Photosynthesis

Comparing Photosynthesis & Respiration

Photosynthesis Cellular Respiration

Function Energy Storage Energy Release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

Equation 6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6 + 6O2 6CO2 + 6H2O

Mitochondrion and Chloroplast structure

Photosynthesis overview

• Process of storing energy in sugar molecules from the energy initially in the sun (radiant energy)

• 1st step: Capture radiant energy and use it to generate our “energy currency”

• 2nd step: Use “energy currency” to convert

CO2 to glucose• Oxygen is released as a byproduct• Happens in the chloroplast

WHWHY ARY ARE PE PLANLANTS GTS GREREEN?EN?

It has to do with sunlight!

Sunlight is a form of electromagnetic energy, which travels in waves.

Different wavelengths of visible light are seen by the human eye as different colors.

WHYWHY ARE ARE PLA PLANTS NTS GREGREEN?EN?

Gammarays

X-rays UV Infrared Micro-waves

Radiowaves

Visible light

Wavelength (nm)

Sunlight minus absorbed Sunlight minus absorbed wavelengths or colors wavelengths or colors equals the apparent color equals the apparent color of an object.of an object.

The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others.

Reflected light

• Chloroplasts contain several pigmentsChloroplast Pigments

Pigments are materials that absorb particular wavelengths of light and reflect others Chlorophyll a: absorbs mainly violet and red light the bestChlorophyll b: absorbs blue and orange light the bestCarotenoids: absorbs blue and green best

* When chlorophyll absorbs light, energy is transferred to electrons and “boosts” them to a higher state.

Figure 7.7

Different pigments absorb light differently

Photosystems:Clusters of pigments in thylakoid membrane

• Photosystem II

- Traps light energy and transfers the light-excited electrons to an electron transport chain.

- Those excited electrons are replaced by splitting a molecule of water, which releases oxygen.

- The electron transport chain releases energy, which is used to make ATP

• Photosystem I

- Produces NADPH by transferring excited electrons and hydrogen ions to NADP+.

Light Reactions Photosystem I and Photosystem II

• SUMMARY: In the light reactions, electron transport chains In the light reactions, electron transport chains generate ATP, NADPH, & Ogenerate ATP, NADPH, & O22

– Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons

– The excited electrons are passed from the primary electron acceptor to electron transport chains

– The light reactions convert light energy to the chemical energy of ATP and NADPH

The Light Dependent Reactions

• The production of ATP in photosynthesis

Thylakoidcompartment(high H+)

Thylakoidmembrane

Stroma(low H+)

Light

Antennamolecules

Light

ELECTRON TRANSPORT CHAIN

PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

Calvin Cycle

• Called a cycle because the starting material, RuBP, is regenerated.

• Uses carbon from carbon dioxide, the energy from ATP, and high energy electrons and hydrogen ions from NADPH to make a small sugar named G3P.

• The plant uses G3P to make glucose and other organic molecules.

Overall input:

CO2, ATP, NADPH

Overall output:

Glucose

Review: Photosynthesis uses light energy to make food molecules

Light

Chloroplast

Photosystem IIElectron transport

chains Photosystem I

CALVIN CYCLE Stroma

Electrons

LIGHT REACTIONS CALVIN CYCLE

Cellular respiration

Cellulose

Starch

Other organic compounds

• Light reactions use water and produce oxygen.

• The Calvin Cycle uses ATP and NADPH created in the the light reactions to convert carbon dioxide to glucose.

Fill out the following chart to compare Photosynthesis and Cellular

Respiration

Photosynthesis Cellular Respiration

Function

Location

Reactants

Products

Equation

Photosynthesis – Cellular Respiration comparison

Photosynthesis Cellular Respiration

Function Energy capture Energy release

Location Chloroplasts Mitochondria

Reactants CO2 and H2O C6H12O6 and O2

Products C6H12O6 and O2 CO2 and H2O

Equation 6CO2 + 6H2O light>

C6H12O6 + 6O2

6O2 + C6H12O6

6CO2 +6H2O +

energy