5.1 Intro to Photosynthesis Flashcards
Photoautotroph
An organism that makes its own food using energy from the Sun
Light-dependent rxns
First stage of photosynthesis, during which water molecules are split as light energy is absorbed/transformed into chemical energy in ATP and NADPH
Calvin cycle
2nd stage of photosynthesis process that uses ATP and NADPH to convert CO2 to sugars
Primary e- transfer
A molecule capable of accepting electrons and becoming reduced during photosynthesis
Antenna complex
Cluster of light-absorbing pigments embedded in the thylakoid membrane able to capture and transfer energy to special chlorophyll a molecules in the rxn center
Rxn center
a complex of proteins and pigments that contains the primary e- acceptor
Action spectrum
A plot of the effectiveness of light energy of different wavelengths in driving a chemical process
Photosystem l
A collection of pigment proteins that includes chlorophyll a and absorbs light at the 700nm wavelength
Photosystem ll
A collection of pigment proteins that includes chlorophyll a and absorbs light at the 680 nm wavelength
Photoautotroph
An organism that makes its own food using sunlight energy
- Plants convert sunlight energy into chemical energy in the form of sugar
- Plants can then convert sugars into other cellular parts or into ATP
Light-dependent rxns
- First stage of photosynthesis which requires light
- Splits water molecule
- Absorbs light energy
- ATP/NADPH are generated
- Chlorophyll used to capture light energy
- Occurs in chloroplast
- NADPH - Nicotinamide adenine dinucleotide phosphate
Overall photosynthesis formula
CO2 + H20 –> C6H12O6 + O2
- Rxn is the reverse of cellular respiration
Calvin cycle (Light-dependent rxns)
Calvin cycle - 2nd stage of photosynthesis that doesn’t require light
* Uses ATP and NADPH to convert CO2 into sugars
* Can also convert fixed carbon into other molecules
Chloroplasts
Plant cell organelle that’s the site of photosynthesis
- Contains 3 membranes
- Contains chlorophyll
Stroma
Fluid surrounds thylakoids
Thylakoid
Pancake-shaped membranes inside chloroplast (site of light absorption, e- transfer, ATP synthesis)
Capturing light energy
Absorption of a photon by chlorophyll (pigment molecule) excites an e-
- The “excited” e- moves to a higher energy level
- As the e- falls back down towards the nucleus it releases energy
- The e- may also be transferred to an energy carrier molecule
What have we learned so far?
1) Energy from e- can be transferred from 1 atom to the next
2) High energy e- can be transferred to other molecules
- These e- can then be used to power rxns
Chlorophylls
Photosynthetic pigments found in plants
Chlorophyll a
Accepts energy from other pigments and transfers e- to Primary e- acceptors
Chlorophyll b
Transfers energy to chlorophyll a
Carotenoids
Other plant pigments which transfer energy to chlorophyll molecules
Antenna complex
A cluster of light absorbing pigments in the thylakoid membrane
- Captures/transfers light energy to chlorophyll a
- Chlorophyll a then transfers an e- to the primary e- acceptor
Absorption Spectrum
The amount of light energy that a substance absorbs
Chlorophyll a
Absorbs blue and red light
Chlorophyll b
Absorbs blue-green and orange light
Carotenoids
Absorbs purple to green light
Pigments and photosystems
Pigments are bound to other molecules in the thylakoid membrane which are collectively called photosystems
Photosystem l
The collection of pigment molecules/chlorophyll a absorbs light at the 700nm wavelength
Photosystem ll
Collection of pigment molecules/chlorophyll a that absorbs light at the 680 nm wavelength
