1. Capturing sunlight to provide energy for life on earth
Photosynthesis
Capturing sunlight to provide energy for life on earth

2. THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON EARTH

3. The Electromagnetic Spectrum
The ES describes all of the various types of radiation.
Radiation is energy that travels and spreads out as it goes– visible light that comes from a light bulb or radio waves that come from a radio station are two types of electromagnetic radiation.
Other examples of EM radiation are microwaves, infrared and ultraviolet (UV) light.

5. Visible Light
The portion of the ES that can be seen by animals is called Visible Light.
Light is given off by the sun in waves.
The waves determine the color and energy.

6. Wavelengths
The length of the waves determines the energy and the light’s color.
The shorter the wave, the greater its energy.

7. Why are plants green? Chlorophylls and accessory pigments
ABSORB blue/violet and orange/red light
REFLECT green light
Makes chlorophyll in plants appear green

8. Two accessory pigments
Chlorophyll
The primary pigments for photosynthesis
Captures sunlight energy
Two accessory pigments
Carotenes
Xanthophyll
absorb light
transfer energy to chlorophyll

9. Pigments absorb light differently

11. Introduction
Photosynthesis – the conversion of sunlight energy to chemical energy (glucose)
CO2 + H2O + light energy C6H12O6 + O2
Carbon Dioxide
Water
Glucose
Oxygen

12. Why is it important? The products are glucose and oxygen:
Many organisms (including humans) use glucose as an energy source
All aerobic organisms use oxygen

13. Plant Photosynthesis
CO2 is obtained through adjustable pores called stomata
Water and minerals provided by a system of veins in the plant
Mostly absorbed through the roots
Veins also carry sugars to other parts of the plant

15. Plant Photosynthesis Photosynthesis takes place in the chloroplasts
Thylakoid= membranous sac
Granum= Stack of thylakoids
Stroma= Fluid inside chloroplast
MAKE A DIAGRAM OF A CHLOROPLAST:
Label: Thylakoid, Granum (p.= grana), Stroma

16. Anatomy of a Chloroplast
Why have stacks?
More surface area (more room to do photosynthesis)

17. Plant Photosynthesis
Photosynthesis can be divided into two types of reactions:
Light-dependent reaction
Light-independent reaction (Dark reactions)

18. AN OVERVIEW OF PHOTOSYNTHESIS
The light reactions convert solar energy to chemical energy
Produce ATP & NADPH
Light
Chloroplast
NADP
ADP
+ P
The Calvin cycle makes sugar from carbon dioxide
ATP generated by the light reactions provides the energy to make sugar
The NADPH produced by the light reactions provides the electrons to make glucose from carbon dioxide
Calvin
cycle
Light
reactions

19. Homework Write out question and answer in complete sentences!
What makes the parts of the electromagnetic spectrum different from each other?
What color of light is not absorbed by plants? What happens to this color?
What are the reactants and products to photosynthesis?

21. ELECTRON TRANSPORT CHAIN
Thylakoid space (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

22. Plant Photosynthesis Steps to Light-Dependent Reactions:
Photosystem II:
Has chlorophyll inside (captures sunlight)
Splits water:
Things made from splitting water:
H+ (protons) O
Electrons (e-)
Electrons from splitting of water get excited by sunlight energy in the reaction center
Electrons and H+ drive ATP synthesis
O2 gas is a by-product

23. Primary electron acceptor
Molecular Game of “Hot Potato”
Primary electron acceptor
Photon
Reaction center
PHOTOSYSTEM
Pigment molecules of antenna

24. ELECTRON TRANSPORT CHAIN
Thylakoid compartment (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

25. Electron Transport Chain Photosystem I:
Has chlorophyll inside
Light excites electrons again, electrons used to produce NADPH (electron carrier)

26. Two types of photosystems cooperate in the light reactions
Photon
ATP
mill
Gold hammers= photon
Photon
Water-splitting
photosystem
NADPH-producing
photosystem

28. Plants produce O2 gas by splitting H2O
The O2 made by photosynthesis is from the oxygen in water

29. Light-dependent rxn
Light-dependent reactions continue as long as water and sunlight are available

30. ETC Continued
The Electron transport chain is made up of proteins that accept and transfer the electrons.
The electrons are passed from protein to protein and energy is given off along the way.
Demonstration:
3 Students in a line passing an electron (any object): students should yelp (give off energy) as they pass the electron quickly
(Could have two desks represent photosystems)

31. Electron Transport Chain
The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane into the thylakoid
Creates a high concentration of H+ inside and low concentration of H+ outside membrane
The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP

32. ELECTRON TRANSPORT CHAIN
Thylakoid compartment (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

33. ATP Synthase and Chemiosmosis
The protons (H+) diffuse out of the thylakoid through an enzyme complex called ATP Synthase
Uses ETC (to pump H+ in)
Protons (H+) move down their concentration gradient through channels of ATP synthase forming ATP from ADP

34. Chemiosmosis
ADP + Pi  ATP

35. Formation of NADPH
Electrons at the end of the “chain” are used to make NADPH from NADP+.
NADP+ + 2e- + H+  NADPH
NADPH is an energy carrier molecule that takes electrons to the stroma for the Calvin Cycle.

36. ELECTRON TRANSPORT CHAIN
The production of ATP by chemiosmosis in photosynthesis
Thylakoid compartment (high H+)
Light
Light
Thylakoid membrane
Antenna molecules
Stroma (low H+)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE

37. Light Rxn Qs Write out question and answer in complete sentences!
What happens in:
photosystem I?
photosystem II?
Describe what happens on the electron transport chain.
Chemiosmosis:
Where does it happen?
What does it make?

38. Photosynthesis Part II
The Calvin Cycle
Photosynthesis
Part II

39. Sun light + CO2 + H2O  C6H12O6 + O2
Equation
Sun light + CO2 + H2O  C6H12O6 + O2

40. The Calvin Cycle Overview
The Calvin Cycle (sometimes called the dark reaction) uses the potential energy (ATP and NADPH) produced in the light reactions to make sugars that organisms can use for growth.

41. Calvin Cycle The Calvin Cycle occurs in the stroma of chloroplasts.
Carbon dioxide is captured by the chemical ribulose biphosphate (RuBP).
Six molecules of carbon dioxide enter the Calvin Cycle, eventually producing one molecule of glucose.

42. Carbon dioxide comes in through the stomata and is fixed (attached)
Steps to Calvin Cycle:
Carbon dioxide comes in through
the stomata and is fixed (attached)
to a molecule called RuBP to make
PGA
The energy from ATP and electrons from NADPH (both from the light rxn) are used to convert PGA to PGAL
PGAL =3 carbon molecule.
One PGAL is released from the cycle to be made into glucose later
Rest of PGAL is used to regenerate RuBP
** Must go through the cycle twice
Glucose is a 6-carbon sugar (3 + 3 = 6)

44. Energy Cycles
The glucose produced and the O2 released by plants are used by other organisms to produce energy
(and the other
organisms release CO2)
This CO2 is then used
by plants to produce
more glucose via
photosynthesis

45. Alternative Pathways
Typical plants are called C3 plants because they use a three-carbon compound .
One of the alternative pathways is the C4 pathway (C4 plants)
Uses a four-carbon compound to store CO2
Corn, sugar cane, and crabgrass
Store CO2 and do Calvin Cycle different cells (allows plant to be more efficient)
-The fourth carbon is storage for carbon dioxide (so the Calvin Cycle can run during times of low CO2 levels)
-Fixes a CO2 molecule withl a 3-c molecule
-Separates these reactions into different cells

46. CAM Pathway
Cacti, pineapples, and others have an adaptation to hot, dry climates.
These plants use a four-carbon compound in a pathway called CAM.
CAM plants open their stomata at night and close them during the day (the opposite of C3 plants).
Prevents water loss to evaporation
Most CO2 available at night
Most desert animals are nocturnal
At night, CAM plants fix (store) CO2 so that during the day these compounds enter the Calvin cycle (Opposite of C4 plants).
Typical C4 plants take in and store CO2 during the day for use at night
Stomata close during the day to prevent water loss
Four-c molecule stores CO2 for when CO2 levels are low during day (most desert animals are nocturnal- most CO2 available at night)
Stranded in desert? Eat the plants during the day (CAM plants are sour in morning (due to acid build-up) and become bland during the day due to running Calvin Cycle, and bitter at night bc c-fixing molecule presence)
WARNING- most desert plants are poisonous

48. Dark Rxn Qs Write out question and answer in complete sentences!
What does the dark RXN use from the light RXN?
How many carbons does PGAL have? Why does it go through the cycle twice to make glucose?
How are CAM plants able to store water better than others?