1. PHOTOSYNTHESIS

2. Photosynthesis process by which green plants & some organisms
seaweed, algae & certain bacteria
use light energy to convert CO2 + water glucose
all life on Earth, directly or indirectly, depends on photosynthesis as source of food, energy & O2

4. Autotrophs self feeders
organisms that make their own organic matter from inorganic matter
producers
use inorganic molecules such as CO2, H2O & minerals to make organic molecules

5. Heterotrophs consumers other feeders
depend on glucose as energy source
cannot produce it
obtained by eating plants or animals that have eaten plants

6. Carbon and Energy Flow Light energy Heat energy CO2 + H2O
Photosynthesis
Carbs
Proteins
Lipids + O2
Cellular (Aerobic)
Respiration
(ATP Produced)

7. Food Chain byproduct of photosynthesis is O2
humans & other animals breathe in oxygen
used in cellular respiration

8. Other Benefits of Photosynthesis
humans also dependent on ancient products of photosynthesis
fossil fuels
natural gas, coal & petroleum
needed for modern industrial energy
complex mix of hydrocarbons
represent remains of organisms that relied on photosynthesis millions of years ago

9. Photosynthesis plants produce more glucose than can use
stored as starch & other carbohydrates in roots, stems & leaves
can draw on these reserves for extra energy or building materials as needed

10. Sites of Photosynthesis
leaves & green stems
in cell organelles
chloroplasts
concentrated in green tissue in interior of leaf
mesophyll
green due to presence of green pigment chlorophyll

11. Chloroplasts each cell has 40-50 chloroplasts
oval-shaped structures with double membrane
inner membrane encloses compartment filled with stroma
suspended in stroma are disk-shaped compartments-thylakoids
arranged vertically like stack of plates
one stack-granum (plural, grana)
embedded in membranes of thylakoids are hundreds of chlorophyll molecules

12. Chlorophyll light-trapping pigment
other light-trapping pigments, enzymes & other molecules needed for photosynthesis are also found in thylakoid membranes

13. How Photosynthesis Works
Requires
CO2
Water
Sunlight
Makes O2
Glucose

14. How Photosynthesis Works
CO2 enters plant via pores- stomata in leaves
water-absorbed by roots from soil
membranes in chloroplasts provide sites for reactions of photosynthesis
chlorophyll molecules in thylakoids capture energy from sunlight
chloroplasts rearrange atoms of inorganic molecules into sugars & other organic molecules

15. Photosynthesis redox reaction
6CO2 + 12H2OC6H12O6 + 6O2 + 6H2O in presence of light
must be an oxidation & a reduction
water is oxidized
loses electrons & hydrogen ions
carbon dioxide is reduced
gains electrons & hydrogens

17. Photosynthesis 2 stages light-dependent reactions
chloroplasts trap light energy
convert it to chemical energy
contained in nicotinamide adenine dinucleotide phosphate-(NADPH) & ATP
used in second stage
light-independent reactions
Calvin cycle
formerly called dark reactions
NADPH (electron carrier) provides hydrogens to form glucose
ATP provides energy

18. Light Energy for Photosynthesis
sun energy is radiation
electromagnetic energy
travels as waves
distance between 2 waves- wavelength
light contains many colors
each has defined range of wavelengths measured in nanometers
range of wavelengths is electromagnetic spectrum
part can be seen by humans
visible light

19. Pigments light absorbing molecules built into thylakoid membranes
absorb some wavelengths & reflect others
plants appear green because chlorophyll-does not absorb green light
reflected back.
as light is absorbedenergy is absorbed
chloroplasts contain several kinds of pigments
different pigments absorb different wavelengths of light
red & blue wavelengths are most effective in photosynthesis
other pigments are accessory pigments
absorb different wavelengths
enhance light-absorbing capacity of a leaf by capturing a broader spectrum of blue & red wavelengths along with yellow and orange wavelengths

20. Pigment Color & Maximum Absoption
Violet:   nm
Indigo:   nm
Blue:   nm
Green:   nm
Yellow:   nm
Orange:   nm
Red:   nm

21. Chlorophylls Chlorophyll A absorbs blue-violet & red light
reflects green
participates in light reactions
Chlorophyll B
absorbs blue & orange light
reflects yellow-green
does not directly participate in light reactions
broadens range of light plant can use by sending its absorbed energy to chlorophyll A

22. Carotenoids yellow-orange pigments absorb blue-green wavelengths
reflect yellow-orange
pass absorbed energy to chlorophyll A
have protective function
absorb & dissipate excessive light energy that would damage chlorophylls

23. Photosynthesis Pigments Absorb light Excites electrons
Energy passed to sites in cell
Energy used to make glucose

24. Photosystems
chlorophyll & other pigments clustered next to one another in a photosystem
when photon strikes one pigment molecule
energy jumps from pigment to pigment until arrives at reaction center

25. Reaction Center
electron acceptor traps a light excited electron from reaction center chlorophyll
passes it to electron transport chain which uses energy to make ATP & NADPH

26. Photosystems two photosystems participate in light reactions
photosystems II & I

27. Light Reactions make ATP & NADPH
electrons are removed from molecules of water
oxygen escapes to air
electrons are passed from photosystem II to photosystem I to NADP+
light drives electrons from H2O to NADP+ which is oxidized NADPH which is reduced

28. Photosystem II water is split
oxygen atom combines with oxygen from another split water forming molecular oxygen-O2
each excited electron passes from photosystem II to photosystem I via electron transport chain

30. Photosystem I electron acceptor captures an excited electron
excited electrons are passed through a short electron transport chain to NADP+ reducing it to NADPH
NADP+ -final electron acceptor
electrons are stored in high state of potential energy in NADPH molecule
NADPH, ATP and O2 are products of light reactions

31. ATP Formation-Chemiosmosis
uses potential energy of hydrogen ion concentration gradient across membrane
gradient forms when electron transport chain pumps hydrogen ions across thylakoid membrane as it passes electrons down chain that connects two photosystems

32. ATP Formation-Chemiosmosis
ATP synthase (enzyme) uses energy stored by H gradient to make ATP
ATP is produced from ADP & Pi when hydrogen ions pass out of thylakoid through ATP synthase
photophosphorylation

33. Calvin Cycle/Dark Reactions
light independent reactions
depend on light indirectly for inputs-ATP & NADPH
occurs-stroma of chloroplast
each step controlled by different enzyme
cycle of reactions
makes sugar from CO2 & energy
ATP provides chemical energy
NADPH provides high energy electrons for reduction of CO2 to sugar

34. Steps of Calvin Cycle starting material-ribulose bisphosphate (RuBP)
first step-carbon fixation
rubisco (an enzyme) attaches CO2 to RuBP
Next-reduction reaction takes place
to do this cycle uses carbons from 3 CO2 molecules
to complete cycle must regenerate beginning component-RuBP
for every 3 molecules of CO2 fixed, one G3P molecule leaves cycle as product of cycle
remaining 5 G3P molecules are rearranged using ATP to make 3 RuBP molecules

36. Calvin Cycle regenerated RuBP is used to start Calvin cycle again
process occurs repeatedly in each chloroplast as long as CO2, ATP & NADPH are available
thousands of glucose molecules are produced
used by plants to produce energy in aerobic respiration
used as structural materials
stored