1. Photosynthesis
Chapter 7

2. Photosynthesis Almost all plants are photosynthetic autotrophs
As are some bacteria and protists
Generate their own organic matter through photosynthesis
Photosynthesis
Occurs in chloroplasts
Energized electrons are added to carbon dioxide to make sugar
Converts solar energy into the chemical energy of a carbohydrate
Sunlight provides the energy

3. Anatomy of a Plant Carried out by the green portions of plants
Leaves contain mesophyll tissue specialized for photosynthesis
Water taken up by roots and transported to leaves by veins

4. Anatomy of a Plant
Carbon dioxide enters through openings in the leaves called stomata
Light energy absorbed by chlorophyll and other pigments in thylakoids of chloroplasts
Main organelle that carries out photosynthesis!!!!

5. Chloroplasts Are found in the interior cells of leaves
Contain stroma, a thick fluid
Contain thylakoids, membranous sacs

6. Photosynthetic Reaction
Glucose and oxygen are the products of photosynthesis
Oxygen given off comes from water
CO2 gains hydrogen atoms and becomes a carbohydrate
Reaction written as:

7. Two Steps…..
1. Light reactions convert solar energy to chemical energy
Light-dependent reactions
take place only in presence of light
produce ATP and NADPH
2. Calvin cycle makes sugar from carbon dioxide
Light-independent reactions
do not need light to occur
result in the formation of organic molecules

8. Light Reactions

9. An Overview of Photosynthesis
Photosystem
Starting point of photosynthesis
Network of pigments in the membrane of the thylakoid
molecules that absorb light energy
primary pigment of a photosystem is chlorophyll
pigments act as an antenna to capture energy from sunlight
individual chlorophyll pigments pass the captured energy between them

10. How Plants Capture Energy from Sunlight
Light comprised of packets of energy called photons
Sunlight has photons of varying energy levels
possible range of energy levels is represented by an electromagnetic spectrum

11. Human eyes only perceive photons of intermediate energy levels
this range of the spectrum is known as visible light
Chloroplasts absorb select wavelengths of light that drive photosynthesis

12. The light reactions of photosynthesis
Two types of photosystems cooperate in the light reactions
Photosystem II
captures a photon of light and releases an excited electron to the electron transport system (ETS)
Photosystem I
absorbs another photon of light and releases an excited electron to another ETS

13. Electron transport chain
Connects the two photosystems
Releases energy that the chloroplast uses to make ATP

14. Calvin Cycle

15. Calvin Cycle Light-independent
These reactions are the second stage of photosynthesis
Functions like a sugar factory within a chloroplast
Regenerates the starting material with each turn
NADPH and ATP produced in light reactions used to reduce carbon dioxide to a carbohydrate

17. Overview of Photosynthesis

18. Photosynthesis Versus Cellular Respiration
Both plant and animal cells carry out cell respiration
Only plant cells photosynthesize
Both processes utilize an electron transport chain and chemiosmosis for ATP production
Photosynthesis reduces CO2 to carbohydrates and releases O2
Respiration utilizes O2 and gives off CO2

19. Photosynthesis and Respiration Compared

20. Environmental Impacts
Photosynthesis has an enormous impact on atmosphere.
swaps O2 for CO2
Greenhouses used to grow plant indoors
Trap sunlight that warms the air inside
The greenhouse effect
Warms the atmosphere
Caused by atmospheric CO2
Greenhouse gases are the most likely cause of global warming
Slow but steady rise in the Earth’s surface temperature
Destruction of forests may be increasing this effect