Photosynthesis-Summary Irish Leaving Cert-Only-(Ireland) Leaving Cert Biology Photosynthesis

Summary

This video provides a concise summary of photosynthesis, focusing on key concepts for students revising for the Irish Leaving Cert. It explains how plants use light energy to convert carbon dioxide and water into glucose and oxygen. The video outlines the two main stages of photosynthesis: the light-dependent reactions, which occur in the chloroplast's thylakoid membranes, and the Calvin cycle, which occurs in the stroma. The importance of ATP and NADPH in this process is highlighted, along with the role of chlorophyll and photosystems. The video also covers leaf adaptations for efficient photosynthesis.

Takeaways

• 🌿 Photosynthesis is the process by which green plants make their own food using light energy.
• 🔬 NADPH and ATP are essential molecules for understanding photosynthesis.
• 🌱 Plants are autotrophs, meaning they can produce their own food, and are the producers at the base of the food pyramid in ecology.
• 🔆 Photosynthesis requires four factors: carbon dioxide, water, chlorophyll, and light.
• 🌳 The process mostly occurs in the leaves of plants, which are well adapted for photosynthesis.
• 🍃 Leaves are thin and flat to allow for rapid diffusion of gases and increased surface area for sunlight absorption.
• 🌿 Chlorophyll pigments are found in the thylakoid membranes of chloroplasts where photosynthesis takes place.
• 🔵 Chlorophyll absorbs light energy across the spectrum except for green and yellow, which are reflected.
• 🔄 There are two pathways in the light-dependent stage of photosynthesis: cyclic and non-cyclic.
• 💧 Photolysis of water occurs in the non-cyclic pathway, producing electrons, protons, and oxygen.
• 🔋 The light-independent stage, or Calvin cycle, uses ATP and NADPH to convert carbon dioxide into glucose.

Q & A

What is photosynthesis?

Photosynthesis is the process by which green plants make their own food using light energy.

Why are plants called autotrophs?

Plants are called autotrophs because they are capable of making their own food, which is a characteristic of photosynthesis.

What are the four factors necessary for photosynthesis?

The four factors necessary for photosynthesis are carbon dioxide, water, chlorophyll, and light.

What happens if any of the four factors for photosynthesis are missing?

If any one of the four factors is missing, photosynthesis will not occur.

Where does photosynthesis primarily take place in plants?

Photosynthesis primarily takes place in the leaves of plants.

Why are leaves well adapted for photosynthesis?

Leaves are thin and flat, allowing for rapid diffusion of gases and increased surface area for absorbing sunlight.

What is the role of the chloroplast in photosynthesis?

The chloroplast is the site of photosynthesis within plant cells, containing structures called thylakoids where chlorophyll pigments are located.

What are the two types of photosystems mentioned in the script?

The two types of photosystems mentioned are photosystem II and photosystem I.

What is the light-dependent stage of photosynthesis?

The light-dependent stage of photosynthesis involves the absorption of light energy by pigments and the production of ATP and NADPH.

What is the light-independent stage of photosynthesis?

The light-independent stage, also known as the Calvin cycle, uses the products ATP and NADPH from the light stage to convert carbon dioxide into glucose.

What is the role of NADPH in the Calvin cycle?

NADPH carries electrons and protons to the Calvin cycle, where they combine with carbon dioxide to produce glucose.

What is the end product of the light stage of photosynthesis?

The end products of the light stage are ATP, NADPH, and oxygen, with the latter being a result of photolysis of water.

Outlines

00:00

🌿 Photosynthesis Overview

This paragraph introduces the topic of photosynthesis, specifically tailored for the Irish Leaving Cert boundary course. It emphasizes the importance of understanding NADPH and ATP for grasping photosynthesis. Photosynthesis is described as the process by which green plants, known as autotrophs, produce their own food using light energy. The paragraph outlines the four essential factors for photosynthesis: carbon dioxide, water, chlorophyll, and light. It also presents the chemical equation for photosynthesis and explains how these elements come together in the leaves, which are adapted for rapid gas exchange and light absorption. The focus then shifts to the chloroplast, the site of photosynthesis, and the structure of the thylakoids and grana where chlorophyll is located.

05:00

🔬 The Light-Dependent Reactions of Photosynthesis

This section delves into the light-dependent stage of photosynthesis, which occurs in the thylakoid membranes of the chloroplast. It explains the role of pigments, particularly chlorophyll, in absorbing light energy across the spectrum, with the exception of green and yellow light, which are reflected. The paragraph describes two pathways within this stage: the cyclic pathway, involving only photosystem one, and the non-cyclic pathway, which involves both photosystems one and two. The cyclic pathway results in the formation of ATP, while the non-cyclic pathway leads to the production of ATP and NADPH, as well as oxygen through the photolysis of water. The paragraph also discusses the role of electrons in these processes and how they move through the electron transport chain.

10:01

🌱 The Light-Independent Reactions: Calvin Cycle

The final paragraph covers the light-independent stage of photosynthesis, also known as the Calvin cycle or dark reactions. It takes place in the stroma of the chloroplast and utilizes the products of the light-dependent stage, ATP and NADPH, to fix carbon dioxide into glucose. The paragraph explains how NADPH delivers electrons and protons to combine with carbon dioxide, facilitated by enzymes in the stroma. The breakdown of ATP provides the energy for these reactions, and the cycle is completed as ADP and phosphate are recycled back to the light-dependent stage to regenerate ATP. The summary concludes with a recap of the entire photosynthesis process, highlighting the interdependence of the light and dark stages and the importance of the chloroplast as the organelle where these reactions occur.

Keywords

💡Photosynthesis

Photosynthesis is the biological process by which green plants use light energy to convert carbon dioxide and water into glucose and oxygen. It is fundamental to the survival of plants as it allows them to produce their own food, classifying them as autotrophs. This process is described in detail in the video, emphasizing its role in sustaining life on Earth by placing plants at the bottom of the food pyramid.

💡Chloroplast

Chloroplasts are organelles within plant cells where photosynthesis takes place. They contain thylakoids, which house the pigment chlorophyll necessary for absorbing light energy. The video emphasizes that understanding the structure of chloroplasts, including the thylakoids and grana, is essential for understanding the mechanics of photosynthesis.

💡Thylakoid

Thylakoids are the membrane-bound structures found within chloroplasts, where the light-dependent reactions of photosynthesis occur. These structures contain pigments like chlorophyll, which capture light energy. In the video, thylakoids are shown to be integral to photosystems and the electron transport chain, which are key to producing ATP and NADPH.

💡ATP (Adenosine Triphosphate)

ATP is the energy currency of the cell, generated during the light-dependent stage of photosynthesis. The video explains that ATP is produced when energized electrons pass through the electron transport chain, and it provides the energy needed for the Calvin cycle to synthesize glucose in the light-independent stage.

💡NADPH

NADPH is an electron carrier molecule produced in the light-dependent reactions of photosynthesis. It carries high-energy electrons and protons to the Calvin cycle (dark stage) where they are used to convert carbon dioxide into glucose. The video highlights NADPH as a critical product of the non-cyclic pathway that drives the synthesis of carbohydrates.

💡Light-dependent reactions

These reactions occur in the thylakoid membranes of the chloroplasts and are powered by light. The video discusses two main pathways—cyclic and non-cyclic—where ATP and NADPH are produced, and oxygen is released through the photolysis of water. These reactions are essential for providing the energy and electron carriers needed for the Calvin cycle.

💡Calvin cycle (Dark stage)

The Calvin cycle, also known as the light-independent stage, occurs in the stroma of the chloroplasts and uses ATP and NADPH from the light-dependent reactions to convert carbon dioxide into glucose. The video emphasizes that while this stage doesn't require light, it depends on the products of the light stage, making it crucial for synthesizing the carbohydrate glucose.

💡Chlorophyll

Chlorophyll is the green pigment located in the thylakoid membranes of chloroplasts that absorbs light energy during photosynthesis. It plays a central role in the light-dependent reactions, especially in capturing light and transferring its energy to electrons. The video mentions chlorophyll in the context of photosystems and how it drives the excitation of electrons.

💡Photolysis

Photolysis is the process of using light energy to split water molecules into oxygen, protons, and electrons. This occurs during the non-cyclic pathway of the light-dependent reactions. The video explains that photolysis replenishes the electrons lost by chlorophyll in Photosystem II and contributes oxygen to the atmosphere.

💡Photosystem

Photosystems are complexes of chlorophyll molecules and other pigments in the thylakoid membrane that absorb light energy during photosynthesis. The video explains the function of Photosystem I and Photosystem II, describing how they work to excite electrons and drive the production of ATP and NADPH in the light-dependent reactions.

Highlights

Photosynthesis is the process by which green plants make their own food using light energy, which is why they are considered autotrophs.

The four factors necessary for photosynthesis are carbon dioxide, water, chlorophyll, and light.

The key equation for photosynthesis is: Carbon dioxide + Water + Light Energy → Glucose + Oxygen.

Photosynthesis mainly occurs in the leaves of plants because of their thin, flat structure, which allows for efficient gas exchange and increased surface area for light absorption.

The chloroplast is the site of photosynthesis, and inside it, the thylakoids and grana are responsible for light absorption.

Pigments like chlorophyll absorb different wavelengths of light, with chlorophyll absorbing most colors except green and yellow.

The light-dependent stage of photosynthesis occurs in the thylakoid membranes and involves two pathways: cyclic (pathway 1) and non-cyclic (pathway 2).

Pathway 1, the cyclic pathway, involves only Photosystem 1 and results in the production of ATP through electron transport.

Pathway 2, the non-cyclic pathway, involves Photosystem 2 and Photosystem 1 and produces ATP, NADPH, and oxygen through the photolysis of water.

Photolysis of water is essential in the non-cyclic pathway as it replaces the electrons lost in Photosystem 2 and produces oxygen as a byproduct.

The light-independent stage, or the Calvin Cycle, occurs in the stroma of the chloroplast and does not require light, but it needs ATP and NADPH produced in the light-dependent stage.

During the Calvin Cycle, carbon dioxide combines with electrons and protons carried by NADPH to produce glucose.

The breakdown of ATP during the Calvin Cycle provides the necessary energy for the synthesis of glucose.

The products of photosynthesis are crucial: glucose is used as an energy source, while oxygen is released into the atmosphere or used for plant respiration.

The light-dependent stage produces ATP and NADPH, while the Calvin Cycle uses these to convert carbon dioxide into glucose.

Transcripts

this is a summary video on

photosynthesis it's geared towards the

Irish Leaving Cert boundary course it's

made to help my class revise so please

be aware that it is a very much

summarized version of this topic so just

a little piece of advice generally if

you don't know about NADPH and ATP those

two molecules you will find

photosynthesis extremely difficult go

back and revise them first

photosynthesis is the process by which

green plants could make their own food

using light energy and it's one of the

reasons why we refer to plants as being

autotrophs their ultra trophic capable

of making their own food and it's also

the reason why plants are always found

at the bottom of the food pyramids in

ecology they are the producers so one of

the other things you have to know about

photosynthesis is that it's a biological

process where light energy is converted

to chemical energy by the plant there

are four factors necessary for

photosynthesis carbon dioxide water

chlorophyll and light and if any one of

these four factors is missing well then

photosynthesis simply will not happen

this is the equation that you need to

know for your exams

it describes what's going on in the

process of photosynthesis and it helps

you understand what's happening carbon

dioxide diffuses into the stomata of the

leaves water enters the roots by osmosis

and goes upwards to the leaves light

gets trapped by chlorophyll in the

chloroplast

of those plant cells and at the end of

the process glucose is produced and so

too is oxygen the process mostly happens

in the leaves of plants and the reason

for this is because the leaves are so

well adapted for photosynthesis how well

firstly the leaves are thin flat lamina

being very thin is good because it

allows for the rapid diffusion of carbon

dioxide into those cells and the rapid

diffusion of oxygen out of the leaf and

being flat means that it's very good

because it increases the surface area

for absorbing all of that sunlight so

that's just some of the adaptations of

the leaf but be aware that there is a

separate video and you have to know the

internal structure of the leaf very well

so I would watch that later on so let's

go into the specifics of what happens in

photosynthesis and the trick to this is

knowing the structure of the chloroplast

really well plant cells you know have

the

structures known as clear applause and

this is where photosynthesis takes place

inside the chloroplast you see these

green dislike structures flat structures

and they're called Tyler codes they're

usually stacked in two groups or bundles

known as a Granum and when you have a

few Granum it's referred to as grana so

it's inside these thylakoids are these

grana that you find the chlorophyll

pigment so chlorophyll and all the other

pigments are found in the membrane of

the thylakoid so you can see here this

is one single thylakoid and remember

that they're usually arranged in two

Granum photosynthesis is taking place in

the chloroplast and specifically we're

now looking at the membranes of the

thylakoids inside the chloroplast where

we find these substances known as

pigments these are capable of absorbing

different wavelengths of light energy

the most important is chlorophyll but

there is chlorophyll a and chlorophyll B

and many other types of pigments too

light is made up of a spectrum of seven

colors which represent different

wavelengths of light energy chlorophyll

the various types of chlorophyll are

very well suited to absorbing light

energy at either end of the spectrum so

they absorb most of the colors of white

light except for green and yellow which

are reflected to ensure that light is

harvested in a very efficient way the

pigment molecules are arranged into

these structures known as photo systems

in the thylakoid membranes photo systems

are basically the chlorophyll molecules

and the other pigments arranged next to

proteins and at the center of which is

this reaction center which contains

special chlorophyll molecules and an

electron acceptor that can accept the

electrons that are going to be excited

when they absorb all of that light

energy so there are two photosystems of

note there's photosystem ii and

photosystem one photosystem one was

discovered first and photosystem ii was

discovered second they're basically the

same except that their arrangement is

slightly different in that one can

absorb different wavelengths of energy

so the first part of photosynthesis is

the light dependent stage and there are

two pathways there is pathway one and

pathway two let's start with pathway one

it's known as the cyclic pathway and

it's happening in the thylakoid

membranes inside those chloroplasts and

it involves only photosystem one so

light energy gets absorbed by these

pigment

Jews that are arranged this photosystem

one the light energy is passed from

pigment molecule to pigment molecule

until it reaches a reaction center

chlorophyll

this results in electrons being

energized and are passed to an electron

acceptor molecule energized electrons

then get passed over an electron

transport chain losing a lot of their

excess energy and resulting in the

formation of ATP eventually those now

low energy electrons return back to

chlorophyll in photosystem one so now

let's go onto pathway 2 which is known

as the non cyclic pathway and you can

see from the diagram here that it

involves two photosystems photosystem 2

and photosystem one so pathway 2 begins

in much the same way as pathway 1 except

it begins with photosystem 2 where the

pigment molecules absorb their light

energy it gets passed from molecule to

molecule until it reaches the reaction

center chlorophyll here energized

electrons then are picked up by the

electron acceptor molecule and they are

eventually passed over an electron

transport chain where ATP is generated

the electrons continue on to photosystem

1 so you can see what has happened so

far in pathway to basically the

electrons have been energized they've

passed over an electron transport chain

generating a bit of ATP in the process

and now they've been passed into

photosystem 1 so we're halfway true

pathway to energized electrons have so

far left chlorophyll in photosystem 2

and gone to photosystem 1 so electrons

are now needed to replace those lost by

the chlorophyll in photosystem 2 so this

is when photolysis of water takes place

this is using light energy to split

water molecules and it's really done to

replace those electrons photolysis of

water produces three very important

products electrons protons and oxygen

the electrons go to replace those lost

by chlorophyll in photosystem two the

protons go into a proton pool and will

eventually be transported by NADPH to

the dark stage reactions or the Calvin

cycle and the oxygen either gets used

internally by the plant cell for

respiration but most of it gets released

to the atmosphere through the stomata so

let's recap energized electrons left

reaction Center chlorophyll in

photosystem 2 they were picked up by an

acceptor molecule and passed over an

electron transport chain

this resulted in the generation of ATP

they then made their way into

photosystem one which is now going to

absorb more light energy and results in

electrons being energized the electrons

are now going to be passed by that

acceptor molecule to a new molecule and

ADP and this is where they're trapped so

basically then you have this molecule

called nicotinamide adenine dinucleotide

phosphate and you have to know its full

name it's otherwise referred to as nadp+

it's going to combine or trap two

electrons and a proton those protons

from the proton pool remember and it's

going to form NADPH NADPH is a carrier

molecule it's going to carry those

electrons and that proton to the dark

stage of photosynthesis or the Calvin

cycle so the products of the non cyclic

pathway are ATP and NADPH the oxygen was

produced it was produced as a result of

photolysis of water so be very specific

so with the light stage completed we're

now on to the light independent stage

it's so called because it does not use

light or need light however it does need

the products that were formed in the

light stage that ATP and NADPH

so it's otherwise referred to as the

Calvin cycle or the dark stage reactions

the calvin cycle or the dark stage

reactions they take place in the stroma

of the chloroplast you can see here in

the diagram this contains many enzymes

and so all the factors that affect

enzyme controlled reactions such as

temperature and pH they can impact the

reactions of the calvin cycle also bear

in mind that the reactions of the light

stage that the light dependent reactions

these happen too quickly are too fast

and so are not enzyme controlled so

let's get back to the Calvin cycle

carbon dioxide which has diffused into

the stomata of the leaves is basically

going to combine with those electrons

and those protons that will be

transferred to the stroma by the

molecule NADPH once it transfers those

electrons and the proton it reverts back

to being nadp+ and it goes back to the

light dependent stage to do more work so

in the calvin cycle then carbon dioxide

combines with the electrons and the

protons to give glucose that

carbohydrate

and the reactions are all fueled by the

breakdown of ATP which was formed in the

light-dependent stage and you know that

when ATP breaks down it gives rise to

adp and a phosphate and that goes back

to the light-dependent stage to generate

some more ATP so this diagram is

excellent for helping you review just

what's gone on in photosynthesis so you

know that the whole process takes place

in these organelles known as

chloroplasts found in plant cells it

involves two types of reactions light

dependent reactions and light

independent reactions so the light stage

or the light dependent reactions happens

in the Granum or the grana the stacks of

thylakoids and it involves the photo

lysis of water so that's very unique to

the light stage important products such

as ATP and NADPH are formed as a result

of the light stage reactions are the

light dependent reactions and because of

photolysis of water oxygen is also

formed then the second stage of

photosynthesis is known as the calvin

cycle sometimes referred to as the dark

stage reactions it happens in the stroma

of the chloroplast so the liquid part of

the chloroplast and it involves the two

products made in the light dependent

stage ATP and NADPH

so NADPH is going to bring electrons and

protons which will then combine with the

carbon-dioxide to produce glucose and

all of their reactions are fueled by the

breakdown of ATP that was photosynthesis

I hope the video has helped in some way

with this topic because I know it's

tricky so the very best of look make

sure you go on and do pass papers now

and you go and use your textbook please

be aware that I do include a lot of

detail about photosystems they're not on

your course I just include them so that

if you want to go and look at other

videos such as kadek atom II which is

amazing and you'll be able to understand

them better if you know about

photosystems so best of luck and please

be aware that these videos are not

intended for commercial use and they're

not made for monetary gain good luck