module 5.2.1 Flashcards
what are autotrophs
organisms that use light energy or chemical energy and inorganic molecules (carbon dioxide and water) to synthesise complex organic molecules
what are heterotrophs
organisms that ingest or digest complex organic molecules, releasing the chemical potential energy stored in them
what are phototrophs
organisms that uses energy from sunlight to synthesise organic compounds for nutrition
what are chemoautotrophs
organisms which synthesise complex organic molecules using energy derived from exergonic chemical reactions
what is carbon fixation
the process by which CO2 is converted into sugars
what is photosynthesis
the process whereby light energy from the Sun is transformed into chemical energy and used to synthesis large/complex organic molecules from inorganic substances
what can both photoautotrophs and heterotrophs release
they can release the chemical potential energy in complex organic molecules (made during photosynthesis) - this is respiration
they can also use the oxygen for aerobic respiration
what is the equation for photosynthesis
6CO2 + 6H2O (+ light energy) → C6H12O6 + 6O2
what type of reaction is photosynthesis
endothermic
what happens after the oxygen is release back into the atmosphere
organisms can use the oxygen for aerobic respiration
this releases carbon dioxide back into the atmosphere and produces water
in plants, what are the 2 stages of photosynthesis
light-dependent and light-independent
where does light-dependent and light-independent take place
in the chloroplasts
when do plants respire
all the time
when do plants photosynthesise
in the daytime
what does compensation point mean
when photosynthesis and respiration proceed at the same rate, so there is no net gain or loss of carbohydrate
what does compensation period mean
the time taken for photosynthesis and respiration to occur at the same time
explain, with examples, why the compensation period varies between plants
shade plants have a shorter compensation period than sun plants, which require a higher light intensity to reach their optimum rate of photosynthesis
how is a chloroplast shaped and how long is it
most are disc-shaped and between 2-10µm long
how long is the intermembrane space
10-20nm wide
what does the outer membrane of the chloroplast allow to go through
it is permeable to small ions
is the inner membrane more or less permeable than the outer membrane
less permeable
how does transport through the inner membrane of a chloroplast work
it has transport proteins embedded in it
these can control entry and exit of substances between the cytoplasm and the stroma
what does a grana consist of and what does this contribute to
stacks of up to 100 thylakoid membranes
a large surface area for the photosynthetic pigments, electron carriers and ATP synthase enzymes (light-dependent reaction)
what are photosynthetic pigments arranged into
photosystems
how are the photosystems held in place
by the proteins embedded in the grana
what does the fluid-filled stroma contain and what does it do
it contains the enzymes needed to catalyse the reactions of the light-independent stage of photosynthesis
why is the grana surrounded by the stroma
so the products of the light-dependent reactions, which is needed for the light - independent reaction, can readily pass into the stroma
what can chloroplasts make and what are they used for
some of the proteins they need for photosynthesis, using genetic instructions in the chloroplast DNA
what are photosynthetic pigments
light absorbing pigments to excite the electrons and has a long hydrocarbon. this is found in the thylakoid membrane. different pigments absorb different wavelengths
what is a photosystem
a funnel-shaped light-harvesting cluster of photosynthetic pigments, held in place in the thylakoid membrane of a chloroplast. the primary pigment reaction centre is a molecule of chlorophyll a. The accessory pigments consist of molecules of chlorophyll b and carotenoids
what happens to the energy
- light harvested in the chloroplast membranes via primary and accessory pigments form photosystem/antenna complex
- photon/light energy absorbed by pigment molecules
- electron becomes excited and moves to a higher energy level
- energy is passed from one pigment to another
- energy is passed to reaction centre /chlorophyll a/ primary pigment
- a range of accessory pigments allow range of wavelengths to be absorbed