1. Photosynthesis
Energy & Life

2. Overview of Photosynthesis

3. Autotrophs
Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food.

4. Autotrophs Autotrophs include organisms that make their own food
Autotrophs can use the sun’s energy directly
Euglena

5. Heterotrophs
Heterotrophs are organisms that can NOT make their own food
Heterotrophs can NOT directly use the sun’s energy

6. Candles release energy as HEAT & LIGHT
Energy Takes Many Forms such as light, heat, electrical, chemical, mechanical
Energy can be changed from one form to another
Energy can be stored in chemical bonds & then released later
Candles release energy as HEAT & LIGHT

7. ATP – Cellular Energy Adenosine Triphosphate
Contains two, high-energy phosphate bonds
Also contains the nitrogen base adenine & a ribose sugar

8. One phosphate bond has been removed
ADP
Adenosine Diphosphate
ATP releases energy, a free phosphate, & ADP when cells take energy from ATP
One phosphate bond has been removed

9. Sugar in ADP & ATP
Called ribose
Pentose sugar
Also found on RNA

10. Importance of ATP
Principal Compound Used To Store Energy In Living Organisms

11. Releasing Energy From ATP
ATP is constantly being used and remade by cells
ATP provides all of the energy for cell activities
The high energy phosphate bonds can be BROKEN to release energy
The process of releasing ATP’s energy & reforming the molecule is called phosphorylation

12. Releasing Energy From ATP
Adding A Phosphate Group To ADP stores Energy in ATP
Removing A Phosphate Group From ATP Releases Energy & forms ADP
Loose
Gain

13. Cells Using Biochemical Energy
Cells Use ATP For:
Active transport
Movement
Photosynthesis
Protein Synthesis
Cellular respiration
All other cellular reactions

14. More on ATP Cells Have Enough ATP To Last For A Few Seconds
ATP must constantly be made
ATP Transfers Energy Very Well
ATP Is NOT Good At Energy Storage

15. Glucose Glucose is a monosaccharide C6H12O6
One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

16. History of Photosynthesis & Plant Pigments

17. Photosynthesis
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

18. Investigating Photosynthesis
Many Scientists Have Contributed To Understanding Photosynthesis
Early Research Focused On The Overall Process
Later Researchers Investigated The Detailed Chemical Pathways

19. Early Questions on Plants
Several Centuries Ago, The Question Was: Does the increase in mass of a plant come from the air? The soil? The Water?

20. Van Helmont’s Experiment 1643
Planted a seed into A pre-measured amount of soil and watered for 5 years
Weighed Plant & Soil. Plant Was 75 kg, Soil The Same.
Concluded Mass Came From Water

21. Priestley’s Experiment 1771
Burned Candle In Bell Jar Until It Went Out.
Placed Sprig Of Mint In Bell Jar For A Few Days.
Candle Could Be Relit And Burn.
Concluded Plants Released Substance (O2) Necessary For burning.

22. Ingenhousz’s Experiment 1779
Repeated Priestly experiment with & without sunlight

23. Results of Ingenhousz’s Experiment
Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight.
Light Was Necessary For Plants To Produce The “Burning Gas” or oxygen

24. Julius Robert Mayer 1845
Proposed That Plants can Convert Light Energy Into Chemical Energy

25. Samuel Ruben & Martin Kamen 1941
Used Isotopes To Determine That The Oxygen Liberated In Photosynthesis Comes From Water
RUBIN
KAMEN

26. Melvin Calvin 1948 Does NOT require sunlight
First to trace the path that carbon (CO2) takes in forming Glucose
Does NOT require sunlight
Called the Calvin Cycle or Light Independent Reaction
Also known as the Dark Reaction

27. Rudolph Marcus 1992 Studied the Light Independent Reactions
First to describe the Electron transport Chain

28. The Photosynthesis Equation

29. 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

30. Light and Pigments Photon = Light Energy Unit
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

31. Light & Pigments
Different pigments absorb different wavelengths of light
Photons of light “excite” electrons in the plant’s pigments
Excited electrons carry the absorbed energy
Excited electrons move to HIGHER energy levels

32. Magnesium atom at the center of chlorophyll
There are 2 main types of chlorophyll molecules:
Chlorophyll a
Chlorophyll b
A third type, chlorophyll c, is found in dinoflagellates
Magnesium atom at the center of chlorophyll

33. Chlorophyll a Found in all plants, algae, & cyanobacteria
Makes photosynthesis possible
Participates directly in the Light Reactions
Can accept energy from chlorophyll b

34. Chlorophyll b Chlorophyll b is an accessory pigment
Chlorophyll b acts indirectly in photosynthesis by transferring the light it absorbs to chlorophyll a
Like chlorophyll a, it absorbs red & blue light and REFLECTS GREEN

35. The Biochemical Reactions

36. It Begins with Sunlight!

37. Photoautotrophs Absorb Light Energy

38. Inside A Chloroplast

39. Structure of the Chloroplast
Double membrane organelle
Outer membrane smooth
Inner membrane forms stacks of connected sacs called thylakoids
Thylakoid stack is called the granun (grana-plural)
Gel-like material around grana called stroma

40. Function of the Stroma Light Independent reactions occur here
ATP used to make carbohydrates like glucose
Location of the Calvin Cycle

42. Thylakoid membranes Light Dependent reactions occur here
Photosystems are made up of clusters of chlorophyll molecules
Photosystems are embedded in the thylakoid membranes
The two photosystems are:
Photosytem I
Photosystem II

43. Photosynthesis Overview

44. Energy Carriers NADP+ = Reduced Form
Nicotinamide Adenine Dinucleotide Phosphate (NADP+)
NADP+ = Reduced Form
Picks Up 2 high-energy electrons and H+ from the Light Reaction to form NADPH
NADPH carries energy to be passed on to another molecule

45. Light Dependent Reactions
Occurs across the thylakoid membranes
Uses light energy
Produce Oxygen from water
Convert ADP to ATP
Also convert NADP+ into the energy carrier NADPH

46. Light Dependent Reaction

47. Light Dependent Reaction

48. Photosystem I Discovered First
Active in the final stage of the Light Dependent Reaction
Made of 300 molecules of Chlorophyll
Almost completely chlorophyll “a”

49. Photosystem II Discovered Second
Active in the beginning stage Of the Light Dependent Reaction
Contains about equal amounts of chlorophyll a and chlorophyll b

50. Photosynthesis Begins
Photosystem II absorbs light energy
Electrons are energized and passed to the Electron Transport Chain
Lost electrons are replaced from the splitting of water into 2H+, free electrons, and Oxygen
2H+ pumped across thylakoid membrane

51. Photosystem I
High-energy electrons are moved to Photosystem I through the Electron Transport Chain
Energy is used to transport H+ from stroma to inner thylakoid membrane
NADP+ converted to NADPH when it picks up 2 electrons & H+

52. Phosphorylation Enzyme in thylakoid membrane called ATP Synthase
As H+ ions passed through thylakoid membrane, enzyme binds them to ADP
Forms ATP for cellular

54. Light Reaction Summary
Reactants:
H2O
Light Energy
Energy Products:
ATP
NADPH

55. Light Independent Reaction
ATP & NADPH from light reactions used as energy
Atmospheric C02 is used to make sugars like glucose and fructose
Six-carbon Sugars made during the Calvin Cycle
Occurs in the stroma

56. The Calvin Cycle

57. The Calvin Cycle
Two turns of the Calvin Cycle are required to make one molecule of glucose
3-CO2 molecules enter the cycle to form several intermediate compounds (PGA)
A 3-carbon molecule called Ribulose Biphosphate (RuBP) is used to regenerate the Calvin cycle

59. Factors Affecting the Rate of Photosynthesis
Amount of available water
Temperature
Amount of available light energy