Photosynthesis Flashcards
where in the chloroplast does light dependent and light independent photosynthesis occurs?
light dependent photosynthesis: thylakoid
light independent photosynthesis: stroma
why are there many photosynthetic pigments?
each pigment absorbs light most efficiently at specific wavelengths
having multiple pigments allows the organism to capture more energy from sun, compared to having just one pigment
describe the role of accessory pigments in photosynthesis?
absorbs light energy
at wavelengths not readily absorbed by primary pigments
pass energy to primary pigment at reaction centre
forms part of light harvesting cluster of pigments
which colours of light do chlorophyll pigments absorb and which do they reflect?
chlorophyll a and b absorb red (wavelength 650-700nm) and blue light (wavelength 400-450nm)
the chlorophyll pigments reflect green light (wavelength 500-550nm). this is why most plants are green
plants containing carotenoid pigments (xanthophyll and carotene) tend to be which colours?
Red, orange and yellow. carotene absorbs blue light (wavelength 400-450nm) and reflect red, orange and yellow (wavelengths 550-700nm).
the presence of these pigments gives carrots, pumpkins and tomatoes their colours.
explain the difference between an absorption spectrum and an action spectrum?
an absorption spectrum measures which wavelengths of light are absorbed by the chlorophyll pigments
an action spectrum measures the rate of photosynthesis occurring at a particular wavelengths.
describe the arrangement and location of chloroplast pigments and discuss their effects on absorption spectra?/8
chlorophyll a is the primary pigment
carotenoids are accessory pigments
they are arranged in photosystems on the thylakoid membrane
photosystem I and photosystem II
primary pigment is in the reaction center
accessory pigments surround primary pigment
light energy absorbed by the accessory pigment
energy passed on to primary pigment
chlorophyll a and b absorb red and and blue wavelengths of light
carotenoids absorb blue wavelengths of light
outline the process of cyclic photophosphorylation?
- only involves photosystem I
- light energy absorbed by accessory pigments
- is passed on to, chlorophyll a which is primary pigment at reaction center
- electron is excited to higher energy level/photoactivation
- electron is captured by electron acceptor
- it is passed along electron transport chain and is transferred back to chlorophyll by ETC
- This releases energy
- Energy used to synthesise ATP from ADP and Pi
- ATP produced by chemiosmosis which will be used in light independent reaction
outline the process of non cyclic photophosphorylation?
- both photosystem I and photosystem II are involved in trapping light energy
- light absorbed by accessory pigments and passed on to chlorophyll a which is primary pigment
- electrons excited to higher energy level from both photosystems
- electrons accepted by electron acceptor
- electrons are passed along ETC
- Photosystem 1’s electrons are accepted by NADP to becomes reduced NADP
- Photosystem I receives electrons from photosystem II
- photosystem II receives electron from photolysis of water
- photons from photolysis are pumped into membrane space to synthesise ATP from ADP and Pi by chemiosmosis
- ATP will be used in light independent reaction
outline the process of photolysis of water and describe what happens to the product of photolysis?
- photosystem II absorbs light
- enzyme in photosystem II breaks down water
- 2H2O— 4H+ + 4e- + O2
- oxygen produced
- used by cells for aerobic respiration
- or released out through stomata
- protons used to reduce NADP with electrons from Photosystem I
- reduced NADP used in light independent stage
- to convert GP to TP
- electrons used in ETC
- to release energy in photophosphorylation
- to produce ATP
- electrons go to photosystem I
Describe the structure of photosystems and explain how a photosystem functions in cyclic phosphorylation? /8
- arranged in light harvesting system
- primary pigments at reaction centre
- PI absorbs light at 700nm
- PII absorbs light at 680nm
- accessory pigments surround primary pigments
- accessory pigments pass energy to primary pigments
- PI involved in cyclic photophosphorylation. and non cyclic photophosphorylation has photosystem I and photosystem II
- light absorbed results in electron excitement
- electron flows along ETC
- ATP synthesis
- electron returns to PI
similarities and differences between cyclic photophosphorylation and non cyclic photophosphorylation?
similarities:
- photoactivation of
chlorophyll in both
- ETC is involved in both
- ATP produced in both
differences:
1. cyclic: only PSI
non cyclic: PSI and
PSII both involved
2. cyclic: no reduced
NADP/oxygen
produced
non cyclic: reduced
NADP/ oxygen
produced
3. cyclic: no photolysis
non cyclic: photolysis
4. cyclic: electrons
emitted from PSI
returned to PSI
non cyclic: electrons
emitted from PSII
are replaced by
water
what is the difference between chemiosmosis in mitochondria and chloroplast?
- mitochondria: oxidative
phosphorylation
chloroplast:
photophosphorylation - mitochondria: cristae
chloroplast: thylakoid
membrane - mitochondria: reduced
NAD and FAD gives e-
and H+
chloroplast: photolysis of
water gives e- and H+ - mitochondria: H+ is
pumped into
intermembrane space
chloroplast: H+ is
pumped into thylakoid
lumen - mitochondria: oxygen
final acceptor
chloroplast: NADP final
acceptor - mitochondria: Makes
water
chloroplast: makes
reduced NADP
what are the two important product of the light dependent stage that are used in light independent stage?
ATP and reduced NADP
outline the main features of Calvin cycle. /9
- RuBP, a 5C compound combines with CO2. This is catalysed by enzyme Rubisco
- an unstable 6C compound is formed
- 6C compound splits into two molecules of GP
- GP is reduced using reduced NADP and ATP to form TP
- 1/6 TP is used to form glucose/ amino acid/ lipids/ carbohydrates
- 5/6 TP produced is used to regenerate RuBP using ATP
- Calvin cycle is light independent stage
