Biology chapter 7 photosynthesis
what is chlorophyll?
- light absorbing pigment -found in chloroplasts -give plants green color -role in converting solar to chemical energy
chlorophyll b
-absorbs blue & orange -reflects yellow-green
chlorophyll a
-absorbs blue-violet & red light -reflects green
what do carotenoids do?
-broaden spectrum of colors that can drive photosynthesis -provide photoprotection -reflects red, orange, or yellow
explain how photosynthesis is a redox reaction
-carbon dioxide becomes reduced to sugar as electrons and hydrogen ions from water are added to it -water molecules are oxidized when they lose electrons and hydrogen ions
what are the steps of the Calvin cycle?
-carbon fixation -reduction -release of G3P -regeneration of RuBP
what happens to c3 plants in hot, dry weather?
-close stomata -prevent CO2 from entering/ O2 from exiting -rubisco adds o2 to RuBP instead of CO2 -use ATP (not produce)
what happens to unstable electrons?
-drop back to ground state -release excess energy as heat
what causes the leaves to change color in the fall?
-green chlorophyll pigments are reduced -carotenoids revealed ( reflect yellow, orange, red)
what does absorbing photons do to a pigment's electrons?
-increases potential energy -puts electrons in unstable state
what occurs in the light reactions?
-water is split, providing electrons & giving off O2 as a by-product -ATP is generated from ADP and a phosphate group -light energy absorbed by chlorophyll to drive transfer of electrons and hydrogen ions from water to the electron acceptor NADP+ -NADP+ reduced to NADPH
when does the light reaction occur in CAM plants?
during the day
what does water provide when is splits?
electrons, hydrogen ions, and oxygen
tiny pores in the leaf
stomata
internal compartment of the thylakoid membrane
thylakoid space
membranous sacs interconnected in stacks called grana
thylakoids
why do c3 plants close their stomata?
to reduce water loss
what is the first step in the transformation of light energy into chemical energy?
transfer of an electron from a photosystem to a primary electron acceptor
since the ______'s, scientists have known that plants produce oxygen.
1800
chloroplasts have ___ membrane(s).
2
how many photosystems are there?
2
how many stages does photosynthesis have?
2
RuBP and CO2 form....?
3-PGA
the six molecule of carbon dioxide and RuBP is then split into what?
3-PGA
ATP and NADPH are used to reduce _______ to _____ in the calvin cycle
3-PGA; G3P
visible light consists of wavelengths from about ____ nm to about ______ nm.
380; 750
what percent of plants are CAM plants?
5%
how many G3P molecules are regenerated?
5/6
for every ___ G3P produced in the Calvin cycle, 1 is sent out
6
To synthesize one glucose molecule, the Calvin cycle uses _____ CO2, ______ ATP, and ____ NADPH.
6; 18; 12
between the two photosystems, the electrons passing down the electron transport chain provide energy for the synthesis of ____.
ATP
what provides chemical energy that powers several steps of the Calvin cycle?
ATP
for chloroplasts to produce sugar from carbon dioxide in the dark, they would need to be supplied with ______ and _________.
ATP; NADPH
photosystem II and photosystem I generate ____ and ______.
ATP; NADPH
the two stages of photosynthesis are linked by ___ and _____.
ATP; NADPH
bundle sheath cells are found in ____ plants
C4
in ____ plants, carbon fixation and calvin cycle occur in same place but at different times
CAM
in which type of plants do stomata close during the day and open at night?
CAM plants
what are the inputs of the Calvin cycle?
CO2 (from air); ATP; NADPH (both from light reactions)
what are the products of light reactions?
NADPH, ATP, and oxygen
what is carbon dioxide bonded with to form oxaloacetate?
PEP
what enzyme bonds carbon dioxide and PEP together to form oxaloacetate?
PEP carboxylase
in the Calvin cycle, ______ is recycled.
RuBP
what is carbon dioxide bonded to by the enzyme Rubisco?
RuBP
what is the enzyme that binds carbon dioxide to RuBP?
Rubisco
the reaction-center complex of a photosystem contains a pair of special chlorophyll __ molecules.
a
photosynthesis converts ________ and ______ into ______ and releases _______.
carbon dioxide; water; organic molecules; oxygen
process of CO2 being incorporated into organic compounds
carbon fixation
how is photorespiration different from cellular respiration?
cellular respiration-produces ATP photorespiration- uses ATP
light energy is converted into ________ energy.
chemical
where is chemical energy stored?
chemical bonds of sugars
the diffusion of hydrogen ions across a membrane is called what?
chemiosmosis
mechanism that generates ATP in chloroplasts
chemiosmosis/ photophosphorylation
_________ is responsible for the green color of plants
chlorophyll
___________ are the major sites of photosynthesis in green plants.
chloroplasts
photosynthesis takes place in here
chloroplasts
where is chlorophyll found?
chloroplasts
in CAM plants, carbon dioxide is fixed into a four-carbon compound, then released into the Calvin cycle during the ____.
day
the full range of electromagnetic wavelengths
electromagnetic spectrum
increasing the potential energy of an electron
electron excitement
photosystem II and photosystem I are connected by a(n) __________________.
electron transport chain
what is the smallest wavelength?
gamma rays
thylakoids are concentrated in stacks called ______.
grana
what is an example of a C4 plant?
grasses corn sugarcane
does the thylakoid space have a high or low H+ concentration?
high
where are CAM plants located?
hot, dry environments
where do C4 plants thrive?
hot, moist environments
what is photophosphorylation?
initial energy input from light is used to pump hydrogen ions into the thylakoid space, the hydrogen ions are then pumped back down the concentration gradient through ATP synthase, producing ATP.
where is the stroma located?
inner compartment of the chloroplasts
where are the thylakoid membranes located?
inside chloroplast
where is the thylakoid space located?
inside the thylakoid membrane
scientists traced the process of photosynthesis using these
isotopes
chlorophyll molecules capture ______ energy.
light
photosystems are ______-harvesting complexes
light
pigments absorb _______.
light
after absorbing photons, what does chlorophyll emit?
light (flouresence) and heat
what provides energy for hydrogen ions to go up their concentration gradient?
light energy
where are the 2 places photosynthesis occurs in C4 plants?
light reaction- mesophyll cells calvin cycle- bundle sheath cells
are photosystems used in light reactions or the Calvin cycle?
light reactions
what is the first stage of photosynthesis?
light reactions
what are the stages of photosynthesis?
light reactions and calvin cycle
chlorophyll is a _____________ pigment.
light-absorbing
photosystems function as a _____-gathering _________.
light; antenna
the ______ the wavelength, the weaker the energy
longer
does the stroma have a high or low hydrogen ion concentration?
low
chloroplasts are concentrated in cells of the __________.
mesophyll
why is the Calvin cycle often called light-independent or dark reactions?
none of the steps require light directly
what is a photosystem?
number of light harvesting complexes surrounding a reaction center complex
how do CAM plants conserve water?
opening stomata & admitting CO2 only at night
in C4 plants, what is the first product of carbon fixation?
oxaloacetate
during photosynthesis, H20 is ______.
oxidized
what happens when electrons drop back down (from excitement) to ground state?
release heat
what does RuBP stand for?
ribulose biphosphate
what occurs during carbon fixation?
rubisco (enzyme) adds carbon dioxide to RuBP
photosystems capture ________ energy.
solar
thick fluid enclosed in inner compartment of chloroplast
stroma
where the Calvin cycle occurs
stroma
H+ is pumped from the ______ into the __________.
stroma; thylakoid space
plants store chemical energy in _______.
sugar
the Calvin cycle assembles _____ molecules using carbon dioxide and the energy-rich products of light reactions.
sugar
______ contains energy called electromagnetic radiation
sunlight
what is the second stage of photosynthesis?
the Calvin cycle
why are some plants called C4 plants?
the first product CO2 is fixed into is a four-carbon compound
why are some plants called c3 plants?
the first product of carbon fixation is a three carbon compound, 3-PGA.
where do light reactions occur?
thylakoid membranes
the excited state of an electron is _______.
unstable
what is photorespiration?
using O2 to bind to RuBP instead of CO2 because of closed stomata/hot weather.
how is water spread throughout a plant?
veins in the leaf deliver water absorbed by roots
_______ radiation absorbed by pigments drives the light reactions.
visible
C4 plants have evolved traits to save ______.
water
where does the oxygen released by plants come from?
water
distance between the crests of two adjacent waves
wavelength
electromagnetic energy travels in ______.
waves
when does the Calvin cycle occur in CAM plants?
whenever CO2 is present
green tissue in the interior of the leaf
mesophyll
where does the Calvin cycle get it's carbon from?
carbon dioxide from the atmosphere
plant pigments absorb some wavelengths of light and _____ other wavelength
reflect
what three molecules are needed to produce sugar?
CO2, ATP, & NADPH
what is sometimes referred to as dark-reactions or light-independent reactions?
Calvin cycle
when does carbon fixation occur?
Calvin cycle
what is the three-carbon sugar that the Calvin cycle produces?
G3P (glyceraldehyde-3-phosphate)
________ produced by the light reactions provides the electrons for reducing carbon in the Calvin cycle
NADPH
what provides the electrons for reducing carbon compounds in the Calvin cycle?
NADPH
how is 3-PGA made into G3P?
addition of ATP & electrons from NADPH
c3 plants use carbon dioxide directly from the ____.
air
what is the function of the stomata?
allows carbon dioxide to enter and oxygen to exit
make their own food through photosynthesis
autotrophs
sustain themselves, do not usually consume organic molecules from other organisms
autotrophs
chlorophyll __ broadens the range of light that a plant can use.
b
autotrophs are the producers of the ___________.
biosphere
what color light does chlorophyll b absorb?
blue & orange
what color light does chlorophyll a absorb?
blue-violet/ red
light energy is captured by chlorophyll molecules to _____ the energy of electrons.
boost
where are chlorophyll molecules found?
built into thylakoid membranes
in ___ plants, carbon fixation and calvin cycle occur in different types of cells.
c4
what are examples of CAM plants?
cacti pineapples
use the energy of light to produce organic molecules
photoautotrophs
absorbing _______ increases the potential energy of a pigment's electrons, sending them to an unstable state.
photons
how do autotrophs make their own food?
photosynthesis
which photosystem functions second?
photosystem I
which photosystem functions first?
photosystem II
what do the light harvesting complex of photosystems contain?
pigment molecules
________ are built into the thylakoid membrane
pigments
what do heterotrophs feed on?
plants, animals, decompose organic material
when an electron gets excited, it has more _____ energy.
potential
what is the largest wavelength?
radio waves
NADP+ is ________ to NADPH
reduced
