1. Energy can be transformed from one form to another
FREE ENERGY
(available for work)
vs.
HEAT
(not available for work)

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

3. THE BASICS OF PHOTOSYNTHESIS
Almost all plants are photosynthetic autotrophs, as are some bacteria and protists
Autotrophs generate their own organic matter through photosynthesis
Sunlight energy is transformed to energy stored in the form of chemical bonds
(c) Euglena
(d) Cyanobacteria
(b) Kelp
(a) Mosses, ferns, and
flowering plants

4. What do cells use for energy?
Question:
What do cells use for energy?

5. Energy for Life on Earth
Sunlight is the ULTIMATE energy for all life on Earth
Plants store energy in the chemical bonds of sugars
Chemical energy is released as ATP during cellular respiration

6. Structure of ATP ATP stands for adenosine triphosphate
It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups
The LAST phosphate group is bonded with a HIGH ENERGY chemical bond
This bond can be BROKEN to release ENERGY for CELLS to use

7. Removing a Phosphate from ATP
Breaking the LAST PHOSPHATE bond from ATP, will ---
Release ENERGY for cells to use
Form ADP
Produce a FREE PHOSPHATE GROUP

8. High Energy Phosphate Bond

9. FREE PHOSPHATE can be re-attached to ADP reforming ATP
Process called Phosphorylation

10. Phosphorylation

11. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

12. Food Chain

13. Light-Harvesting Complex
Light Receptors
Pigments capture light energy
photon
Light-Harvesting Complex

14. Photosynthesis Anabolic (small molecules combined)
Endergonic (stores energy)
Carbon dioxide (CO2) requiring process that uses light energy (photons) and water (H2O) to produce organic macromolecules (glucose).
6CO H2O  C6H12O O2
glucose
SUN
photons

15. Overall Reaction What is the equation for photosynthesis?
carbon dioxide + water  glucose + oxygen + energy
6CO H2O  C6H12O O2

16. THE FOOD WEB

17. WHY ARE PLANTS GREEN?
It's not that easy bein' green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that…
Kermit the Frog

18. Electromagnetic Spectrum and Visible Light
Gamma rays
Infrared & Microwaves
X-rays UV
Radio waves
Visible light
Wavelength (nm)

19. WHY ARE PLANTS GREEN?
Different wavelengths of visible light are seen by the human eye as different colors.
Gamma rays
Micro- waves
Radio
waves
X-rays UV
Infrared
Visible light
Wavelength (nm)

20. The feathers of male cardinals are loaded with carotenoid pigments
The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others.
Reflected light
Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.

21. Why are plants green?
Reflected light
Transmitted light

22. WHY ARE PLANTS GREEN? Plant Cells have Green Chloroplasts
The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

23. THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED
Chloroplasts absorb light energy and convert it to chemical energy
Reflected
light
Light
Absorbed
light
Transmitted
light
Chloroplast

24. AN OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
Carbon dioxide
Water
Glucose
Oxygen gas
PHOTOSYNTHESIS

25. Overview Carbon dioxide and water are taken in by plants
Plants absorb light energy and convert it to a usable form.
ATP
Energy is used to “fix” carbon dioxide into sugar molecules
Chemical energy
Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.

26. Chloroplasts: Sites of Photosynthesis
Occurs in chloroplasts, organelles in certain plants
All green plant parts have chloroplasts and carry out photosynthesis
The leaves have the most chloroplasts
The green color comes from chlorophyll in the chloroplasts
The pigments absorb light energy

27. The location and structure of chloroplasts
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
CHLOROPLAST
Intermembrane space
Outer
membrane
Granum
Inner membrane
Grana
Stroma
Thylakoid compartment
Stroma
Thylakoid

28. Chloroplasts Have TWO membranes
A “bi-bilayer!”
The inner membrane is called the thylakoid.
The thylakoid is folded and looks like stacks of coins called granum (grana singular).
The stroma is the space surrounding the granum
Image source:

29. Chloroplasts
Chlorophyll molecules are embedded in the thylakoid membrane
Act like a light “antenna”
These molecules can absorb sunlight energy.
Image from Biology 11: College Preparation. Pg 73. Nelson, Toronto

30. The Environmental Impact of Photosynthesis
Greenhouse effect
Natural effect
Occurs when greenhouse gases trap heat in the atmosphere
Without the greenhouse effect, earth would be much colder
CO2 is a major greenhouse gas
Where is it coming from???

31. The Environmental Impact of Photosynthesis
Too much CO2 may cause an enhanced greenhouse effect (global climate change)
Plants take in large quantities of CO2
Protect large tracts of forests?
Cut them down, as young trees take in more CO2 than older trees?

32. During the fall, what causes the leaves to change colors?
Question:
During the fall, what causes the leaves to change colors?