Photosynthesis Notes

A crucial endothermic reaction for all life

Prior Knowledge: 1. How do plants obtain food?2. What is an endothermic reaction?3. Why is photosynthesis an endothermic reaction?

Remember: Endothermic Reactions

● it takes more energy to break bonds in the reactants than is released

when new bonds form in the products.

● The word "endothermic" literally means "taking in heat."

● A constant input of energy, often in the form of heat/light, is needed in an

endothermic reaction.

● In many endothermic reactions, heat is absorbed from the surroundings.

As a result, the temperature drops.

● The general equation for an endothermic reaction is:

Reactants+Energy→Products

How does this relate to

Photosynthesis?Explain in your own words what goes into and what comes out of photosynthesis

Explain in your own words why this process is endothermic.

Photosynthesis in the most basic definition...

The Endother

mic Reaction

Photosynthesis is a CHEMICAL REACTION

6CO2 + 6H2O + light → C6H12O6 + 6O2

REACTANTS PRODUCTS

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.

The carbon dioxide and water molecules are being broken up and rearranged into glucose!

More than just Water, Carbon Dioxide and

Light are needed!

Plants need Chloroplast

Chloroplast are the location of photosynthesis.

Two important parts:-stroma: open space-stacks (granum) of thylakoids

Each chloroplast also contains the pigment cholorphyll.

What is Chlorophyll and

Why is it importan

t?The purpose of chlorophyll is to absorb light

energy.

Why are plants green...sometime

s?

...a side note

Write this in your own words when your teacher is done explaining

Have you ever noticed that the leaves on trees turn different colors

in the fall?

Why does this happen?

Plant cells contain pigments.

During the spring and summer, the most common pigment is

chlorophyll.

Chlorophyll does not absorb green light.

That’s why plants appear to be green.

Sunlight decreases during the fall and winter.

It requires energy for plant cells to make chlorophyll.

And, it is less useful when there is little sunlight.

So, plants stop making chlorophyll during the fall and winter.

When plants stop making chlorophyll, you see the other

pigments in their leaves.

During spring and summer, plants use their chlorophyll to make

glucose.

There are two reactions in photosynthesis:

the light-dependent reactions

the light-independent reactions

and

What happens during the light-dependent reactions?

Sunlight is necessary, so these happen during the day.

This step occurs in the the chloroplast, specifically in the thylakoid membrane

What happens during the light-dependent reactions occur?

Two Important Things:

1.Sunlight energy splits water to form oxygen and 2 hydrogens.

2. Sunlight energy makes ADP into ATP.

What happens during the light-dependent reactions occur?

1.Sunlight energy splits water to form oxygen and 2 hydrogens.

H2O → 2H + O

These hydrogen are carried to the next step and are used later and

oxygen is released as waste!

The hydrogen is transferred to “carrier molecules” called NADP+

NADP+ turns into NADPH when “carrying” a hydrogen

NADPH (Hydrogen Carrier)

• NADPH is found in light dependent and independent reactions.

• Light dependent turns NADP+ into NADPH with oxygen

• The Calvin cycle (light independent reaction)

uses NADPH to form energy sugars.

The hydrogen carriers provide energy (and hydrogen!) to make

glucose

What happens during the light-dependent reactions occur?

2. Sunlight energy mades ADP into ATP

ATP IS CHEMICAL ENERGY

ATP and NADPH provide the energy that is needed to make the

bonds in glucose!

Sunlight is needed to complete the light dependent reactions.

The light-independent reactions can take place with or without

light.

What happens in the light independent reaction?

Overall:

Energy from the hydrogen carriers (NADPH)and the ATP made in the light-dependent reactions are used in combination with CO2 to make glucose

Where does the carbon and oxygen in glucose come from?

Carbon dioxide!

The light independent reaction takes place in the chloroplast,

specifically, in the “stroma”

Let’s review!

The chemical equation for photosynthesis is:

6CO2 + 6H2O → C6H12O6 + 6O2

Glucose will be used by the plant cells to make ATP (energy)

This process is called Cell Respiration

Glucose in plants is also used as energy in the form of food for other organisms

Photosynthesis “Boxes”Putting it all togetherSunlight

Light Dependent reactions

-Energy from light breaks up water into 2H and O and create ATP

H20

02

-H bonds to the hydrogen carrier (NADP+) to be used later to become a part of glucose

Light independent reactions

-Known as the Calvin Cycle

-Uses the H of NADPH and the ATP to break down CO2 and create C6H1206

ATP and NADPH

C6H1206

C02

-Recycles ADP and NADP+ as waste products to be used again

ADP and NADP+

CHECK FOR UNDERSTANDING

1. Where do plants obtain the reactants that they need for photosynthesis?

CHECK FOR UNDERSTANDING

1. Where do plants obtain the reactants that they need for photosynthesis?

(Water from the soil, CO2 from the atmosphere, light energy from the sun)

2. What do plants produce that we need to survive?

CHECK FOR UNDERSTANDING

1. Where do plants obtain the reactants that they need for photosynthesis?

(Water from the soil, CO2 from the atmosphere, light energy from the sun)

2. What do plants produce that we need to survive?

(Oxygen gas and glucose)

3. What is the purpose of ATP?

CHECK FOR UNDERSTANDING

1. Where do plants obtain the reactants that they need for photosynthesis?

Water from the soil, CO2 from the atmosphere, light energy from the sun

2. What do plants produce that we need to survive?

Oxygen gas and glucose

3. What is the purpose of ATP?

It is a form of chemical energy that can be required for many of our cells chemical reactions.