eLog7 Photosynthesis
Summary
TLDRThis educational script delves into the intricacies of photosynthesis, explaining how plants convert light energy into ATP and carbohydrates. It covers the role of chlorophyll, the structure of chloroplasts, and the light-dependent reactions within. The script also explores the Calvin cycle, the process of C3, C4, and CAM photosynthesis, and their adaptations to different environmental conditions, emphasizing the importance of plants in carbon sequestration and oxygen production.
Takeaways
- đ„Ș The script starts with a discussion about a sandwich, symbolizing how food is derived from photosynthesis.
- đż Photosynthesis is crucial for understanding where food components like ham, cheese, and wheat come from.
- đ ATP (adenosine triphosphate) is the cellular energy currency, produced through photosynthesis and cellular respiration.
- đ Light energy plays a critical role in photosynthesis, where it's used to convert ADP and inorganic phosphate into ATP.
- đ Chlorophyll and other pigments absorb different wavelengths of light, essential for the photosynthetic process.
- đ The chloroplast is the organelle in plant cells where photosynthesis occurs, containing its own DNA.
- đ ATP synthase is a key enzyme that operates in both photosynthesis and cellular respiration, catalyzing the conversion of ADP to ATP.
- đ§ The process of photosynthesis involves the conversion of carbon dioxide and water into glucose and oxygen, facilitated by light energy.
- đ± Plants act as carbon sinks, helping to mitigate the greenhouse effect by storing carbon and producing oxygen.
- đ The Calvin cycle is the light-independent reaction of photosynthesis, where carbon dioxide is fixed into glucose using ATP and NADPH.
- đ± C3, C4, and CAM photosynthesis are different evolutionary adaptations plants have developed to optimize photosynthesis under various environmental conditions.
Q & A
What is ATP and why is it important in photosynthesis?
-ATP, or adenosine triphosphate, is a molecule that provides energy for many cellular processes. In photosynthesis, ATP is produced during the light-dependent reactions and is essential for powering the synthesis of carbohydrates during the Calvin cycle.
How is ATP produced in photosynthesis?
-ATP is produced through a process called ATP synthase. Light energy energizes electrons, which move through the electron transport chain, pumping hydrogen ions into the thylakoid. These ions flow back through ATP synthase, causing it to spin and catalyze the production of ATP from ADP and inorganic phosphate.
What is the role of chlorophyll in photosynthesis?
-Chlorophyll is the primary pigment responsible for absorbing light energy, which is used to energize electrons during the light-dependent reactions of photosynthesis. Chlorophyll absorbs mostly blue and red light, while reflecting green, which is why plants appear green.
What are the two stages of photosynthesis?
-Photosynthesis consists of two stages: light-dependent reactions and the Calvin cycle (light-independent reactions). The light-dependent reactions convert light energy into chemical energy (ATP and NADPH), while the Calvin cycle uses that energy to fix carbon dioxide into glucose.
Why do plants change color in the fall?
-Plants change color in the fall because chlorophyll breaks down, revealing other pigments such as beta carotene and xanthophyll. These auxiliary pigments absorb different wavelengths of light and become more visible as chlorophyll is depleted.
What is the function of the electron transport chain in photosynthesis?
-The electron transport chain in photosynthesis moves high-energy electrons between protein complexes. As electrons travel through the chain, their energy is used to pump hydrogen ions into the thylakoid, creating a concentration gradient that drives ATP production.
What is the Calvin cycle and what does it produce?
-The Calvin cycle is a series of reactions that occur in the stroma of the chloroplast. It uses ATP and NADPH from the light-dependent reactions to fix carbon dioxide into a three-carbon molecule, G3P, which is later used to form glucose.
What is the significance of NADPH in photosynthesis?
-NADPH is a high-energy electron carrier produced during the light-dependent reactions of photosynthesis. It provides the reducing power needed to convert carbon dioxide into glucose during the Calvin cycle.
What is C4 photosynthesis and when do plants use it?
-C4 photosynthesis is an adaptation for plants in environments with low carbon dioxide concentrations, such as dense plant populations (e.g., cornfields). It spatially separates the light-dependent reactions and the Calvin cycle to optimize carbon dioxide usage and reduce photorespiration.
What is CAM photosynthesis and how does it help plants in dry environments?
-CAM photosynthesis is an adaptation that allows plants to survive in dry environments. These plants open their stomata at night to take in carbon dioxide and close them during the day to reduce water loss. The carbon dioxide is stored at night and used during the day for photosynthesis when light is available.
Outlines
đ„Ș Discussing a Sandwich and Photosynthesis Connection
The speaker begins by casually enjoying a ham and cheese sandwich, hinting at a deeper topic â photosynthesis. The connection between the sandwich ingredients (lettuce, wheat) and photosynthesis is introduced, stressing the importance of understanding how cellular energy, particularly ATP (adenosine triphosphate), is produced through photosynthesis and its role in creating carbohydrates.
đ ATP Synthase and Photosynthesis Pigments
This paragraph delves into the process of ATP synthesis in photosynthesis, explaining how light energy converts ADP (adenine diphosphate) and inorganic phosphate into ATP. The significance of chlorophyll and other pigments, such as beta-carotene and xanthophyll, is highlighted as the plant absorbs various light wavelengths. The role of chloroplasts, where photosynthesis occurs, is introduced with a focus on the internal structures like the grana and thylakoid membranes.
đ Photosystems and the Electron Transport Chain
The speaker introduces Photosystem II, which absorbs light energy to excite electrons, starting the electron transport chain. Water provides the necessary electrons for this process, resulting in hydrogen ions and oxygen. As these excited electrons move through the electron transport chain, they generate the energy required to pump hydrogen ions into the thylakoid, setting up a concentration gradient crucial for later stages of ATP synthesis.
⥠Energizing Electrons in Photosystem I
After electrons pass through Photosystem II, they reach Photosystem I, where they are re-energized by another photon of light. These energized electrons contribute to creating high-energy molecules like NADPH, a vital electron carrier. The movement of hydrogen ions through ATP synthase generates ATP, with the enzyme itself observed spinning during this process. The ATP and NADPH produced are essential for the light-independent reactions of photosynthesis.
đż Calvin Cycle and the Role of Plants in Carbon Storage
The speaker explains the chemical reaction of photosynthesis, where carbon dioxide and water are converted into glucose and oxygen using light energy. This process, crucial for producing food and oxygen, also helps in carbon storage, reducing greenhouse gases. Plants, acting as carbon sinks, are vital in combating global warming. The Calvin Cycle is introduced as the core process of carbon fixation in plants, using ATP and NADPH to convert carbon dioxide into G3P, a precursor to glucose.
đ Regenerating RuBP and Energy Use in the Calvin Cycle
Continuing with the Calvin Cycle, the process of regenerating RuBP (ribulose bisphosphate) is described, highlighting the energy expenditure in the form of ATP required for this phase.
Mindmap
Keywords
đĄPhotosynthesis
đĄATP Synthase
đĄChlorophyll
đĄChloroplast
đĄGranum
đĄElectron Transport Chain
đĄNADPH
đĄCalvin Cycle
đĄC3 Photosynthesis
đĄC4 Photosynthesis
đĄCAM Photosynthesis
Highlights
The sandwich contains ham, cheese, arugula, and mayo on wheat grit.
Photosynthesis is essential for understanding where our food comes from.
ATP is the cellular energy molecule, synthesized with ATP synthase.
Photosynthesis uses light energy to create ATP from ADP and inorganic phosphate.
Different wavelengths of light are required for photosynthesis.
Chlorophyll and auxiliary pigments like beta carotene and xanthophyll are involved in light absorption.
Chloroplasts, unique to plant cells, contain their own DNA and are the site of photosynthesis.
The granum, a stack of thylakoid membranes, is where light-dependent reactions occur.
The stroma is the site of light-independent reactions, such as the Calvin cycle.
Photosystem II is involved in the initial steps of light-dependent reactions.
Water is split to provide electrons for the electron transport chain in photosynthesis.
The ATP synthase enzyme is likened to a spinning motor, converting ADP and phosphate into ATP.
NADPH is a high-energy electron carrier produced in the light-dependent reactions.
The overall photosynthesis reaction converts CO2 and H2O into glucose and oxygen using light energy.
Plants act as carbon sinks, reducing the greenhouse effect by storing carbon.
The Calvin cycle is the main light-independent reaction that produces glucose from CO2.
C4 photosynthesis is an adaptation to low CO2 environments, involving spatial separation of reactions.
CAM photosynthesis is an adaptation to low water environments, involving temporal separation of reactions.
Stomata are the pores on plant leaves responsible for gas exchange, including water loss through transpiration.
Transcripts
yeah that's
that's a good sandwich
[Music]
it's ham and cheese and arugula mayo
a wheat grit you know this stuff
came do you know where this stuff came
from
it's not the grocery store that's not
the answer
we're gonna find out the next couple
weeks
that's good
all right sandwich eaten it was good
coffee made might be better
so let's get out of here
so it might be kind of weird to talk
about photosynthesis
as where we get our like ham and cheese
um
not so weird to talk about where i got
that like
the lettuce and stuff that we put on our
sandwiches or or maybe even the wheat
but understanding photosynthesis is
super important to understanding
the ham and cheese as well so we got to
start with
cellular energy and that's atp
so atp
which is cellular energy
is made with a molecule called atp
synthase and atp synthase we're going to
talk about
two different times one's in
photosynthesis and once in
cellular respiration so atp synthase
takes
adenine diphosphate
adp plus inorganic phosphate
and we'll represent this with like a p
with a little i
and it turns it into adenine
triphosphate or atp
so photosynthesis is gonna is going to
do this or make atp so that they can
actually make those carbohydrates that
that we've talked about that plants need
and you and i need
okay so photosynthesis is going to use
light energy
to make atp from adenine diphosphate
and inorganic phosphate using atp
synthase
we need like certain kinds of light
energy and then
this picture shows you the different
wavelengths of light now you're going to
see on this picture that's not just
chlorophyll
and that's what you can see outside that
all the leaves as the leaves are
changing colors
we lose all of the green color to the
leaves which is the chlorophyll
different kinds of chlorophyll and what
we're left with are the other
auxiliary pigments like beta carotene or
xanthophyll other the other pigments
that are going to be
used you can see that in this graph
right here okay before we go any farther
we need to understand where this is
taking place the organelle that is in
plant cells that's not in a animal cell
are called chloroplast and chloroplast
where all of the photosynthetic pigments
are located
so you can see in the chloroplast that
there are there's an inner membrane
and an outer membrane and then what we
find is there's the
these membrane kind of like network
inside the chloroplast
and they form these like kind of little
stacks of membranes
similar to maybe what we looked at with
the golgi body maybe a little
and these these stacks this one
stack is called a gran
granum okay um all of them together
plural would be grand
i think you'll hear this a lot said as
like stacks of coins
because they're pretty pretty disc shape
maybe that's different
than the um then the golgi body but this
is where
the chlorophyll and other pigments are
located
and so this is where the all of the
light dependent reactions take place
other interesting aspects about the
chloroplast is that
chloroplasts contain their own dna
this this idea or the
idea that chloroplasts contain their own
dna is
a piece of evidence one of the pieces of
evidence
that link eukaryotes to a
eukaryotes to prokaryotes as this like
the endosymbiotic theory
where at one point we have a ancient
prokaryote eat another prokaryote
and the dna and everything of that
prokaryote that was eaten stays intact
and provides a benefit in this case
energy
to the the the one that ate it another
part that's really going to be important
as we move on uh with regards to parts
of the chloroplast
is going to be the stroma the stroma is
the space
inside the membrane but not
part or outside of the grana
so all of this membrane that makes up
the grana is called
the thylakoid
in here in the picture that you're
looking at
just realize that the stroma that's the
space
inside the membranes of the chloroplast
but outside the thylakoid membrane
um so this is kind of the interior part
and then and then ins that's the top of
the screen and then the bottom of the
screen
is going to be inside the membrane of
the thylakoid so inside a grana
or a granum okay so this is going to be
kind of weird because
what we do is we start with photosystem
so what's kind of weird is we start with
photosystem 2.
photosystem two we start with
photosystem two because it was
discovered after photosystem one
not because it happens first but it was
discovered af um
after photosystem one so what happens is
that we get light
from our environment certain wavelengths
of light
hit photosystem two
and then um you know that you have to
water a plant right
so when we water a plant this is how
we're
providing these electrons for
photosystem 2 and actually this whole
electron transport chain process to work
so we start we can put in some water
and we get out hydrogens
and oxygen atoms
okay so um these elect and then
we drop off the electrons so the light
when it comes down
it energizes these electrons so it
just it doesn't like actually mean that
it moves up inside
um photosystem 2 but just to show that
it moves to a higher
energy state it's
an excited electron okay so
what we see is then that this electron
moves through
the this electron transport chain and as
it moves through the electron transport
chain we have
ion or hydrogen ion pumps so the
hydrogen
ions are going to get pumped through
to the inside of the thylakoid
the energy used to pump these hydrogens
inside the thylakoid
is the high are are the high energy
electrons so this is where we have all
of these hydrogen ions
so we're moving it against the
concentration gradient from high
or we're moving it from low
concentration to high concentration all
right that's going to be important
later so we keep filling this up with
hydrogen ions
all right so when the electrons reach
photosystem one
we're gonna energize them again with
another
photon of light another packet of light
alright so the
the electrons then get re-energized
and this will be important as we get
down down the line
okay so these re-energized electrons
get moved into these
specific proteins to to transfer them
and to react with and
make high-energy electron carriers so
when they get in here these are going to
make
high-energy electron carrier called
n-a-d-p-h
all right we'll talk about that a little
bit more in in a second
all right so here's here is the gist of
this whole thing
okay so we've got all these hydrogen
ions that were built up
and they're going to now move through
the atp synthase from high concentration
we had to pump them in there with using
those high energy electrons
it's going to move through that atp
synthase
and actually what scientists have been
able to like
like image is that this atp synthase is
actually
spinning when it does this which is i
don't know i think kind of interesting
and so we put in as those as that's
spinning right
we put in a dp
and inorganic phosphate
and then what we get out is a
tp all right so the energy used to make
this chemical reaction happen
is the energy from the moving hydrogen
ion
you remember i said we were going to get
back to what happened to the high energy
electrons
after photosystem one well here it is so
what we've got is the
so the high energy electrons
that are re in or the inner the
electrons that are re-energized back to
this higher energy state
from another second photon of light
they are used to make these high energy
electron carriers
and as they move through these proteins
that make this or that
i guess act as enzymes to make this
chemical reaction happen
happen we take n a
d p plus
plus hydrogen and ion
and we use and trap those high energy
electrons
in that in that chemical bond so then
what we get is we have
n a d p
h all right so this is a high energy
electron carrier
okay and this high energy electron
carrier is going to be really important
to the light
independent reactions which we'll talk
about in just a second
i think i may have kind of almost messed
up we didn't even talk about the
um the actual reaction of photosynthesis
so here it is you probably already know
what happens here but let's just
kind of go over it anyways so
photosynthesis
plants take in carbon dioxide
co2 and they react that with water
h2o and then they use
light energy
to to make
glucose c6h12o6
plus oxygen all right so
this is kind of the important part of of
why we need plants
not just for food consumption and not
just
so that we have oxygen to breathe but
what they do is plants big trees
um lots of plants right store
and store carbon as a carbon sink
when we release carbon dioxide out into
the environment
right it's a greenhouse gas part of
global warming
global climate change but if we can trap
the carbon into plants
that carbon isn't affecting the
greenhouse
right so it isn't causing a greenhouse
effect it is not
that carbon is not part of the carbon
dioxide that's causing the greenhouse
effect right the warming causing the
warming of the planet
and the more plants we have the more
oxygen is being produced
so when we um like if we
like a lot of countries or a lot of
places will have like green buildings
where
there's more plant material on the side
or on the roof of the
of the building versus just like making
a concrete structure
um where there is no photosynthesis
going on
any way we can add photosynthesis to our
lives
is going to help trap that carbon
okay so you saw in the light dependent
reactions that's where we use the
water part of the photosynthetic
equation
right in the light independent reaction
is where we're going to use the carbon
dioxide
all right so the light independent
reactions
um there's a lot of reactions the one
like kind of the the main part of this
what we'll call
our what we will say is the main part of
this is called the calvin cycle
this is named after a guy named calvin
they discovered so with the calvin cycle
what we're doing is we're taking our
carbon dioxide and we actually put in
three carbon dioxides into
the calvin cycle so you can see we have
rubp which is a five carbon molecule the
blue dots represent the carbon
and then we take one carbon from one of
the co2 molecules and we add it
to our ubp making it not
making a six carbon molecule now
this is done by rubisco okay so after
this i mean there's a lot of steps and a
lot of enzymes
involved in this and i'm not gonna ask
you to know this but what we have
after we get this six carbon molecule is
that we put in 6 atp
to make some of this stuff happen it
means we get out 6 adp
we put in 6 nadphs and then we get out
6 nadp plus because we've like used up
that electron and the energy in those
bonds so we use these energy molecules
to
make this molecule called g3p
and g3p is a three
carbon molecule that leaves the calvin
cycle
and goes to make glucose all right so
as it continues on really all we're
going to do now is we need to regenerate
our ubp so we have a three carbon
molecule and we're going to add some
more
add some of them together to make
using atp add them together to get our
ubp to regenerate our ubp
so we can make the process right so
this part of where like this is what
we're doing this cycle is going and
going not us
sorry the plants this cycle is going and
going and going
and really all this is doing is making
these three carbon molecules that we're
going to keep stitching
together to make glucose if you remember
the formula for glucose is
c6h12o6
okay so this is all fine and good this
is all fine and good if you have
co2 and water
but what if you don't what if you don't
have what you
need to make what if you don't have what
you need
to make photosynthesis happen so there's
some evolutionary ways that plants have
have developed to deal with this sort of
things
so the normal way plants
photosynthesize is called through a
process called c3 or c3 photosynthesis
so
that's what we just kind of described
and it is kind of what you know of
photosynthesis but
if there's area where there is low
carbon dioxide now it's kind of weird i
just
mentioned that if we don't have plants
then we then we have too much carbon
dioxide in the environment
so what situations would you think of
where there are too many plants
like maybe a corn field right if you
think about the corn
corn plant in the middle of the corn
field the
idea that all of those corn plants are
taking in
carbon dioxide might indicate that there
is a low carbon dioxide environment
there
so they have to have a way to deal with
it and that is called c4
photosynthesis
what part of the photosynthetic process
um
that we've talked about c3
photosynthesis
would need to like have some at
some sort of adaptation if you're in a
low co2 environment
think about it when do we use co2
well we put co2 in in the light
independent reactions
right so that's what c4 photosynthesis
does it has a way to like build up
carbon dioxide before starting the light
independent reactions i just realized i
skipped something else
something about a plant anatomy that
maybe you don't know
um but if we have like if you look at a
leaf on the bottom side of a leaf
typically the bottom side there are
little pores
and i'm not this is not drawn to scale
at all but those pores
or yeah those pores
are called stomata and stomata are super
important this is how all
gas exchange with plants happen so like
we don't think of
plants taking in water because of a gas
exchange but that's exactly how they
take in water
if you water leaves the plant
through the stomata right water leaves
as
water vapor through the stomata and when
it leaves it can suck up more water
through the roots right this is called
transpiration
this process is super important in in
actually the water cycle plants produce
a lot
a lot of water vapor through the process
of transpiration
so c4 photosynthesis separates some of
the processes
in space so there are two different
kinds of cells we have
a mesophyll cell
and then a kind of attached or adjacent
to the mesophyll
cell is another cell called a
a bundle sheath cell
so what happens is that in the mesophyll
cell this is kind of where
co2 is entering from
the stomata and this is where we kind of
go through this process
of c4 photosynthesis so c4
photosynthesis
will actually kind of store and
dump into the bundle sheath
cells extra carbon dioxide
and then it's re then it's kind of
recycled through the same
c3 process so inside the bundle sheath
cells the bundle sheath cells is where
we're going to find
the chloroplast right and this is where
the calvin cycle is going to take place
in c4 photosynthesis calvin cycle is
going to take place in
the bundle sheet cells
so another type of evolutionary
adaptation for plants is called
cam photosynthesis
cam photosynthesis uh let's back up c4
photosynthesis
deals with low carbon dioxide
environments cam photosynthesis
deals with low water environment because
remember those are the two things that
we need to make photosynthesis happen
okay so cam photosynthesis separates
the processes of photosynthesis by time
if you remember c4 separated by space we
had mesophyll and bundle sheet cells
cam photosynthesis separates it by time
so if your stomata if you're a plant and
your stomata are open during the daytime
in a very hot dry place
you're going to lose too much water so
what happens is the
cam plants close the stomata during the
day
and open the stomata at night well this
can pose a problem because
you can't get rid of or you can't take
in co2 and you can't get rid of your
oxygen
when your stomata are closed so what
happens is
at night when the stomata are open they
take in
and store co2 so that during the day
when there is light available then the
light dependent reactions can happen
[Music]
you
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