Chapter 8: Photosynthesis Flashcards
(21 cards)
What is carried out by oxygenic photosynthesis?
Cyanobacteria, 7 group of algae, all land plants
Photosynthesis is divided into
Light-dependent reaction and carbon fixation reactions
What is light-dependent reaction?
it is captures energy from sunlight
make ATP and reduce NADP+ to NADPH
What is carbon fixation reactions?
Use ATP and NADPH to synthesize organic molecules from CO2
Where is photosynthesis happen?
it takes place in chloroplasts
What is thylakoid membrane?
Internal membrane arranged in flattened sacs
Contains chlorophy ll and other pigments
What is grana?
Stacks of thylokoid membranes
what is stroma?
Semiliquid substance surrounding thylakoid membrane
Named several scientists who led to the discovery of how photosynthesis works
Jan Baptista Van Helmont (1580-1644)
Joseph Priestly (1733-1804)
Jan Ingen-Housz (1730-1799)
F.F. Blackman (1866-1947)
What is photon?
- A particle of light
- Acts as a discrete bundle of energy
- Energy content of a photon is inversely proportional to the wavelength of the light
What is photoelectric effect?
Removal of an electron from a molecule by light
Occurs when photons transfer energy to electrons
What is pigments?
- Molecules that absorb visible light
- Each pigment has a characteristic absorption spectrum, the range and efficiency of photons it is capable of absorbing.
What is chlorophyll a?
- Primary pigment in plants and cyanobacteria
- Absorbs violet-blue and red light
What is chlorophyll b?
Secondary pigment absorbing light wavelengths that chlorophyll a doesn’t absorb
What is the structure of pigments?
- PORPHYRIN RING: Complex ring structure with alternating double and single bonds
- Magnesium ion at the center of the ring
- Photons excite electrons in the ring
- Electrons are shuttled away from the ring
- ACCESSORY pigments: secondary pigments absorbing light wavelengths other than those absorbed by chlorophyll a
- increase the range of light wavelengths that can be used in photosynthesis
- include: chlorophyll b, carotenoids, phycobiloproteins
- carotenoids also acts as antioxidants
A photosystem consists of:
Antenna complex of hundreds of accessory pigments molecules and reaction center of one or more chlorophyll a molecules
Where is the energy transferred?
Energy of electrons is transferred through the antenna complex to the reaction center
Photosystem organization
- At the reaction center, the energy from the antenna complex is transferred to chlorophyll a.
- This energy causes an electron from chlorophyll to become excited
- The excited electron is transferred from chlorophyll a to an electron acceptor
- Water donates an electron to chlorophyll a to replace the excited electron
Listed 4 stages are occurred in light-dependent reactions
- Primary photoevent- a photon of light is captured by a pigment molecule
- Charge separation- energy in transferred to the reaction center, an excited electron is transferred to an acceptor molecule
- Electron transport- electrons move through carriers to reduce NADP+
- Chemiosmosis- Produces ATP
In sulfur bacteria, what is the only one can used for Cyclic Photo phosphorylation?
Photosystem
- An electron joins a proton to produce hydrogen
- An electron is reduced to chlorophyll – This process drives the chemiosmotic synthesis of ATP
What are the two linked photosystems are used in noncyclic phosphorylation?
- Photosystem l: Reaction center pigment (P700) with a peak absorption at 700nm
- Photosystem ll: Reaction center pigment (P680) has a peak absorption at 680 nm
