorophyll b (+other pigments) are embedded in the thylakoid membrane of the chloroplasts = light harvesting system
7
Q
what stages occur in
- light dependant
- light independent
A
non-cyclic/cyclic phosphorylation :
- energy from sun absorbed
- forms ATP
- reduced NADP
Calvin cycle
- ATP supplies energy
- H from reduced NADP + CO2 build glucose
8
Q
non - cyclic phosphorylation
A
- PSII = 680nm
- PS1 = 700nm
- PSII absorbed light
- excites electron
- released from reaction centre
- passed through ETC to PSI
- e- lost from PSII replaced by photolysis
- excited e- lose energy
- energy used to pump H+ into thylakoid via proton pumps
- chemiosmosis
- PG
- H+ diffuse down PG into stroma
- via enzyme ATP synthase
- energy released combines ADP+Pi = ATP
- PSI absorbs light
- excites e-
- e- leaving ETC from PSI accepted
- along with H+
- by coenzyme NADP
- forms reduced NADP
- reduced NADP provides hydrogen to form glucose
9
Q
photolysis
A
H2O = 2H+ + 2E- + 1/2O2
- H2O split using energy from the sun
10
Q
cyclic phosphorylation
A
- e- leaving PSI are returned to PSI
- reduced NADP isn’t formed
- ATP still produced without e- from PSII
11
Q
calvin cycle
A
- CO2 into spongy mesophyll of leaves
- through stomata
- into stroma of chloroplasts
- C in CO2 is fixed
- combines with RuBP
- RuBisCO catalyses reaction
- unstable 6c intermediate formed
- breaks down
- 2x GP (3c)
- GP converted to 2x TP (3c)
- using H atom from reduced NADP + ATP from light dependant
- 5c from 2xTP regenerates RuBP so cycle continues (used rest of ATP from light dependant)
- 1c is converted into organic mol (glucose/lipids)
- 6x of cycle to make 1 hexose sugar : 18ATP : 12 reduced NADP
12
Q
photorespiration
A
- oxygen is a competitive inhibitor of RuBisCO
- produces phosphoglycolate
- reduces GP production
- when CO2 conc is low
- phosphoglycolate = toxic 2c
- converted into other organic mol using ATP
- RuBisCO has a higher affinity for CO2 than O2
- reduces efficiency of photosynthesis
13
Q
factors affecting rate of photosynthesis
A
- light intensity (ATP + RNADP produced at higher rate
- CO2 conc - inc C fixation in CC + inc rate of TP production
- temperature : affects enzyme controlled reactions (C fixation) : denature proteins/inc ROR : stomata close to avoid water loss stopping diffusion of CO2 reducing rate of light independent then stopping photosynthesis.
14
Q
limiting factor
A
- when one of the factors needed for a process is in short supply and reduces the rate of the process
15
Q
effect of reducing light intensity on Calvin cycle
A
- reduce ATP
- reduce NADPH
- conc of GP will inc
- TP will dec
- conc of RuBP dec
