Photosynthesis:Life from Light and Air

Energy needs of life All life needs a constant input of energy

Animals = Heterotrophs get their energy from “eating others”

eat food = other organisms = organic molecules

make energy through respiration Plants = Autotrophs

get their energy from “self”get their energy from sunlightbuild organic molecules (food) from CO2

make energy through photosynthesis

Photosynthesis

This is the equation you are used to seeing, but this is not the whole story…

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2light

energy+ ++

What is the main chemical fuel that most living organisms use to store energy?

ATP – adenosine triphosphate

What does an ATP molecule

consist of?Adenine, ribose, and three phosphate groups

What do the lines between the parts of the molecule represent?

Chemical bonds

ATP

WHAT IS THE ROLE OF ATP IN CELLULAR ACTIVITIES?

The characteristics of ATP make it an exceptionally useful molecule that is used by all types of cells as their basic energy source

Even though ATP is very efficient at transferring energy, it is not very good for storing energy over the long term.

Living organisms store large amounts of energy in the form of glucose (90 times more energy than ATP)

Cells can break apart glucose and make ATP molecules very easily to release the energy slowly

How do plants live? Photosynthesis

Energy building reactions collect sun energy make ATP

Sugar building reactions use ATP for energy use CO2 as carbon for new sugars

build sugars glucose, cellulose, starch

build all other organic molecules proteins, lipids, carbohydrates, DNA

store energy for future use starch in seeds & roots

Photosynthesis Actually 2 separate reactions

Energy building use sunlight make energy (ATP)

Sugar building use ATP use CO2

make sugars (C6H12O6)

Energybuilding reactions

Sugarbuilding reactions

sun

ATPADP

CO2sugar

CO2

Chloroplasts

Chloroplasts

LeafLeaf

Chloroplast

absorbsunlight & CO2

makeenergy & sugar

Chloroplastscontain

Chlorophyll

Energy Building Reactions

O2

H2O

Energy BuildingReactions

sunlight

ATP

H2O ATP O2light

energy ++

makes ATP energy releases oxygen

as a waste product

Sugar Building Reactions

sugarsC6H12O6

CO2

SugarBuilding

Reactions

ATP

CO2 C6H12O6 ADPATP ++

ADP

builds sugars uses ATP cycles ADP

back to make more ATP

Putting it all together

sugarsC6H12O6

CO2

ATP

ADP

H2O

O2

sunlight

CO2 H2O C6H12O6 O2light

energy + ++

SugarBuilding

Reactions

Energy Building

Reactions

Plants make both: ATP sugars

WHAT IS THE ROLE OF CHLOROPHYLL IN PHOTOSYNTHESIS?

In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll, a molecule in chloroplasts

Sunlight, which your eyes perceive as “white” light, is actually a mixture of different wavelengths of light of various colors

Any compound that absorbs light also absorbs energy from that light. When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons make photosynthesis work

HOW WELL WOULD A PLANT GROW UNDER PURE

YELLOW LIGHT?The plant would not grow well because neither chlorophyll a

nor b absorbs much light in the yellow region of visible light

8-3 THE REACTIONS OF PHOTOSYNTHESIS

Take a look at the picture of a chloroplast on page 208

Photosynthesis is broken down into two reactions light-dependent reactions- occur in

thylakoid membrane light-independent reactions (Calvin

Cycle) – occur in the stroma

WHAT HAPPENS IN THE LIGHT-DEPENDENT REACTIONS?

The light-dependent reactions produce oxygen gas and convert ADP and NADH+ into the energy carriers ATP and NADPH

NADP+ - a carrier molecule that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule; NADP+ converts to NADPH when it accepts electrons

WHAT IS THE CALVIN CYCLE?

The Calvin Cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars

Factors that can affect photosynthesis

water temperature intensity of light

Bring In CO2

H2O light

Let Out O2

Move Around sugars

So what does a plant need?

6CO2 6H2O C6H12O6 6O2light

energy + ++

roots

shoot

leaves

Leaf Structure

H2O CO2

CO2

O2 H2O

phloem (sugar)xylem (water)

stomate guardcell

palisadeslayer

spongylayer

cuticleepidermis

gases in & out water out

transpiration O2

Stomates Function of stomates

CO2 in

O2 out

H2O out

guard cell

stomate

Xylemcarry water up from roots

Phloem: food-conducting cells

carry sugars around the plant wherever they are needed new leavesfruitseeds

Putting it all together Making a living…

sunlight leaves = solar collectors photosynthesis

gases: CO2 in & O2 out stomates = gases in & out

H2O roots take in water from soil pulled up by leaf evaporation

nutrients roots take in from soil

How are they connected?

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O2 6CO2 6H2O ATP+ + +

Respiration

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2light

energy + ++

Photosynthesis

H2O

Energy cycle

Photosynthesis

Cellular Respiration

sun

The Great Circleof Life!

Where’s Mufasa?

glucose O2CO2

plants

animals, plants

ATP

The poetic perspective All of the solid material of every plant

was built out of thin air All of the solid material of every animal

was built from plant material

Then all the cats, dogs, mice, people & elephants…

are really strands of air woven together by sunlight!

sunair

Any Questions??