Photosynthesis in Higher pLants Flashcards
what is the movement of chloroplasts called?
It is called phototactic movement.
-> high amount of light, the chloroplasts align themselves away from the direction of light
-> moderate light- they remain scatted over the cytoplasm
-> low light - the chloroplasts move towards the source of light to absrob more light
What is pigments
PIgments are molecules which absorb light of a specific wavelength and reflect a correspondings light. =
how do we find out which pigments a plant has?
separate the leaf pigments of any green plant
through paper chromatography. A
chromatographic separation of the leaf pigments
shows that the colour that we see in leaves is
not due to a single pigment but due to four
pigments: Chlorophyll a (bright or blue green
in the chromatogram), chlorophyll b (yellow
green), xanthophylls (yellow) and carotenoids
(yellow to yellow-orange).
- chlorophyll a
-chlorophyll b
-carotenoids
(i) xanthophylls
(ii) carotene
what is absorption spectrum
- Graphical presentation of the absorption of different wavelength of light by a
particular pigment. - According to the graph, chlorophyll a absorbs maximum amount of light from 400-500nm and also very cloe to 700nm.
- it shows chlorophyll b absorbs a large amt of light of wavelength 450nm
- it shows carotenoids absorbs lights of lower wavelength from 400-500nm only
wht is action spectrum
The graphic curve depicting the relative rates of photosynthesis at different
wavelengths of light is called Action spectrum.
.s The rate of photosynthesis is highest from 400-500nm and also very close to 700nm.
chlorophyll is the main photosynthetic pigment.
ynthesis
occurs in a plant. Can you see that the
wavelengths at which there is maximum
absorption by chlorophyll a, i.e., in the blue and
the red regions, also shows higher rate of
photosynthesis. Hence, we can conclude that
chlorophyll a is the chief pigment associated
with photosynthesis.
what are accessory pigments?
Though chlorophyll is the major pigment
responsible for trapping light, other thylakoid pigments like chlorophyll
b, xanthophylls and carotenoids, which are called accessory pigments,
also absorb light and transfer the energy to chlorophyll a. Indeed, they
not only enable a wider range of wavelength of incoming light to be utilised
for photosyntesis but also protect chlorophyll a from photo-oxidation( exposure of chlorophyll to large amt of sunlight can cause it to get damage).
what is the arrangement of pigments called
PIgments are arranged in the form of Photosystems. T
he LHC are made up of hundreds of
pigment molecules bound to proteins. Each
photosystem has all the pigments (except one
molecule of chlorophyll a) forming a light
harvesting system also called antennae (Figure
11.4). These pigments help to make
photosynthesis more efficient by absorbing
different wavelengths of light. The single chlorophyll a molecule forms the
reaction centre. The reaction centre is different in both the photosystems.
what are the two types of photosystems
There are two types of photosystems: Photosystem I and Photosystenm II. These are named
in the sequence of their discovery, and not in the
sequence in which they function during the light
reaction.
In PS I the reaction centre chlorophyll a has an absorption peak at 700
nm, hence is called P700, while in PS II it has absorption maxima at 680
nm, and is called P680.
PSi is found in thylakoids and stromal lamella while psii is fund only in thylakoids.
what are light reactions
Reactions that are directly driven by light is called light reactions. They initiate photosynthesis. The membrane system is
responsible for trapping the light energy and also for the synthesis of ATP( Adenosine triphosphate)
and NADPH( Nicotinamide dinucleotide phosphate-reduced). These are energy rich substrates which are used in dark reactions
what are dark reactions
Dark reactions do not require light. They take place in the stroma. They are not be construed to mean that they occur in darkness or that they are not
light-dependent. It uses the products ATP and NADPH as it is obtained from light phase.
