ch. 8 photosynthesis Flashcards
what is the equation for photosynthesis?
6CO2 + 12H2O ——> C6H12O6 + 6H2O + 6O2
what specialized leaf tissues tend to be abundant with chloroplasts?
parenchyma and mesophyll
what organisms carry out oxygenic photosynthesis?
cyanobacteria, 7 groups of algae, and plants
what organisms carry out non-oxygenic photosynthesis?
some bacteria
photosynthesis involves what two types of reactions?
light dependent and light independent (calvin cycle)
light dependent reactions capture ______ to make ___ and _____.
light energy, ATP, NADPH
light independent reactions use energy from ____ and _____ to synthesize_______from__________.
ATP, NADPH, glucose, CO2
where do light dependent reactions take place?
thylakoid membrane
where do light independent reactions take place?
stroma
what do the products of LD do for LI reactions?
they feed them
what do thylakoids contain?
chlorophyll a and accessory pigments
what is the grana?
stacks of thylakoids
what is the stroma?
semiliquid substance surrounding thylakoids
what is a photon?
a discrete packet of light energy
in a photon, what is the relationship between wavelengths and energy?
inverse relationship
what is the photoelectric effect?
removal of an electron from a molecule by light energy
when does the photoelectric effect occur?
when photons sufficiently energize electrons
what are pigments?
molecules that absorb light
what does each pigment have?
a characteristic absorption spectrum
what is an absorption spectrum?
the range and efficiency of photon absorbance
what is chlorophyll a?
the primary photosynthetic pigment in plants and cyanobacteria
what colors of light does chlorophyll a absorb and what color does it appear?
absorbs violet-blue and red light, appears yellow-green
what colors of light does chlorophyll b absorb and what color does it appear?
absorbs wavelengths that chlorophyll a does not absorb well; appears blue-green
what is chlorophyll b?
secondary or accessory pigment
what is the porphyrin ring?
a chlorophyll pigment that is a ring with alternating double and single bonds, with Mg at the center
what does a photo system consist of?
- an antenna complex of 100s of accessory pigment molecules
- a reaction center of one or more chlorophyll a molecules
where is light energy from the antenna complex transferred and what does it cause?
chlorophyll a, causes an electron to become excited and then to be transferred to an adjacent electron acceptor molecule
what does it mean for an electron to become excited?
boosted to a higher energy level
what does water donate in oxygenic photosynthesis? What does it replace?
an oxygen; the oxygen lost from chlorophyll
what are electrons returned to through an ETC? (LDR)
bacteriochlorophyll
In some (non-oxygenic) bacteria, a single _________ is used in ________ _________.
photosystem; cyclic photophosphorylation
what do light dependent reactions produce?
ATP and H2
what three things do cells need to build carbohydrates?
- Energy (ATP molecules)
- Redox potential (NADPH molecules)
- Source of carbon (CO2 gas)
how many molecules of CO2 must be fixed for every glucose molecule produced? (calvin cycle)
6
how much will it cost to fix CO2 molecules for glucose production?
18 ATP and 12 NADPH
_______ is not the immediate product of the Calvin cycle
glucose
what is required to make glucose after the calvin cycle?
G3P
for every 6 molecules of CO2 fixed, how many G3Ps leave the cycle?
2 (each contains 3 carbons)
what is combined to eventually produce 1 glucose in the cytoplasm?
2 G3Ps
during the calvin cycle, how much chemical energy is needed to produce a single glucose?
18 ATP and 12 NADPH
what are the 2 enzymatic activities of rubisco?
Carboxylation and Photorespiration
what is carboxylation?
the addition of CO2 to RuBP (favored under normal conditions)
what is photorespiration?
the oxidation of RuBP by O2
when is Photorespiration favored?
in hot conditions
what does Photorespiration cause the loss of?
CO2
when is Carboxylation favored?
under normal conditiions
what two molecules compete for the active site on the Rubisco enzyme?
CO2 and O2
why do stomata close at night?
to conserve moisture
why might stomata close in the day under hot, dry conditions?
to conserve moisture
how do C4 plants avoid photorespiration?
by fixing CO2 in a mesophyll cell and then releasing it in a bundle sheath cell where the Calvin Cycle is operational
what are CAM plants?
plants where the stomata open only at night
why are CAM plants stomata open only at night?
cool, moist conditions prevent excessive water loss but still allow CO2 uptake
what happens in photorespiration of CAM plants?
-PEP carboxylase adds CO2 to PEP to produce a 4 carbon malate molecule (carbon fixation only at night).
-malate releases CO2 during the day when stomata are closed to conserve moisture.
-CO2 is then used by Rubisco in the Calvin cycle (Calvin Cycle during day).
what is an example of a CAM plant?
a pineapple
