Photosynthesis Flashcards
photosynthesis
process by which plants, algae, and some bacteria use the sun’s energy to produce its own food (energy)
autotrophs
self-feeder - use inorganic molecules to produce organic compounds
heterotrophs
consume organic compounds
What is the photosynthesis equation
6 H2O + 6 CO2 —–> C6H12O6 + 6O2
6 molecules of water plus 6 molecules of carbon dioxide equals glucose plus 6 molecules of oxygen
Where does photosynthesis occur
in the chloroplasts
pigments
capture light energy at various wavelengths
what are the type of pigments?
Chlorophyll A and Accessory pigments (chlorophyll b and carotenoids)
Chlorophyll a
most abundant with a green pigment - it reflects green light and absorbs red and blue light
Accessory pigments
allows plant to absorb more energy than with chlorophyll a alone
Chlorophyll B
reflects green light and absorbs red and blue
carotenoids
appear red, orange, and yellow (absorb longer wavelengths)
stomata (stoma)
small openings in the epidermis of the stem or leaf that allow for an exchange of CO2 and O2
mesophyll
internal cells of the leaf where the chloroplasts are located
Stroma
(NOT STOMA) gelatinous fluid that contains DNA, ribosomes, enzymes, and Grana and are composed of stacks of thylakoids which are studded with photosynthetic pigments (enclosed: makes the thylakoid space)
Photosystem
Very organized system that consists of chlorophyll a and accessory pigments
How many chlorophyll a and accessory pigments?
300 Chlorophyll A and 50 accessory pigments - all absorb energy but only 1 (chlorophyll a) molecule uses the energy
Reaction center
chlorophyll a molecule in photosynthetic reaction
antenna pigments
all other pigments in system (chlorophyll a and accessory) that relay/pass along their absorbed energy to the reaction center
What are the two stages of photosynthesis?
light reactions (photo) and carbon reactions (synthesis)
light reactions
convert the sun’s energy to chemical energy - light dependent reaction that occurs in the thylakoid membrane and produces ATP and NADPH
Carbon reactions
light independent reaction that occurs in the stroma and converts ATP and NADPH to glucose
NADPH
electron carrier that reduces CO2 in the carbon reactions
Carbon reactions: Calvin cycle
uses NADPH and ATP to assemble CO2 into sugars (Cyclic and all plants use this cycle
C3 (Calvin Cycle
3 carbon molecule (PGA) is the first stable compound; C3 plants use ONLY this pathway to fix carbon
weakness of C3
inefficient on cloudy days
photorespiration
when rubisco uses O2 instead of CO2 and loses CO2 that is already fixed, wasting ATP and NADPH
where does photorespiration usually occur?
in hot, dry climates
dilemma of photorespiration
stomata open or closed; open: risk losing water, dry up, wilt; closed: run out of O2 and build up of CO2
C4
light reactions occur in mesophyll cells and CO2 combines with a 4-C compound
what happens when CO2 combines with a 4-C compound?
molecule then moves to bundle-sheath cells for Calvin cycle; no exposure to atmospheric O2 (rubisco more likely to bump into CO2); this is COSTLY as molecules must transport CO2 to bundle-sheath (2 ATP)
CAM (crassulacean acid metabolism)
open stomata to fix carbon at night only (closed during the day); combines with a 4-C compound and is stored in large vacuoles
What happens when the carbon combines with a 4-C compound and is stored in large vacuoles?
stored molecule moves from vacuoles to chloroplast and releases CO2 and the Calvin cycle begins, then less CO2 is available
