Unit 2 - Intro to Photosynthesis Flashcards
Photosynthesis Chemical equation
6CO2 + 6H2O =(water synthesis) glucose + 6O2
Process of Photosynthesis two main steps?
1) Photo light dependent rxn
2) Synthesis light-independent reaction of Calvin cycle
Photo light dependent rxn
- light energy is captured by pigment mols
- energy is used to make ATP and NADPH
Synthesis Light Independent Reaction or Calvin cycle
- free energy or ATP and electrons of NADPH r used to synthesize sugars such as glucose from CO2
- process is also called CO2 fixation
Light
- only 5% of the light that hits the earths surface is converted to organic compounds by photosynthesis
Light travels in…
wave packets called photons
Light from the sun is a…
mixture of photons of different energies (called wavelengths measured in nanometers (nm)
where r photons captured in plants
plastids ie chloroplasts
Chloroplasts functions
- photosynthesis factories for plants and algae
- store excess glucose as starch
Chloroplasts structure
- 2 membranes (like mitochondria)
- interior space filled w stroma
in stroma r thylakoids (membrane-bound sacs) - thylakoid membrane contains light-gathering pigments
Thylakoids Structure
1) grana
2) lamelae
3) lumen
Grana
stack of thylakoids (60 grana per chloroplast with 30-50 thylakoids each)
Lamellae
unstacked thylakoids that link grana together
Lumen
interior of the thylakoid, water-filled
Pigments Chlorophyll
- green plants algae and cyanobacteria contain chloroplasts w the pigments chlorophyll a and b.
Both a and b structures
absorb blue and red light and reflected green light
chlorophyll a is used…
to transfer energy from light into chemical energy
chlorophyll b
is an accessory pigment
Chlorophylls a and b side groups contain:
a = CH3 groups
b = CHO groups
Accessory Pigments
in addition to chlorophyll b there r other accessory pigments. Their job is to absorb light that can damage chlorophyll and lose it as heat instead
Carotenoids
appear yellow and orange + had double and single bonds
ie. carrots
betacarotene = protects ur eyes
Xanthaphylls
reflect yellow light also found in the thylakoid
what waste is produced during photosynthesis
water
what is the useful production from photosynthesis
glucose
what is the name of the pigment needed for photosynthesis
chlorophyll a
in which organelle is this pigment found
chloroplast
photoexcitation
- electrons in chlorophyll r normally at ground state (lowest energy level)
excitation (photoexcitation)
the energy from a photon of light excites the electrons to a higher potential energy level but as electrons return to ground state they release energy
primary electron acceptors
isolated chlorophyll mol fluoresce when their e- return to ground state, but in a photosynthetic membrane
Photosystem
protein-based complex composed of clusters of pigments that absorb light energy
antenna complex
has chlorophyll mol and accessory pigments in a protein matrix; the pigments absorb light E and transfer it to the reaction centre.
reaction centre
a protein complex that contains chlorophyll A whose e- get excite then transferred to primary electron acceptors
Antenna complex
pigment mol (chlorophyll b, carotenoids etc) captures the inital photons of light and transfers the energy between accessory pigments unitl it reaches… the reaction centre
reaction centre
a protein complex composed of chlorophyll a, whose electrons get excited and then r transferred to the primary electron acceptor
Photosystems
two e- from the reaction centre r excited and jump up in energy level. These electrons r captured by an electron carrier
PI (P700) and PII (P680)
depending on the chlorophyll in the reaction centre they can absorb different wavelengths of light. there r two photosystems present in the thylakoid membrane: Photosystem 1 and Photosystem 2
Photosystem 1 (P700)
the reaction centre can absorb wavelengths of 700nm
Photosystem 2 (P680)
the reaction centre can absorb wavelengths of 680nm
Engelmann Experiment: do plants absorb certain colours?
he tested this using algae in different colours of light and aerobic bacteria
- spirogyra algae is long with spiral chloroplast
Splitting Light
Engelmann then split the light into colours (ROYGBIV) and shined it on the spirogyra (there was enough CO2 for photosynthesis
other accessory pigments in leaves
they maximize absorption of wavelengths.
AUTUMN
-cooler temps, chlorophylls is destroyed
-other hidden colours show
