1. Photosynthesis and Cellular Respiration

2. Energy
Energy that living things gain from eating comes indirectly from the sun.
Plants receive this energy directly, while we receive the energy indirectly.
This energy makes organic compounds found in our food.

3. Flow of Energy

4. Autotrophs
Organisms that use energy from sunlight to make organic compounds
Most are photosynthetic
Ex: Plants
Some do not have access to sunlight, and use chemical energy instead
Ex: bacteria in extreme environments

5. Photosynthesis
The process by which light energy is converted to chemical energy

6. Heterotrophs Organisms that must get energy from food
Humans and other animals
Go through cellular respiration processes for energy

7. Cellular Respiration Releases energy from food to make ATP
Energy released gradually through chemical reactions
ATP is a result of these reactions
ATP goes wherever it is needed in the cells

8. ATP
ATP (Adenosine Triphosphate) goes to the areas that need energy in the cell
A phosphate group breaks off to release the energy needed and forms ADP.
ATP  ADP + P + Energy

9. Let’s Look at Photosynthesis and Cellular Respiration a little closer!

10. Photosynthesis All foods that we eat eventually lead back to plants.
These plants go through photosynthesis to get their energy.
Ex: Hamburger Beef comes from cow that ate grass.

11. Photosynthesis
Photosynthesis occurs in chloroplasts of plant cells and cell membrane of bacteria.
3CO2 + 3H2O  C3H6O3 + 3O2

12. Three Stages of Photosynthesis
1.) Energy is captured from sunlight 2.) Light energy is converted to chemical energy (stored in ATP and NADPH) 3.) Chemical energy in ATP and NADPH power the formation of organic compounds Steps 1 & 2 are light-dependent NADPH is an energy carrier molecule

13. Stage 1: Energy is Captured From Sunlight
When sun shines on us, there are several types of radiation hitting us at different wavelengths. We can only see visible light and sunlight contains all of the wavelengths of visible light.

15. Stage 1: Energy is Captured From Sunlight
How do we see light?

16. Stage 1: Energy is Captured From Sunlight
We see light through light-absorbing substances called pigments. These absorb and reflect certain wavelengths.
These pigments are held in disk-shaped thylakoids in chloroplasts. These pigments are held in clusters.

18. Two Types of Pigments to Know
Chlorophyll
Reflects green and yellow light so we see leaves as green.
Carotenoids
Reflects yellow and red light so we see leaves as yellow and orange in fall.

19. Stage 1: Energy is Captured From Sunlight
Light strikes thylakoid Energy transferred to electrons in pigments Electrons now “excited” and jump to higher energy level These electrons used to power Stage 2 Electrons used now replaced through water molecules This forms oxygen gas (O2)

20. Stage 2: Light Energy is Converted to Chemical Energy
The excited electrons from Stage 1 jump through molecules along the thylakoid membrane.
Like a basketball being passed down a line of people
This is known as an electron transport chain
One chain helps make ATP
One chain helps make NADPH

21. Electron Transport Chain: ATP
Excited electrons move through protein Electrons lose energy, energy used to pump in H+ ions Eventually these ions diffuse out of the thylakoid through a carrier protein This protein causes ADP to add a phosphate group and it becomes ATP

22. Electron Transport Chain: NADPH
Excited electrons combine with hydrogen ions and NADP+ Forms NADPH

23. Stage 3: Energy Stored in Organic Compounds
Carbon dioxide fixation: transfer of carbon dioxide to organic compounds
“dark reaction” or light-independent
Most common method of carbon dioxide fixation is the Calvin Cycle

24. Calvin Cycle
1.) Each carbon dioxide molecule is added to a five-carbon compound. 2.) Each of the three resulting six-carbon compounds is unstable and immediately splits, forming a total of six three- carbon compounds. 3.) One of the resulting three-carbon sugars is used to make organic compounds that the organism uses for energy. 4.) The five other three-carbon sugars are used to regenerate the five-carbon compound that began the cycle.

26. Factors that Affect Photosynthesis
Light
Rate of Photosynthesis increases as light intensity increases
Carbon Dioxide Concentration
Same as light
Temperature
Enzymes assist reactions and have to stay within certain temperature range