Photosynthesis Flashcards
what is photosynthesis? what kind of organisms does it occur in? where does it occur?
Process that converts light energy into chemical
energy stored in organic molecules
-photoautotrophs
-Occurs in chloroplasts
what are photoautotrophs?
organisms that use light energy to synthesis organic molecules from inorganic molecules
what are the 3 major groups of autotrophs?
- plants
- algae (photosynthetic protists)
- Cyanobacteria (photosynthetic bacteria)
what causes the green colour in chloroplasts? where is this located?
colour is due to chlorophyll which is a light-absorbing
pigment located in the chloroplasts
-Pigment molecules embedded in thylakoid membrane
name the layers of the chloroplast
- outer membrane
- intermembrane space
- inner membrane
- stroma
- thykaloid membrane
- thykaloid space
what do the thykaloid space and the stroma have in common?
both are fluid filled spaces used in photosynthesis
what kind of a process is photosynthesis? does it require energy?
an oxidation-reduction process
-it is an energy requiring process
what is the formula for photosynthesis? what is happening to the starting molecules?
6 CO2 + 6 H2O –> C6H12O6 + 6 O2
Water molecules are split –> Lose electrons and H+ - OXIDATION
CO2 forms sugar –> gains electrons and H+ - REDUCTION
how is CO2 reduced to glucose?
the light energy captured by the chloroplast provides
the energy needed to reduce CO2 to glucose
light is a form of ….
Also known as?
how does light travel?
what is visible light?
energy
- electromagnetic radiation
- travels through space as waves of energy from the sun
- only small part of electromagnetic spectrum
the shorter the wavelength the … the energy
greater
what are the 3 things that can happen when light meets matter?
- it can be reflected
- it can be transmitted
- it can be absorbed
what are substances that absorb light? how are different wavelengths of lights absorbed?
pigments
-with different pigments
what do we see when we look at a leaf?
we see wavelengths that the pigment molecules in the thykaloid reflect, as they only absorb some wavelengths
what is a photon? how are they absorbed?
fixed quantity of light energy (discrete packets of energy)
-Photons of light energy are absorbed by pigment
molecules
what happens when a pigment absorbs light energy?
-an electron is elevated from a ground state to an excited state
what does it mean when an electron is an excited state? can electrons remain in this state? what happens when an electron changes to ground state?
-means it is in a higher energy state and it is unstable
-Electrons cannot remain in unstable excited state
-When electron drops back to ground state energy is
released
what happens when a pigment absorbs light energy but is isolated from chloroplast?
energy is released as light or heat, and then electron is returned to ground state
what happens when a pigment in the thykaloid membrane absorbs light energy?
energy not released as light or heat
-instead pigment molecules in thylakoid membrane pass
energy of excited electrons to neighboring pigment
molecules
what is a photosystem? what are its 2 main actions?which complexes do photosystems contain? where are they found?
- Photosystems are functional and structural units of protein complexes involved in photosynthesis
1. the absorption of light
2. the transfer of energy and electrons. - light-harvesting complexes and a reaction-center complex
- found in the thylakoid membranes of plants, algae and cyanobacteria
what does light harvesting complex do? how does it do this/what parts are involved? what is it composed of? what is another name for it?
captures light energy and transfers it to the reaction center
- Accessory pigment molecules –> absorbs a photon of light
- Energy is transferred from pigment molecule to pigment molecule (within light-harvesting complex)
- Energy eventually transferred to chlorophyll A molecule in reaction center
- various pigment molecules and assoc. proteins
- antenna complex
what is the reaction center? what does it do/how does it do this?
its a protein complex containing a pair of chlorophyll A molecules and a primary electron acceptor
- its chlorophyll A molecules are transferred energy from pigment molecules which it uses to boost electrons to a high energy state
- High energy electrons are transferred to primary electron acceptor (which is a protein), that then becomes reduced
- primary electron acceptor then passes electron to transport chain
what is the Primary electron acceptor?
protein that captures light-excited electron from Chlorophyll A molecules and passes it to electron transport chain
what is the thykaloid membrane?
double phospholipid bilayer
what do accessory pigment molecules do?
absorb photons of light and the pass the energy between them
what are the 2 types of photosystems? how are they different? what causes this difference? how are they similar?
- photosystem II
- photosystem I
- differ slightly in which wavelengths of light they absorb most strongly
- Difference in absorption due to differences in the pigment protein molecules associated with chlorophyll A
- Both part of light reactions
which wavelengths of light do the different photosystems absorb most strongly?
- Photosystem I absorbs 700 nm
- Photosystem II absorbs 680 nm
what are the 2 pathways of electron transport?
- Noncyclic electron flow
2. Cyclic electron flow
