PHOTOSYNTHESIS: CALVIN CYCLE || Grade 9 Science _ BIOLOGY

Summary

This educational video delves into the light-independent reaction of photosynthesis, known as the Calvin Cycle. It explains how plants convert carbon dioxide and water into glucose using ATP and NADPH from the light-dependent reaction. The Calvin Cycle, named after Nobel laureate Melvin Calvin, occurs in the chloroplast stroma and consists of three stages: carbon fixation, reduction, and regeneration. The video uses an interactive simulation to illustrate these stages, concluding with a summary of photosynthesis, emphasizing the conversion of light energy into chemical energy stored in glucose.

Takeaways

• 🌿 Photosynthesis is a process where plants make their own food using light energy, carbon dioxide, and water.
• 🔬 The process involves two stages: the light-dependent reaction and the light-independent reaction, also known as the Calvin cycle.
• 🏆 The Calvin cycle is named after Melvin Calvin, who won the 1961 Nobel Prize for his work on this set of chemical reactions.
• 🌱 The Calvin cycle occurs in the chloroplast stroma and is initiated after the light-dependent reaction, which provides ATP and NADPH.
• ➡️ The cycle has three stages: carbon fixation, reduction, and regeneration, each catalyzed by different enzymes.
• 🔄 Carbon fixation involves the combination of CO2 with RuBP (ribulose bisphosphate) to form an unstable 6-carbon compound, which then splits into two 3-PGA (3-phosphoglycerate) molecules.
• ⚡️ The reduction phase uses ATP and NADPH to convert 3-PGA into G3P (glyceraldehyde 3-phosphate), which involves the enzyme glyceraldehyde 3-phosphate dehydrogenase.
• 🔁 The regeneration stage involves using G3P to regenerate RuBP, allowing the cycle to continue, with energy from ATP.
• 🌱 For every six CO2 molecules that enter, two molecules of glucose are produced, and the rest are used to regenerate RuBP for the next cycle.
• 🔗 The Calvin cycle is crucial for converting inorganic carbon into organic compounds like glucose, which are essential for plant growth and energy storage.

Q & A

What is the meaning of the term 'photosynthesis'?

Photosynthesis means to put together by light, referring to the process where plants make their own food using light energy.

What are the raw materials needed for photosynthesis?

The raw materials needed for photosynthesis are carbon dioxide and water.

What are the products of the light-dependent reaction in photosynthesis?

The products of the light-dependent reaction are ATP, NADPH, and oxygen.

Who is the Calvin cycle named after and why?

The Calvin cycle is named after Melvin Calvin, who won the 1961 Nobel Prize for working out the complex set of chemical reactions involved in this cycle.

Where does the Calvin cycle occur in a plant cell?

The Calvin cycle occurs in the chloroplast stroma of plant cells, just after the light reaction of photosynthesis.

What are the three stages of the Calvin cycle?

The three stages of the Calvin cycle are carbon fixation, reduction, and regeneration.

What is the role of ATP and NADPH in the Calvin cycle?

ATP provides the energy for the Calvin cycle, and NADPH provides the reducing ability, both of which are supplied by the light-dependent reactions of photosynthesis.

How does carbon dioxide enter the Calvin cycle?

Carbon dioxide enters the Calvin cycle by diffusing into the stroma of the chloroplast and combining with RuBP (ribulose bisphosphate).

What is the enzyme that catalyzes the carbon fixation stage of the Calvin cycle?

The enzyme that catalyzes the carbon fixation stage of the Calvin cycle is RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase).

What is the role of G3P (glyceraldehyde 3-phosphate) in the Calvin cycle?

G3P is the final product of the Calvin cycle, with one molecule being used to form glucose and the others being recycled to regenerate RuBP for the continuation of the cycle.

How does the Calvin cycle regenerate RuBP?

The Calvin cycle regenerates RuBP by using five G3P molecules, which are converted back into RuBP using energy from ATP.

Outlines

00:00

🌿 Introduction to the Calvin Cycle

This paragraph introduces the Calvin cycle, also known as the light-independent reaction of photosynthesis. It explains that the Calvin cycle occurs in the chloroplast stroma and is named after Melvin Calvin, who won the 1961 Nobel Prize for his work on this process. The cycle is dependent on the ATP and NADPH produced during the light-dependent reaction of photosynthesis. The paragraph outlines the three stages of the Calvin cycle: carbon fixation, reduction, and regeneration. It describes the first stage, carbon fixation, where carbon dioxide enters the chloroplast and combines with RuBP (ribulose bisphosphate) to form an unstable six-carbon compound, which then splits into two three-carbon molecules of 3-phosphoglycerate. The enzyme Rubisco plays a crucial role in this phase.

05:02

🔬 The Calvin Cycle's Three Phases

The second paragraph delves deeper into the Calvin cycle's three phases. It begins with the reduction phase, where the three-carbon molecules from carbon fixation are converted into glyceraldehyde-3-phosphate (G3P) using ATP and NADPH from the light-dependent reaction. The paragraph explains the role of the enzyme glyceraldehyde-3-phosphate dehydrogenase and how NADPH acts as an electron donor. It then moves on to the regeneration phase, where five of the G3P molecules are used to regenerate RuBP, allowing the cycle to continue. The paragraph concludes with a summary of the Calvin cycle's function in converting carbon dioxide into glucose using the energy from ATP and NADPH, and it invites viewers to use an interactive simulation for a better understanding. It also provides a brief overview of photosynthesis, highlighting the light reaction's role in producing ATP and NADPH, and the Calvin cycle's role in synthesizing glucose.

Keywords

💡Photosynthesis

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll pigments. It involves the conversion of carbon dioxide and water into glucose and oxygen. In the video, photosynthesis is the central theme, with the script detailing how plants make their own food through this process, highlighting the importance of light energy and the role of chlorophyll.

💡Chlorophyll

Chlorophyll is the green pigment present in the chloroplasts of plants, which is essential for the absorption of light energy during photosynthesis. The script mentions that chlorophyll is where the light-dependent reaction of photosynthesis occurs, emphasizing its role in capturing light energy and facilitating the chemical reactions necessary for food production in plants.

💡Carbon Dioxide

Carbon dioxide (CO2) is a raw material used by plants during photosynthesis. The script explains that CO2 enters the plant through stomata and is combined with a five-carbon molecule to form an unstable six-carbon compound, which is a crucial step in the Calvin cycle. This highlights CO2's role as a key reactant in the process of glucose production.

💡Calvin Cycle

The Calvin Cycle, also known as the light-independent reaction, is the second stage of photosynthesis where carbon dioxide is fixed into an organic molecule. Named after Melvin Calvin, who won the Nobel Prize for elucidating this process, the Calvin Cycle is detailed in the script as a series of chemical reactions that occur in the stroma of chloroplasts, utilizing ATP and NADPH from the light-dependent reaction.

💡ATP

ATP, or adenosine triphosphate, is the primary energy currency of cells. In the context of the video, ATP is produced during the light-dependent reaction of photosynthesis and is then used in the Calvin Cycle to power the conversion of three-carbon compounds into glucose. The script emphasizes ATP's role as a source of energy that drives the synthesis of glucose from carbon dioxide.

💡NADPH

NADPH, or nicotinamide adenine dinucleotide phosphate, is a coenzyme that carries high-energy electrons. In the video script, NADPH is generated during the light-dependent reaction and acts as an electron donor in the Calvin Cycle, facilitating the reduction of three-carbon compounds. It is essential for the synthesis of glucose from carbon dioxide.

💡Carbon Fixation

Carbon fixation is the first stage of the Calvin Cycle, where CO2 is combined with a five-carbon sugar molecule (RuBP) to form an unstable six-carbon compound. The script describes this process as a critical step in the incorporation of atmospheric carbon into organic molecules within the plant, catalyzed by the enzyme RuBisCO.

💡Reduction Phase

The reduction phase is the second stage of the Calvin Cycle, where the three-carbon compounds (3-PGA) are converted into glyceraldehyde-3-phosphate (G3P) using the energy from ATP and electrons from NADPH. The script explains that this phase is essential for the production of usable energy-rich molecules within the plant, with NADPH acting as an electron donor.

💡Regulation

Regulation in the context of the Calvin Cycle refers to the final stage where some G3P molecules are used to regenerate RuBP, allowing the cycle to continue. The script mentions that this stage requires energy from ATP, indicating the cyclical nature of the Calvin Cycle and the importance of energy balance in sustaining the process of photosynthesis.

💡Rubisco

Rubisco, or ribulose-1,5-bisphosphate carboxylase/oxygenase, is the enzyme that catalyzes the first step of carbon fixation in the Calvin Cycle. The script describes Rubisco as the enzyme that combines CO2 with RuBP, forming the six-carbon compound that eventually splits into two three-carbon molecules. Rubisco is central to the process of carbon fixation and is the most abundant enzyme on Earth.

💡Glucose

Glucose is a simple sugar and a primary product of the Calvin Cycle. The script explains that some G3P molecules produced in the Calvin Cycle are used to form glucose, which is a crucial energy source for the plant and can be used to build other organic molecules. Glucose synthesis is a key outcome of the Calvin Cycle, highlighting the cycle's role in energy production and carbon assimilation.

Highlights

Photosynthesis is a life-dependent reaction that occurs inside leaves where plants make their own food.

The process of photosynthesis involves raw materials such as carbon dioxide and water.

The chemical equation for photosynthesis is carbon dioxide plus water equals glucose and oxygen using light energy.

Photosynthesis has two stages: the light-dependent reaction and the light-independent reaction (Calvin cycle).

The light-dependent reaction produces ATP, NADPH, and oxygen.

The Calvin cycle is named after Melvin Calvin, who won the 1961 Nobel Prize for his work on this process.

The Calvin cycle occurs in the chloroplast stroma and is aided by ATP and NADPH from the light reaction.

There are three stages in the Calvin cycle: carbon fixation, reduction, and regeneration.

Carbon dioxide fixation involves the combination of CO2 with RuBP (ribulose diphosphate) to form an unstable six-carbon compound.

The reduction phase uses ATP to convert phosphoglycerate into glyceraldehyde 3-phosphate (G3P) with NADPH acting as an electron donor.

In the regeneration stage, G3P molecules are used to regenerate RuBP, allowing the cycle to continue.

The Calvin cycle can produce glucose and other organic compounds from G3P.

The interactive simulation provided visualizes the three phases of the Calvin cycle: carbon fixation, reduction, and regeneration of RuBP.

Rubisco is the enzyme that catalyzes the carbon fixation stage of the Calvin cycle.

G3P is the final product of the Calvin cycle, with one molecule used for glucose and others for regenerating RuBP.

The light reaction converts light energy into chemical energy stored in ATP and NADPH, releasing oxygen as a byproduct.

The Calvin cycle combines carbon from CO2 with chemical energy to produce glucose.

The lesson concludes with a summary of photosynthesis, highlighting the roles of the light reaction and the Calvin cycle.

Transcripts

[Music]

good day Learners Welcome to our new

lesson in our previous lesson we talk

about photosynthesis specifically the

life dependent reaction it happens

inside the leaves where plants make

their own food through the process of

photosynthesis photosynthesis means to

put together by light so in the process

of photosynthesis they will need raw

materials such as carbon dioxide and

water now here are the chemical equation

for photosynthesis carbon dioxide plus

water putting together through light

energy inside the chlorophyll to form

glucose and oxygen now the overall

product of light dependent reaction ATP

nadph and oxygen again there are two

stages of photosynthesis the light

dependent reaction and the light

independent reaction we already

discussed the light dependent reaction

in our previous video and for this video

we're going to talk about the light

independent reaction or what we called

the Calvin cycle Calin cycled is named

after Melvin Calvin who won a 1961 Nobel

Prize for working out this complex set

of chemical reaction Calin cycle occurs

in the chloroplast troma just after

completing the light reaction of

photosynthesis the light reaction helps

Calin cycle by providing ATP which is

its source of energy and nadph for

reducing ability now there are three

stages of Calin cycle stage one is the

carbon fixation stage two the reduction

and stage three is the Regeneration now

let's start with stage one which is

carbon dioxide fixation carbon dioxide

enters through the stomata then diffuse

into the stroma of the chloroplast

carbon dioxide combined with rudp 5 or

ribulose diphosphate to form an unstable

six carbon or what we call the

rp6 in other books or reference rudp 5

is also called as five carbon molecule

ribulose biphosphate carbon dioxide

combined with rudp 5 to for form an

unstable six carbon dioxide or R udp6

rudp 5 is also known as carbon dioxide

acceptor now rp6 splits into two

molecules or phosphoglycerate or three

phosphoglyceric acid or three PGA now

this stage of Calvin cycle is catalyzed

by the enzymes rubisco now for stage two

the reduction phase using the energy

from ATP three PGA molecules are

converted into three carbon sugar or

glycer alide three phosphate or g3p or

phosphoglyceride or pigal this stage

involves the enzyme of glycer alide

three phosphate dehydrogenase in which

nadph from light reaction acts as a

donor or acts as electron donor now here

are the summary of the change of PGA to

pigal PGA plus ATP Plus nadph become

pigal plus nadp plus ADP nadp and ADP

are available again for conversion

during cyclic and noncyclic reaction now

for stage three which is the final stage

it starts with

g3p some g3p or pigal is utilized in

making glucose well others are recycled

to continue the cycle by combining with

a carbon acceptor or rp5 assuming that

there are six carbon dioxide enters the

reaction 12 pigal will be form 10 of

this will be enzymatically rearranged to

replace the loss of rudp 5 and only two

will become glucose now for us to better

understand the Calvin cycle let us use

the interactive simulation that I

presented to you last video so here

we're going to choose Calvin cycle as

you can see there are three phases for

Calvin cycle for phase one we have the

carbon fixation phase two the reduction

phase and phase three we have the

Regeneration of rubp or

rp5 now let's proceed with phase one

which is the carbon fixation so this is

the Risco or the enzyme used in this

phase the rubp or rp5 as you can see

there are five carbons rubp or rp5 is

also known as carbon dioxide acceptor

during this phase carbon dioxide is

attached to rubp through the use of the

enzymes rubisco then it will become rudp

6 R udp6 will split into two molecules

of phosphoglycerate or three

phosphoglyceric acid again during carbon

fixation carbon dioxide is attached to

RPI by the enzymes Risco this forms two

molecules of three phosphor lerate for

each carbon dioxide added next we have

phase two the reduction phase here we're

going to use the phosphoglycerate the

nadph and ATP from the light dependent

reaction using the energy from ATP

phosphoglycerate are converted into

three carbon sugar while nadph will act

as an electron donor so from

phosphoglycerate it will become glycer

alhy 3 phosphate or G3 3p so we already

have one molecule of g3p so let's repeat

the

process as you can see after the

conversion of

ATP it will reduce to ADP and nadph will

become NP plus and Pi now ADP nadp plus

and Pi will be available again for the

light reaction again during the

reduction phase each molecule of three

phosphoglycerate is reduced to form g3p

and this requires energy from ATP and

electrons from nadph g3p is the final

product of the Calvin cycle one molecule

of g3p will leave the Calvin cycle and

be used to form organic compounds like

glucose or sugar now for the last phase

which is the Regeneration of rubp or

rp5 the other five g3p molecules are

used to regenerate rubp so that Calvin

cycle can continue the reactions that

regenerate rubp require energy to occur

this energy comes from ATP so here we're

going to drag the three ATP molecules to

the reaction site as you can see the

rubp or rudp 5 is readily available

again to continue the cycle the Calvin

cycle can now start over again with the

carbon fixation now to summarize

photosynthesis let us explain this

diagram

for light reaction this stage uses water

and changes light energy from the Sun

into chemical energy stored in ATP and

nadph this stage also releases oxygen as

a waste product for Calvin cycle this

stage combines carbon from carbon

dioxide in the air and uses the chemical

energy in ATP and nadph to make glucose

so that's it see you in our next lesson

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