Photosynthesis Flashcards
What does life depend on?
light energy from sun thru photosynthesis
what is the conversion of photosynthesis?
light energy to chemical energy (carbohydates)
Yes or No
Is photosynthesis efficient?
No
What can photosynthesis can carry out?
both photosynthetic and respiration process
what does organisms require?
constant input of energy to offset entropy
what are the two major metabolic pathways used to acquire energy?
- respiration (heterotrophs/autotrophs)
- photosynthesis (autotrophs)
What happens in photosynthesis?
transforms light energy into usable energy in ATP or NADPH (in light or light-dependent reactions) then later stored in the chemical bonds of carbohydrates during carbon fixation or light-independent reactions
What are the photosynthetic reactants?
- light (energy source)
- water (electron donor - oxidized)
- CO2 is reduced (e- acceptor)
What are the photosynthetic products?
- Carbohydrates (sugars)
- oxygen
what plant is the most evolved?
angiosperms
what structure has optimized light capture and gas exchange?
leaves
how do leaves optimize light capture and gas exchange?
- thin cross-section
- flat surface
- cell organization that maximizes light capture
what is the most active photosynthetic tissue?
mesophyll cells of leaves (palisade/spongy)
what does mesophyll cells contain?
chloroplasts
what does chloroplasts contain?
chlorophyll
what are chlorophyll?
light absorbing green pigments
what to examine to understand photosynthetic process?
- Nature of light
- Properties of pigments
- Roles of pigments
what light does reach earth in?
waves
what is quanta?
different wavelengths contain different amounts of energy
what are photons?
energy packets
what does photosynthetic organism use special molecules called?
pigments
what is the range of pigments absorb light in ?
visible spectrum from 400 to 700 nm
What does chlorophyll absorbs?
blue (400-450nm) and red (650-700nm) wavelengths
what does chlorophyll reflect?
green (500 - 550nm)
what does it mean when it does not absorb colour?
reflecting colour
what is the molecular structure of chlorophyll a and b?
porphyrin-like ring structure with central Mg
ring contain loosely-bound electrons
what is the absorption maximum of blue?
430nm
what is the absorption maximum of red?
660nm
What is absorb wavelengths of light not absorbed?
chlorophyll
what is the carotenoids ?
accessory pigments
what is the maximum absorption of carotenoids?
400-500nm
what does carotenoids have?
- photo-protective role
- protect against high light
- have anti-oxidant properties protect against light damage
What is bilin pigments?
- phycobilin
- phycoerythrin
what is the bilin pigment for?
accessory pigments
what is the maximum absorption of bilin pigment?
400 - 500 nm
what is absorbed by pigments in chloroplast?
sunlight energy
what are the main pigments?
chlorophylls
what is present in all photosynthetic organisms?
chlorophyll a
what happens in chlorophyll absorption of blue light?
excites chlorophyll molecule to higher energy state than absorption of red light
what happens in chlorophyll with absorption of light photons?
changes its energy state by altering distribution of electrons
what happens when pigment absorbs light?
goes from ground state to an excited state (very unstable)
- release as light and heat
what happens when excited electrons fall back to the ground state?
photos are given off = fluorescence
- light released is at lower energy level
what happens in unstable high energy state?
chlorophyll gives up energy as heat to surrounding and drop to lower excited state
what are the four routes to dissipate energy from lowest excited state in order to return to stable ground state?
- heat (energy loss)
- re-emit photon of longer wavelength (fluorescence)
- energy transfer to another molecule (resonance transfer)
- photochemistry (absorption with electron transfer)
