Exam #4 - Photosynthesis Flashcards
Photosynthesis is the synthesis of _______.
sugar
Just as cellular respiration releases energy, photosynthesis _______ energy.
requires
In photosynthesis, we ______ energy to make sugar.
harvest
How do we store energy? Within….?
Electrons
Biochemically speaking, what is needed to make sugar?
1) Carbon source - raw material
2) Energy - sun
3) Electrons - store energy
We need a source of carbon to _____ those electrons to store that energy.
carry
Carbon fixation means making carbon _______.
organic
What does that mean? Making carbon “organic”?
Making carbon bonded to Hydrogen
Plants take carbon from the ___ and make it organic.
air. THAT’S THE SOURCE!
What is the process of photosynthesis?
6CO2 + 6H20 + Light energy —> CH2O + O2
What is the delta G of this process?
Endothermic or exothermic?
+ 686 kcal/mol
Endothermic, requires energy
Is photosynthesis the reverse of cellular respiration?
NO. It’s not the same process backwards
_______ is not the immediate product of photosynthesis . You can make glucose from the sugar product, but it is not the actual product.
Glucose
Only ___ CO2 is fixed at a time in the calvin cycle.
In other words, CO2 is metabolized ___ at a time.
one
6CO2 + 6H20 + Light energy —>CH2O + O2
Which reactant is oxidized?
H20
If you lose hydrogen, you’re ________.
If you gain hydrogen, you’re ________.
oxidized
reduced
6CO2 + 6H20 + Light energy —> CH2O + O2
Which reactant is reduced?
CO2
What is CH2O?
A symbol for sugar.
A carbohydrate, CH2O
What do all organisms require?
Organic compounds
Who MAKES organic compounds from CO2?
Autotroph
What does autotroph mean?
Self feeder. You make your own food.
Who must OBTAIN organic compounds from other organisms?
Heterotrophs
Animals are ________.
heterotrophs
Photosynthesis is making _____ from the energy of ______.
sugar, light
It’s an energy transformation, from light energy into ______ energy stored in sugar.
chemical
In eukaryotes, photosynthesis occurs in _________.
chloroplasts
Do prokaryotes do photosynthesis? If so, which ones?
Cyanobacteria are photosynthetic, but they don’t do photosynthesis because they don’t have chloroplasts
Eukaryotes do photosynthesis in _______, and in plants, it happens in _______.
chloroplasts, leaves
Are there any non-plant eukaryotes that can do photosynthesis?
The protist Euglena - photosynthetic
The leaf absorbs ___ from the atmosphere.
CO2
CO2 is the source of ______ to make sugar.
carbon
It is the leaf that releases _______. We said it’s one of the byproducts of photosynthesis.
oxygen
That leaves us with water…where does water come from?
Water comes from the ______ which the plants brings up through vessels known as _____ vessels into the leaf where it can be used to make sugar.
ground, xylem
Why do plants need water?
We need CARBON…we need energy (SUNLIGHT), we need to store the energy….ELECTRONS. Where do you get electrons?
HYDROGEN. H20, water, is a source of electrons!
Leaves have pores called ______.
stomata
What are the leaf cells where photosynthesis happens?
Mesophyll cells
What is located within the mesophyll cells?
Chloroplast
Mesophyll cells are loaded with ________…that’s the whole purpose! To do photosynthesis!
Chloroplast
The chloroplast is a complex organelle, bounded by ___ membranes
two
Does the inter membrane space of chloroplast have any significance?
No significance
What is important is the fluid filled space bounded by the inter membrane, and this is called the ______.
stroma
The _____ is where the soluble biochemistry happens.
stroma
Where does the calvin cycle occur?
In the stroma
Floating within the stroma is this third extended membrane, and it’s called the _______.
thylakoid
Again, the thylakoid is an extended membrane. In some regions they’re organized into these columns. These columns are called _______.
grana
What is a singular column called ?
What are multiple columns called ?
Granum
Grana
Where does the membrane biochemistry happen?
Grana
Where is the chlorophyll found?
In the thylakoid membrane
The thylakoid is an enclosed space. There is a lumen within, and it’s called the thylakoid ______.
lumen
Photosynthesis has ___ stages.
two
What are the two stages called?
1) Light reactions
2) Light independent-reactions
Light reactions use the energy of light to energize ________.
electrons
Whose electrons?
Water’s electrons
Water’s electrons are energy _____.
We’re going to get those electrons and in order to energize them…we need to rip them away from the oxygen!
poor.
Once we take those electrons (hydrogens) away, we need to transfer them to an electron carrier. An electron carrier is called a ________.
coenzyme.
What is the coenzyme that’s going to carry the electrons from hydrogen?
NADP+
How is NADP+ different from NAD?
It has a phosphate on it
We have a dedicated coenzyme for photosynthesis, which is called ____.
NADP+ (You can think “NADP+, P for photosynthesis”
How many electrons and protons does NADP+ carry?
2e and 1p
What is the reduced coenzyme of NADP+?
NADPH
That’s the whole point of the light reactions…to get those high energy electrons in the form of ______.
NADPH
The NADPH will then _____ the electrons to the next stage (light-independent reactions).
carry
NADPH will reduce ___ to make sugar.
CO2
Light reactions take electrons from H2O, give it to _____, then we get NADPH.
NADPH takes the electrons and reduces ___. So we get sugar.
NADP+, CO2
It’s at this stage where we oxidize NADPH and we get _____ again.
NADP+
But we also need some ____ to run this light-independent reaction.
ATP
Where do we get the ATP?
It’s a product of the light reactions
Light enters the leaf, enters the mesophyll cell, enters the chloroplast and strikes the ______.
Granum
The _____ is where the light is harvested. And that’s where the ______ must be obtained.
granum, electrons
When you take electrons away from water, what are you left with?
Oxygen
Who do you give the electrons to?
The NADP+ and you get NADPH
How is the ATP made?
From ADP and inorganic phosphate. Reattach them and you get ATP
What are the two products of the light reactions?
NADPH and ATP.
They’re going to feed into the calvin cycle.
Light has properties of ______ and _______.
waves and particles
The particle is called a _______.
photon
Photons are ______ particles with fixed amounts of energy.
discrete
There is a relationship between the amount of energy and the wavelength.
The shorter the wavelength, the ______ the energy.
The lower the energy, the ______ the wavelength.
greater
longer
We can see light between (approximately) ___ nm - ___ nm
400-800nm
It is that portion, ______ light, that also fuels photosynthesis.
visible
When light strikes matter, what three things can happen?
1) reflected
2) transmitted - passes through the matter
3) ABSORBED
It is only light _______ that can do any work.
absorbed
How is light harvested?
Light is absorbed by the ________ of the chloroplast.
thylakoids
What do thylakoids have in order to absorb light?
Pigments
Pigments are the chemical that ______ light.
absorb
What is the main pigment for photosynthesis?
Chlorophyll a
The photosystem is the light harvesting unit of the _________.
chloroplast.
These photosystem units have three components.
What are the three units?
1) Antenne complex
2) Reaction center chlorophyll
3) Primary electron acceptor - accepts the excited electron so that it doesn’t drop down to the ground state.
What is that called, when you pass an electron from molecule to another?
Redox
Which photosystem operates first in the light reactions?
Photosystem II
What’s the difference between the two photosystems?
They operate at different times in the light reactions and that is because their reaction center chlorophylls have slightly DIFFERENT ABSORBANCE PEAKS , so they’re going to function in either this stage or that.
Light reactions have ____ parts.
four
What are the four parts of the light reactions?
1) Photosystem II - going to capture the excited electron
2) Electron transport chain - use the excited electron and to create a proton gradient
- use the proton gradient to make ATP
-at this point, the energy of the electron is low, need to re-energize it.
3) Photosystem I - re-energizes the electron, then passes it
4) Electron transport chain - short chain, then passes it to NADP+, and we got the electron.
DONE.
All of this is happening in the _______ membrane.
thylakoid
Steps of the light reactions…
1) Photosystem II absorbs _____.
-electron is transferred to the _______ _______ _______.
-reaction center is oxidized/reduced?
-primary electron center is oxidized/reduced?
(FIRST REDOX OF photosynthesis)
light
primary electron acceptor
reaction center is oxidized
primary electron center is reduced
If this photosystem is ever going to function again, what do we have to do?
A source of electrons from water in order to keep this process going
Steps of the light reactions…
2) Obtain an electron from ___.
- This requires an ______ to split the water, removing its electrons, removing the protons and putting them into solution.
- highly ________ process.
- Where does the energy source come from to energize the electrons?
H2O
enzyme
endergonic
The energy to take electrons from water is coming from the SUNLIGHT . This allows us to oxidize the water.
At the end of the light reactions, the energy rich electrons will go to ______.
NADP+, then reducing it, making NADPH, which is the primary product of the light reactions.
Light-independent reactions is in the form of a cyclical pathway known as the ______ cycle.
Calvin
It is the Calvin cycle which will _______ NADPH. We use the electrons to _______ CO2, and we get sugar.
oxidize, reduce
Steps of the light reactions…
3) Excited electron is transferred to an E.T.C
- ATP is made by ___________.
chemiosmosis
Protons moving across the thylakoid membrane from the ______ to the _______ ______.
stroma to thylakoid lumen
Making ATP from ADP and an inorganic phosphate driven by light energy is called ____________.
photophosphorylation
In chloroplasts, we concentrate protons in the ________ ______.
thylakoid lumen
Protons flow back into the _______.
stroma
Where do the electrons go?
Electrons come off the chain and reduce photosystem I
Steps of the light reactions…
4) P.S I absorbs ______.
- It is Re-excited by another photon
- Transferred to a 2nd primary electron acceptor
light
Steps of the light reactions…
5) Excited electron is transferred to a 2nd ____.
E.T.C
Steps of the light reactions…
6) Electron passed to NADP+ —> _______.
NADPH.
Done.
Goal of the light reactions: Make NADPH, make ATP
Steps of the light reactions…
1) P.S II absorbs _____
2) Obtain an _______.
3) Excited electron is transferred to an ____.
4) P.S I absorbs ____.
5) Excited electron is transferred to a 2nd ____.
6) Electron passed to NADP+ —> _______
light electron E.T.C light E.T.C NADPH
How many photons are required to make one NADPH?
4 photons
Stage 2 : ______ cycle.
Occurs in the ______.
Calvin cycle
stroma
The calvin cycle is what produces ______.
sugar
The Calvin cycle has __ parts.
3
The first part of the Calvin cycle is _______ _______.
The second part is ________.
The third part is the ___________ of the CO2 acceptor.
carbon fixation
reduction
regeneration
What is the CO2 acceptor?
RuBP.
When CO2 joins with RuBP, you get an organic product. Carbon fixation.
What is the sugar product of photosynthesis?
G3P
How many cycles generate ONE G3P?
3
You need 3 CO2 to make ONE 3 carbon sugar
What is the molecule used to “fix” CO2?
RuBP.
What is the enzyme that catalyzes carbon fixation?
Rubisco
