CHAPTER 8: PHOTOSYNTHESIS

AUTOTROPHS

Plants and some other types of organisms are able to use light energy from the sun to produce food.

Contain chlorophyll, a pigment that captures sunlight.

HETEROTROPHS

Organisms that cannot make their own food.

Cannot use sun’s energy directly.

ENERGY

Comes in many forms including light, heat, and electricity.

Can be changed from one form to another.

Can be stored in chemical compounds.

Candles release energy as HEAT & LIGHT

ATP – CELLULAR ENERGY

Adenosine triphosphate Contains two, high-energy phosphate

bonds Also contains the nitrogen base

adenine & a ribose sugar

ENERGY

Energy is stored in the bond between the 2nd and 3rd phosphates.

ADP

Adenosine Diphosphate ATP releases energy, a free phosphate, &

ADP when cells take energy from ATP

USING ENERGY IN ATP

ATP only provides energy for a few seconds. It is constantly being used and remade by

cells. Provides energy for all cell’s activities:

Active Transport Movement Photosynthesis Protein Synthesis Cellular Respiration Many more!

STORING AND RELEASING ENERGY

Adding A Phosphate Group To ADP stores Energy in ATP

Removing A Phosphate Group From ATP Releases Energy & forms ADP

Loose

Gain

GLUCOSE Glucose is a

monosaccharide C6H12O6

One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

PHOTOSYNTHESIS In words:

Involves the use Of light energy to convert Water (H20) and Carbon Dioxide (CO2) into Oxygen (O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches.

THE PHOTOSYNTHESIS EQUATION

6CO2 + 6 H2O + energy C6H12O6 +

6O2

Carbon Dioxide + Water + Sunlight Glucose + Oxygen

THE PHOTOSYNTHESIS EQUATION

PIGMENTS

• In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments

• Chlorophyll is the primary light-absorbing pigment in autotrophs

• Chlorophyll is found inside chloroplasts

LIGHT AND PIGMENTS Energy From The Sun

Enters Earth’s Biosphere As Photons

Photon = Light Energy Unit

Light Contains A Mixture Of Wavelengths

Different Wavelengths Have Different Colors

LIGHT AND PIGMENTS Different pigments absorb different

wavelengths of light Photons of light “excite” electrons in

the plant’s pigments Excited electrons carry the absorbed

energy The main pigments found in plants is

chlorophyll. Chlorophyll is found in

chloroplasts.

CHLOROPHYLLChlorophyll absorbs light well in the blue-violet

and red regions of the visible spectrum.

INSIDE A CHLOROPLAST Contain saclike photosynthetic membranes

called thylakoids. Thylakoids are arranged in stacks called

grana (singular: granum). Contain clusters of chlorophyll and other

pigments as well as proteins known as photosystems that capture sunlight energy.

Singlethylakoid

INSIDE A CHLOROPLAST Gel-like material surrounding the grana

= stroma.

ELECTRON CARRIERS When electrons in chlorophyll absorb

sunlight, the electrons gain A LOT of energy.

Chloroplasts use electron carriers to transfer these electrons from chlorophyll to other molecules.

NADP+

One electron carrier is NADP+.

It accepts and holds 2 high-energy electrons along with a hydrogen ion (H+).

LIGHT-DEPENDENT REACTIONS Part 1 of Photosynthesis Occurs across thylakoid membranes. Uses light energy. Produce oxygen from water. Convert ADP to ATP and NADP+ to

NADPH.

LIGHT-DEPENDENT REACTIONS

LIGHT-DEPENDENT REACTIONS SUMMARY Reactants

Water (H2O) Sunlight energy

Products ATP NADPH

THE CALVIN CYCLE Also known as:

Light-Independent Reactions

Occur in stroma Uses ATP and

NADPH from the Light-Dependent Reactions to form high-energy sugars.

THE CALVIN CYCLE Six CO2 molecules

enter the cycle. Bonds in the ATP

and NADPH molecules are broken to release the stored energy.

This energy is used to turn the CO2

molecules into a 6-carbon sugar (glucose).

CALVIN CYCLE SUMMARY Reactants

CO2

ATP

NADPH Products

C6H12O6 (high-energy sugar)

ADP NADP+

PHOTOSYNTHESIS SUMMARY

Reactants Products

•H2O•Sunlight

•ATP + O2

•NADPH

Reactants Products

•CO2 (from environment)•ATP•NADPH

•C6H12O6

• ADP•NADP+

Light-Dependent Reactions

Calvin Cycle/Light-Independent Reactions

PHOTOSYNTHESIS SUMMARY

FACTORS AFFECTING RATE OF PHOTOSYNTHESIS

Temperature Amount of

Water Light

availability