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structure of chloroplast
- Photosynthesis occurs in organelles
called chloroplast, this is its structure:
- Most are disc shaped and between 2-10 um long
- Has a double membrane, also called an
envelope, the intermembrane space is
10-20 nm wide
- Outer membrane is permeable to many
small ions while the inner one is less
permeable
- Inner one has transport proteins embedded in it
and is folded into lamellae which are stacked up to
make a granum. Many granums are a grana
- Between granas are intergranal
lamellae. Granas can be seen with
light microscopes
- Grana consist of stacks of flattened
membrane compartments called thylakoids.
These absorb light and synthesise ATP during
the light depended stage. Can be seen via
electron microscope
- Grana consist of stacks of flattened
membrane compartments called thylakoids.
These absorb light and synthesise ATP during
the light depended stage. Can be seen via
electron microscope
- Between granas are intergranal
lamellae. Granas can be seen with
light microscopes
- Inner one has transport proteins embedded in it
and is folded into lamellae which are stacked up to
make a granum. Many granums are a grana
- Outer membrane is permeable to many
small ions while the inner one is less
permeable
- Stroma is a fluid filled matrix. Reactions of
the l.d.s. occur here because the needed
enzymes are there. It also contains starch
grains, oil droplets, as well as DNA and
prokaryote type ribosomes
- Has a double membrane, also called an
envelope, the intermembrane space is
10-20 nm wide
- Most are disc shaped and between 2-10 um long
- Adaption:
- Inner membrane has transport proteins the controls entry
and exit of substances between stroma and cytoplasm of cell
- The many grana gives a large S.A for photosynthetic pigments,
electron carriers and ATP synthase enzymes all of which are in the
LDS
- Photosynthetic pigments are molecules that absorb light
energy. Each pigment absorbs a range of wavelengths in the
visible region while other wavelengths are reflected. They're in
thylakoid membranes arranged in funnel shaped structures
called photosystems and held in place by proteins. Normally
the primary pigment is chlorophyll a while the accessory
pigments consist of molecules of chlorophyll b and carotenoids
- Chlorophylls: mixture of pigments of similar
molecular structure. They have a long phytol
chain (hydrocarbon) and a porphyrin group like
the one found in haemoglobin except here it
has mg instead of fe
- Light hits chlorophyll and causes a pair of electrons from Mg
to become excited. There are 2 types of chlorophyll a, P680 or
P700, both are yellow - green and absorb red light at slight
different wavelengths (absorption peaks).
- Both are at the centre of the photosystems as they're
primary pigment reaction centre. P680 has an absorption
peak of 680nm and is found in photosystem II while P700 has
an absorption peak of 700nm and is found in photosystem I
- Chlorophyll a absorbs blue light of a wavelength of 450nm and
chlorophyll b absorbs 500nm-640nm so blue to green
- Chlorophyll a absorbs blue light of a wavelength of 450nm and
chlorophyll b absorbs 500nm-640nm so blue to green
- Both are at the centre of the photosystems as they're
primary pigment reaction centre. P680 has an absorption
peak of 680nm and is found in photosystem II while P700 has
an absorption peak of 700nm and is found in photosystem I
- Light hits chlorophyll and causes a pair of electrons from Mg
to become excited. There are 2 types of chlorophyll a, P680 or
P700, both are yellow - green and absorb red light at slight
different wavelengths (absorption peaks).
- Accessory pigments:
- Carotenoids reflect yellow and orange light but absorb blue . Also doesnt
have a porphyrin group so is not directly involved in LDS
- They absorb light wavelengths that chlorophylls cant and pass on the energy
from that light to the chlorophyll a at the base of the photosystem
- Carotene orange and xanthophyll yellow are the main carotenoid pigments
- Carotene orange and xanthophyll yellow are the main carotenoid pigments
- They absorb light wavelengths that chlorophylls cant and pass on the energy
from that light to the chlorophyll a at the base of the photosystem
- Carotenoids reflect yellow and orange light but absorb blue . Also doesnt
have a porphyrin group so is not directly involved in LDS
- Chlorophylls: mixture of pigments of similar
molecular structure. They have a long phytol
chain (hydrocarbon) and a porphyrin group like
the one found in haemoglobin except here it
has mg instead of fe
- Proteins in grana hold photosystems in place
- Stroma has enzymes needed to catalyse reactions of LDS in photosynthesis
- Grana surrounded by stroma so products from LDS can pass to stroma for LIS
- DNA in chloroplast can be used by the ribosomes there to make some of the
proteins needed for photosynthesis
- DNA in chloroplast can be used by the ribosomes there to make some of the
proteins needed for photosynthesis
- Grana surrounded by stroma so products from LDS can pass to stroma for LIS
- Stroma has enzymes needed to catalyse reactions of LDS in photosynthesis
- Photosynthetic pigments are molecules that absorb light
energy. Each pigment absorbs a range of wavelengths in the
visible region while other wavelengths are reflected. They're in
thylakoid membranes arranged in funnel shaped structures
called photosystems and held in place by proteins. Normally
the primary pigment is chlorophyll a while the accessory
pigments consist of molecules of chlorophyll b and carotenoids
- The many grana gives a large S.A for photosynthetic pigments,
electron carriers and ATP synthase enzymes all of which are in the
LDS
- Inner membrane has transport proteins the controls entry
and exit of substances between stroma and cytoplasm of cell
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