Photosynthesis Flashcards
What is the purpose of photosynthesis?
The purpose of photosynthesis is to transform energy from
light into energy stored in glucose (and other organic
molecules).
What is an autotroph? Photoautrotroph?
Autotrophs are organisms that gain their energy from processes other than eating other organisms.
Photoautotrophs get their energy from light.
What is a heterotroph?
Heterotrophs (that’s us!) get their energy from consuming other organisms.
Why are leaves green?
Chloroplasts (and chlorophyll) are not green however, from absorbing green light. In fact, they are green because they transmit green light, rather than absorbing it.
What is the long form of the photosynthesis equation?
6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O
Through microscopic pores called ______, CO2 enters the leaf and O2 exits
stomata
Chloroplasts are found mainly in cells of the _______, the interior tissue of the leaf.
mesophyll
The chlorophyll is in the membranes of ______ (connected sacs in the chloroplast); they may be stacked in columns called _______
thylakoids
grana
Chloroplasts split ________ into hydrogen and oxygen, incorporating the electrons of hydrogen into ______ molecules. The water molecule releases electrons which will be used in the ______ stage of photosynthesis.
water
sugar
first
Where do the light reactions take place? And what do they do?
The light reactions (in the thylakoids) split water, release O2, produce ATP, and form NADPH
Where does the Calvin cycle take place and what does it do?
The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH
ATP and NADPH go from the ______ reactions to the ______ dark reactions while ADP and NADP+ go from _______ reactions to the _______ reactions.
Light to dark
Dark to light
What does a spectrophotometer do?
A spectrophotometer measures a pigment’s ability to absorb various wavelengths
This machine sends light through pigments and measures the fraction of light transmitted at each wavelength
What color light works best for photosynthesis?
The absorption spectrum of chlorophyll a suggests that violet-blue and red light work best for photosynthesis
What are the three pigments used in photosynthesis? What do they do?
Chlorophyll a is the main photosynthetic pigment
Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis
Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll as well as broadening the absorption spectrum.
What is a photosystem? What does it do?
A photosystem consists of a reaction center surrounded by light-harvesting complexes
The light-harvesting complexes (pigment molecules bound to proteins) funnel the energy of photons to the reaction center
Which route for electron flow involves both photosystems and produces ATP and NADPH?
Non-cyclic
What is the difference between cyclic and noncyclic electron flow?
Cyclic electron flow uses only photosystem I and produces only ATP
Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle
What is the difference is spatial organization of chemiosmosis between a mitochondrion and chloroplast?
Mitochondrion: Pump “outside-in” from matrix to intramembrane space
Thylakoid: Pump “inside-out” from thylakoid to stroma
The Calvin cycle builds sugar from smaller molecules by using _____ and the reducing power of electrons carried by _______.
ATP
NADPH
Mitochondria transfer chemical energy from food to _____; chloroplasts transform ______ ______ into the chemical energy of ATP
ATP
light energy
Carbon enters the Calvin cycle as CO2 and leaves as a sugar named _____
G3P (NOT GLUCOSE)
For net synthesis of one G3P, the cycle must take place _____ times, fixing _____ molecules of CO2
three
three
What enzyme catalyzes carbon fixation?
Rubisco
