CHAPTER 7
PHOTOSYNTHESIS: USING LIGHT
TO MAKE FOOD
General Biology
CM Lamberty
BIOLOGY AND SOCIETY
Green Energy
 Wood…fossil fuels….biomass/biofuels
 Renewable, less S, wildlife habitats, reduce
erosion, disversification
 4% of all E in US

THE BASICS OF PHOTOSYNTHESIS
Process by which plants, algae and certain
bacteria transform light E into chemical E
 Uses CO2 and H2O as starting materials
 Chemical E then stored in bonds of sugar
 Plants = autotrophs

CHLOROPLASTS: SITES OF PHOTOSYNTHESIS
Chloroplasts:
 Found


Chlorophyll
Stomata:
 Stroma:
 Thylakoids:
 Grana:

THE OVERALL EQUATION FOR PHOTOSYNTHESIS
6 CO2 + 6 H2O
C6H12O6 + 6 O2
 CO2 and H2O were waste products of cell. resp

A PHOTOSYNTHESIS ROAD MAP
2 stages of photosynthesis
 Light Reactions


Calvin Cycle
THE LIGHT REACTIONS: SOLAR…CHEMICAL
THE NATURE OF SUNLIGHT
Radiation
 Electromagnetic energy
 Waves
 Wavelength


EM spectrum

Light hits object and is either absorbed or reflect
CHLOROPLAST PIGMENTS

Chlorophyll a

Chlorophyll b

Carotenoids
HOW PHOTOSYSTEMS HARVEST LIGHT E
Photon:
 Shorter wavelength
 Pigment MQ absorb photon


Thylakoid membrane
HOW LIGHT RXNS GENERATE ATP & NADPH
2 types of photosystems cooperate
 Water-splitting photosystem


Transfer between systems

NADPH-producing photosystem
HOW LIGHT RXNS GENERATE ATP & NADPH
Light reactions taking place in thylakoid
membrane
 2 photosystems and electron transport chain


ATP production is similar to cellular respiration

Difference:
THE CALVIN CYCLE: MAKING SUGAR FROM
CO2
Sugar factory within stroma of chloroplast
 Cycle: starting material regenerated each turn

SOLAR DRIVEN EVOLUTION
Hot, dry climates plants continue photosynthesis
while conserving water
 C4


CAM