Up next in 10
Photosynthesis Crash Course in 45 Minutes ?☀️|| Plant Physiology @biologyexams4u
39K views
Sep 10, 2023
Welcome to our Crash Course on photosynthesis, where we'll dive deep into unraveling the mysteries behind this fundamental process of plants and algae! Get ready to discover the secrets behind how sunlight and green organisms work together to create energy and oxygen. This educational video will provide you with a comprehensive overview of photosynthesis, shedding light on all its intricate details. Join us as we explore the fascinating world of chloroplasts, where the magic of photosynthesis takes place. We'll explain how chlorophyll, the pigment responsible for the vibrant green color, captures sunlight, and initiates the energy conversion journey. You'll gain insights into the two main stages of photosynthesis: the light-dependent reactions and the light-independent reactions, also known as the Calvin cycle. Delving further, we will unveil the importance of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate) as energy carriers during this process. Understanding how these molecules fuel the growth and survival of plants will give you a new appreciation for the incredible complexity of photosynthesis. Additionally, we will explore the environmental factors that affect photosynthesis, such as light intensity, temperature, and carbon dioxide levels. You'll learn how changes in these conditions can impact the efficiency of photosynthesis, shaping the very existence of life on Earth. So, whether you're a student needing to ace your biology exam or simply an avid learner with a passion for science, this Crash Course on photosynthesis is tailored just for you! Get ready to unlock the secrets and embark on a captivating journey through nature's incredible energy conversion process. Don't miss out on this opportunity to gain a solid understanding of photosynthesis! Like, share, and subscribe to our channel for more captivating educational content. Prepare to be fascinated by the wonders of "Unveiling the Secrets of Photosynthesis: A Crash Course"! ⌚ Stamps 00:00|| Introduction 00:45|| Equation of Photosynthesis 05:44|| Site of Photosynthesis 10:47||Pigments in Photosynthesis 16:50||What are Photosystems? 21:47||Light dependent reaction 27:09||Light independent reaction or Calvin Cycle 32:55||C3 and C4 cycle 43:01||CAM cycle? Happy Learning ✌️ =============================================================== We really appreciate your support ? Thank you so much :) @biologyexams4u ▶Enroll now. Our free certificate course on Introduction to Recombinant DNA Technology https://alison.com/course/introduction-to-recombinant-dna-technology?utm_source=alison_user&utm_medium=affiliates&utm_campaign=22177687
View Video Transcript
0:00
Hi friends, happy learning with biology exams for you. In this video we have combined all core
0:05
concept videos on photosynthesis for a clear-cut sequential understanding of the topic within 45
0:11
minutes. At the end of the discussion you will be able to understand the equation of photosynthesis
0:16
that is followed by the site of photosynthesis exactly where the reaction is happening that is
0:21
followed by the pigments in photosynthesis then light dependent reaction and also the steps involved
0:27
in Kelvin cycle or light independent reaction and the difference between C3
0:32
cycle and C4 cycle and finally will be winding up with CAM cycle. You can use
0:38
the timestamps to move directly into specific topics. Let's begin with the
0:43
equation of photosynthesis. So let's start with the definition of photosynthesis. Photosynthesis is an amazing process that is responsible for life on this
0:53
planet. The reactants are water that is absorbed by the roots plus the carbon
0:59
dioxide from the atmosphere. Sunlight is a source of energy and leaves are the
1:04
site of photosynthesis. Inside the leaf there is a pigment called chlorophyll
1:08
that trap the light energy and convert it into chemical energy as glucose and
1:13
this is directly or indirectly utilized by all organisms on earth except some
1:18
microbes and oxygen is released as byproduct. So this is the overall
1:23
equation of photosynthesis. Six molecules of carbon dioxide plus 12 molecules of
1:28
water in the presence of sunlight and chlorophyll give rise to glucose water
1:31
and oxygen. Let us see how we get this equation. Till 1940 this was the
1:41
equation six carbon dioxide plus six water molecule give rise to glucose plus
1:46
oxygen. It is believed that photosynthesis is just a reverse of respiration. In the case of respiration, this glucose molecule is broken down into
1:59
carbon dioxide and water with the release of energy. So photosynthesis is a
2:04
synthetic process whereas respiration is a catabolic process or breakdown process releasing energy. But this equation doesn't tell much about what is
2:13
actually happening. What is the exact source of oxygen evolved? Is it from water
2:19
or is it from carbon dioxide? So this is the experiment that solved the question
2:25
Ruben et al. in 1940 used radioisotopes to find out the exact source of oxygen
2:32
and this was a paper published and this was the experiment and the experiment
2:39
one they used radioactive labeled water as a reactant and found out that the
2:45
oxygen released is also radioactively labeled and this was the equation carbon dioxide plus radioactive labeled water and oxygen evolved is also
2:53
radioactively labeled indicating that this oxygen is formed from water for the
2:58
confirmation they did a second experiment using radioactively labeled carbon dioxide here they used radioactively labeled carbon dioxide and
3:07
found out that the oxygen released is not radioactively labeled indicating that this oxygen is evolved by the splitting of water molecule. They got
3:17
water in the product also which is radioactively labeled. Thus Ruben et al
3:24
confirmed that oxygen evolved during photosynthesis comes from water. Now we know that it is by the photolysis of water. So these are the two experiments
3:35
summary of the two experiment. Now we need to change the equation, now we know
3:40
that oxygen evolved during photosynthesis comes from water. Let us take the old
3:45
equation. 6 carbon dioxide molecule plus 6 water molecule gives C6H12O6 that is glucose plus 6 oxygen. Let us see what is happening. So now we know that
3:58
that water splitting give rise to oxygen number of oxygen is 6 here the number of
4:05
oxygen required is 12 so we need to rearrange this equation we should balance
4:10
this equation once again so this is a balanced overall equation of
4:15
photosynthesis 6 carbon dioxide molecule plus 12 water molecule in the presence
4:20
of light and chlorophyll give rise to glucose that is C6H12O6 plus 6 water
4:26
molecule plus 6 oxygen. Let us see this is 12 H2O so we have 12 oxygen here also
4:35
we have 12 oxygen so this is balanced. Now let us check the complete equation is
4:40
balanced or not. Number of carbon it is 6, number of oxygen 6 into 2 that is 12
4:47
plus 12 that is 24 oxygen molecule in the reactant side, number of hydrogen 12
4:53
into 2 that is 24. In the product side number of carbon it is of glucose that is
4:59
6, number of oxygen here it is 6, here also 6, 6 plus 6 plus 6 into 2 that is
5:05
12, 24 oxygen molecule and number of hydrogen here it is 12 plus 6 into 2
5:12
that is 12 that is 24. The equation is balanced. Now the correct balanced
5:19
overall equation of photosynthesis is 6 carbon dioxide plus 12 H2O give rise to
5:27
C6H12O6 plus 6 H2O plus 6 O2 where this O2 is derived from water. Now we know the
5:38
process, the process is called as a photolysis of water. Hopefully we will be
5:42
discussing that in our later videos. Which is a primary site of photosynthesis
5:47
it is undoubtedly the leaf leaf is the primary site of photosynthesis and in the
5:52
case of serophytes they may not be having leaf then the stem is green all
5:56
green parts of the plant are capable of photosynthesis leaf is an organ that is
6:03
designed for photosynthesis the function of leaf is to absorb light energy and
6:07
also carbon dioxide these are some of the adaptations of leaf there is large
6:12
surface area to absorb more light it's very thin so that so that the diffusion
6:17
carbon dioxide is very easy and the distance traveled by carbon dioxide is
6:21
very short then there is an opening called stomata that allows the carbon
6:25
dioxide entry and also the removal of water vapor by transpiration and there
6:31
is a vasculature that allows the translocation of water from root to the
6:36
site of photosynthesis that is the leaf apart from that these there is a cuticular
6:40
upper epidermis and this epidermal layer is transparent that allows the light to
6:44
penetrate into the mesophyll cell directly which is a prominent site of
6:48
photosynthesis. Next question, inside the leaf which is a cell that is primarily
6:54
involved in photosynthesis. Leaf anatomy shows that there is an upper epidermis
6:59
that is followed by palisade layer then there is a spongy mesophyll layer and
7:03
lower epidermis with stomata. Mesophyll cells, the stacked cells that is seen
7:08
just below the epidermis is a site of photosynthesis. Nearly 80% of photosynthesis
7:14
or Custis in these cells these cells are abundant in chloroplast and you can see
7:20
these cells are rich in chloroplast so it a primary site of photosynthesis now inside the mesophyll cell there is a wonderful organ which is called as chloroplast that is responsible for photosynthesis this organelle contains
7:35
pigment that is capable of trapping light energy and capable of converting
7:39
that light energy to chemical energy finally converting it into glucose this
7:44
is a structure of chloroplast it is a double membrane bound organelle and you
7:48
can see there are membranes sacs that is stacked one above the other which is called as granum individual membranous sacks are called as thylakoid and the
7:56
fluid fill matrix is called as a stroma now let us see what is the exact location
8:01
of each reaction in photosynthesis light dependent reaction light independent reaction and also the photolysis of water so this is a structure of chloroplast
8:10
and you can see this is the thylakoid membrane that is stacked one about the
8:14
other so let us zoom in so this is a tyloid membrane and on zooming in this
8:22
is the tyloid membrane tyloid membrane is a place where light reaction occurs
8:28
or light dependent reaction takes place in the tyloid membrane for the system 1
8:33
and photosystem 2 all other proteins and electron carriers are located on the
8:37
tyloid membrane therefore the exact location of light reaction is a tyloid
8:43
membrane. By this process the energy of sunlight is trapped and is converted to
8:50
chemical energy as ATP and NADPH. In non-cyclic photo phosphorylation the electrons should be continuously refilled and there is a process which is called
9:02
as photolysis or splitting of water that occurs in the thylakoid lumen
9:07
The thylakoid membrane is having a space which is called as thylakoid lumen. So
9:12
the site of water splitting or photolysis of water is a thylakoid lumen
9:16
which will refill the electron to the photo system too and also provide H plus
9:21
and that is utilized for creating a gradient for ATP synthesis you just see
9:27
the orientation of ATP synthase after light reaction the light energy is
9:32
converted to ATP and NADPH this ATP synthase is oriented towards trauma so
9:38
for Calvin cycle now the energy is right here in the stroma as NADPH and ATP
9:45
Next is the Calvin cycle where carbon dioxide is converted to carbohydrate. The
9:50
site of Calvin cycle or light independent reaction is a stroma where
9:56
ATP is already there that is synthesized by light dependent reaction and also
10:01
NADPH is also there that is utilized for the reduction of carbon dioxide to
10:07
carbohydrate. So this is a summary in photosynthesis there are two reactions
10:12
two are two major reactions there is light dependent reaction and also light
10:16
independent reaction. Light dependent reaction takes place in the grana or thylakoid membrane of the chloroplast where light energy is trapped and
10:26
converted to chemical energy in the form of ATP and NADPH. Whereas light
10:31
independent reaction that is a second step it is also called as dark reaction
10:35
it takes place in the stroma where the ATP and NADPH that is synthesized in the
10:41
light reaction is utilized to convert carbon dioxide to carbohydrate and we'll
10:48
be finding answers to the following questions what are the pigments in photosynthesis what is the site of pigments three major classes of pigments
10:56
and the characteristics of each pigment in detail first of all starting with the
11:02
basics of pigments in photosynthesis. Pigments are chemicals that can absorb light in the visible region. This is a visible region that is from 400 to 700
11:12
nanometer and these pigments include chlorophyll, carotenoid, xanthophyll, phycoeurethrine and phycocyanin. Chlorophyll is the most predominant
11:21
pigment that is why these leaves appear green. These pigments are located on an
11:27
organ which is called as a chloroplast in leaf inside the chloroplast there is
11:33
thylakoid this stack is called as granum and each unit is called as
11:37
thylakoid and this is an enlarged view of this thylakoid this is a thylakoid
11:42
membrane so pigments are actually located on the thylakoid membrane you can see for us for the system 2 and for the system 1 these pigments are located
11:51
and these pigments can absorb light energy and convert it into chemical
11:56
energy as ATP and NADPH we call it as light dependent reaction of photosynthesis
12:01
so these are amazing chemicals capable of converting the light energy from the
12:07
Sun and making it into converting it into chemical energy as ATP and NADPH
12:13
that is utilized for the formation of glucose in dark reaction or light
12:19
independent reaction now moving into the details of different types of photogenic pigments this is there are principal pigment which includes
12:28
chlorophyll A that is present in all plants and also bacterial chlorophyll
12:32
that is present in bacteria accessory pigments include chlorophyll B C D etc
12:40
carotenoids which is somewhat yellow or orange red in color that includes
12:45
carotene and xanthophyll then phycopylin is the third class that includes phycoeurethrine and phycocyanine moving into the detail of each pigment
12:58
chlorophyll a chlorophyll a is a primary pigment in all plants chlorophyll a the
13:05
structure of chlorophyll a you can see there is a central magnesium that is surrounded by four nitrogen atom and altogether this structure is called as a
13:12
tetrapyrrole or porphyrin head the formula is 6 c 55 h 72 o 5 n 4 mg this
13:21
is a hydrophilic viral head and this is the phytol tail which is hydrophobic that
13:27
is embedded in the thylakoid membrane and this one two three four these rings
13:33
are joined by methane group and maximum absorption is in the red and blue
13:37
region and reflects green light that's why the leaves appear green its bluish
13:42
green pigment and the side group at the second ring this is a second ring side
13:47
group at the second ring is a medial group that's a CH3 group second
13:52
principal pigment that is bacteriochlorophyll in bacteriochlorophyll is primary pigment in green and purple sulfur bacteria the formula is C55 at
14:03
74 or 6 and 4 mg it's a reddish purple pigment with the side group in the CH3
14:10
position it is having CH3C double bond though in the first ring the maximum
14:14
is in the infrared region that is greater than 720 nanometer now accessory
14:19
pigments accessory pigments first one is chlorophyll B that is present in blue
14:24
green algae and also in all green plants chlorophyll B is same as that of the
14:28
chlorophyll A except that in the second ring the side group instead of methyl
14:34
group in chlorophyll A it is CHO group in chlorophyll B the formula is C 55 H 70
14:42
O6N4MG the rest is the same maximum absorption at red and blue region and
14:49
reflects green light the only difference from chlorophyll A and B is in chlorophyll
14:54
B the side group in the second region in the second ring the side group is a CHO group rather than a CH3 group as in chlorophyll A Now the second class of
15:05
pigments that accessory pigment that is carotenoids it includes carotene and xanthophyll. Carotenoids are accessory pigments in all plants. Beta carotene is
15:14
an example C40, H56 is a formula, red or orange colored hydrocarbons, maximum
15:21
absorption in the blue violet region. Whereas xanthophils are oxygenated carotene, it can be called as oxygenated carotene. Example is lutein C40H56O2
15:31
you can see that this is oxygenated. Brown or yellow colored oxygenated
15:37
hydrocarbons, these are responsible for the color of autumn leaves. This is a
15:42
yellow color of xanthophil and reddish color, reddish orange color of Carotenoids, as the leaf matures the chlorophyll deteriorates and is replaced
15:53
by these accessory pigments carotenoids and xanthophyll that is why ripened leaf
15:57
appear as orange or yellowish. Next class of pigments include is the
16:03
phycopylenes that include phycoereutrine and phycocyanin and this is a structure. Phycoereutrine these are accessory pigments in red algae and cyanobacteria
16:13
or blue-green algae. It's water soluble pigment and this is wallbox that is a blue green algae and also in red algae this is laminaria this
16:23
is red colored and maximum absorption dim and blue-green light whereas phycocyanin
16:30
is a bluish pigment that is present in red algae and blue-green algae it's also
16:34
water soluble it's blue colored a maximum absorption it's extra orange and red
16:39
light and that these pigments enables algae to live in deep underwaters of sea
16:45
due to the property of these pigments and this is a summary of what we have
16:49
discussed. we are going to discuss about what are photosystems, what are the
16:54
major differences between photosystem 1 and photosystem 2 in detail. inside the
16:59
chloroplast there are membranous sacks that is stacked one above the other which
17:03
is called as granum and this is called as this is a granum and which is a site
17:07
of light reaction. so this is a thylakoid membrane let us zoom in this region. so
17:13
this is a thylakoid membrane. On the thylakoid membrane, photosystems and all
17:18
other associated electron carriers and proteins are located or thylakoid membrane is a site of light dependent reaction. Photosystems are also located
17:27
on the thylakoid membrane. These are the photosystems, photostem 2 and photosystem 1 and this is a picture of non cyclic photophosphorylation. So
17:38
photosystems are light harvesting complexes that is made up of pigment molecules, accessory pigments and associated proteins. Photosystems are
17:46
located on the thylakoid membrane of the chloroplast in the case of green plants
17:51
and algae whereas in the case of bacterium these photosystems are located
17:56
on the cell membrane. Let us zoom in this region. Each photosystem consists of two
18:04
closely linked components that is a reaction center chlorophyll molecule and accessory pigment which is called as antonyum molecules. Accessory pigments
18:13
include chlorophyll B, carotene, sandophyll etc. what is happening is this energy of
18:20
sunlight or photons is received by this accessory pigments. This accessory pigments transfer this energy to other molecules to the adjacent pigment
18:31
molecules by means of resonance transfer which is a kind of vibratory transfer
18:36
mechanism. Ultimately this energy is channeled into the reaction center chlorophyll, a molecule
18:43
from where electrons are moved from ground state to the excited state that is received by electron
18:49
acceptor and that moves through different electron carriers providing energy for the creation of
18:55
electron gradient ultimate and ultimately the synthesis of ATP and NADPH and we have discussed
19:02
that part in the video cyclic and non cyclic photo phosphorylation in detail
19:07
so in summary these are the functions of photosystem it is involved in light
19:11
absorption transfer of energy and ultimately transfer of electrons let us move into the difference first of all starting with difference in absorption
19:20
peak so photosystem one maximum absorption is 700 nanometer or far edge
19:27
region of light or it absorbs long longer wavelength of light and it has an
19:32
iron sulfur type reaction center and is rich in chlorophyll A. In the case of
19:38
photosystem II maximum absorption peak is at 680 nanometer it has a quinone type
19:44
reaction center and is rich in chlorophyll B. Second difference is it's
19:48
regarding the location inside the chloroplast. There are two regions which is called as oppressed and non-oppress region in chloroplast. So I would assume
19:57
this region and this is the granum and individual units are called as
20:01
thylakoid membrane so photosystem 1 in green color is located on the non
20:08
oppressed gr region and this is a non oppressed gr region or the
20:11
region that is exposed to stroma the region that is exposed to stroma or it
20:16
can be called as the outer layers of grana so photosystem 1 in green color
20:22
that is primarily or that is located on the non-upress granule region and also
20:28
on the stroma lamellae that connects the adjacent granule whereas photosystem 2
20:33
is located on the upress granule region this is a upress region you can see here
20:39
there is stacking or the internal part of the granule for stem 2 is with green
20:45
and black color and this is seen on the internal part of granule or the
20:49
upper region of grana. Difference number three that is regarding the role in light reaction
20:56
Photosystem I that is involved in both cyclic and non-cyclic photophosphorylation. In cyclic photophosphorylation, photosystem I contributes to the formation of ATP
21:08
electrons returns back to photosystem I, whereas in non-cyclic electrons are received from photosystem II
21:15
and it forms NADPH whereas in the case of photostem-2 it is only involved
21:22
in non-cyclic photophosphorylation and also involved in a process called as photolysis of water as these electrons when moves from
21:31
photo stem-2 there is an electron hole so in order to refill that electron hole
21:35
a process occurs that is called as a photolysis of water or water splitting
21:40
providing electrons and protons it is involved in ATP synthesis about the four stages in light dependent reaction of photosynthesis
21:49
so we have divided the entire process into four stages for the sake of understanding remember all may be happening at the
21:55
same time so these are the stages photo excitation photolysis photo phosphorylation and photo reduction
22:03
and we'll be discussing these within three to five minutes Starting with the first stage that is a photo excitation of chlorophyll molecule or pigment systems
22:14
So this is a thylakoid membrane where photosystems and all other electron carriers are located along with ATP synthase
22:22
Or thylakoid membrane is a site of light dependent reaction of photosynthesis So this is a chloroplastoma and this is a thalacoid lumen or thalacoid space so first step is the
22:35
photo excitation of pigment systems so that this is a pigment system 2 and this
22:40
is pigment system 1 and this is a picture of non cyclic photophosphorylation
22:45
that is predominant in higher plants let's see what are photosystems so
22:51
photosystems are light harvesting complexes that consists of accessory pigments and a reaction center chlorophyll a molecule. light energy is
23:01
trapped by these accessory pigments and this and this energy is transferred to
23:06
adjacent pigment molecules by means of resonance transfer or a kind of
23:11
vibratory transfer and ultimately this energy is passed on to the reaction
23:15
center chlorophyll molecule and from where the electrons are rejected or or raised to the excited state from the ground state and that is received by electron acceptors
23:26
and that will be passed on to other acceptors okay so photosystems are the light harvesting
23:31
complexes in the light dependent reaction of photosynthesis now the electrons are rejected
23:36
from the photosystem 2 there is an electron hole or an electron gap in photosystem 2 that should be
23:42
refilled then there occurs a process which is called as photolysis of water that occurs in the
23:49
the thylakoid lumen where the water molecule splits up to form protons and
23:54
electrons with the release of oxygen. this protons refills this photosystem too, protons helps in creating gradient in the thylakoid lumen and oxygen that
24:07
is released and that is the oxygen that is released during photosynthesis. so the
24:12
second step stage 2 is a fertilizes of water in thylakoid lumen that refills the
24:18
lost electron in photosystem and also contribute in creating proton gradient stage 3 is a photo phosphorylation of ADP to ATP now there is a proton gradient
24:32
that is created by the photolysis of water and also during the electron
24:37
transfer the energy is utilized to pump protons from the chloroplastomal region
24:42
into the thylakoid lumen space now here there is more protons compared to this
24:47
thermal region so there is no way out for this protons to this side to create
24:52
an equilibrium these thylakoid membranes are impermeable the only way out is a
24:58
protein which is called as ATP synthase when the protein moves through this ATP
25:03
synthase the energy is utilized for the catalytic activity or for adding
25:09
phosphate into ADP forming ATP and this is called as chemiosmotic hypothesis and
25:15
this force is called as proton motive force so simply this proton gradient is
25:21
created by fertilizers of water and also by the pumping of protons from the
25:27
chloroplastomal region into the thylakoid lumen region utilizing the energy of electron transfer or electron flow so while this H plus moves through
25:37
ATP synthase the only way for H plus to move out of thylakoid lumen that energy
25:42
is utilized for combining this ADP to PI forming the ATP or the energy-rich
25:50
molecule and that's the third step and the final step is the photo reduction of
25:57
NADP to NADPH as the electrons moves from photosystem 2 then moves to
26:03
blastocinone B6F which is a proton channel then plastocyanin and that is
26:08
received by photosystem one this is further energized by the sunlight and
26:13
there is a ferridoxin reductase enzyme that is close to photosystem one and
26:19
that will reduce NADP in the chloroplastomal region to NADPH so at the
26:27
end of light dependent reaction the energy of sunlight that is received by
26:33
the photosystems or chlorophyll molecule is converted into chemical energy in the
26:38
form of ATP and NADPH these two energy rich molecules that is ATP and NADPH
26:45
will be used in converting carbon dioxide or CO2 to glucose C6 H12 O6 in
26:55
Calvin cycle or C3 cycle and we'll be discussing that in the next video and
27:00
that's it these are the four stages of light dependent reaction of photosynthesis
27:05
remember all these things may be happening simultaneously. I think it is
27:10
better to understand Calvin cycle by knowing the exact reaction that is
27:14
happening. Calvin cycle is also called as C3 cycle, Calvin Benson Bajam cycle or
27:22
CBB cycle reductive bendose phosphate cycle. Let's begin. Starting with the reactions. The first reaction is carbon fixation where carbon dioxide combines
27:38
with RUBP ribulose bi-phosphate in the presence of enzyme rubisco forming a
27:44
three carbon compound. First there is a formation of a short-lived six carbon
27:51
compound then that splits to form a three carbon compound which is three
27:56
phosphoglyceric acid therefore the cycle is also called as C3 cycle. Step
28:02
number one is carbon fixation where carbon dioxide combines with RUBP forming a stable 3 phosphoglyceric acid. Step two is phosphorylation. This step is
28:17
added for better understanding so that what is happening in these reactions
28:21
this 3-phosphoglyceric acid is converted to 1-3-biphosphoglyceric acid a phosphate group is added therefore ATP is required therefore in this step ATP is
28:34
utilized step 3 is reduction in reduction this 1-3-biphosphoglyceric acid is
28:44
converted to glyceroldehyde 3-phosphate acid is converted to aldehyde where NADPH is reduced to NADP and this glyceraldehyde 3-phosphate which is a
28:59
very common metabolite inside the cell is used to synthesize glucose. Two
29:07
glyceraldehyde 3-phosphate molecules are used to make a glucose molecule. Step 4
29:13
is glucose synthesis. Two glyceraldehyde 3-phosphate molecules as it is 3-carbon is used to make a glucose molecule and the step 5 is regeneration of rUPP from
29:27
this glyceraldehyde 3-phosphate here also ATP is utilized for regenerating rUPP now let us see the exact reactions with numbers 6 carbon dioxide molecules
29:43
combines with 6 rubb now we have 36 carbon 6 carbon plus 5 into 6 that is
29:53
30 30 plus 6 36 carbon atom in both these compounds to form three forms
29:59
phosphoglycerate therefore this is a three carbon compound therefore 36 by 3
30:06
12 phosphoglyceric acid will be formed then this 12 phosphoglyceric acid then
30:15
it is converted to 1 3 pi phosphoglycerate or glyceric acid whenever
30:19
there is an addition of phosphate the enzyme is kinase here the enzyme is
30:24
phosphoglycerokinase this is the substrate name. Here 12 ATP is used as 12
30:31
1 3-biphosphoglycerate is formed. Then in the reduction stage the enzyme is
30:38
dehydrogenase, the stryosphosphate dehydrogenase. 12 NADPH is used in this
30:48
step then 12 glyceraldehyde 3-phosphate is formed. Out of this 12 glyceraldehyde
30:57
3-phosphate, 2 glyceraldehyde 3-phosphate is used to make one glucose molecule. As
31:04
glucose is 6 carbon, 2 glyceraldehyde 3-phosphate molecule is required. Now we
31:15
have 10 glyceraldehyde 3-phosphate molecule and that is used for regeneration of
31:21
RUBP 10 glyceraldehyde 3-phosphate that is 30 carbon and it will form 30 by 5
31:30
RUBP is having 5 carbon therefore it will regenerate to form 6 RUBP thus
31:37
completing the cycle. here also 6 ATP is utilized for regeneration. so in total
31:48
18 ATP is utilized for synthesis of a glucose molecule where 12 ATP is
31:55
utilized at the beginning for phosphorylation then 6 ATP for regeneration and 12 NADPH is utilized for the synthesis of a glucose molecule. so this
32:07
is two glyceraldehyde 3-phosphate molecule forming a glucose molecule which is having six carbon. it's better to understand by remembering the exact
32:18
reaction than using some mnemonics or abbreviations. let me repeat once more
32:24
ReBP combines with carbon dioxide forming the first stable compound is 3-phosphoglyceric
32:30
acid then it is phosphorylated to form 1-3-biphosphoglyceric acid then it is
32:36
reduced to glyceraldahide 3-phosphate. two molecules of glyceraldahide 3-phosphate makes a glucose and the rest is used for regeneration of RUBB. the enzymes
32:48
involved in regeneration are transketolase, ribosophate isomerase, phosphoribolokinase. the difference between Calvin cycle and C4 cycle or C3
33:00
cycle versus C4 cycle. so why C3 C4 and CAM? C3 is a normal cycle what's the
33:09
reason for certain plants exhibiting C4 and CAM cycle? the first and the most
33:15
important thing to remember is all plants makes glucose by C3 cycle or
33:21
Calvin cycle and it is a default cycle for the synthesis of glucose. Calvin cycle
33:28
is a cyclic reaction involved in the synthesis of glucose from carbon dioxide
33:32
with the use of ATP and NADPH that is synthesized during the light dependent
33:37
reaction of photosynthesis we have discussed that in detail in the video
33:41
regarding four stages of light dependent reaction of photosynthesis now C4 cycle actually it is an adaptation to survive in dry habitats for two reasons
33:54
to minimize transpiration and also to nullify photo respiration a process that
33:59
involves wastage of energy thereby increasing the photosynthetic efficiency CAM cycle it's an adaptation to live in desert condition and we'll be discussing
34:09
that in the next video so the most important thing is c3 cycle is the cycle
34:16
that is in all plants that is responsible for the synthesis of glucose wheat is a C3 plant and maize is a C4 plant now moving into the differences first difference number one YC4 cycle primary carbon dioxide acceptor and
34:31
enzyme involved in the first step. Let us discuss about the most important enzyme
34:36
in the process that is a Rubisco. This is a Calvin cycle. In C3 cycle carbon
34:42
dioxide combines with RUBP or ribulose bi-phosphate and the enzyme is rubisco ribulose 1,5-biphosphate carboxylase oxygenase. It is having carboxylase activity
34:55
it can bind to carbon dioxide and forming a C3 compound and during the C3 cycle ATP and NADPH
35:03
that is synthesized in the light reaction is utilized and ultimately forming glucose. This
35:08
rubisco is having yet another activity which is the oxygenase activity. If the concentration of
35:15
oxygen is high this rubisco will bind to oxygen rather than carbon dioxide on
35:22
binding of oxygen rubisco forms 2 phosphoglycolate therefore the first stable compound is 2 phosphoglycolate therefore called a C2 cycle then in
35:33
order to regenerate this 2 phosphoglycolate a great amount of ATP and
35:38
NADPH that is you that is synthesized in the light dependent reaction is used
35:42
and the net result is simply the release of carbon dioxide that is why this is
35:47
called as photorespiration just like our respiration oxygen is taken in and
35:52
carbon dioxide is released without the production of sugar or glucose in order
35:57
to regenerate this C2 compound phosphoglycolate phosphoglycolate should pass through three organelles chloroplast peroxisome and mitochondria with the
36:07
expenditure of ATP and NADPH so this cycle is a wastage of NRG with a huge
36:14
expenditure of NRG without having any beneficial aspect so the plants that is
36:21
living in dry condition always tries to avoid this photo respiration that is why
36:27
there is C4 cycle now moving into the differences and this is a C3 cycle or
36:34
Calvin cycle here the first stable compound RUBP combines with carbon dioxide in the presence of enzyme Rubisco forming a 6 carbon short-lived
36:44
intermediate the first stable compound is 3 phosphoglycerate therefore the cycle is called as C3 cycle and the primary carbon dioxide acceptor is RUBP
36:55
rubylose by phosphate that combines with carbon dioxide and the enzyme involved
37:00
is rupees code in C4 cycle carbon dioxide combines with phosphoenol pyruvate or
37:09
PEP forming oxaloacetic acid and it's a C4 compound you can see there are four
37:15
carbons therefore the cycle is called as C4 cycle here the primary carbon dioxide
37:20
acceptor in mesophyll cell is PEP or phosphoenol pyruvate and that is
37:27
converted to oxaloacetate for carbon compound and the enzyme involved is pep
37:34
carboxylase difference number two it's regarding the occurrence C3 cycle this is common very common in wheat potatoes I have been rice etc occur in all plants
37:46
including C4 and camp plants more than 85% of plants are C3 only C3 cycle is
37:52
going on in such plants optimum temperature is 20 to 25 degrees Celsius
37:56
and this cycle works well in environment where there is sufficient water with
38:00
moderate temperature and sunlight in that condition even though there is photorespiration that will not have this plant whereas C4 cycle is and actually
38:10
an adaptation examples include maize sorkum sugarcane millet plants etc and and it occurs in nine approximately 900 species it's an adaptation to reduce
38:20
photorespiration majority are monocots and the C4 plants can grow well in
38:25
environment with limited supply of water or dry habitats and high temperature and
38:30
high sunlight so during high temperature and high sunlight if there is
38:34
photorespiration these plants cannot survive that's why there is a cycle called
38:39
C4 cycle that will nullify the effect of photorespiration now moving into the
38:45
difference number three that is site of carbon dioxide fixation and Calvin cycle in C3 cycle initial carbon dioxide fixation and Calvin cycle everything occurs inside
38:57
the mesophil cells you can see carbon dioxide entering toxin is moving out
39:04
water is also released by transpiration whereas in C4 cycle initial step that is
39:10
initial carbon dioxide fixation takes place in the mesophil cells later it is
39:15
transported into the bundle sheet cell where Calvin cycle occurs therefore initial carbon dioxide fixation and Calvin cycle is separated in space at
39:27
two locations this picture will tell you the details initial carbon dioxide
39:32
fixation by PEP occurs in the mesothold cell then that is converted to malate
39:37
malate is transported to bundle sheet cell where carbon dioxide is decarboxylated
39:43
so that carbon dioxide is made available for Calvin cycle. So in bundle
39:49
sheet cells carbon dioxide is accumulated. Bundle sheet cells acts as a carbon
39:54
dioxide concentrator providing Rubisco with an option of optimum carbon dioxide concentration thereby nullifying or completely avoiding photorespiration or
40:06
the inhibitory effect of oxygen and later this malate is converted to
40:12
pyruvate and later trans converted to phosphoenol pyruvate. Difference number four regarding leaf anatomy. There is no Kranz anatomy in the leaves of C3 plants
40:24
there is a single type of chloroplast vascular bundle that is surrounded by
40:29
bundle sheet cell without chloroplast and the site of photosynthesis is a
40:33
mesophyll cell you can see the green color whereas in C4 cycle there is a
40:38
specific anatomy that is designed for this C4 cycle, vasculature is surrounded
40:44
by bundle sheet cells with chloroplast and that is surrounded by mesophyll cells
40:50
with chloroplast and mesophyll cells are the site of initial carbon dioxide
40:56
fixation and light reaction therefore this site is rich in krana it is having
41:02
well developed krana whereas bundle sheet cells are the site of Calvin cycle or
41:06
light independent reaction or dark reaction therefore this chloroplast is agr or grani is poorly developed in bundle sheet cells therefore there are
41:16
two types of chloroplasts gr in mesophyll cells and agr in bundle
41:21
sheet cells and this anatomy is called as Kranz anatomy this 2d picture will
41:26
give you a better clarity vasculature that is surrounded by bundle sheet cells
41:31
with chloroplast that is further surrounded by mesophyll cells without much space or direct contact with the bundle-seed cells without much space and
41:40
this anatomy is called as Kranz anatomy a bokeh like arrangement. Difference
41:45
number five that is regarding the photosynthetic efficiency and photorespiration. C3 cycle is a cycle that is meant for plants that is that
41:54
that is having sufficient water so photorespiration occurs that reduces the photosynthetic efficiency. 12 NADPH and 18 ATP molecules are required for
42:04
synthesis of one glucose molecule and we have discussed in detail in the last
42:08
video on Calvin cycle so in the C4 cycle C4 cycle is an adaptation thereby the
42:16
photorespiration is completely nullified or absent that increases the photosynthetic efficiency yield up to 50% approximately 50% more efficient than C3 plant C4
42:26
plants are well adapted to survive in dry habitats but for transporting all
42:32
these things malate from mesophyll cell to bundle sheet cells then regeneration
42:37
of this malate to phosphoenol pyruvate ATP is required so per glucose molecule
42:45
12 NADPH and 30 ATP molecules are required in the case of C4 cycle it's the
42:51
cycle is bit expensive as far as ATP is concerned but can avoid photorespiration
42:58
which is much more adverse and that's it interesting topic that is camp cycle in
43:03
plants. Camp cycle is an adaptation of desert plants to survive in water
43:08
deficient environment If you are new to this channel please subscribe and support this channel Moving into the topic starting with camp pathway So this is a desert plant and you can see this mesophyll cells of this plant Suppose
43:24
this is a mesophyll cell of this plant. The major concern of this plant is to
43:32
conserve water. So this pathway allows the plants to conserve water. So let us
43:38
move into the cycle. First step is during nighttime stomata open in camp plants
43:45
Camp plants the stomata is having a speciality which is called as scotoactive
43:50
It can open during nighttime and it can close during daytime. That type of
43:57
stomata is called as scotoactive. Stomata opens during night and carbon dioxide enters and it combines with pep forming oxaloacetic acid in the
44:08
presence of enzyme pep carboxylase just like C4 pathway and that oxaloacetate
44:15
is converted to malic acid and that is transported to vacuole and it is stored
44:19
during nighttime therefore the intracellular acidity increases that is why this phase is called as acidification phase during daytime in
44:31
order to avoid water loss by transpiration, this plants closes its stomata and malic acid is stored in the vacuole and that malic acid is taken out
44:45
and that is decarboxylated to release carbon dioxide. This carbon dioxide runs
44:50
the Calvin cycle, it enters the chloroplast and runs the Calvin cycle and
44:56
this malate is decarboxylated to pyruvate and that is recycled back. So the
45:04
advantage of this pathway is even without opening the stomata during daytime
45:12
Calvin cycle can run using the carbon dioxide that is produced by the
45:20
decarboxylation of malic acid that is stored in the vacuum during night time
45:26
So the point in CAM cycle is that initial carbon dioxide fixation occurs
45:31
during night and Calvin cycle occurs during daytime and both these are
45:38
separated in time and both reactions occurs in mesophyll cells. Here the first
45:44
stable compound just like C4 cycle, here also it is oxyloacetic acid and this
45:50
pathway ensures minimum photorespiration and prevents water loss by transpiration that allows such plants to survive in desert condition. Now why C3
46:03
C4 and CAM pathway? The first and the most important point is all plants makes
46:09
glucose by C3 cycle or Calvin cycle. Calvin cycle as we know it is a cycle
46:16
that is involved in the synthesis of glucose from carbon dioxide with the use
46:20
of ATP and NADPH that is synthesized during light reaction of photosynthesis
46:25
and that is the cycle that is universal to plants for the synthesis of glucose
46:30
whereas there is C4 cycle which is also an adaptation to surviving dry habitats
46:35
that minimizes the wastage of energy by photorespiration thus increases the photosynthetic efficiency of the plants. Then the third pathway is a CAM pathway
46:47
which is called as crecelation acid metabolism cycle as this pathway was
46:51
first observed in the members of family Cressulaceae, it's an adaptation to live
46:57
in desert condition that ensures minimum water loss by transpiration. Now examples
47:03
of camp plants. Examples include pineapple, acabe, cacti, orchid all are examples. Plants that are adapted to live in hot dry desert environment
47:16
approximately 8% of all land plants are camp plants, majority are succulents. The
47:23
advantage of camp plants is photorespiration is very much minimized or suppressed and transpiration rate is very much reduced as stomata opens only
47:33
at nighttime. Hope you understand the concept. Thank you so much for your
47:40
support. You are with biologicsums4u.com
#Biological Sciences
#Ecology & Environment
#Science