Zusammenfassung der Ressource
Photosynthesis
- Light-Dependent stage
- Water is a source of:
- Hydrogen ions, which are used in
CHEMIOSMOSIS to product ATP. These
protons are then accepted by NAD to form
reduced NAD
- Electrons to replace those lost by the oxidised
chlorophyll
- Non-cyclic photophosphorylation
- Light strikes PS2, exciting a pair of
electrons that leave the chlorophyll molecule form
the primary pigment reaction centre
- Electrons pass along a chain of electron carriers
and the energy is released to synthesis ATP
- Light has also struck PS1 and a pair of electrons is lost
- Electrons along with protons, join NAD which becomes
reduced NAD
- Electrons from the oxidised PS2 replace the
electrons lost from PS1
- Electrons from photolysed water replace those lost by the
oxidised chlorophyll in PS2
- Protons from water take part in chemiosmosis to make ATP and
are then captured by NAD, in the stroma.
- Light-independent stage
- Products if Calvin cycle
- Some GP can make amino acids and fatty acids
- TP molecules can combine to form
hexose sugars (e.g. Glucose)
- Glucose can be used to form fructose
- TP can be converted to
glycerol and can combine with
fatty acids to make lipids
- Hexose sugars can be
polymerised into other
carbohydrates such as
cellulose and starch.
- Limiting Factors
- Carbon dioxide concentration
- Temperature
- Light intensity
- Chloroplasts
- Structure
- Disc shaped and
between 2-10 um long
- Surrounded by a
double membrane - an
envelope
- Intermembrane space
- Outer membrane is
permeable to many
small ions
- Innner
membrane
- Has embedded
transport proteins
- Folded into
lamellae, which
are stacked to
form a granum
- Stroma is a fluid-filled matrix.
Reactions of the
light-independent stage occur
here where the necessary
enzymes are located.
- Grana are stacks of
flattened membrane
sacs, called
thylakoids. These are
the sites of light
absorption and ATP
synthesis during the
light-dependant
stage.
- Adaptations
- Inner membrane can
control entry and exit of
substances between
cytoplasm and the stroma
- Many grana provide a
large surface area for the
photosynthetic pigments,
electron carriers and ATP
synthase enzymes, all
involved in LI reaction
- Photosynthetic pigments are
arranged into photosystems
- Keywords
- AUTOTROPH - are organisms that use
light energy or chemical energy and
inorganic molecules (CO2 & Water) to
synthesise complex organic molecules
- HETEROTROPHS - are organisms that ingest
and digest complex organic molecules,
releasing the chemical potential energy stored
in them.