Photosynthesis

Synthesizing food

from light

7.5A recognize that radiant energy from the Sun is transformed

into chemical energy through the process of photosynthesis

Consider a Hamburger…..

It contains meat that was once a part of a

cow. Where did the cow get the energy to

make the muscle that became meat? A

cow must take in food, such as plants,

that already contain chemical energy. So

where do plants get this energy?

The sun – through the

process of

photosynthesis!

Let’s go over a few terms

Energy – is the ability to do work

Forms of energy – potential and kinetic

Tell me what you know about potential

and kinetic energy

Kinetic and Potential Energy

Potential Energy is stored

energy.

Kinetic Energy is the energy

of motion.

Stored energy due to an object's

position or chemical composition

Potential Energy

Kinetic Energy

Energy in motion.

Energy changes -

As energy travels through the universe, it

changes from one type or form to

another.

This is known as “energy transformation”

Lets take a look at the types.

En

erg

y T

ra

nsfo

rm

atio

n Energy Transformation is: The

change of energy from one form to

another.

Example:

Types of energy we will

focus on:

Of all of the forms or types of energy that

exist, we will focus on just three:

Chemical energy, mechanical energy and

light (radiant) energy

Chemical Energy

Energy STORED in matter because of its

CHEMICAL bonds. It is released during

a chemical reaction.

Examples:

Battery

Digestion

Burning Wood/Fuel

Chemical Energy

Chemical Energy is required to bond

atoms together.

And when bonds are broken, energy

is released.

Chemical Energy

Fuel and food

are forms of

stored chemical

energy.

Mechanical Energy

Energy that an object has because of its

movement or position.

Examples:

Moving Cars

Waterfalls

Running

Sound

Radiant or light Energy

• Type of energy from the sun. Energy

carried by ELECTROMAGNETIC

RADIATION.

• Radiant=LIGHT (but it

Isn’t always visible)

• Examples:

– Visible Light/Sunlight (What you see)

– X-Rays (invisible)

– Microwaves (invisible)

– UV Light (invisible)

Law of Conservation of

Energy

The law states: Energy cannot be created nor

destroyed.

What does this mean? It means that energy

can only change its form from one type to

another.

The energy of the world is a constant because

the total amount of the energy does not

change.

Law of Conservation of

Energy

For example: Let’s look at a flashlight. It runs on

batteries. The battery has chemical energy.

When the flashlight is turned on, the chemical

energy is first transformed into electrical energy

and then into light energy.

Law of Conservation of

Energy

Another example: Sunlight absorbed by plants.

This radiant or light energy is converted into

food (chemical energy) by the plant going

through photosynthesis.

Photosynthesis

The process through which

plants make their own food

through a chemical change.

‘photo’ = LIGHT ‘synthesis’ = BUILD

Photosynthesis means building with Light

What are chemical changes

and chemical reactions?

Chemical change is when you start with

one molecule and turn it into another.

Chemical reaction is: when two or more

molecules interact and the molecules

change. Bonds between atoms are

broken and created to form new

molecules.

Chemical reaction ex:

The Chemical change

A chemical reaction takes place in

plants in which light energy is

converted to chemical energy in the

form of food

Food = Carbohydrates are used by

all living things as fuel for energy.

• It is the means by which the energy in sunlight

becomes usable to living things.

So…Where does

photosynthesis occur?

Photosynthesis occurs in the

leaves of a plant.

Inside the leaf – lots of cells!

Parts of a plant cell

Chloroplast –

Mitochondria –

Stomata -

Close up of plant cell:

The chloroplast – the chloroplast has

chlorophyll in it (the chemical that makes

plants green). Chlorophyll allows the plant

to absorb radiant energy or sunlight.

Close up of plant cell:

The mitochondria – the organelle that

generates (make) the energy in the cell

Close up of plant cell:

The stomata – this is the cell part that

releases the waste oxygen and takes in

carbon dioxide.

All of these

parts work

together to

capture

sunlight and

to convert

this radiant

energy into

chemical

energy or

glucose

(sugar).

The Chemical Reaction Explained

(what happens at the molecular level):

Sunlight provides the energy needed by

chlorophyll to change molecules of

carbon dioxide and water into glucose.

Oxygen is released in this reaction.

What do all of these letters and numbers mean?

Elemental or atomic

symbol reminder!

If you don’t know what these symbols

are, you need to spend some time

studying the periodic table!

C =

O =

H =

These elements constantly recombine to

form molecules.

Carbon

Oxygen

Hydrogen

“Reading” a chemical

molecule:

Let’s take a closer

look…

Make a small T chart:

Reactants Products

Some simple steps to

understand chemical formula

terms

Reactants – what

goes in to the

chemical reaction

(the first part)

Products – what is

made after the

chemical reaction

occurs (the

second part)

Reactants Products

C6H12O6 + 6O2

From

the air

Water

taken up

by roots

Energy

(sunlight)

Glucose

Energy

Fuel

Oxygen

Radiant

Energy

6CO2 + 6H2O

six molecules of carbon dioxide plus six

molecules of water produce one molecule of

sugar plus six molecules of oxygen

Write the formula down!

Note how each of the raw

materials (reactants) end up in

the chloroplasts so that the

whole photosynthesis process

can happen.

Pay attention to what

happens to the products

of photosynthesis.

What about oxygen?

If you noticed before, oxygen is released

as a product that is NOT used by the

plant.

This is known as a “by-product or waste”

Who does use oxygen?

Earth Guide

What do plants do with

the energy?

As a result of

photosynthesis, plants

meet their immediate

need for energy—to

grow, develop, respond,

and reproduce.

The food not used right

away is stored by plants

in their roots, stems,

leaves, fruit, or flowers

The glucose is very useful for the plant

glucose

Can be used in respiration to release energy

can be joined together to make starch for storage

Can be converted into fats and oils for the seeds

Can be joined together to make cellulose for the cell walls

Can be combined with nutrients from the soil to make proteins for the new growth

Can be converted to fructose for the fruit

The Importance of Plants

Photosynthesis in plants and a few bacteria is responsible for feeding nearly all life on Earth.

It does this by taking energy from the sun and converting it into a storable form, usually glucose, which plants use for their own life processes.

Animals that consume plants also make use of this energy, as do those that consume those that consume plants, and so on to the top of the food chain.

Our Part

As important a job as

making all of the world's

food is, there's another vital function that

photosynthesis performs:

It generates the oxygen that oxygen-

breathing animals need to survive. But

here we animals repay the favor. We

exhale the carbon dioxide that plants

need for photosynthesis.

Respiration (not the

breathing kind)

Cellular respiration is the process in

which nutrients are converted in useful

energy in the cell.

This “useful energy” is known as sugar.

Different organisms make different types

of sugars

Some examples are glucose and fructose

Cellular Respiration

Animals like us need energy which is obtained

from sugars.

This process of obtaining energy from sugar is

known as respiration. Respiration occurs in

the mitochondria of cells.

So now that the plant has made the sugar

energy, it needs to use it. But how does it

do this?

Photosynthesis and Respiration

are reverse operations!

Photosynthesis: making the energy

Respiration: using the energy

Photosynthesis RespirationFood is formed (made) Food broken down (used)

Energy from the sun stored in glucose

Energy stored in organic moleculesis released

Carbon dioxide taken in Carbon dioxide given off

Oxygen given off Oxygen taken in

Goes on only in light Goes on day and night

Occurs in presence of chlorophyll Occurs in all living cells

Comparison

Illuminating

Photosynthesis

Nova - Photosynthesis

Illuminating Photosynthesis

Photosynthesis – Water Plant

BrainPop Photosynthesis

Photosynthesis Song

Photosynthesis Song with lyrics